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C

 
c
   (Space Flight Glossary - JPL)
The speed of light, 299,792 km per second.
C band
   (Space Flight Glossary - JPL)
A range of microwave radio frequencies in the neighborhood of 4 to 8 GHz.
C&DH
   (Space Flight Glossary - JPL)
Command and Data Handling subsystem on board a spacecraft, similar to CDS.
C-8A augmentor wing aircraft
   (NASA Thesaurus)
NASA's research, short haul, jet aircraft.
C-band
   (NASA SP-7, 1965)
See frequency band.
C-display
   (NASA SP-7, 1965)
In radar, a rectangular display in which targets appear as blips with bearing indicated by the horizontal coordinate and angles of elevation by the vertical coordinate. Also called C-scan and C-scope.
C-figure
   (NASA SP-7, 1965)
= C-index
C-index
   (NASA SP-7, 1965)
A subjectively obtained daily index of geomagnetic activity. Each day's record is evaluated on the basis of 0 for quiet, 1 for moderately disturbed, and 2 for very disturbed. Also called C-figure, magnetic character figure. See geomagnetism.
C-scan
   (NASA SP-7, 1965)
= C-display.
C-scope
   (NASA SP-7, 1965)
= C-display.
cadastral mapping
   (NASA Thesaurus)
Large-scale mapping for showing the boundaries of subdivisions of land, usually with the directions and lengths thereof and the areas of individual tracts, compiled for the purpose of describing and recording ownership. The map may also show culture, drainage, and other features related to the use of the land.
Cae, Cael
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Caelum. See constellation.
Caelum
   (NASA SP-7, 1965)
(abbr Cae, Cael)
See constellation.
cage
   (NASA SP-7, 1965)
To lock a gyro in a fixed position in its case.
caging
   (NASA SP-7, 1965)
The process of orienting and mechanically locking the spin axis of a gyro to an internal reference position.
caisson disease
   (NASA SP-7, 1965)
Those conditions including collapse, neurological changes, and pain, associated with relatively rapid reduction of ambient pressure from levels appreciably higher than 1 atmosphere to 1 atmosphere; and due to the release of inert gases in the body. Also called compressed air illness, bends.
calculating punch
   (NASA SP-7, 1965)
A punched-card machine in which information is read from cards, and the results of sequential operations are punched on cards as they pass through the machine.
caldera
   (NASA Thesaurus)
Large, basin-shaped volcanic depression, more or less circular in form, the diameter of which is many times greater than that of the included vent or vents.
caldera
   (Photoglossary of Volcanic Terms - USGS)
A caldera is a large, usually circular depression at the summit of a volcano formed when magma is withdrawn or erupted from a shallow underground magma reservoir. The removal of large volumes of magma may result in loss of structural support for the overlying rock, thereby leading to collapse of the ground and formation of a large depression. Calderas are different from craters, which are smaller, circular depressions created primarily by explosive excavation of rock during eruptions.
calendar
   (From Stargazers to Starships Glossary - GSFC)
A system of marking days of the year, usually devised in a way to give each date a fixed place in the cycle of seasons.
calendar
   (NASA Thesaurus / NASA SP-7, 1965)
An orderly arrangement of days, weeks, months, etc. to suit a particular need such as civil life. See Julian Day.
calendar day
   (NASA SP-7, 1965)
The period from midnight to midnight. The calendar day is 24 hours of mean solar time in length and coincides with the civil day unless a time change occurs during the day.
calendar year
   (NASA SP-7, 1965)
The year of the Gregorian calendar, common years having 365 days and leap years 366 days.
Each year exactly divisible by 4 is a leap year, except century years (1800, 1900, etc.), which must be exactly divisible by 400 (2000, 2400, etc.) to be leap years. The calendar year is based on the tropical year. Also called civil year.
calibrating
   (High Energy Astrophysics Dictionary- GSFC)
A process for translating the signals produced by a measuring instrument (such as a telescope) into something that is scientifically useful. This procedure removes most of the errors caused by environmental and instrumental instabilities
calibration
   (Glossary of Hydrologic Terms - NOAA)
The process of using historical data to estimate parameters in hydrologic forecast techniques.
calibration marker
   (NASA SP-7, 1965)
In radar, a calibration mark on the display to delineate bearing, distance, height, or time.
caliper
   (Global Land Information System Glossary - USGS)
This is the method of examining the diameter of a drill hole to determine the hardness or softness of the individual rocks.
call number
   (NASA SP-7, 1965)
In computer operations, a set of characters identifying a subroutine and containing (a) information concerning parameters to be inserted in the subroutine, (b) information to be used in generating the subroutine, or (c) information related to the operands.
Callipic cycle
   (NASA SP-7, 1965)
Four Metonic cycles or 76 years.
Callisto
   (NASA Thesaurus / NASA SP-7, 1965)
A satellite of Jupiter orbiting at a mean distance of 1,884,000 kilometers. Also called Jupiter IV.
calorie
   (From Stargazers to Starships Glossary - GSFC)
Unit used in measuring the energy of heat or chemical energy. A "small" calorie is the heat needed to increase the temperature of one gram of water by 1 degree centigrade and equals about 4.18 joule. A "kilocalorie" or "big calorie" equals 1000 calories and is the unit usually used in describing the energy content of food.
calorie
   (NASA SP-7, 1965)
(abbr cal)
A unit of heat originally defined as the amount of heat required to raise the temperature of 1 gram of water through 1° C (the gram-calorie or small calorie).
Several calories are now in use: International Steam Table calorie = 4.1868 joules, mean calorie = 4.19002 joules, thermochemical calorie = 4.184 joules, 15° C calorie = 4.18580 joules, 20° C = 4.1890 joules. The kilogram calorie or kilocalorie is 1000 times as large as a calorie.
calorimeter
   (NASA Thesaurus / NASA SP-7, 1965)
An instrument designed to measure heat evolved or absorbed.
Calorimeters are used in some pyrheliometers.
Calypso
   (NASA Thesaurus)
A natural satellite of Saturn orbiting at a mean distance of 294,660 kilometers.
Cam, Caml
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Camelopardus. See constellation.
CAMAC
   (Plasma Physics and Fusion Energy Glossary)
Computer Automated Measurement and Control
Camelopardus
   (NASA SP-7, 1965)
(abbr Cam, Caml)
See constellation.
Caml
   (NASA SP-7, 1965)
International Astronomical Union abbreviation for Camelopardus. See constellation.
Canadian space program
   (NASA Thesaurus)
Space research, programs, and activities undertaken by Canada.
Canadian spacecraft
   (NASA Thesaurus)
Spacecraft of the Canadian Government. The following satellites have been developed: Alouette satellites, ISIS satellites, Anik satellites, and Hermes satellite. RADARSAT and MSAT are in the process of being developed.
canard
   (NASA Thesaurus / NASA SP-7, 1965)
Pertaining to an aerodynamic vehicle in which horizontal surfaces used for trim and control are forward of the main lifting surface; the horizontal trim and control surfaces in such an arrangement.
canards
   (AS&T Dictionary)
Horizontal surfaces forward of the wing or main lifting surface and which are used for trim, pitch, and control.
Canc
   (NASA SP-7, 1965)
International Astronomical Union abbreviation for Cancer. See constellation.
Cancer
   (NASA SP-7, 1965)
(abbr Cnc, Canc)
See constellation.
candela
   (NASA SP-7, 1965)
(symbol cd)
The luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 * 1012 hertz and that has a radiant intensity in that direction of (1/683) watt per steradian (16th CGPM (1979), Resolution 3).

The previous is an excerpt from WWW version of the National Institute of Standards and Technology: Physics Laboratory's International System of Units (SI)

Also called candle.

candle
   (NASA SP-7, 1965)
= candela.
Canes Venatici
   (NASA SP-7, 1965)
(abbr Cvn, C Ven)
See constellation.
Canis Major
   (NASA SP-7, 1965)
(abbr CMa, C Maj)
See constellation.
Canis Minor
   (NASA SP-7, 1965)
(abbr CMi, C Min)
See constellation.
canonical time unit
   (NASA SP-7, 1965)
For geocentric orbits, the time required by a hypothetical satellite to move one radian in a circular orbit of the earth's equatorial radius; 13.447052 minutes.
canopies (vegetation)
   (NASA Thesaurus)
The topmost layers of leaves and branches of forest trees or other plants.
Cap, Capr
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Capricornus. See constellation.
capability
   (NASA SP-7, 1965)
A power or capacity to do something. Compare characteristic.
Capabilities belong to people, organized forces, or things.
capacitance
   (NASA Thesaurus)
That property of a system of conductors and dielectrics which permits the storage of electrically separated charges when potential differences exist between the conductors. It is the ratio of a quantity, Q, of electricity to a potential difference, V. A capacitance value is always positive. The units are farads when the charge is expressed in coulombs and the potential in volts: C = Q/V. Capacitance is symbolized as C.
capacitance-voltage characteristics
   (NASA Thesaurus)
The characteristics of a metal semiconductor contact or a semiconductor junction that manifests a measured capacitance as a function of a dc bias voltage with small, superimposed ac voltage applied to that junction or contact.
capacitors
   (Plasma Physics and Fusion Energy Glossary)
device used to store electrical energy by accumulating charge on conductors situated close to one another. Energy may be stored and withdrawn at varying rates. Used in short-pulse plasma devices where only a moderate amount of energy is needed.
capacity
   (NASA SP-7, 1965)
In computer operations, (a) the largest quantity which can be stored, processed, or transferred; (b) the largest number of digits or characters which may regularly be processed; (c) the upper and lower limits of the quantities which may be processed.
capillarity
   (Glossary of Hydrologic Terms - NOAA)
The degree to which a material or object containing minute openings or passages, when immersed in a liquid, will draw the surface of the liquid above the hydrostatic level. Unless otherwise defined, the liquid is generally assumed to be water. Also, the phenomenon by which water is held in interstices above the normal hydrostatic level, due to attraction between water molecules.
capillary fringe
   (Glossary of Hydrologic Terms - NOAA)
The soil area just above the water table where water can rise up slightly through the cohesive force of capillary action. This layer ranges in depth from a couple of inches to a few feet (few centimeters to couple of meters), and it depends on the pore sizes of the materials. The capillary fringe is also called the capillary zone.
capillary zone
   (Glossary of Hydrologic Terms - NOAA)
The soil area just above the water table where water can rise up slightly through the cohesive force of capillary action. This layer ranges in depth from a couple of inches to a few feet (few centimeters to couple of meters), and it depends on the pore sizes of the materials. The capillary zone is also called the capillary fringe.
Capr
   (NASA SP-7, 1965)
International Astronomical Union abbreviation for Capricornus. See constellation.
Capricornus
   (NASA SP-7, 1965)
(abbr Cap, Capr)
See constellation.
capsule
   (NASA SP-7, 1965)
1. A boxlike component or unit, often sealed. See aneroid.
2. A small, sealed, pressurized cabin with an internal environment which will support life in a man or animal during extremely high altitude flight, space flight, or emergency escape. See ejection capsule.
The term spacecraft is preferred to capsule for any man-carrying vehicle.
3. A container carried on a rocket or spacecraft, as an instrument capsule holding instruments intended to be recovered after a flight.
captive test
   (NASA Thesaurus / NASA SP-7, 1965)
A holddown test of a propulsion subsystem, rocket engine or motor. Distinguished from a flight test.
capture
   (NASA SP-7, 1965)
1. Of a central force filed, as of a planet; to overcome by gravitational force the velocity of a passing body and bring the body under the control of the central force field, in some cases absorbing its mass.
2. Acquisition or absorption of an additional particle by an atomic nucleus.
capture effect
   (NASA Thesaurus / NASA SP-7, 1965)
An effect in frequency modulation (FM) reception where the stronger signal of two stations on the same frequency completely suppresses the weaker signal.
capturing
   (NASA SP-7, 1965)
The use of a torquer to restrain the spin axis of a gyro to a specified position relative to the spin reference axis.
Car, Cari
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Carina. See constellation.
carbenes
   (NASA Thesaurus)
An organic radical containing divalent carbon.
carbide
   (NASA SP-7, 1965)
A compound of carbon with one or more metallic elements.
carbon
   (Plasma Physics and Fusion Energy Glossary)
Sixth element (Z=6) in the periodic table; has 6 protons; often described as the basis of life on earth because of its chemical properties; has potential for use with silicon as a low-activation structural material for fusion reactors, in the form silicon carbide. Carbon tiles are often used in plasma-facing components because its low Z makes carbon a relatively "nice" impurity. It is also useful as a neutron moderator.
carbon cycle
   (NASA Thesaurus)
The path of carbon in living beings in which carbon dioxide is fixed by photosynthesis to form organic nutrients and ultimately restored to the inorganic state by respiration and protoplasmic decay.
carbon cycle
   (NASA SP-7, 1965)
A sequence of atomic nuclear reactions and spontaneous radioactive decay which serves to convert matter into energy in the form of radiation and high-speed particles, and which is regarded as one of the principal sources of the energy of the sun and other similar stars.
This cycle, first suggested by Bethe in 1938, gets its name from the fact that carbon plays the role of a kind of catalyst in that it is both used by and produced by the reaction, but is not consumed itself. Four protons are, in net, converted into an alpha particle and two positrons (with accompanying neutrinos); and three gamma-ray emissions are emitted directly in addition to the two gamma emissions that ensue from annihilation of the positrons by ambient electrons. This cycle sets in at stellar interior temperatures of the order of 5 million degrees Kelvin.
An even simpler reaction, the proton-proton reaction, is also believed to occur within the sun and may be of equal or greater importance.
carbon dioxide lasers
   (Plasma Physics and Fusion Energy Glossary)
laser in which carbon dioxide gas is the active medium.
carbon suboxides
   (NASA Thesaurus)
Colorless lacrimatory gases having unpleasant odors and boiling points of approximately -7 degrees C.
carbonaceous chondrites
   (NASA Thesaurus)
A group name for friable, dull-black, chondritic stoney meteorites, characterized by the presence of hydrated clay type silicate minerals, by considerable amounts and a great variety of organic compounds believed to be of extraterrestrial origin; by a near or total lack of free nickel-iron; and by an abnormally high content of inert gases.
carbonaceous materials
   (NASA Thesaurus)
Substance composed of or containing carbon or carbon compounds.
carburizing
   (NASA Thesaurus)
Introducing carbon into a solid ferrous alloy by holding above Ac1 in contact with a suitable carbonaceous material. The carborized alloy is usually quench hardened.
carcinogenesis
   (NASA SP-7, 1965)
The origination or production of cancer.
carcinogens
   (NASA Thesaurus)
Agents producing or inciting cancerous growth.
card
   (NASA SP-7, 1965)
1. A punched card, used in computer operations for the storage of information in the form of holes punched through the card material.
Standard punched cards are 7.375 x 3.250 x 0.007 inches, containing either 80 columns in each of which any of 12 positions may be punched or 90 columns in each of which any combination of 6 places may be punched.
2. Any card adapted for the storage of information.
3. A printed-circuit board, usually before other parts are mounted therein. See module, package.
card punch
   (NASA SP-7, 1965)
A mechanism which punches holes in cards used in computer operations.
An automatic card punch punches cards according to a stored program.
card reader
   (NASA SP-7, 1965)
A mechanism that reproduces the information on punched cards in another form, usually electrical signals.
cardiovascular
   (NASA SP-7, 1965)
Pertaining to the heart and the blood vessels.
cardiovascular system
   (NASA Thesaurus)
The system of an animal pertaining to the heart and blood vessels. Used for vascular system.
Cari
   (NASA SP-7, 1965)
International Astronomical Union abbreviation for Carina. See constellation.
Caribbean region
   (NASA Thesaurus)
The region that consists of all or parts of the islands of the Caribbean Sea, the Bahamas, the British dependent territories, the Virgin Islands, and the mainland areas of the three Guianas and Belize.
Carme
   (NASA Thesaurus)
A natural satellite of Jupiter orbiting at a mean distance of 22,600,000 kilometers.
Carnot cycle
   (NASA Thesaurus / NASA SP-7, 1965)
An idealized reversible thermodynamic cycle. The Carnot cycle consists of four stages: (a) an isothermal expansion of the gas at temperature T1; (b) an adiabatic expansion to temperature T2; (c) an isothermal compression at temperature T2; (d) an adiabatic compression to the original state of the gas to complete the cycle. See Carnot engine, thermodynamic efficiency.
In a Carnot cycle, the net work done is the difference between the heat inputQ1at higher temperatureT1and the heat extractedQ2at the lower temperatureT2.
Carnot efficiency
   (Plasma Physics and Fusion Energy Glossary)
The maximum possible efficiency for conversion of thermal energy to useful work (such as electrical energy) as determined by the laws of thermodynamics. The Carnot efficiency (eta) for conversion of thermal to electric energy (e.g., the upper limit on efficiency of a steam turbine) is given by (eta) = [ (T-hot) - (T-cold) ] / (T-hot). That is, one gets the efficiency from the values of the input and output temperatures (measured in Kelvin).
Carnot efficiency
   (NASA SP-7, 1965)
= thermodynamic efficiency.
Carnot engine
   (NASA SP-7, 1965)
An idealized reversible heat engine working in a Carnot cycle. It is the most efficient engine that can operate between two specified temperatures; its efficiency is equivalent to the thermodynamic efficiency. The Carnot engine is capable of being run either as a conventional engine or as a refrigerator.
carrier
   (NASA SP-7, 1965)
1. In a semiconductor, a mobile conduction electron or hole.
2. In modulation of a signal, a wave suitable for being modulated as a sine wave, a recurring series of pulses, or a direct current.
carrier density (solid state)
   (NASA Thesaurus)
The charge carrier concentrations of holes and/or electrons in a semiconductor which determines its electronic characteristics and function.
carrier frequency
   (NASA SP-7, 1965)
The frequency of a carrier wave.
carrier operated device, anti-noise
   (NASA SP-7, 1965)
= codan
carrier rocket
   (NASA SP-7, 1965)
A rocket vehicle used to carry something, as in the carrier rocket of the first artificial earth satellite.
carrier to noise ratios
   (NASA Thesaurus)
RF signal power input to the receiver divided by the noise power input.
carrier transport (solid state)
   (NASA Thesaurus)
The mobility of conduction electrons or holes in semiconductors.
carrier wave
   (NASA Thesaurus / NASA SP-7, 1965)
(abbr cw)
A wave generated at a point in the transmitting system and modulated by the signal.
carry time
   (NASA SP-7, 1965)
In computer operations, the time required for a binary chain to complete its response to an input pulse.
Cartesian coordinates
   (NASA Thesaurus / NASA SP-7, 1965)
A coordinate system in which the locations of points in space are expressed by reference to three planes, called coordinate planes, no two of which are parallel. Compare curvilinear coordinates.
The three planes intersect in three straight lines, called coordinate axes. The coordinate planes and coordinate axes intersect in a common point, called the origin. From any point P in space three straight lines may be drawn, each of which is parallel to one of the three coordinate planes. If A, B, C denote these points of intersection, the Cartesian coordinates of P are the distances PA, PB, and PC. If the coordinate axes are mutually perpendicular, the coordinate system is rectangular; otherwise, oblique.
cartographic
   (Galileo Project Glossary - JPL)
Having to do with the science and art of constructing maps and charts.
cartography
   (Galileo Project Glossary - JPL)
The science and art of constructing maps and charts.
Cas, Cass
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Cassiopeia. See constellation.
cascade shower
   (NASA SP-7, 1965)
A group occurrence of cosmic rays. Also called air shower.
cascaded
   (NASA SP-7, 1965)
Of a series of elements or devices, arranged so that the output of one feeds directly into the input of another, as a series of dynodes or a series of airfoils.
The cascaded series usually serves to amplify the effect.
cascades
   (Plasma Physics and Fusion Energy Glossary)
Inertial-fusion energy conversion concept where a flowing, replenished layer of ceramic granules (in a rotating chamber) protects the chamber wall from the fusion environment while absorbing neutrons, breeding tritium fuel, and serving as the high-temperature heat exchange fluid.
cascode devices
   (NASA Thesaurus)
Amplifier devices consisting of a common grounded-emitter (cathode) or source stage that drives a grounded-base output stage, resulting in high-impedance, high-gain, and low-noise,
Cass
   (NASA SP-7, 1965)
International Astronomical Union abbreviation for Cassiopeia. See constellation.
Cassegrain
   (NASA SP-7, 1965)
= Cassegrain telescope.
Cassegrain telescope
   (NASA SP-7, 1965)
A reflecting telescope in which a small hyperboloidal mirror reflects the convergent beam from the paraboloidal primary mirror through a hole in the primary mirror to an eyepiece in back of the primary mirror. Also called Cassegrainian telescope, Cassegrain. See Newtonian telescope.
Cassegrainian telescope
   (NASA SP-7, 1965)
= Cassegrain telescope.
Cassiopeia
   (NASA SP-7, 1965)
(abbr Cas, Cass)
See constellation.
cat whisker
   (NASA SP-7, 1965)
A fine wire pickoff, specifically a gyro pickoff.
catalogue
   (NASA SP-7, 1965)
= star catalogue.
catalogue number
   (NASA SP-7, 1965)
The designation of a star by the name of a particular star catalogue and the number of the star in that catalogue.
catapult
   (NASA Thesaurus / NASA SP-7, 1965)
A power-actuated machine or device for hurling forth something, an airplane or missile, at a high initial speed; also, a device, usually explosive, for ejecting a person from an aircraft. Compare launcher, senses 1 and 2.
catheter
   (NASA SP-7, 1965)
A hollow tube of metal, glass, hard or soft rubber, rubberized silk, etc., for introduction into a body cavity through a narrow canal, for the purpose of discharging the fluid contents of a cavity or for establishing that the canal is unobstructed.
cathode
   (NASA Thesaurus / NASA SP-7, 1965)
In an electron tube, an electrode through which a primary stream of electrons enters the interelectrode space. See cold cathode, hot cathode (thermionic cathode), photocathode.
cathode rays
   (NASA SP-7, 1965)
Electrons that are driven from the negative electrode (the cathode) of a discharge tube.
cathode-ray indicator
   (NASA SP-7, 1965)
= cathode-ray oscilloscope.
cathode-ray oscillograph
   (NASA SP-7, 1965)
= cathode-ray oscilloscope.
cathode-ray oscilloscope
   (NASA SP-7, 1965)
An instrument which displays visually on the face of a cathode-ray tube instantaneous voltages of electrical signals. Either the intensity or the displacement of the trace may be controlled by the signal voltage. More commonly called oscilloscope. Also called cathode-ray oscillograph. See radarscope.
cathode-ray screen
   (NASA SP-7, 1965)
See cathode-ray tube.
cathode-ray tube
   (NASA SP-7, 1965)
(abbr CRT)
A vacuum tube consisting essentially of an electron gun producing a concentrated electron beam (or cathode ray) which impinges on a phosphorescent coating on the back of a viewing face (or screen). The excitation of the phosphor produces light, the intensity of which is controlled by regulating the flow of electrons. Deflection of the beam is achieved either electromagnetically by currents in coils around the tube, or electrostatically by voltages on internal deflection plates.
cathodic coatings
   (NASA Thesaurus)
Material forming a continuous film on a base metal by mechanical coating or by electroplating.
cathodoluminescence
   (NASA Thesaurus)
Luminescence produced when high velocity electrons bombard a metal in a vacuum, thus vaporizing small amounts of the metal which, in an excited state, emit radiation characteristic of the metal.
cations
   (NASA Thesaurus)
Positively-charged ions.
catoptric light
   (NASA SP-7, 1965)
A light concentrated into a parallel beam by means of a reflector.
A light so concentrated by means of refracting lenses or prisms is a dioptric light.
CATT devices
   (NASA Thesaurus)
Controlled avalanche transit time triodes which use avalanche multiplication in the collector depletion region of a silicon, bipolar, transistor-like structure to increase the gain and thereby achieve a higher frequency operation of silicon bipolar transistors. Used for controlled avalanche transit time devices.
Cauchy number
   (NASA SP-7, 1965)
A nondimensional number arising in the study of the elastic properties of a fluid. It may be written U2p/E, where U is a characteristic velocity; p (lower case Rho) is the density; and E the modulus of elasticity of the fluid. It is the square of the Mach number.
caulking
   (NASA Thesaurus)
Material ranging in physical characteristics from plastic to solid to preformed. Used to seal and waterproof joints and overlaps in structures, other assemblies or portions thereof where movement may occur.
caustic lines
   (NASA Thesaurus)
The locations of wave front interactions induced by the maneuvers of supersonic aircraft in changing direction and/or attitude.
caustics (optics)
   (NASA Thesaurus)
The envelope of rays diffracted by surface defects in materials.
caution stage
   (Glossary of Hydrologic Terms - NOAA)
The stage at which some action needs to be taken.
cavitation
   (NASA SP-7, 1965)
The formation of bubbles in a liquid, occurring whenever the static pressure at any point in the fluid flow becomes less than the fluid vapor pressure.
cavitation flow
   (NASA Thesaurus)
The formation of bubbles in a liquid, occurring whenever the static pressure at any point in the fluid flow becomes less than the fluid vapor pressure. Used for cavitation and gaseous cavitation.
cavitons
   (NASA Thesaurus)
Density cavities created by localized oscillating electric fields.
cavity heat receiver
   (NASA SP-7, 1965)
= hohlraum.
cavity resonator
   (NASA SP-7, 1965)
See resonator.
CCD
   (SOHO Glossary - GSFC)
Charge Coupled Device--A semiconductor light detector which converts light to electrical impulses.
CCD star tracker
   (NASA Thesaurus)
Navigation instrument designed for the NASA space transportation system. Used for stellar (star tracker).
CCS
   (Space Flight Glossary - JPL)
Computer Command subsystem on board a spacecraft, similar to CDS.
CD-ROM
   (Global Land Information System Glossary - USGS)
CD-ROM, Compact Disc-Read Only Memory, is a computer peripheral that employs compact disc technology to store large amounts of data for later retrieval. The capacity of a CD-ROM disk is over 600 megabytes, the equivalent of over 250,000 typewritten pages.
CDS
   (SOHO Glossary - GSFC)
(Coronal Diagnostic Spectrometer) An ultraviolet spectrometer aboard SOHO.
CDU
   (Space Flight Glossary - JPL)
Command Detector Unit onboard a spacecraft.
ceilings (meteorology)
   (NASA Thesaurus)
The height above the Earth's surface of the lowest layer of clouds or obscuring phenomena that is reported as "broken", overcast" or "obscuration" and not classified as "thin" or "partial".
celestial
   (NASA SP-7, 1965)
1. Of or pertaining to the heavens.
2. Short for celestial navigation.
celestial body
   (NASA Thesaurus / NASA SP-7, 1965)
Any aggregation of matter in space constituting a unit for astronomical study, as the sun, moon, a planet, comet, star, nebula, etc. Also called heavenly body.
celestial coordinates
   (NASA SP-7, 1965)
Any set of coordinates used to define a point on the celestial sphere.
The horizon, celestial equator, ecliptic, and galactic systems of celestial coordinates are based on the celestial horizon, celestial equator, ecliptic, and galactic equator, respectively, as the primary great circle. See coordinate, Table VI, for a comparison of the systems.
celestial equator
   (NASA SP-7, 1965)
The primary great circle of the celestial sphere in the equatorial system, everywhere 90° from the celestial poles; the intersection of the extended plane of the equator and the celestial sphere. Also called equinoctial.
celestial equator system of coordinates
   (NASA SP-7, 1965)
= equatorial system.
celestial geodesy
   (NASA Thesaurus)
The determination of the form of the Earth, of the Earth's graviational field, and of relative positions of satellite trajectories.
celestial guidance
   (NASA SP-7, 1965)
The process of directing movements of an aircraft or spacecraft, especially in the selection of a flight path, by reference to celestial bodies. Also called automatic celestial navigation. See guidance, celestial navigation.
celestial horizon
   (NASA SP-7, 1965)
That great circle of the celestial sphere formed by the intersection of the celestial sphere and a plane through the center of the earth and perpendicular to the zenith-nadir line. Also called rational horizon. See horizon, horizon system.
celestial latitude
   (NASA SP-7, 1965)
Angular distance north or south of the ecliptic; the arc of a circle of latitude between the ecliptic and a point on the celestial sphere, measured northward or southward from the ecliptic through 90°, and labeled N or S to indicate the direction of measurement. See ecliptic system of coordinates.
celestial line of position
   (NASA SP-7, 1965)
A line of position determined by observation of one (or more) celestial bodies.
celestial longitude
   (NASA SP-7, 1965)
Angular distance east of the vernal equinox, along the ecliptic; the arc of the ecliptic or the angle at the ecliptic pole between the circle of latitude of the vernal equinox and the circle of latitude of a point on the celestial sphere, measured eastward from the circle of latitude of the vernal equinox, through 360°. See ecliptic system of coordinates.
celestial mechanics
   (NASA Thesaurus / NASA SP-7, 1965)
The study of the theory of the motions of celestial bodies under the influence of gravitational fields. See gravitation.
celestial meridian
   (NASA SP-7, 1965)
A great circle of the celestial sphere, through the celestial poles and the zenith.
The expression usually refers to the upper branch, that half of the great circle from pole to pole which passes through the zenith; the other half being the lower branch. The celestial meridian coincides with the hour circle through the zenith and the vertical circle through the elevated pole.
celestial navigation
   (NASA Thesaurus / NASA SP-7, 1965)
The process of directing a craft from one point to another by reference to celestial bodies of known coordinates.
Celestial navigation usually refers to the process as accomplished by a human operator. The same process accomplished automatically by a machine is usually termedcelestial guidanceor sometimes automatic celestial navigation.
celestial observation
   (NASA SP-7, 1965)
In navigation, the measurement of the altitude of a celestial body, or the measurement of azimuth, or measurement of both altitude and azimuth. Also called sight.
The expression may also be applied to the data obtained by such measurement.
celestial pole
   (From Stargazers to Starships Glossary - GSFC)
One of the two points in the sky around which the celestial sphere seems to rotate.
celestial pole
   (NASA SP-7, 1965)
Either of the two points of intersection of the celestial sphere and the extended axis of the earth, labeled N or S to indicate whether the north celestial pole or the south celestial pole.
celestial sphere
   (NASA Thesaurus / NASA SP-7, 1965)
An imaginary sphere of infinite radius concentric with the earth, on which all celestial bodies except the earth are assumed to be projected.
celestial triangle
   (NASA SP-7, 1965)
A spherical triangle on the celestial sphere, especially the navigational triangle.
celestial-inertial guidance
   (NASA SP-7, 1965)
The process of directing the movements of an aircraft or spacecraft, especially in the selection of a flight path, by an inertial guidance system which also receives inputs from observations of celestial bodies.
CELIAS
   (AS&T Dictionary)
Charge, Element, and Isotope Analysis System.
Instrument aboard SOHO which analyzes the constituents of the solar wind.
cell
   (NASA SP-7, 1965)
In computers, an elementary unit of storage, as binary cell, decimal cell.
cellulose
   (NASA Thesaurus)
The carbohydrate that is the principal constituent of wood and forms of structural framework of the wood cells.
Celsius temperature scale
   (NASA SP-7, 1965)
(abbr C)
Same as centigrade temperature scale.
The Ninth General Conference on Weights and Measures (1948) replaced the designation degree centigrade by degree Celsius.
cementite
   (NASA Thesaurus)
An intermetallic compound containing iron and carbon.
Cen, Cent
   (NASA SP-7, 1965)
International Astronomical Union abbreviation for Centaurus. See constellation.
Cenozoic Era
   (NASA Thesaurus)
An era of geologic time, from the beginning of the Tertiary Period to the present. (Some authors do not include the Quarternary, considering it a separate era.) It is characterized by the evolution and abundance of mammals, advanced mollusks, and birds and paleobotanically, by angiosperms. The Cenozoic Era is considered to have begun about 65 million years ago.
cent
   (NASA SP-7, 1965)
In acoustics, the interval between two sounds whose basic frequency ratio is the twelve-hundredth root of 2.
Centaurus
   (NASA SP-7, 1965)
(abbr Cen, Cent)
See constellation.
center frequency
   (NASA SP-7, 1965)
The assigned carrier frequency of a frequency modulation (FM) station; the unmodulated frequency of an FM system.
center of gravity
   (NASA Thesaurus)
The center of mass of a system of masses, as the barycenter of the Earth-moon system. Used for barycenter.
center of mass
   (NASA Thesaurus)
A point of a material body or system of bodies which moves as though the system's total mass existed at that point and all external forces were applied at the point.
center of mass
   (NASA SP-7, 1965)
That point in a given body, or in a system of two or more bodies that act together in respect to another body, which represents the mean position of the matter in the body of bodies. See barycenter.
center of thrust
   (NASA SP-7, 1965)
= thrust axis.
centering force
   (Plasma Physics and Fusion Energy Glossary)
Term for the mutual attraction between the parallel currents in the inboard leg of the toroidal field coils in a toroidal magnetic fusion system (e.g., a tokamak). The portion of the coil running "through the doughnut hole" is attracted towards the center of the hole.
centi
   (NASA SP-7, 1965)
(abbr C)
A prefix meaning one-hundredth.
centigrade temperature scale
   (NASA SP-7, 1965)
(abbr C)
A temperature scale with the ice point at 0° and the boiling point of water at 100°. Now called Celsius temperature scale.
Conversion to the Fahrenheit temperature scale is according to the formula
° C = 5/9 (°F - 32)
centimeter
   (NASA SP-7, 1965)
(abbr cm)
One-hundredth of a meter; approximately 0.3937 U.S. inch, exactly 1/2.54 inch.
centimeter waves
   (NASA Thesaurus)
Electromagnetic radiation in the 3,000 to 30,000 MHz range.
centimeter-gram-second system
   (NASA SP-7, 1965)
(abbr cgs)
A system of units based on the centimeter as the
centimetric waves
   (NASA SP-7, 1965)
See frequency band.
centipoise
   (NASA SP-7, 1965)
(abbr cp)
A unit of viscosity. See poise.
central control
   (NASA SP-7, 1965)
1. Control exercised over an extensive and complicated system from a single center.
2. Usually capitalized. The place, facility, or activity from which this control is exercised; specifically, at Cape Canaveral or at Vandenberg AFB, the place, facility, or activity at which the whole action incident to a test launch and flight is coordinated and controlled, from the make-ready at the launch site and on the range, to the end of the rocket flight downrange.
For a few seconds during the actual launch, control of a missile is exercised from the blockhouse, but it almost immediately reverts to Central Control for guidance and tracking, with two men in essential control. One of these is the supervisor of range operations, the other is the range safety officer.
central force
   (NASA SP-7, 1965)
A force which for purposes of computation can be considered to be concentrated at one central point with its intensity at any other point being a function of the distance from the central point.
Gravitation is considered as a central force in celestial mechanics.
central force field
   (NASA SP-7, 1965)
The spatial distribution of the influence of a central force.
central processing units
   (NASA Thesaurus)
The units of computing systems that include the circuits controlling the interpretation of instructions and their execution. Used for processors (computers).
Centralized Automated Data Acquisition System
   (Glossary of Hydrologic Terms - NOAA)
A system of two minicomputers at National Weather Service headquarters that interrogates LARCs by telephone every 6 hours and transmits the data to NWS forecast offices and river forecast centers.
centrifugal acceleration
   (NASA SP-7, 1965)
= centrifugal force.
centrifugal compressor
   (NASA SP-7, 1965)
A compressor having one or more vaned rotary impellers which accelerate the incoming fluid radially outward into a diffuser, compressing by centrifugal force. Sometimes called a centrifugal-flow compressor . Compare axial-flow compressor.
centrifugal force
   (NASA Thesaurus / NASA SP-7, 1965)
The apparent force in a rotating system, deflecting masses radially outward from the axis of rotation, with magnitude per unit mass lower case omega 2R, where lower case omega is the angular speed of rotation; and R is the radius of curvature of the path. This magnitude may also be written as V2/R, in terms of the linear speed V. This force (per unit mass) is equal and opposite to the centripetal acceleration. Also called centrifugal acceleration.
The centrifugal force on the earth and atmosphere due to rotation about the earth's axis is incorporated with the field of gravitation to form the field of gravity.
centrifugal-flow compressor
   (NASA SP-7, 1965)
= centrifugal compressor.
centrifuge
   (NASA Thesaurus / NASA SP-7, 1965)
Specifically, a large motor-driven apparatus with a long arm at the end of which human and animal subjects or equipment can be revolved and rotated at various speeds to simulate (very closely) the (prolonged) accelerations encountered in high-performance aircraft, rockets, and spacecraft. Sometimes called astronautic centrifuge.
centripetal acceleration
   (Space Flight Glossary - JPL)
The inward acceleration of a body revolving around another body.
centripetal acceleration
   (NASA SP-7, 1965)
The acceleration on a particle moving in a curved path, directed toward the instantaneous center of curvature of the path, with magnitude v2/R, where v is the speed of the particle and R the radius of curvature of the path. This acceleration is equal and opposite to the centrifugal force per unit mass.
centripetal force
   (From Stargazers to Starships Glossary - GSFC)
The force in a rotating system directed toward the axis of rotation.
CEP (abbr)
   (NASA SP-7, 1965)
= circle of equal probability.
Cep, Ceph
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Cepheus. See constellation.
Cepheid
   (High Energy Astrophysics Dictionary- GSFC)
A pulsating variable star. This type of star undergoes a rhythmic pulsation as indicated by its regular pattern of changing brightness as a function of time. The period of pulsation has been demonstrated to be directly related to a Cepheid's intrinsic brightness making observations of these stars one of the most powerful tools for determining distance known to modern day astronomy.
Cepheus
   (NASA SP-7, 1965)
(abbr, Cep, Ceph) See constellation.
cepstra
   (NASA Thesaurus)
The Fourier transformation of the logarithm of the power spectrum.
cepstral analysis
   (NASA Thesaurus)
The application of cepstral methods to wave or signal phenomena in seismology, speech analysis, echos, underwater acoustics, etc.
ceramal
   (NASA SP-7, 1965)
= cermet.
ceramic
   (NASA Thesaurus / NASA SP-7, 1965)
An inorganic compound or mixture requiring heat treatment to fuse it into a homogeneous mass usually possessing high temperature strength but low ductility. Types and uses range from china for dishes to refractory liner for nozzles.
ceramic fibers
   (NASA Thesaurus)
Fibers composed of ceramic materials. They are usually used for reinforcement.
ceramic matrix composites
   (NASA Thesaurus)
Composite materials consisting of a reinforced ceramic matrix.
Cerenkov radiation
   (NASA Thesaurus / NASA SP-7, 1965)
The radiation from a charged particle whose velocity is greater than the phase velocity that an electromagnetic wave would have if it were propagating in the medium. The particle will continue to lose energy by radiation until its velocity is less than this phase velocity.
This phenomenon is analogous to the generation of a shock wave when an object is traveling faster than the sound velocity of the medium. A bow wave is set up which radiates energy into the medium and slows down the object.
The angle that the cone of luminescence makes with the direction of motion of the particle can be used to measure the velocity of the particle.
cermet
   (NASA Thesaurus / NASA SP-7, 1965)
[ceramic + metal] A body consisting of ceramic particles bonded with a metal; used in aircraft, rockets, and spacecraft for high strength, high temperature applications. Also called ceramal [ceramic + alloy].
certification
   (NASA Thesaurus)
Personnel - The act of verifying and documenting that personnel have completed required training and have demonstrated specific proficiency. Process & Software - An act, whereby a responsible official provides a written guarantee that a product, process, or service satisfies all performance and design requirements.
Cessna 402B aircraft
   (NASA Thesaurus)
A lighter, twin-engine, short-haul cargo/passenger aircraft manufactured by the Cessna Aircraft Company.
Cet, Ceti
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Cetus . See constellation.
cetane number
   (NASA SP-7, 1965)
A number indicating the relative ignitability of a fuel oil for compression-ignition engines.
Ceti
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Cetus . See constellation.
Cetus
   (NASA SP-7, 1965)
(abbr Cet, Ceti)
See constellation.
CGS system
   (NASA SP-7, 1965)
A system of units based on the centimeter, the gram, and the second.
Cha, Cham
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Chamaeleon. See constellation.
chad
   (NASA SP-7, 1965)
The piece removed when punching a hole, as in a card. See chadless.
chadless
   (NASA SP-7, 1965)
A type of punching in which the chad is left attached by about 25 percent of the circumference of the hole, at the leading edge.
Chadless punching is used where it is undesirable to mutilate information written or printed on the punched medium.
chaff
   (NASA SP-7, 1965)
= window.
chain radar beacon
   (NASA SP-7, 1965)
A radar beacon with a very fast recovery time.
This recovery time provides the possibility of simultaneously interrogating and tracking the beacon by as many radars as required so long as they are phased, synchronized, or the sum total pulse recurrence frequency does not exceed the maximum pulse recurrence frequency characteristics of the beacon.
chain reaction
   (NASA SP-7, 1965)
A reaction in which one of the agents necessary to the reaction is itself produced by the reaction, thus causing like reactions.
In the neutron-fission chain reaction, a neutron striking a fissionable atom causes a fission releasing neutrons which cause other fissions.
chain reactions (nuclear physics)
   (Plasma Physics and Fusion Energy Glossary)
A self-sustaining series of chemical or nuclear reactions in which the products of the reaction contribute directly to the propagation of the process.
challenger
   (NASA SP-7, 1965)
= interrogator-responsor.
Cham
   (NASA SP-7, 1965)
International Astronomical Union abbreviation for Chamaeleon. See constellation.
Chamaeleon
   (NASA SP-7, 1965)
(abbr Cha, Cham)
See constellation.
chamber
   (NASA SP-7, 1965)
= combustion chamber.
chamber pressure
   (NASA SP-7, 1965)
(symbol Pc)
The pressure of gases within the combustion chamber of a rocket engine.
chamber volume
   (NASA SP-7, 1965)
(symbol Vc)
The volume of the rocket combustion chamber including the convergent portion of the nozzle up to the throat.
Chandler wobble
   (NASA Thesaurus)
A movement in the Earth's axis of rotation whose period of motion is about 14 months. Used for Eulerian nutation.
Chandrasekhar limit
   (Imagine the Universe Dictionary - NASA GSFC)
A limit which mandates that no white dwarf (a collapsed, degenerate star) can be more massive than about 1.4 solar masses. Any degenerate object more massive must inevitably collapse into a neutron star.
change detection
   (NASA Thesaurus)
A process of examining imagery to detect changes on a planetary surface or astronomical body.
change of the moon
   (NASA SP-7, 1965)
= new moon.
channel
   (NASA SP-7, 1965)
1. Short for frequency channel.
2. In computer operations: (a) That portion of a storage medium which is accessible to a given reading station. See track. (b) A path of flow, usually including one or more operations.
channel inflow
   (Glossary of Hydrologic Terms - NOAA)
Water, which at any instant, is flowing into the channel system form surface flow, subsurface flow, base flow, and rainfall that has directly fallen onto the channel.
channel lead
   (Glossary of Hydrologic Terms - NOAA)
An elongated opening in the ice cover caused by a water current.
channel noise
   (NASA Thesaurus)
In communications bursts of interruptive pulses caused mainly by contact closures in electromagnetic equipment or by transient voltages in electric cables during transmission of signals or data. Impulsive noise is the frequent cause of transmission errors.
channel routing
   (Glossary of Hydrologic Terms - NOAA)
The process of determing progressively the timing and shape of the flood wave at successive points along a river.
channel storage
   (Glossary of Hydrologic Terms - NOAA)
The volume of water at a give time in the channel or over a flood plain in a drainage basin or river reach. Channel storage is large during the progress of a flood event.
channel transport
   (Plasma Physics and Fusion Energy Glossary)
In inertial fusion research using light ion drivers, describes the use of current-carrying plasma channels (which are magnetically confined to the channel) to transport electron or ion beams between the ion diode and the fusion target. This allows the ion source to stand back from the target.
channelization
   (Glossary of Hydrologic Terms - NOAA)
The modification of a natural river channel/a>; may include deepening, widening, or straightening.
channels
   (Glossary of Hydrologic Terms - NOAA)
Open conduits either naturally or artifically created which periodically or continuously contain moving water. "Watercourse," "river," "creek," "run," "branch," and "tributary" are some of the terms used to describe natural channels.
Chapman region
   (NASA SP-7, 1965)
A hypothetical region in the upper atmosphere in which the distribution of electron density with height can be described by a theoretical equation derived by Sydney Chapman.
Some of the basic assumptions used to develop the equation were that the ionizing radiation from the sun is essentially monochromatic, that the ionized constituent is distributed exponentially (with a constant scale height), and that there is an equilibrium condition between the creation of free electrons and their loss by recombination.
Chappius bands
   (NASA SP-7, 1965)
See absorption band.
character
   (NASA SP-7, 1965)
One of a set of elementary marks or events which may be combined to express information.
For example, a decimal digit (0 to 9), a letter (A to Z), or a symbol (comma, plus, minus, etc.).
characteristic
   (NASA SP-7, 1965)
Specifically, a distinguishing quality, property, feature, or capability of a machine or piece of equipment, or of a component part.
The characteristics of an aircraft are (1) qualities such as stability, maneuverability, and strength; (2) features such as number, kind, or power of engines, and size, shape, or number of wings; and (3) capabilities such as range, speed, and payload.
characteristic chamber length
   (NASA SP-7, 1965)
(symbol L*)
The length of a straight cylindrical tube having the same volume as the chamber of a rocket engine would have if it had no converging section.
characteristic equation
   (NASA SP-7, 1965)
1. An equation defining the characteristics of a set of partial differential equations.
2. A linear algebraic equation determining the eigenvalues or free waves of a boundary value problem. See characteristic value problem.
characteristic exhaust velocity
   (NASA SP-7, 1965)
(symbol c*)
Of a rocket engine, a descriptive parameter,
c* = Ve/CF
where Ve is effective exhaust velocity and CF is thrust coefficient. Also called characteristic velocity.
characteristic Larmor radius
   (NASA SP-7, 1965)
The size of the Larmor orbit of a charged particle whose rotational velocity is equal to the Alfvén speed.
characteristic length
   (NASA SP-7, 1965)
(symbol l, l)
A convenient reference length (usually constant) of a given configuration, such as overall length of an aircraft, the maximum diameter or radius of a body of revolution, a chord or span of a lifting surface, etc.
characteristic mode
   (NASA SP-7, 1965)
= normal mode of vibration.
characteristic value
   (NASA SP-7, 1965)
See characteristic value problem.
characteristic value problem
   (NASA SP-7, 1965)
A problem in which an undetermined parameter is involved in the coefficients of a differential equation, and in which the solution of the differential equation, with associated boundary conditions, exists only for certain discrete values of the parameter, called eigenvalues, or characteristic values, sometimes principal values.
An important example of a physical problem which leads to a characteristic value problem is the determination of the modes and frequencies of a vibrating system. In this case the dependent variable of the differential equation represents the displacements of the system and the parameter represents the frequencies of vibration.
characteristic velocity
   (NASA SP-7, 1965)
(symbol c*) = characteristic exhaust velocity.
characteristics
   (NASA Thesaurus / NASA SP-7, 1965)
Lines or surfaces associated with a partial differential equation, or with a set of such equations, which are at all points tangent to characteristics directions, determined by certain specified linear combinations of the equations.
The use of these lines or surfaces may facilitate the solution of the equations and is known as the method of characteristics. The method has been particularly successful, for example, in the problem of finite-amplitude expansion and shock waves.
charge coupled devices
   (NASA Thesaurus)
Semiconductor devices arrayed so that the electric charge at the output of one provides the input stimulus to the next. Use for CCD.
charge efficiency
   (NASA Thesaurus)
The efficiency of electric cell recharging.
charge exchange
   (NASA Thesaurus)
The collisional transfer of an electron from a neutral atom or molecule to an ion.
charge flow devices
   (NASA Thesaurus)
Metal oxide semiconductor (MOS) devices used for fire detectors and humidity sensors. Used for CFD.
charge neutrality
   (NASA SP-7, 1965)
The approximate equality of positive and negative particles in high-density plasmas.
This phenomenon, which is sometimes called electrical neutrality, is a result of the extremely large electric space charge fields that would arise if the densities were not equal. Although the positive and negative charge densities are seldom exactly equal, their percentage difference is so small as to be negligible. It is not difficult to maintain this condition in an active plasma since ionization or recombination always produces or destroys an ion pair together.
charge spectrum
   (NASA SP-7, 1965)
The range and magnitude of electric charges with reference to cosmic rays at a specific altitude.
charged particles
   (Plasma Physics and Fusion Energy Glossary)
particles which carries positive or negative electrical charges.
Charles law
   (NASA SP-7, 1965)
= Charles-Gay-Lussac law.
Charles-Gay-Lussac law
   (NASA SP-7, 1965)
An empirical generalization that in a gaseous system at constant pressure, the temperature increase and the relative volume increase stand in approximately the same proportion for so-called perfect gases. Mathematically,
t - t0 + (1 / c [ ( v - v0 ) / v0]
where t is temperature; v is volume; and c is a coefficient of thermal expansion independent of the particular gas. If the centrigrade temperature scale is used and v0 is the volume at 0° C, then the value of the constant c is approximately 1/273. Also called Charles law, Gay-Lussac law.
charm (particle physics)
   (NASA Thesaurus)
A quantum number which has been proposed to account for an apparent lack of symmetry in the behavior of hadrons relative to that of leptons, to explain why certain reactions of elementary particles do not occur, and to account for the longevity of the J particle.
Charon
   (NASA Thesaurus)
Natural satellite of the planet Pluto, discovered and named by Dr. James W. Christy.
charring ablator
   (NASA SP-7, 1965)
An ablation material characterized by the formation of a carbonaceous layer at the heated surface which impedes heat flow into the material by it insulating and reradiating characteristics.
chase pilot
   (NASA SP-7, 1965)
A pilot who flies an escort airplane advising a pilot who is making a check, training, or research flight in another craft.
chaser
   (NASA SP-7, 1965)
The vehicle that maneuvers in order to effect a rendezvous with an orbiting object.
chassignites
   (NASA Thesaurus)
Achondritic stony meteorites composed almost entirely (95%) of olivine, with accessory amounts of chromite, and lacking nickel-iron. It resembles terrestrial dunite.
check flight
   (NASA SP-7, 1965)
1. A flight made to check or test the performance of an aircraft, rocket, or spacecraft, or a piece of equipment or component, or to obtain measurements or other data on performance; a test flight.
2. A familiarization flight in an aircraft, or a flight in which a pilot or other aircrew member or members are tested or examined for proficiency.
checking
   (NASA SP-7, 1965)
Presence of a network of fine hairline cracks on the surface of a structure usually induced by poor machining technique.
checkout
   (NASA Thesaurus / NASA SP-7, 1965)
1. A sequence of actions taken to test or examine a thing as to its readiness for incorporation into a new phase of use, or for the performance of its intended function.
2. The sequence of steps taken to familiarize a person with the operation of an airplane or other piece of equipment.
In sense 1, a checkout is usually taken at a transition point between one phase of action and another. To shorten the time of checkout, automation is frequently employed.
checkout GSE
   (NASA SP-7, 1965)
Ground support equipment used to make a checkout, which see, sense 1.
cheese antenna
   (NASA SP-7, 1965)
A cylindrical parabolic reflector enclosed by two plates perpendicular to the cylinder, so spaced as to permit the propagation of more than one mode in the desired direction of polarization.
chemical clouds
   (NASA Thesaurus)
Artificial clouds of chemical compounds released in the ionosphere for observation of dispersion and other characteristics.
chemical compounds
   (NASA Thesaurus)
Distinct substances formed by a union of two or more ingredients in definite proportions by weight.
chemical defense
   (NASA Thesaurus)
All actions and counteractions designed for the protection of personnel and material against offensive chemical agents.
chemical energy
   (NASA Thesaurus / NASA SP-7, 1965)
Energy produced or absorbed in the process of a chemical reaction. In such a reaction, energy losses or gains usually involve only the outermost electrons of the atoms or ions of the system undergoing change; here a chemical bond of some type is established or broken without disrupting the original atomic or ionic identities of the constituents.
Chemical changes, according to the nature of the materials entering into the change, may be induced by heat (thermochemical), light (photochemical), and electric (electrochemical) energies.
chemical evolution
   (NASA Thesaurus)
The theory of the creation or production of living matter from nonliving matter.
chemical fuel
   (NASA SP-7, 1965)
1. A fuel that depends upon an oxidizer for combustion or for development of thrust, such as liquid or solid rocket fuel or internal-combustion-engine fuel; distinguished from nuclear fuel.
2. A fuel that uses special chemicals, such as the fuel once projected for the afterburner of the B-70.
chemical fuels
   (NASA Thesaurus)
Fuels that depend upon an oxidizer for combustion or for development of thrust, such as liquid or solid rocket fuel or internal combustion engine fuel; distinguished from nuclear fuel.
chemical pressurization
   (NASA SP-7, 1965)
The pressurization of propellants tanks in a rocket by means of high-pressure gases developed by the combustion of a fuel and oxidizer or by the decomposition of a substance.
chemical release modules
   (NASA Thesaurus)
Shuttle launched, free-flying spacecraft containing canisters for injecting chemicals into the upper atmosphere and the measurement of the reactions.
chemiluminescence
   (NASA Thesaurus / NASA SP-7, 1965)
Any luminescence produced by chemical action. See airglow.
chemisorption
   (NASA Thesaurus / NASA SP-7, 1965)
The binding of a liquid or gas on the surface or in the interior of a solid by chemical bonds or forces.
chemistry
   (NASA Thesaurus)
The science that studies the composition, structure, properties, interactions, and transformations of elemental matter and compounds.
chemosphere
   (NASA Thesaurus / NASA SP-7, 1965)
The vaguely defined region of the upper atmosphere in which photochemical reactions take place. It is generally considered to include the stratosphere (or the top thereof) and the mesosphere, and sometimes the lower part of the thermosphere. See atmospheric shell.
This entire region is the seat of a number of important photochemical reactions involving atomic oxygen O, molecular oxygen O2, ozone O3, hydroxyl OH, nitrogen N2, sodium Na, and other constituents to a lesser degree.
chest-to-back acceleration
   (NASA SP-7, 1965)
See physiological acceleration.
chi-square test
   (NASA SP-7, 1965)
A statistical significance test based on frequency of occurrence; it is applicable both to qualitative attributes and quantitative variables. Among its many uses, the most common are test of hypothesized probabilities or probability distributions (goodness of fit), statistical dependence or independence (association), and common population (homogeneity).
The formula for chi square (x2) depends upon intended use, but is often expressible as a sum of terms of the type (f - h)2 / h where f is an observed frequency and h is its hypothetical value.
Chicxulub crater
   (Galileo Project Glossary - JPL)
A very large impact crater near the Yucatan Peninsula in Mexico. The effects of this particular impact may have been responsible for the extinction of the dinosaurs 65 million years ago.
Chinese spacecraft
   (NASA Thesaurus)
Satellites built and launched by the Chinese Peoples Republic.
chips (electronics)
   (NASA Thesaurus)
Integrated microcircuits mounted on substrates and performing significant numbers of functions.
chips (memory devices)
   (NASA Thesaurus)
Integrated microcircuit devices used collectively to perform the functions of data storage: accepting, retaining, and emitting bits of data.
Chiron
   (NASA Thesaurus)
Minor planet 2060, a solar system asteroid discovered by Charles T. Kowal of Hale Observatories. Used for Minor Planet 2060.
chirp
   (NASA Thesaurus / NASA SP-7, 1965)
An all-encompassing term for the various techniques of pulse expansion-pulse compression applied to pulse radar; a technique to expand narrow pulses to wide pulses for transmission, and compress wide received pulses to the original narrow pulse width and wave shape, to gain improvement in signal-to-noise ratio without degradation to range resolution and range discrimination.
chitin
   (NASA Thesaurus)
A polysaccharide which is the principal constituent of the shells of crabs and lobsters and of the shards of beetles. It is also found in certain fungi.
chlorate candle
   (NASA SP-7, 1965)
A mixture of solid chemical compounds which, when ignited, liberates free oxygen.
Chlorella
   (NASA SP-7, 1965)
A genus of unicellular green algae, considered to be adapted to converting carbon dioxide into oxygen in a closed ecological system See closed ecological system.
chlorocarbons
   (NASA Thesaurus)
All compounds containing chlorine and carbon with or without other elements.
chlorofluorocarbons
   (NASA Thesaurus)
A family of compounds of chlorine, fluorine, and carbon, entirely of industrial origin. CFCs include refrigerants, propellants for spray cans and for blowing plastic-foam insulation, styrofoam packaging, and solvents for cleaning electronic circuit boards.
choked flow
   (NASA SP-7, 1965)
Flow in a duct or passage such that the flow upstream of a certain critical section cannot be increased by a reduction of downstream pressure.
chokes
   (NASA SP-7, 1965)
Pain and irritation in the chest and throat as a result of reduced ambient pressure.
choking Mach number
   (NASA SP-7, 1965)
The Mach number at some reference point in a duct or passage (e.g., at the inlet) at which the flow in the passage becomes choked. See choked flow.
Cholesky factorization
   (NASA Thesaurus)
A numerical algorithm used to solve linear systems of equations.
chondrite
   (NASA SP-7, 1965)
A meteoritic stone characterized by small rounded grains or spherules.
chopper
   (NASA SP-7, 1965)
A device used to interrupt the path of radiation, as a beam of light, from a single source or to alternate it between two sources.
chord
   (NASA SP-7, 1965)
1. A straight line intersecting a circle or other curve, or a straight line connecting the ends of an arc.
2. (symbol c). In aeronautics, a straight line intersecting or touching an airfoil profile at two points; specifically, that part of such a line between two points of intersection.
This line is usually a datum line joining the leading and trailing edges of an airfoil, joining the ends of the mean line of an airfoil profile, from which the ordinates and angles of the airfoil are measured. As such a datum line, it is sometimes called the geometric chord, to distinguish it from a chord established on the basis of any other considerations.
3. = chord length.
In sense 3, points or stations along a chord are designated in percentages or fractions of the chord or chord length from the leading edge, as, a point at 25 percent, or one-quarter, chord.
chord length
   (NASA SP-7, 1965)
The length of the chord of an airfoil section between the extremities of the section.
For many airfoils, the chord is established intersecting the airfoil profile at its extremities, and the chord length is equal to the length of the chord between the points of intersection; for airfoils where the chord is established by a point or points of tangency or intersection not at the extremities, however, the chord length is considered to extend beyond either or both points, as necessary, to equal the maximum length of the profile. See chord, senses 2 and 3.
chords (geometry)
   (NASA Thesaurus)
Straight lines intersecting circles or other curves, or straight lines connecting the ends of arcs. In aeronautics, straight lines intersecting or touching airfoil profiles at two points; specifically, those parts of lines between two points of intersections. Used for aerodynamic chords.
choroisotherm
   (NASA SP-7, 1965)
See isotherm, note.
chromatography
   (NASA Thesaurus / NASA SP-7, 1965)
The separation of chemical substances by making use of differences in the rates at which the substances travel through or along a stationary medium.
chromium steels
   (NASA Thesaurus)
Steels containing chromium as the main alloying element.
chromophores
   (Galileo Project Glossary - JPL)
Groups of atoms or molecules that are responsible for pigmentation (color).
chromosomes
   (NASA Thesaurus)
The self replicating genetic structure of cells containing the celllular DNA that bears in it's nucleotidesequence the linear array of genes.
chromosphere
   (NASA Thesaurus / NASA SP-7, 1965)
A thin layer or relatively transparent gases above the photosphere of the sun.
chronoisotherm
   (NASA SP-7, 1965)
See isotherm, note.
chronometer noon
   (NASA SP-7, 1965)
See solar noon.
chronometer time
   (NASA SP-7, 1965)
See time.
chronometric data
   (NASA SP-7, 1965)
Data in which the desired quantity is the time of occurrence of an event or the time interval between two events.
chronotron
   (NASA SP-7, 1965)
A device which utilizes a measurement of the position of the superposed loci of a pair of pulses on a transmission line to determine the time between the events which initiate the pulses.
chuffing
   (NASA SP-7, 1965)
= chugging.
chugging
   (NASA SP-7, 1965)
A form of combustion instability in a rocket engine, characterized by a pulsing operation at a fairly low frequency, sometimes defined as occurring between particular frequency limits; the noise made in this kind of combustion. Also called chuffing, bumping.
Chukchi Sea
   (NASA Thesaurus)
Part of the Arctic Ocean north of the Bering Strait between Asia and North America.
cinder cone
   (Photoglossary of Volcanic Terms - USGS)
A cinder cone is a steep, conical hill of volcanic fragments that accumulate around and downwind from a vent. The rock fragments, often called cinders or scoria, are glassy and contain numerous gas bubbles "frozen" into place as magma exploded into the air and then cooled quickly. Cinder cones range in size from tens to hundreds of meters tall.
cine-theodolite
   (NASA SP-7, 1965)
A photographic tracking instrument which records on each film frame the target and the azimuth and elevation angles of the optical axis of the instrument. Also called Askania.
Cir, Circ
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Circinus. See constellation.
circadian rhythm
   (NASA Thesaurus / NASA SP-7, 1965)
A regular change in physiological function occurring in approximately 24-hour cycles.
Circinus
   (NASA SP-7, 1965)
(abbr Cir, Circ)
See constellation.
circle of declination
   (NASA SP-7, 1965)
= hour circle.
circle of equal altitude
   (NASA SP-7, 1965)
= parallel of altitude
circle of equal declination
   (NASA SP-7, 1965)
= parallel of declination.
circle of equal probability
   (NASA SP-7, 1965)
(abbr CEP)
A measure of the accuracy with which a rocket or missile can be guided; the radius of the circle at a specific distance in which 50 percent of the reliable shots land. Also called circular error probable, circle of probable error.
circle of latitude
   (NASA SP-7, 1965)
A great circle of the celestial sphere through the ecliptic poles, and hence perpendicular to the plane of the ecliptic.
circle of longitude
   (NASA SP-7, 1965)
A circle of the celestial sphere, parallel to the ecliptic. Also called parallel of latitude.
circle of probable error
   (NASA SP-7, 1965)
= circle of equal probability.
circle of right ascension
   (NASA SP-7, 1965)
= hour circle.
circuit
   (NASA SP-7, 1965)
A network providing one or more closed paths.
circuit element
   (NASA SP-7, 1965)
See element, sense 2.
circuits
   (NASA Thesaurus)
Networks providing one or more closed paths. Used for electric circuits, exploding conductor circuits, shunts, and subcircuits.
circular area
   (NASA SP-7, 1965)
Of a circle, the square of the diameter.
Circular area = 1.2733 * true area.
True area = 0.785398 * circular area.
circular cylindrical coordinates
   (NASA SP-7, 1965)
= cylindrical coordinates.
circular dispersion
   (NASA SP-7, 1965)
(abbr CD)
In rocketry, the diameter of a circle within which 75 percent of the events under study occur. CD = 3.330sigma where sigma = standard deviation.
Circular dispersion is most often used as a measure of error of the accuracy with which rockets reach their intended target.
circular error probable
   (NASA SP-7, 1965)
= circle of equal probability.
circular frequency
   (NASA SP-7, 1965)
= angular frequency (symbol lower case omega).
circular inch
   (NASA SP-7, 1965)
The area of a circle 1 inch in diameter.
circular mil
   (NASA SP-7, 1965)
The area of a circle with a diameter of 0.001 inch; a unit used for the measurement of small circular areas, such as the cross section of a wire.
One circular mil = 7.85 x 10-7 square inch.
circular polarization
   (NASA SP-7, 1965)
The polarization of a wave radiated by a constant electric vector rotating in a plane so as to describe a circle. See elliptical polarization.
circular scanning
   (NASA SP-7, 1965)
Scanning in which the direction of maximum radiation generates a plane or a right circular cone whose vertex angle is close to 180°.
circular velocity
   (NASA SP-7, 1965)
At any specific distance from the primary, the orbital velocity required to maintain a constant-radius orbit.
circular waveguides
   (NASA Thesaurus)
Small hollow tubes that are designed to transmit a specific wavelength along the length of the tube.
circularly polarized sound wave
   (NASA SP-7, 1965)
A transverse wave in an elastic medium in which the displacement vector at any point rotates about the point with constant angular velocity and has a constant magnitude.
A circularly polarized wave is equivalent to two super-posed plane polarized waves of sinusoidal form in which the displacements have the same amplitude, lie in perpendicular planes, and are in quadrature.
circularly polarized wave
   (NASA SP-7, 1965)
An electromagnetic wave for which the electric or the magnetic field vector, or both, at a point describe a circle.
This term is usually applied to transverse waves.
circulating memory
   (NASA SP-7, 1965)
=delay-line storage.
circulating register
   (NASA SP-7, 1965)
= delay-line storage.
circulation
   (NASA Thesaurus / NASA SP-7, 1965)
1. The flow or motion of a fluid in or through a given area or volume.
2. A precise measure of the average flow of fluid along a given closed curve. Mathematically, circulation is the line integral.
the line integral of v dot d r
about the closed curve, where v is the fluid velocity, and dr is a vector element of the curve.
By Stokes theorem, the circulation about a plane curve is equal to the total vorticity of the fluid enclosed by the curve.
The given curve may be fixed in space or may be defined by moving fluid parcels.
circulation control airfoils
   (NASA Thesaurus)
Airfoils in which a high lift capability is produced by supercirculation where control of the stagnation points by the jet sheet produces high lift coefficients.
circulation control rotors
   (NASA Thesaurus)
Rotors that provide STOL capability on high performance aircraft by means of tangential blowing over a rounded trailing edge and mass flow characteristic of turbine engine bleed.
circulation distribution
   (NASA Thesaurus)
The line integral of the velocity component around a curve along the closed contour.
circulation integral
   (NASA SP-7, 1965)
The line integral of an arbitrary vector taken around a closed curve. Thus,
the line integral of a dot d r
is the circulation integral of the vector a around the closed curve; dr is an infinitesimal vector element of the curve. If the vector is the velocity, this integral is called the circulation.
circumlunar
   (NASA SP-7, 1965)
Around the moon, generally applied to trajectories.
circumsolar radiation
   (NASA Thesaurus)
Radiation from small angle scattering of direct sunlight from atmospheric aerosols with dimensions on the order of or greater than the wavelength of light.
circumsolar telescopes
   (NASA Thesaurus)
Optical instruments for measuring the circumsolar radiation for application to solar energy systems. Mirrors and lenses are utilized for incident sunlight concentration.
cirrocumulus clouds
   (NASA Thesaurus)
Cerriform clouds appearing as a thin sheet of small white puffs resembling flakes or patches of cotton without shadows.
cirrostratus clouds
   (NASA Thesaurus)
Cirriform clouds appearing as a whitish veil. Usually fibrous, sometimes smooth, they often produce halo phenomena. This form may totally cover the sky.
cirrus clouds
   (NASA Thesaurus)
Cirriform clouds in the form of thin, white featherlike shapes in patches or narrow bands. They have a fibrous and/or silky sheen. Large ice crystals often trail downward a considerable vertical distance in fibrous, slanted, or irregualrly curved wisps called mares' tails.
cislunar
   (NASA SP-7, 1965)
[Latin cis, on this side]. Of or pertaining to phenomena, projects, or activity in the space between the earth and moon, or between the earth and the moon's orbit. Compare translunar, circumlunar.
cislunar space
   (NASA Thesaurus)
Of or pertaining to phenomena, projects, or activity in the space between the Earth and the moon, or between the Earth and the moon's orbit.
civil day
   (NASA SP-7, 1965)
See mean solar day.
civil time
   (NASA SP-7, 1965)
See mean time, note.
civil twilight
   (NASA SP-7, 1965)
See twilight, note.
civil year
   (NASA SP-7, 1965)
= calendar year.
CL-600 challenger aircraft
   (NASA Thesaurus)
Canadair turbofan aircraft with supercritical wings.
clad
   (NASA SP-7, 1965)
= cladding.
cladding
   (NASA Thesaurus / NASA SP-7, 1965)
A coating placed on the surface of a material and usually bonded to the material. Also called clad.
Cladding is used extensively in nuclear reactor cores to prevent corrosion of the fissionable material by the coolant.
clamping circuit
   (NASA Thesaurus / NASA SP-7, 1965)
1. A circuit which maintains either extremity of a waveform at a prescribed potential.
2. A network for adjusting the absolute voltage level of a waveform.
Clapeyron equation
   (NASA SP-7, 1965)
= Clapeyron-Clausius equation.
Clapeyron-Clausius equation
   (NASA SP-7, 1965)
The differential equation relating pressure to temperature in a system in which two phases of a substance are in equilibrium. dp/dT = L/(T V) where p is pressure; T is temperature; L is the latent heat of the phase change; and delta or triangle (upward pointing)V is the difference in volume of the phases. Also called Clapeyron equation, Clausius-Clapeyron equation.
Clausius-Clapeyron equation
   (NASA SP-7, 1965)
= Clapeyron-Clausius equation.
clean fuels
   (NASA Thesaurus)
Energy sources from which pollutants and other impurities have been removed by refining, purification, and other means, to produce fuels less conducive to pollution.
clean rooms
   (NASA Thesaurus)
Areas in which the temperature, humidity, and the airborne particulate contamination are controlled as required.
cleanup
   (NASA SP-7, 1965)
1. The process of removing gas from a vacuum system or device by sorption or ion pumping.
2. In aeronautics, the process of improving external shape and smoothness of an aircraft to reduce its drag.
clear
   (NASA SP-7, 1965)
To restore a storage or memory device to a prescribed state, usually that denoting zero. See reset.
Clementine spacecraft
   (NASA Thesaurus)
A spacecraft launched in January 1994 as part of a joint NASA/DoD-BMDO (Ballistic Missile Defense Organization) mission to space-qualify several lightweight electronic instruments and systems (including an ultraviolet/visible CCD camera, a near infrared and long-wavelength infrared camera, and a combined high-resolution CCD camera and laser ranging system). The Clementine mission also provided the first complete systematic surface mapping of the moon from the ultraviolet to near infrared spectral regions. A software malfunction in May of 1994 precluded a planned flyby of the asteroid Geographos.+
climatology
   (NASA Thesaurus)
Branch of meteorology that studies the average weather conditions and statistical variations for a specified region over an extended period of time.
climatology
   (NASA SP-7, 1965)
See meteorology, note.
clipper
   (NASA SP-7, 1965)
= clipping circuit.
clipping circuit
   (NASA SP-7, 1965)
A pulse-shaping network which removes that part of a waveform which tends to extend above, or below, a chosen voltage level. Also called clipper.
clo
   (NASA SP-7, 1965)
The amount of insulation which will maintain normal skin temperature of the human body when heat production is 50 kilogram-calorie per meter squared per hour, air temperature is 70° F, and the air is still.
One clo is roughly equivalent to the amount of insulation provided by the average businessman's suit in a temperature climate.
clock frequency
   (NASA SP-7, 1965)
The master frequency of periodic pulses which schedule the operation of a machine, as a computer.
clock pulse
   (NASA SP-7, 1965)
A pulse used for timing purposes. In pulse-code-modulation systems, a timing pulse which occurs at the bit rate.
closed basin
   (Glossary of Hydrologic Terms - NOAA)
A basin draining to some depression or pond within its area, from which water is lost only by evaporation or percolation. A basin without a surface outlet for precipitation falling precipitation.
closed basin lake flooding
   (Glossary of Hydrologic Terms - NOAA)
Flooding that occurs on lakes with either no outlet or a relatively small one. Seasonal increases in rainfall cause the lake level to rise faster than it can drain. The water may stay at flood stage for weeks, months, or years.
closed ecological system
   (NASA Thesaurus / NASA SP-7, 1965)
A system that provides for the maintenance of life in an isolated living chamber through complete reutilization of the material available, in particular, by means of a cycle wherein exhaled carbon dioxide, urine, and other waste matter are converted chemically or by photosynthesis into oxygen, water, and food. Compare controlled-leakage system, open system.
closed respiratory gas system
   (NASA SP-7, 1965)
A completely self-contained system within a sealed cabin, capsule, or spacecraft that will provide adequate oxygen for breathing, maintain adequate cabin pressure, and absorb the exhaled carbon dioxide and water vapor.
closed system
   (NASA SP-7, 1965)
1. In thermodynamics, a system so chosen that no transfer of mass takes place across its boundaries; for example, a fluid parcel undergoing a saturation-adiabatic process, as opposed to a pseudoadiabatic expansion. See open system.
2. In mathematics, a system of differential equations and supplementary conditions such that the values of all the unknowns (dependent variables) of the system are mathematically determined for all values of the independent variables (usually space and time) to which the system applies.
3. = closed ecological system.
4. A system which constitutes a feedback loop so that the inputs and controls depend on the resulting output. For example, an automatic radar-controlled tracking system.
closed-loop system
   (NASA SP-7, 1965)
A system in which the output is used to control the input. See feedback control loop.
closed-loop telemetry
   (NASA SP-7, 1965)
1. A telemetry system which is used as the indicating portion of a remote-control system.
2. A system used to check out test vehicle or telemetry performance without radiation of radio-frequency energy.
closet approach
   (NASA SP-7, 1965)
1. The event that occurs when two planets or other celestial bodies are nearest to each other as they orbit about the sun or other primary.
2. The place or time of such an event.
cloud absorption
   (NASA SP-7, 1965)
The absorption of electromagnetic radiation by the water drops and water vapor within a cloud. Compare cloud attenuation.
For insolation (incoming solar radiation), clouds absorb rather small fractions, particularly of the shorter wavelengths. Even for depths of clouds of the order of 20,000 feet, measurements suggest absorptions of less than 30 percent, while layers only 1000 to 2000 feet thick may absorb only about 5 percent. However, for long wave terrestrial radiation, even very thin layers of cloud act as almost complete blackbody absorbers.
cloud attenuation
   (NASA SP-7, 1965)
Usually, the reduction in intensity of microwave radiation by clouds in the earth's atmosphere. For the centimeter wavelength band, clouds produce Rayleigh scattering. The attenuation is due largely to scattering, rather than to absorption, for both ice and water clouds. See precipitation attenuation. Compare cloud absorption.
cloud band
   (NASA SP-7, 1965)
A broad band of clouds, from about 10 to 100 or more miles wide, and varying in length from a few tens of miles to hundreds of miles. See cloud streets.
cloud chamber
   (NASA Thesaurus / NASA SP-7, 1965)
A device for observing the paths of ionizing particles, based on the principle that supersaturated vapor condenses more readily on ions than on neutral molecules.
cloud physics
   (NASA Thesaurus / NASA SP-7, 1965)
A subdivision of physical meteorology concerned with physical properties of clouds in the atmosphere and the processes occurring therein.
Cloud physics, broadly considered, embraces not only the study of condensation and precipitation processes in clouds, but also radiative transfer, optical phenomena, electrical phenomena, and a wide variety of hydrodynamic and thermodynamic processes peculiar to natural clouds.
cloud rate
   (NASA SP-7, 1965)
The speed at which two bodies approach each other.
cloud seeding
   (NASA Thesaurus / NASA SP-7, 1965)
Any technique carried out with the intent of adding to a natural cloud in a planetary atmosphere certain substances that will altar the natural development of that cloud.
cloud street
   (NASA SP-7, 1965)
A line of cumuliform clouds frequently one cumulus element wide, but ranging upward in width so that it is sometimes difficult to differentiate between streets and bands. Typical dimensions are: axis spacing, 1 to 30 miles; length of cloud streets, 10 to 200 miles; cell spacing along axis, 1/2 to 2 miles. See cloud band.
clouds (meteorology)
   (NASA Thesaurus)
A visible mass of water vapor suspended in the atmosphere above the Earth's surface.
clusec
   (NASA SP-7, 1965)
A flow rate equal to 0.01 lusec.
cluster
   (Global Land Information System Glossary - USGS)
A homogeneous group of units which vary "like" one another. "Likeness" is usually determined by the association, similarity, or distance among the measurement patterns associated with the units.
cluster
   (NASA SP-7, 1965)
Two or more rocket motors bound together so as to function as one propulsion unit.
cluster analysis
   (NASA Thesaurus)
The analysis of data with the object of finding natural groupings within the data either by hand or with the aid of a computer.
cluster of galaxies
   (High Energy Astrophysics Dictionary- GSFC)
A system of galaxies containing from a few to a few thousand member galaxies which are all gravitationally bound to each other.
cluster variation method
   (NASA Thesaurus)
An exact, statistical-mechanical technique for approximating the configurational entropy of a crystalline material, such as an alloy. The method is based on the cluster-cumulant expansion of entropy, that involves the expansion of the thermodynamic quantities of an infinite system in terms of the density matrices of finite groups of lattice sites called clusters. The method, first proposed by Kikuchi, was developed as a theoretical tool for dealing with atomic ordering.
clutter
   (NASA Thesaurus / NASA SP-7, 1965)
1. Atmospheric noise, extraneous signals, etc., which tend to obscure the reception of a desired signal in a radio receiver, radarscope, etc.
As compared with interference, clutter refers more particularly to unwanted reflections on a radar plan position indicator, such as ground return, but the terms are often used interchangeably.
2. = window.
CMa, C Maj
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Canis Major. See constellation.
CMC
   (Space Flight Glossary - JPL)
Complex Monitor and Control, a subsystem at DSCCs.
CMi, C Min
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Canis Minor. See constellation
CMOS
   (NASA Thesaurus)
The combination of a PMOS (p-type channel metal oxide semiconductor) with an NMOS (n-type channel metal oxide semiconductor). Used for complementary metal oxide semiconductors.
CN emission
   (NASA Thesaurus)
Radio waves emitted from incandescent gaseous cyanide (CN) in space under low pressures at wavelengths characteristic of the elements comprising the gas. Used for cyanide emission.
Cnc, Canc
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Cancer. See constellation.
CNES
   (Space Flight Glossary - JPL)
Centre National d'Études Spatiales, France.
cnoidal waves
   (NASA Thesaurus)
Finite amplitude progressive waves in shallow water having a wave profile represented by the Jacobian elliptic function "CN."
co
   (NASA SP-7, 1965)
1. A prefix meaning 90° minus the value with which it is used. Thus, if the latitude is 30°, the colatitude is 90° - 30° = 60°.
2. A prefix meaning in common, as in coaxial, having a common axis.
coal
   (NASA Thesaurus)
A brown to black combustible sedimentary rock (in the geological sense) composed principally of consolidated and chemically altered plant remains.
coal derived gases
   (NASA Thesaurus)
The gases which are derived from various coal gasification processes.
coal derived liquids
   (NASA Thesaurus)
Fluid hydrocarbons derived from the liquefaction of coal.
coalescing
   (NASA Thesaurus)
Growing of grains at the expense of the remainder by adsorption or the growth of a phase or particle at the expense of the remainder by absorption or by reprecipitation. Used for coalescence.
coaltitude
   (NASA SP-7, 1965)
= zenith distance.
coast
   (NASA SP-7, 1965)
A memory feature on a radar which, when activated, causes the range and angle systems to continue to move in the same direction and at the same speed as that required to track an original target.
Coast is used to prevent lock-on to a stronger target if approached by the target being tracked.
coastal currents
   (NASA Thesaurus)
Ocean currents caused by the approach of waves to coasts at an angle. They flow parallel to and near the shore. Used for littoral currents and longshore currents.
coastal flooding
   (Glossary of Hydrologic Terms - NOAA)
Flooding which occurs from storms where water is driven onto land from an adjacent body of water. These can be hurricanes, "nor'easters," or tropical storms, but even a strong winter storm or thunderstorm can cause this type of flooding
Coastal Zone Color Scanner
   (NASA Thesaurus)
A spaceborne instrument devoted to the measurement of ocean color. Every parameter is optimized for use over water to the exclusion of other types of sensing.
coasting flight
   (NASA Thesaurus / NASA SP-7, 1965)
The flight of a rocket between burnout or thrust cutoff of one stage and ignition of another, or between burnout and summit altitude or maximum horizontal range.
coasts
   (NASA Thesaurus)
The strips of land of indefinite width (may be many kilometers) that extend from the low tide line inland to the first major change in landforms.
coated optics
   (NASA SP-7, 1965)
Optical elements (lenses, prisms, etc.) which have their surfaces covered with a thin transparent film to minimize reflection and loss of light in the system.
coatings
   (NASA Thesaurus)
Liquid, liquefiable or mastic compositions which are converted to a solid protective, decorative, or functional adherent film after application as a thin layer.
coaxial cable
   (NASA Thesaurus / NASA SP-7, 1965)
A form of waveguide consisting of two concentric conductors insulated from each other.
coaxial nozzles
   (NASA Thesaurus)
Class of nozzle configurations in jet aircraft for reducing noise.
Cobra Dane (radar)
   (NASA Thesaurus)
Radar installation for monitoring Soviet missiles.
cockpit weather information systems
   (NASA Thesaurus)
A cockpit display system that provides flight crews with a graphical display of interactive weather information, including surface observations, terminal forecasts, radar summaries, and lightning strike data. The system also provides weather trend information and has zooming capabilities that enable the user to see information for the entire nation or to focus on specific areas.
cockpits
   (AS&T Dictionary)
A space, usually enclosed, in the forward fuselage of an aircraft or spacecraft containing the flying controls, instrument panel, and seats for the pilot, copilot, or flight crew.
codan
   (NASA SP-7, 1965)
= carrier operated device, anti-noise. A device which silences a receiver except when a carrier signal is being received.
code
   (NASA SP-7, 1965)
1. A system of symbols or signals for representing information, and the rules for associating them.
2. The set of characters resulting from the use of a code as defined in sense 1.
3. Specifically, to translate a problem to a routine expressed in machine language for a specific computer.
4. To express given information by means of a code, to encode.
code division multiple access
   (NASA Thesaurus)
Multiple access system in which users are segregated by means of pseudorandom signal coding and bandwidth spreading so that the complete time and frequency axes are occupied and only the power is shared. Used for CDMA.
code division multiplexing
   (NASA Thesaurus)
The separation of two or more simultaneous radio transmissions over a common path by signal coding and bandwidth spreading.
codeclination
   (NASA SP-7, 1965)
Ninety degrees minus the declination. When the declination and latitude are of the same name, codeclination is polar distance measured from the elevated pole.
coded decimal digit
coding
   (NASA SP-7, 1965)
The arrangement in a coded form, usually acceptable to a specific computer, of the instructions for the operations necessary to solve a problem.
coefficient
   (NASA SP-7, 1965)
(abbr coeff)
1. A number indicating the amount of some change under certain specified conditions, often expressed as a ratio.
For example, the coefficient of linear expansion of a substance is the ratio of its change in length to the original length for a unit change of temperature from a standard.
2. A constant in an algebraic equation.
3. One of several parts which combine to make a whole, as the maximum deviation produced by each of several causes.
coefficient of barotropy.
   (NASA SP-7, 1965)
See barotropy.
coefficient of compressibility
   (NASA SP-7, 1965)
The relative decrease of the volume of a gaseous system with increasing pressure in an isothermal process. This coefficient is
-(1/V)(del (lower case delta)V/ p)T
where V is the volume; p is the pressure; and T is the temperature. The reciprocal of this quantity is the bulk modulus. Also called compressibility. Compare coefficient of thermal expansion, coefficient of tension.
coefficient of diffusion
   (NASA SP-7, 1965)
= diffusivity.
coefficient of friction
   (AS&T Dictionary)
A fixed value that, when multiplied by the normal force between two bodies that are in surface contact, gives the force of friction between them which is necessary to begin sliding; the ratio of the tangential force that is needed to maintain uniform relative motion between two contacting surfaces to the perpendicular force holding them in contact.
coefficient of heat conduction
   (NASA SP-7, 1965)
= thermal conductivity.
coefficient of molecular viscosity
   (NASA SP-7, 1965)
= dynamic viscosity.
coefficient of mutual diffusion
   (NASA SP-7, 1965)
A quantity in the kinetic theory of gases which measures the tendency of gases to diffuse into one another in nonturbulent flow.
This diffusion coefficient is a property of the gases in question and of the assumed nature of the molecular impacts in the diffusion process. For rigid, perfectly elastic, spherical molecules the coefficient of mutual diffusion d1,2 is, in square centimeters per second,
d sub one, two equals three over four n open parens sigma sub one plus sigma sub two close parens squared open bracket two k T open parens m sub one plus m sub two close parens over m sub one m sub two close bracket to the power one half
where
n is Loschmidt number (the number of molecules per cubic centimeter); 1, sigma2 and m1, m2 are the effective molecular diameters and masses of the two gases, respectively; T is the temperature,°K; and k is Boltzmann constant.
coefficient of tension
   (NASA SP-7, 1965)
The relative increase of pressure of a system with increasing temperature in an isochoric process. In symbols this quantity is
(1/p)(del (lower case delta)p/ T)V
where p is pressure; T is temperature; and V is volume. Compare coefficient of compressibility, coefficient of thermal expansion.
coefficient of thermal conduction
   (NASA SP-7, 1965)
= thermal conductivity.
coefficient of thermal conductivity
   (NASA SP-7, 1965)
=thermal conductivity.
coefficient of thermal expansion
   (NASA SP-7, 1965)
The ratio of the change of length per unit length (linear), or change of volume per unit volume (voluminal), to the change of temperature.
coefficient of viscosity
   (NASA SP-7, 1965)
= dynamic viscosity.
coesite
   (NASA Thesaurus)
A polymorph of silicon dioxide.
Coffin-Manson law
   (NASA Thesaurus)
A relationship which enables one to estimate the fatigue life from the cyclic plastic strain range. The specific life for a given metal or alloy is determined by its tensile ductility.
cogeneration
   (NASA Thesaurus)
The generation of electricity or shaft power by an energy conversion system and the concurrent use of the rejected thermal energy from the conversion system as an auxiliary energy source.
coherence
   (NASA SP-7, 1965)
In radar, a relation between two wave trains such that, when they are brought into coincidence, they are capable of producing interpretable interference phenomena.
This is limited to those wave trains which have fixed or slowly varying phase relationships with each other.
In contract are the rapid interference phenomena produced by the superposition of the more or less randomly scattered waves from hydrometeors.
coherent
   (NASA SP-7, 1965)
1. Of electromagnetic radiation, being in phase, so that waves at various points in space act in unison, as in a laser producing coherent light.
2. Having a fixed relation between frequency and phase of input and output signal.
coherent carrier
   (NASA SP-7, 1965)
A carrier wave derived from a continuous-wave signal in such a way that its frequency and phase have a fixed relationship to the frequency and phase of the reference signal.
coherent echo
   (NASA SP-7, 1965)
A radar echo whose phase and amplitude at a given range remain relatively constant.
Hills, buildings, and slowly moving point targets such as ships are examples of objects which produce coherent radar echoes. Volume targets (such as clouds and precipitation) give noncoherent echoes. The classification of an echo as coherent or noncoherent is closely related to the spatial resolution (beam width) of the radar or the volume occupied by the radar pulse. Thus, small atmospheric inhomogeneities which give rise to noncoherent echoes, would give coherent echoes if the radar volume were reduced in size to the order of magnitude of the inhomogeneities themselves.
coherent light
   (NASA Thesaurus)
Light in which the phase relationship between points in a beam remains constant throughout the beam.
coherent oscillator
   (NASA SP-7, 1965)
(abbr Coho)
An oscillator which provides a reference by which the radio frequency phase difference of successive received pulses may be recognized. See coherent reference.
coherent radar
   (NASA Thesaurus / NASA SP-7, 1965)
A type of radar that employs circuitry which permits comparison of the phase of successive received target signals.
coherent radiation
   (Plasma Physics and Fusion Energy Glossary)
Any form of radiation in which the phase relationship between sections of the wave at different locations is not random (or incoherent!).
coherent reference
   (NASA SP-7, 1965)
The reference signal, usually of stable frequency, to which other signals are phase-locked to establish coherence throughout a system.
coherent scattering
   (NASA Thesaurus)
Scattering of photons or particles in which there are define phase relationships between the incoming and scattered waves. Ordinary scattering is coherent. With coherent scattering, interference occurs between the waves scattered by two or more scattering centers. The total intensity is the vector sum of the amplitudes of the various waves.
coherent transponder
   (NASA SP-7, 1965)
A transponder, the output signal of which is coherent with the input signal.
cohesion
   (NASA Thesaurus)
The mutual attraction by which elements of a substance are held together.
Coho (abbr)
   (NASA SP-7, 1965)
= coherent oscillator.
coincidence circuit
   (NASA Thesaurus / NASA SP-7, 1965)
An electronic circuit that produces a usable output pulse only when each of two or more input circuits receive pulses simultaneously or within an assignable time interval.
coincidence counter
   (NASA SP-7, 1965)
A device using ionization counters and coincidence circuits to count and determine the direction of travel of ionized particles, particularly cosmic rays.
coincident-current magnetic core
   (NASA SP-7, 1965)
A binary magnetic core in which information is stored as the result of current flowing simultaneously in two or more independent windings.
Usually a number of cores are arranged in the form of a matrix.
Col, Colm
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Columba. See constellation.
colatitude
   (NASA SP-7, 1965)
Ninety degrees minus the latitude.
cold cathode
   (NASA SP-7, 1965)
A cathode whose operation does not depend on its temperature being above the ambient temperature.
cold cathode tubes
   (NASA Thesaurus)
Electron tubes containing cold cathodes.
cold cathodes
   (NASA Thesaurus)
Cathodes that function without the application of heat.
cold drawing
   (NASA Thesaurus)
Reducing the cross section (of wire) by pulling through a die or dies, at a temperature lower than the recrystallization temperature.
cold flow tests
   (NASA Thesaurus)
Tests of liquid rockets without firing them to check or verify the efficiency of a propulsion subsystem, providing for the conditioning and flow of propellants (including tank pressurization, propellant loading, and propellant feeding).
cold neutrons
   (NASA Thesaurus)
Neutrons of less velocity than thermal neutrons; at 152 deg. C their energy is below 0.01 eV.
cold working
   (NASA Thesaurus / NASA SP-7, 1965)
Deforming metal plastically at a temperature lower than the recrystallization temperature.
cold-cathode gage
   (NASA SP-7, 1965)
= cold-cathode ionization gage.
cold-cathode ionization gage
   (NASA SP-7, 1965)
A ionization gage (vacuum gage) in which the ions are produced by a discharge between two electrodes, both near room temperature. The discharge usually takes place in the presence of a magnetic field which lengthens the path of the electrons between cathode and anode.
One form of gage is a transparent tube in which the color and form of a cold-cathode discharge, without the presence of a magnetic field, give an indication of the pressure and the nature of the gas. The Philips ionization gage, or Penning gage, is a cold-cathode ionization gage in which a magnetic field is used. Various modifications of the Penning gage are named after the inventors, and certain types are referred to as magnetron vacuum gages.
cold-flow test
   (NASA SP-7, 1965)
A test of a liquid rocket without firing it to check or verify the efficiency of a propulsion subsystem, providing for the conditioning and flow of propellants (including tank pressurization, propellant loading, and propellant feeding).
cold-pressor test
   (NASA SP-7, 1965)
A test for measuring the response of heart and blood pressure to the stress of plunging an extremity (foot or hand) into ice water.
The normal response is an increase in both heart rate and blood pressure.
coleopter
   (NASA SP-7, 1965)
An aircraft having an annular (barrel-shaped) wing, the engine and body being mounted within the circle of the wing.
collecting area
   (High Energy Astrophysics Dictionary- GSFC)
The amount of area a telescope has that is capable of collecting electromagnetic radiation. Collecting area is important for a telescope's sensitivity: the more radiation it can collect (that is, the larger its collecting area), the more sensitive it is to dim objects.
collimate
   (NASA SP-7, 1965)
1. To render parallel, as rays of light.
2. To adjust the line of sight of an optical instrument, such as a theodolite, in proper relation to other parts of the instrument.
collimation error
   (NASA SP-7, 1965)
The angular error in magnitude and direction between two nominally parallel lines of sight; specifically, the angle by which the line of sight of an optical instrument or radar differs from what it should be.
collimation tower
   (NASA SP-7, 1965)
A tower on which are mounted a visual and a radio target for use in checking the electrical axis of an antenna.
collimator
   (NASA SP-7, 1965)
An optical device which renders rays of light parallel.
collimators
   (NASA Thesaurus)
Optical devices which render rays of light parallel. Used for autocollimators.
collision
   (NASA SP-7, 1965)
An encounter between two particles that changes their existing momentum and energy conditions. See elastic collision.
The products of the collision may or may not be the same as the precollision particles. The collision may be actual contact or the close approach and deflection of the particles.
collision broadening
   (NASA SP-7, 1965)
In spectroscopy, the broadening or spreading of an emission line, due to the interruption of the radiating process by a collision of the radiator with another particle.
In the case of cyclotron radiation, the collision will actually change the phase of the radiation. For many collisions, this has the effect of broadening the observed frequencies by an amount equal to the collision rate.
collision cross section
   (NASA SP-7, 1965)
See cross section. See also elastic collision, coulomb collision.
collision frequency
   (NASA SP-7, 1965)
= collision rate.
collision frequency per unit volume
   (NASA SP-7, 1965)
The number of collisions between molecules in a gas per unit volume per unit time.
collision parameter
   (NASA SP-7, 1965)
1. In orbit computation, the distance between a center of attraction of a central force field and the extension of the velocity vector of a moving object at a great distance from the center.
2. In gas dynamics and atomic physics, any of several parameters, such as cross section, collision rate, mean free path, etc., which provide a measure of the probability of collision.
collision rate
   (NASA SP-7, 1965)
The average number of collisions per second suffered by a molecule or other particle moving through a gas. Also called collision frequency.
collision rates
   (NASA Thesaurus)
Ratios defined by the average number of collisions per second suffered by a molecule or other particle moving through a gas.
collisionless plasmas
   (Plasma Physics and Fusion Energy Glossary)
plasma in which the density is so low, or the temperature so high, that close binary (two-body) collisions have practically no significance (on certain timescales) because the time scales of interest are shorter than the collision time.
collistion frequency per molecule
   (NASA SP-7, 1965)
= collision rate.
colloid
   (NASA SP-7, 1965)
See colloidal system.
colloidal dispersion
   (NASA SP-7, 1965)
= colloidal system.
colloidal suspension
   (NASA SP-7, 1965)
= colloidal system.
colloidal system
   (NASA SP-7, 1965)
An intimate mixture of two substances one of which, called the dispersed phase (or colloid ) is uniformly distributed in a finely divided state through the second substance, called the dispersion medium (or dispersing medium ). The dispersion medium may be a gas, a liquid, or a solid, and the dispersed phase may also be any of these, with the exception that one does not speak of a colloidal system of one gas in another. Also called colloidal dispersion, colloidal suspension.
A system of liquid or solid particles colloidally dispersed in a gas is called an aerosol. A system of solid substance or water-insoluble liquid colloidally dispersed in liquid water is called a hydrosol. There is no sharp line of demarcation between true solutions and colloidal system on the one hand, or between mere suspensions and colloidal systems on the other. When the particles of the dispersed phase are smaller than about 1 millimicron in diameter, the system begins to assume the properties of a true solution; when the particles dispersed are much greater than 1 micron, separation of the dispersed phase from the dispersing medium becomes so rapid that the system is best regarded as a suspension.
Colm
   (NASA SP-7, 1965)
International Astronomical Union abbreviation for Columba. See constellation.
color
   (From Stargazers to Starships Glossary - GSFC)
A quality of light, depending on its wavelength. Spectral color of an emission of light is its place in the rainbow spectrum. Perceived color (or visual color) is the quality of light emission as conveyed by the human eye, combining the impressions of 3 types of light-sensitive cells which the eye contains. Perceived color can be the response to certain combinations of spectral colors; for instance, brown responds to green and red (or blue, yellow and red).
color coding
   (NASA Thesaurus)
Any system of colors used for purposes of identification. Used for color enhancement.
color equation
   (NASA SP-7, 1965)
In astronomy, a measure of the color sensitivity of a method of observation, equal to the color index of a class K0 star.
color excess
   (NASA SP-7, 1965)
(symbol E)
The difference between the apparent color index of a star and its true color index as computed for its stellar type.
Color excess is a measure of space reddening.
color index
   (NASA SP-7, 1965)
(symbol C)
Of a star, the numerical difference between the apparent photographic magnitude mpg and the apparent photovisual magnitude mpv or
C = mpg - mpv

The color index is zero for class A0 stars of magnitudes between 5.5 and 6.5; it is positive for red stars and negative for bluish stars. Various other color indices can be formed by using apparent magnitudes measured in other systems. Thus, the intrinsic color index is apparent photographic magnitude minus apparent ultraviolet magnitude.
color infrared photography
   (NASA Thesaurus)
A representation of temperature differences using false colors.
color sensitive
   (NASA SP-7, 1965)
Referring to a photographic emulsion which is not colorblind.
An emulsion sensitive not only to blue, violet, and ultraviolet, but also to yellow and green, is called orthochromatic; if sensitive to red as well, it is called panchromatic.
color temperature
   (NASA SP-7, 1965)
1. An estimate of the temperature of an incandescent body, determined by observing the wavelength at which it is emitting with peak intensity (its color) and using that wavelength in Wien law.
If such a body were an ideal blackbody, the temperature so estimated would be its true temperature and would also agree with its effective temperature; but for actual bodies, the color temperature is generally only an approximate value. Thus, the sun's color temperature is about 6100° K, a few hundred degrees hotter than most approximations of its effective temperature.
2. The temperature to which a blackbody radiator must be raised in order that the light it emits may match a given light source in color. [Usually expressed in Kelvin (°K).]
color-color diagram
   (NASA Thesaurus)
A two-axis coordinate graph showing the distribution of stars or other objects with reference to different color indices.
color-magnitude diagram
   (NASA Thesaurus)
The plot of the absolute or apparent magnitude against the color index for a group of stars. Also known as C-M diagram. Used for C-M diagram.
colorblind
   (NASA SP-7, 1965)
Applied to a photographic emulsion sensitive only to blue, violet, and ultraviolet light.
Columba
   (NASA SP-7, 1965)
(abbr Col, Colm)
See constellation.
Columbus space station
   (NASA Thesaurus)
The European Space Agency's manned orbital platform.
column
   (NASA SP-7, 1965)
In a structure, a body whose function is to carry compression loads to its longest dimension.
columnular ice
   (Glossary of Hydrologic Terms - NOAA)
Ice consisting of columnar shaped grain. The ordinary black ice is usually columnar-grained.
Com, Coma
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Coma Berenices. See constellation.
coma
   (Comet Glossary - JPL)
The comet's coma or head is the fuzzy haze that surrounds the comet's true nucleus. The coma (and tail) are really all that we see from Earth.
Coma
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Coma Berenices. See constellation
coma
   (NASA SP-7, 1965)
1. The gaseous envelope that surrounds the nucleus of a comet.
2. In an optical system, a result of spherical aberration in which a point source of light, not on the axis, has a blurred, comet-shaped image.
Coma Berenices
   (NASA SP-7, 1965)
(abbr Com, Coma)
See constellation.
coma diameter
   (Comet Glossary - JPL)
The diameter of the coma is usually given in minutes of arc ('). If the coma is round, this is a straightforward definition. If the coma is elongated or has a tail, the measurement represents the smallest dimension of the coma (usually at a right angle to the tail) and transecting the brightest part of the coma.
combination coefficient
   (NASA SP-7, 1965)
A measure of the specific rate of disappearance of small ions due to either (a) union with neutral Aitken nuclei to form new large ions, or (b) union with large ions of opposite sign to form neutral Aitken nuclei.
combined cycle power generation
   (NASA Thesaurus)
Power generation which combines an open-cycle gas turbine and a closed-cycle steam turbine.
combined error
   (NASA SP-7, 1965)
A term used to specify the largest possible error of an instrument in the presence of adding or interacting effects.
Generally applied to the largest error due to the combined effect of nonlinearity and hysteresis.
combustion
   (NASA Thesaurus)
A chemical process of oxidation that occurs at a rate fast enough to produce heat and usually light either as a glow or flames. Some oxidation such as that of hydrogen emits radiation outside the visible spectrum. Used for burning and burning process.
combustion chamber
   (NASA SP-7, 1965)
(symbol c used as a subscript)
Any chamber for the combustion of fuel, specifically that part of the rocket engine in which the combustion of propellants takes place at high pressure. Also called chamber, firing chamber.
The combustion chamber plus the diverging section of the nozzle comprise the rocket thrust chamber.
combustion chambers
   (NASA Thesaurus)
Containers in which the actual burning of fuel takes place. Used for combustors.
combustion chemistry
   (NASA Thesaurus)
The study of the exothermic oxidation reactions occurring immediately before and during combustion.
combustion control
   (NASA Thesaurus)
Control of factors (temperature, preheating, draft, excess or deficient air, etc.) which affects combustion efficiency.
combustion efficiency
   (NASA Thesaurus / NASA SP-7, 1965)
The efficiency with which fuel is burned, expressed as the ratio of the actual energy released by the combustion to the potential chemical energy of the fuel.
combustion instability
   (NASA SP-7, 1965)
Unsteadiness or abnormality in the combustion of fuel, as may occur, e.g., in a rocket engine.
combustion wave
   (NASA SP-7, 1965)
A zone of burning propagated through a combustible medium.
combustion-chamber liner
   (NASA SP-7, 1965)
= inner liner.
combustor
   (NASA SP-7, 1965)
= combustion chamber.
comes (plural, comites)
   (NASA SP-7, 1965)
The smaller star in a binary system. Also called companion.
comet
   (NASA SP-7, 1965)
A luminous member of the solar system composed of a head, or coma, and often with a spectacular gaseous trail extending a great distance from the head.
The orbits of comets are highly elliptical.
comet nuclei
   (Comet Glossary - JPL)
The true nucleus of a comet has only been seen once (P/Halley by spacecraft). From the ground, the star-like nucleus always includes a cloud of dust and gas around the true nucleus. Hence, terms such as stellar condensation and nuclear condensation are often used when a star-like object is seen in the comet's coma. The magnitude of the "nucleus" is denoted m2 and usually isn't of much use because one is really not such what m2 represents. In general, the value of m2 will get fainter as more magnification is applied.
Comet Nucleus Tour
   (NASA Thesaurus)
A NASA Discovery-class mission to acquire imagery and comparative spectral maps of comet nuclei and analyze comet dust flows. The mission spacecraft will fly to within 100 kilometers of at least three near-Earth comets including Comet Encke, Comet Schwassmann-Wachmann, and Comet d`Arrest.
comet tails
   (Comet Glossary - JPL)
The comet's tail is its most distinctive feature. Generally pointing away from the Sun, these appendages come in a variety of shapes and lengths. The lengths can vary from a small fraction of a degree (tails are always measured as the angular length either in degrees or minutes of arc [', 60' = one degree]) to the rare few that cover a significant fraction of the sky.
cometary atmospheres
   (NASA Thesaurus)
The region of the coma of a comet as well as the gaseous part surrounding the coma that often is a hydrogen atmosphere that contains particulate matter.
comets
   (NASA Thesaurus)
Luminous members of the solar system composed of a head, or coma, and often with a spectacular gaseous tail extending a great distance from the head.
command
   (NASA SP-7, 1965)
A signal which initiates or triggers an action in the device which receives the signal. In computer operations also called instruction.
command control
   (NASA SP-7, 1965)
A system whereby functions are performed as the result of a transmitted signal.
command destruct
   (NASA SP-7, 1965)
A command control system that destroys a flightborne test rocket, actuated on command of the range safety officer whenever the rocket performance indicates a safety hazard.
command guidance
   (NASA Thesaurus / NASA SP-7, 1965)
The guidance of a spacecraft or rocket by means of electronic signals sent to receiving devices in the vehicle.
command languages
   (NASA Thesaurus)
Vocabularies to interactively execute activities such as computer retrieval or input.
commercial spacecraft
   (NASA Thesaurus)
Commercial satellites and other spacecraft operated by the private sector.
common item
   (NASA SP-7, 1965)
An item of supply used in two or more systems, subsystems, or pieces of support equipment, including related components and spares.
commonality
   (NASA Thesaurus)
The factors which are common in equipment or systems.
communication networks
   (NASA Thesaurus)
Organization of facilities for the rapid reception of, transmission of, and/or relaying of electrical impulses for reproduction as printed messages, pictures, or other data.
communication satellites
   (NASA Thesaurus)
Satellites designed to reflect or relay electromagnetic signals used for communication.
communications satellite
   (NASA SP-7, 1965)
A satellite designed to reflect or relay electromagnetic signals used for communication.
commutation
   (NASA Thesaurus / NASA SP-7, 1965)
Sequential sampling, on a repetitive timesharing basis, of multiple data sources for transmitting or recording, or both, on a single channel.
commutation rate
   (NASA SP-7, 1965)
Number of commutator inputs sampled per second.
commutator
   (NASA SP-7, 1965)
A device used to accomplish time division multiplexing by repetitive sequential switching.
commutators
   (NASA Thesaurus)
Devices used to accomplish time division multiplexing by repetitive sequential switching.
companding
   (NASA Thesaurus)
A process in which compression is followed by expansion, as in noise reduction systems.
companion
   (NASA SP-7, 1965)
The smaller body in a physical double-star system. See binary star. Also called comes.
companion body
   (NASA SP-7, 1965)
A nose cone, last-stage rocket, or other body that orbits along with an earth satellite. Compare afterbody.
comparator
   (NASA SP-7, 1965)
In computer operations, a device or circuit for comparing information from two sources.
compass
   (NASA SP-7, 1965)
1. An instrument for indicating a horizontal reference direction, specifically a magnetic compass.
2. Referring to or measured from compass north.
compass meridian
   (NASA SP-7, 1965)
See meridian.
compass north
   (NASA SP-7, 1965)
The direction north as indicated by a magnetic compass; the reference direction for measurement of compass directions.
compasses
   (NASA Thesaurus)
Instruments for indicating a horizontal reference direction, specifically, magnetic compasses.
compatibility
   (NASA Thesaurus / NASA SP-7, 1965)
1. A characteristic ascribed to a major subsystem that indicates it functions well in the overall system.
2. Also applied to the overall system with reference to how well its various subsystems work together, as in the vehicle has good compatibility.
3. Also applied to materials which can be used in conjunction with other materials which can be used in conjunction with other materials and not react with each other under normal operating conditions.
compensation pyrheliometer
   (NASA SP-7, 1965)
An instrument developed by K. Ångström for the measurement of direct solar radiation. The radiation receiver station consists of two identical manganin strips whose temperatures are measured by attached thermocouples. One of the strips is shaded, whereas the other is exposed to sunlight. An electrical heating current is passed through the shaded strip so as to raise its temperature to that of the exposed strip. The electric power required to accomplish this is a measure of the solar radiation. See actinometer, pyrheliometer.
compensation signals
   (NASA SP-7, 1965)
In telemetry, a signal recorded on a tape, along with the data and in the same track as the data, used during the playback of data to correct electrically the effects of tape-speed errors.
compile
   (NASA SP-7, 1965)
In computer terminology, to assemble the necessary subroutines into a main routine for a specific problem.
complement
   (NASA Thesaurus)
An angle equal to 90 deg. minus a given angle. The true complement of any quantity in positional notation, i.e. the quantity which, when added to the first quantity, gives the least quantity containing one more place. The base-minus-one complement of any quantity in positional notation; i.e., the quantity which when added to the first quantity containing the same number of places.
complement
   (NASA SP-7, 1965)
1. An angle equal to 90° minus a given angle.
Thus, 50° is the complement of 40°, and the two are said to be complementary. See explement.
2. The true complement of any quantity in positional notation, i.e., the quantity which, when added to the first quantity, gives the least quantity containing one more place.
3. The base-minus-one complement of any quantity in positional notation; i.e., the quantity which, when added to the first quantity, gives the largest quantity containing the same number of places.
In many computing machines a negative quantity is represented as a complement of the corresponding positive quantity.
complementary angle
   (NASA SP-7, 1965)
= complement.
complementation
   (NASA SP-7, 1965)
In Boolean algebra, an operation in which items are described by stating that they do not belong to a particular class or classes. See NOT circuit.
complementor
   (NASA SP-7, 1965)
In computers, a device which performs a function corresponding to the operation of complementation.
complex
   (NASA SP-7, 1965)
1. Short for launch complex, as in Complex 25B at Cape Kennedy.
2. Pertaining to a magnitude composed of a real number and an imaginary number.
complex compounds
   (NASA Thesaurus)
Chemical compounds in which part of the molecular bonding is of the coordinate type.
complexity units
   (NASA SP-7, 1965)
In reliability studies of electronic devices, an approximate figure of merit for complexity based on the sum of the number of tubes plus the number of relays in a unit or system. The total number of parts is roughly 10 times the number of complexity units.
component
   (NASA SP-7, 1965)
An article which is a self-contained element of a complete operating unit and performs a function necessary to the operation of that unit.
component of vector
   (From Stargazers to Starships Glossary - GSFC)
When a vector is resolved into a sum of vectors in specified directions, each of those vector is the component of the given vector in the specified direction.
components
   (NASA Thesaurus)
An article which is a self-contained element of a complete operating unit and performs a function necessary to the operation of that unit. Used for parts.
composite hydrograph
   (Glossary of Hydrologic Terms - NOAA)
A stream discharge hydrograph which includes baseflow, or one which corresponds to a net rain storm of duration longer than one unit period.
composite materials
   (NASA Thesaurus / NASA SP-7, 1965)
Structural materials of metals, ceramics, or plastics with built-in strengthening agents which may be in the form of filaments, foils, powders, or flakes of a different compatible material.
composite propellant
   (NASA Thesaurus / NASA SP-7, 1965)
A solid rocket propellant consisting of a fuel and an oxidizer neither of which would burn without the presence of the other.
compound centripetal acceleration
   (NASA SP-7, 1965)
= coriolis acceleration.
compressed air illness
   (NASA SP-7, 1965)
= caisson disease.
compressed gas
   (NASA Thesaurus)
Any gaseous materials or mixtures having a container pressure exceeding 40 psi at 70 degrees F, or 104 psi at 130 degrees F. Compressed gases are further defined as flammable or nonflammable.
compressibility
   (NASA Thesaurus / NASA SP-7, 1965)
1. The property of a substance, as air, by virtue of which its density increases with increase in pressure.
2. = coefficient of compressibility.
In aerodynamics, this property of the air is manifested especially at high speeds (speeds approaching that of sound and higher speeds). Compressibility of the air about an aircraft may give rise to buffeting, aileron buzz, shifts in trim, and other phenomena not ordinarily encountered at low speeds, known generally as compressibility effects.
compressibility burble
   (NASA SP-7, 1965)
A region of disturbed flow, produced by, and rearward of, a shock wave. See burble.
compressible flow
   (NASA Thesaurus / NASA SP-7, 1965)
In aerodynamics, flow at speeds sufficiently high that density changes in the fluid cannot be neglected.
compression
   (NASA SP-7, 1965)
1. = ellipticity. See flattening.
2. More generally, the act of compressing, pressing together; as in compression waves, compression ratio.
compression ratio
   (NASA Thesaurus)
In internal combustion engines, the ratio between the volume displaced by the piston plus the clearance space, to the volume of the clearance space.
compression waves
   (NASA Thesaurus / NASA SP-7, 1965)
In acoustics, waves in an elastic medium which cause an element of the medium to change its volume without undergoing rotation. Mathematically, a compressional wave is one whose velocity field has zero curl. Also called longitudinal waves.
compressional wave
   (NASA Thesaurus / NASA SP-7, 1965)
See compression waves.
compressive strength
   (NASA Thesaurus)
The maximum load sustained by a standard specimen of a material when subjected to a crushing force.
compressor
   (NASA SP-7, 1965)
A machine for compressing air or other fluid.
Compressors are distinguished (1) by the manner in which fluid is handled or compressed, as the axial flow, centrifugal, double-entry, free-vortex, mixed-flow, single-entry, and supersonic compressor; or (2) by the number of stages, as the multistage or single-stage compressor. See individual entries on the different types.
compressor blade
   (NASA SP-7, 1965)
Either a rotor blade or a stator blade in an axial-flow compressor; sometimes used restricitevly (and ambiguously) for a compressor rotor blade. Compare impeller vane.
compressors
   (NASA Thesaurus)
Machines for compressing air or other fluids.
Compton effect
   (NASA Thesaurus / NASA SP-7, 1965)
The decrease in frequency and increase in wavelength of X-rays or gamma rays when scattered by free electrons. Also called Compton recoil effect.
Compton electron
   (NASA SP-7, 1965)
An orbital electron of an atom which has been ejected from its quantum of radiation (X-ray or gamma ray). Also called Compton recoil electron.
Compton recoil effect
   (NASA SP-7, 1965)
= Compton effect.
Compton recoil electron
   (NASA SP-7, 1965)
= Compton electron.
Compton wavelength
   (NASA SP-7, 1965)
(symbol lambdac)
Of a particle, the distance h/mc, where h is the Planck constant, m is the mass of the particle, and c is the velocity of light.
The Compton wavelength of the electron (symbol lambdac) is 2.4261 x 10-10 centimeter; of the proton (symbol lambdacp) is 1.32140 x 10-13 centimeter.
compulsators
   (NASA Thesaurus)
Compensated pulsed alternators, i.e., single phased alternators designed for pulsed power duty with air gap armature windings and air gap compensating windings.
computational chemistry
   (NASA Thesaurus)
A complementary method for determining properties of gases, solids, and their interactions from first principle calculations. It extends testing capabilities to realms that are too dangerous or too costly to obtain experimentally.
computational fluid dynamics
   (NASA Thesaurus)
The application of large computer systems for the numerical solutions of complex fluid dynamics equations.
computer
   (NASA SP-7, 1965)
1. A machine for carrying out calculations and performing specified transformations on information. Also called computing machinery.
2. One who computes, or who operates a computer.
computer aided design
   (NASA Thesaurus)
The use of the computer in design work. Used for CAD (design), computer aided engineering, and computerized design.
computer aided manufacturing
   (NASA Thesaurus)
Interactive computing in support of manufacturing. Used for CAM (manufacturing).
computer aided mapping
   (NASA Thesaurus)
Creating data bases of topographic and man-made features for the production of traditional maps and digital maps. Resultant digital maps have great flexibility and can be easily updated. The user can select the appropriate scale, view selected features, and view any desired area.
computer assisted instruction
   (NASA Thesaurus)
The use of a computer to present instructional material and to accept and evaluate student responses.
computer compatible tapes
   (NASA Thesaurus)
Machine readable tapes.
computer conferencing
   (NASA Thesaurus)
A form of teleconferencing that allows one or more users to exchange messages on a computer network.
computer graphics
   (NASA Thesaurus)
The technique of combining computer calculations with various display devices, printers, plotters, etc. to render information in graphical or pictorial format. Used for interactive graphics.
computer information security
   (NASA Thesaurus)
Protective measures to prevent destruction, larceny, and/or unauthorized use of information in computerized files. Used for computer security.
computer networks
   (NASA Thesaurus)
The interconnection of two or more computers for the mutual or individual processing of data to and from a multitude of terminals or stations by utilizing appropriate switching techniques, transmission systems, or miniprocessors.
computer program integrity
   (NASA Thesaurus)
The completeness of a program to execute its intended function.
computer programming
   (NASA Thesaurus)
The preparation of a formalized sequence of instructions that can be recognized and implemented by a computer.
computer systems performance
   (NASA Thesaurus)
The efficiency and reliability that characterize the real operation of the system.
computer systems simulation
   (NASA Thesaurus)
Forecasting of computer requirements by the use of predictive modeling and estimating computer workloads.
computer vision
   (NASA Thesaurus)
Capability of computers to analyze and act on visual input.
computerized simulation
   (NASA Thesaurus)
Computer-calculated representation of a process, device, or concept in mathematical form. Used for ARIP (impact prediction), automatic rocket impact predictors, computer simulation, and IP (impact prediction).
computing efficiency
   (NASA SP-7, 1965)
Of a computer, the percentage of the successful computation time during a defined period to the total time in that period. Also called operating ratio.
computing machinery
   (NASA SP-7, 1965)
Machinery which can take in, give out, and store information, and also perform arithmetic and logical operations with the information. Usually called computer.
ComStar C
   (NASA Thesaurus)
The third in a series of Comsat domestic communications satellites launched in a transfer orbit by NASA for COMSAT.
ComStar satellites
   (NASA Thesaurus)
Series of domestic Comsat communication satellites.
concatenate
   (Global Land Information System Glossary - USGS)
In the LAS (Landsat) environment, concatenate is the overlaying of an input image with one image or a series of images using the lines and samples to calculate the projection coordinates in the creation of a mosaicked image.
concatenated codes
   (NASA Thesaurus)
Two or more codes which are encoded and decoded in series.
concentration
   (NASA Thesaurus)
The quantity of a substance contained in a unit quantity of sample.
concentric spheres
   (NASA Thesaurus)
Structures in which the space between the spheres is utilized for experiments involving fluid flow, etc.
conceptual model
   (Glossary of Hydrologic Terms - NOAA)
A model which represents a physical process such as accumulation and ablation of a snowpack with explicit mathematical functions. Each significant physical component is represented separately rather than using a single index to explain several processes.
concrete structures
   (NASA Thesaurus)
Buildings, dams, stadiums, etc., constructed entirely of a mixture of aggregates, water, and Portland cement.
concretes
   (NASA Thesaurus)
Homogeneous mixtures of portland cement, aggregates, and water and which may contain admixtures.
concurrent engineering
   (NASA Thesaurus)
Use of multi-disciplinary teams to perform simultaneous design of products and production processes from conception through disposal.
condensation
   (NASA SP-7, 1965)
1. The physical process by which a vapor becomes a liquid or solid; the opposite of evaporation.
2. Specifically, in meteorology, the transformation from vapor to liquid. See sublimation.
condensation coefficient
   (NASA SP-7, 1965)
The ratio of condensation rate to impingement rate.
condensation funnel
   (Glossary of Weather Terms for Storm Spotters - NOAA)
A funnel-shaped cloud associated with rotation and consisting of condensed water droplets (as opposed to smoke, dust, debris, etc.).
condensation nuclei
   (NASA Thesaurus)
Liquid or solid particles upon which condensation of water begins in the atmosphere.
condensation nucleus
   (NASA SP-7, 1965)
1. A particle, either liquid or solid, upon which condensation of vapor begins.
2. Specifically, in meteorology, a particle upon which condensation of water begins in the atmosphere.
condensation rate
   (NASA SP-7, 1965)
The number per square centimeter per second at which molecules condense on a surface.
condensation shock
   (NASA SP-7, 1965)
= condensation shock wave.
condensation shock wave
   (NASA SP-7, 1965)
A sheet of discontinuity associated with a sudden condensation and fog formation in a field of flow. It occurs, e.g., on a wing, where a rapid drop in pressure causes the temperature to drop considerably below the dew point. Also called condensation shock.
condensation trail
   (NASA SP-7, 1965)
A visible trail of condensed water vapor or ice particles left behind an aircraft, an airfoil, etc. in motion through the air. Also called a contrail or vapor trail.
There are three kinds of condensation trails: the aerodynamic type, caused by reduced pressure of the air in certain areas as it flows past the aircraft; the convection type, caused by the rising of air warmed by an engine; and the engine-exhaust, or exhaust-moisture, type, formed by the ejection of water vapor from an engine into a cold atmosphere.
conductance
   (NASA SP-7, 1965)
1. In electricity, the ratio of the current flowing through an electric circuit to the difference of potential between the ends of the circuit, the reciprocal of resistance. See conductivity.
2. In vacuum systems, the throughput Q under steady-state conservative conditions divided by the measured difference in pressure p between two specified cross sections inside a pumping system:
G = Q/(p1-p2).
conduction
   (NASA Thesaurus / NASA SP-7, 1965)
The transfer of energy within and through a conductor by means of internal particle or molecular activity and without any net external motion.
Conduction is to be distinguished from convection (of heat) and radiation (of all electromagnetic energy).
conduction band
   (NASA Thesaurus / NASA SP-7, 1965)
A range of states in the energy spectrum of a solid in which electrons can move freely.
conductive equilibrium
   (NASA SP-7, 1965)
= isothermal equilibrium.
conductivity
   (NASA Thesaurus / NASA SP-7, 1965)
1. The ability to transmit, as electricity, heat, sound, etc.
2. A unit measure of electrical conduction; the facility with which a substance conducts electricity, as represented by the current density per unit electrical-potential gradient in the direction of flow.
Electrical conductivity is the reciprocal of electrical resistivity and is expressed in units such as mhos (reciprocal ohms) per centimeter. It is an intrinsic property of a given type of material under given physical conditions (dependent mostly upon temperature). Conductance, on the other hand, varies with the dimensions of the conducting system, and is the reciprocal of the electrical resistance.
conductor
   (NASA SP-7, 1965)
A substance or entity which transmits electricity, heat, sound, etc.
conductors
   (NASA Thesaurus)
Substances or entities which transmit electricity, heat, or sound. Used for conducting media.
cone
   (NASA SP-7, 1965)
1. A geometric configuration having a circular bottom and sides tapering off to an apex (as in nose cone).
2. A type of light-sensitive cell in the retina. Cones are involved in color vision, high visual acuity, and photopic vision.
cone of depression
   (Glossary of Hydrologic Terms - NOAA)
The depression, roughly conical in shape, produced in a water table, or other piezometric surface, by the extraction of water from a well at a given rate. The volume of the cone will vary with the rate of withdrawal of water. Also called the cone of influence.
cone of escape
   (NASA SP-7, 1965)
A hypothetical cone in the exosphere, directed vertically upward, through which an atom or molecule would theoretically be able to pass to outer space without a collision, that is, in which the mean free path is infinite. See fringe region.
Such a cone would open wider with increasing altitude above the critical level of escape, and would be nonexistent below the critical level of escape.
cone of influence
   (Glossary of Hydrologic Terms - NOAA)
The depression, roughly conical in shape, produced in a water table, or other piezometric surface, by the extraction of water from a well at a given rate. The volume of the cone will vary with rate of withdrawal of water. Also called the cone of depression.
cones
   (NASA Thesaurus)
Geometric configurations having a circular bottom and sides tapering off to an apex (as in nose cones). Used for conical flare and fusiform shapes.
confidence interval
   (NASA SP-7, 1965)
In statistics, a range of values which is believed to include, with a preassigned degree of confidence (confidence level), the true characteristic of the lot or universe a given percentage of the time.
For example: 95-percent confidence limits for a sample of 10 with a ratio of successes to total number tested of 0.9 (9 successes and 1 failure) would be 0.54 to 1.0. That is, even with an observed success ratio of 0.9 (90 percent) the best that can be said is that the true ratio lies between 0.54 (54 percent) and 1.0 (100 percent) an estimated 95 percent of the time.
confidence level
   (NASA SP-7, 1965)
In statistics, the degree of desired trust or assurance in a given result.
A confidence level is always associated with some assertion and measures the probability that a given assertion is true. For example, it could be the probability that a particular characteristic will fall within specified limits, i.e., the chance that the true value of P lies between P = a and P = b. See confidence interval.
confidence limits
   (NASA Thesaurus / NASA SP-7, 1965)
In statistics, the upper and lower extremes of the confidence interval.
configuration
   (NASA SP-7, 1965)
1. Relative position or disposition of various things, or the figure or pattern so formed.
2. A geometric figure, usually consisting principally of points and connecting lines.
3. = planetary configuration.
4. A particular type of a specific aircraft, rocket, etc., which differs from others of the same model by virtue of the arrangement of its components or by the addition or omission of auxiliary equipment as long-range configuration, cargo configuration.
Some writers use constellation as a synonym for configuration in referring to the relative positions of spacecraft to each other, as in a rendezvous maneuver, or to celestial bodies. This usage should be discouraged.
configuration interaction
   (NASA Thesaurus)
In physical chemistry, the interaction between two different possible arrangements of the electrons in an atom or molecule.
configuration management
   (NASA Thesaurus)
A discipline applying technical and administrative direction and surveillance to: identify and document the functional and physical characteristics of a configuration item, control changes to those characteristics, record and report change processing and implementation status, and verify conformance with specified requirements.
confined groundwater
   (Glossary of Hydrologic Terms - NOAA)
Groundwater held under an aquiclude or an aquifuge called artesian if the pressure is positive.
confinement
   (Plasma Physics and Fusion Energy Glossary)
Plasma confinement in which particle and energy transport occurs via classical diffusion; best possible case for magnetically confined plasmas.
confluence
   (Glossary of Weather Terms for Storm Spotters - NOAA)
A pattern of wind flow in which air flows inward toward an axis oriented parallel to the general direction of flow. It is the opposite of difluence.
confluence
   (NASA SP-7, 1965)
The rate at which adjacent flow is converging along an axis oriented normal to the flow at the point in question. It is the opposite of difluence. Compare convergence.
conformal
   (NASA SP-7, 1965)
Having correct angular representation.
conic
   (NASA SP-7, 1965)
1. A curve formed by the intersection of a plane and a right circular cone. Originally called conic section.
The conic sections are the ellipse, the parabola, and the hyperbola, curves that are used to describe the path or bodies moving in space. The circle is a special case of the ellipse, an ellipse with an eccentricity of zero.
The conic is the locus of all points the ratio of whose distances from a fixed point, called the
focus, and a fixed line, called the directrix, is constant.
2. In reference to satellite orbital parameters, without consideration of the perturbing effects of the actual shape or distribution of mass of the primary.
Thus, conic perigee is the perigee the satellite would have if all the mass of the primary were concentrated at its center.
conic section
   (NASA SP-7, 1965)
The original name for conic.
conic sections
   (From Stargazers to Starships Glossary - GSFC)
The family of curves generated by planes intersecting with a cone. Several cases are distinguished, depending on the angle between the plane and the axis of the cone. Precise definitions exist for each, but in general terms, when the plane is perpendicular to the axis, the curve is a circle, when the plane is moderately inclined to the axis, the curve is an ellipse, when the plane is parallel to one of the straight lines which generate the cone, the curve is a parabola, and when the plane is even more steeply inclined, the curve is a hyperbola.
conical beam
   (NASA SP-7, 1965)
The radar beam produced by conical scanning methods.
This type of beam has an advantage over that produced by a single radiating element placed at the focus of a parabolic reflector in that much greater angular accuracy is possible in locating targets.
conical scanning
   (NASA Thesaurus / NASA SP-7, 1965)
Scanning in which the direction of maximum radiation generates a cone whose vertex angle is of the order of the beam width. Such scanning may be either rotating or nutating, according as the direction of polarization rotates or remains unchanged.
conjugate gradient method
   (NASA Thesaurus)
An interactive method for solving a system of linear equations of dimension N which terminates in at most N steps if no rounding errors are encountered. Each iterate will bring one closer to the solution.
conjugated circuits
   (NASA Thesaurus)
Branches of an electrical network configured so that a change in the electromotive force in either branch does not result in a current change in the other.
conjunction
   (NASA SP-7, 1965)
1. The situation of two celestial bodies having either the same celestial longitude or the same sidereal hour angle. Compare opposition, quadrature.
A planet is at superior conjunction if the sun is between it and the earth; at inferior conjunction if it is between the sun and the earth.
2. The time at which conjunction, as defined in sense 1, takes place.
conservation of angular momentum
   (NASA SP-7, 1965)
The principle that absolute angular momentum is a property which cannot be created or destroyed by can only be transferred from one physical system to another through the agency of a net torque on the system. As a consequence, the absolute angular momentum of an isolated physical system remains constant.
The principle of conservation of angular momentum can be derived from the Newton second law of motion.
conservation of energy
   (NASA SP-7, 1965)
The principle that the total energy of an isolated system remains constant if no interconversion of mass and energy takes place.
This principle takes into account all forms of energy in the system; if therefore provides a constraint on the conversions from one form to another. See energy equation.
conservation of mass
   (NASA SP-7, 1965)
The principle in Newtonian mechanics which states that mass cannot be created or destroyed but only transferred from one volume to another. See continuity equation.
conservation of momentum
   (From Stargazers to Starships Glossary - GSFC)
A fundamental law of motion which states that in a system of bodies, the sum of all momenta cannot change due to any internal interactions.
conservation of momentum
   (NASA SP-7, 1965)
The principle that in the absence of forces absolute momentum is a property which cannot be created or destroyed. See Newton laws of motion.
conservation storage
   (Glossary of Hydrologic Terms - NOAA)
Storage of water for later release for usual purposes such as municipal water supply, power, or irrigation in contrast with storage capacity used for flood control.
consistency
   (NASA Thesaurus)
A property of a material determined by the complete flow force relation.
console
   (NASA SP-7, 1965)
An array of controls and indicators for the monitoring and control of a particular sequence of actions, as in the checkout of a rocket, a countdown action or a launch procedure.
A console is usually designed around desk-like arrays. It permits the operator to monitor and control different activating instruments, data recording instruments, or event sequences.
consoles
   (NASA Thesaurus)
Arrays of controls and indicators for the monitoring and control of a particular sequence of actions, as in the checkout of a rocket, a countdown action, or a launch procedure.
consolidated ice cover
   (Glossary of Hydrologic Terms - NOAA)
Ice cover formed by the packing and freezing together of floes, brash ice and other forms of floating ice.
constant of aberration
   (NASA SP-7, 1965)
The maximum aberration of a star observed from the surface of the earth, 20.49 seconds of arc.
The maximum occurs at the time the direction of motion of the earth in its orbit is at right angles to a line from the earth to the star.
constant of gravitation
   (NASA SP-7, 1965)
= Newtonian universal constant of gravitation.
constant of nutation
   (NASA SP-7, 1965)
See nutation, note.
constant-level balloon
   (NASA SP-7, 1965)
A balloon designed to float at a constant-pressure level. Also called constant-pressure balloon. See skyhook balloon.
In one design for such a system, a pressure switch actuates a valve which controls the release of ballast so as to maintain flight above a selected pressure level until the supply of ballast is exhausted.
Another design is a simple nonextensible envelope capable of withstanding a differential of pressure, higher inside than out. It is inflated so that the smaller night-time pressure of the gas still fully extends the envelope. Such a superpressure
balloon will keep essentially constant level until enough gas diffuses out of it to allow diurnal changes in volumes.
constant-pressure balloon
   (NASA SP-7, 1965)
= constant-level balloon.
constellation
   (NASA Thesaurus / NASA SP-7, 1965)
Originally a conspicuous configuration of stars; now a region of the celestial sphere marked by arbitrary boundary lines.
The genitive form of constellation names is used in star names and numbers such as Bayer name and Flamsteed number. Table V lists the constellations.
constituent day
   (NASA SP-7, 1965)
The duration of one rotation of the earth on its axis, with respect to an astre fictif, a fictitious star representing one of the periodic elements in the tidal forces. It approximates the length of a lunar or solar day.
construction weight
   (NASA SP-7, 1965)
The weight of a rocket exclusive of propellant, load, and crew, if any. Also called structural weight.
consumables (spacecraft)
   (NASA Thesaurus)
All supplies for spacecraft and spacecrews that will be consumed during a mission.
contact loads
   (NASA Thesaurus)
Dynamic loading by contact between two bodies.
contact potentials
   (NASA Thesaurus)
The potential differences at the junctions of two dissimilar substances.
contact resistance
   (NASA Thesaurus)
The resistance to current flow between two touching bodies, consisting of constriction resistance and film resistance.
containers
   (NASA Thesaurus)
A non-specific term for receptacles capable of closure. Used for receptacles (containers).
containment vessel
   (Plasma Physics and Fusion Energy Glossary)
Gas-tight shell or other enclosure around a fusion (or fission) reactor, to prevent accidental leakage of radioactive contents.
content-addressable memory
   (NASA Thesaurus)
See associative memory.
context
   (NASA Thesaurus)
The composition, structure, or manner in which something is put together. Also refers to the situation or environment of an event.
continental shelves
   (NASA Thesaurus)
The ocean floor that is between the shoreline and the abyssal ocean floor, including various provinces; the continental shelf; continental borderland; continental slope; and the continental rise. Used for continental margins.
continuity equation
   (NASA SP-7, 1965)
In a steady-flow process, the mathematical statement of the principle of the conservation of mass by equating the flow at any section x, wx to the flow at any section y, or wx= wy.
continuous absorption
   (NASA SP-7, 1965)
See absorption spectrum.
continuous spectra
   (NASA Thesaurus)
Spectra in which wavelengths, wave numbers, and frequencies are represented by the continuum of real numbers or a portion thereof, rather than by a discrete sequence of numbers. For electromagnetic radiation, spectra that exhibit no detailed structure and represent a gradual variation of intensity with wavelength from one end to the other, as the spectra of incandescent solids. For particles, spectra that exhibit a continuous variation of the momentum or energy.
continuous spectrum
   (NASA SP-7, 1965)
1. A spectrum in which wavelengths, wave numbers, and frequencies are represented by the continuum of real numbers or a portion thereof, rather than by a discrete sequence of numbers. See discrete spectrum.
2. For electromagnetic radiation, a spectrum that exhibits no detailed structure and represents a gradual variation of intensity with wavelength from one end to the other, as the spectrum from an incandescent solid. Also called continuum, continuum radiation.
3. For particles, a spectrum that exhibits a continuous variation of the momentum or energy.
continuous variable
   (NASA SP-7, 1965)
A variable which can assume any value within a defined range.
continuous waves
   (NASA SP-7, 1965)
(abbr CW)
Waves, the successive oscillations of which are identical under steady-state conditions.
continuous-flow system
   (NASA SP-7, 1965)
An oxygen system in which the oxygen flows during both inspiration and expiration by the individual.
continuous-wave radar
   (NASA SP-7, 1965)
A general species of radar transmitting continuous waves, either modulated or unmodulated. The simplest form transmits a single frequency and detects only moving targets by the Doppler effect. This type of radar determines direction but usually not range. Also called CW radar. Compare pulse radar.
Two advantages of CW radar are the narrow bandwidth and low power required. Range information may be obtained by some form of modulation, e.g., frequency modulation, pulse modulation.
continuum
   (NASA Thesaurus / NASA SP-7, 1965)
1. Something which is continuous, which has no discrete parts, as the continuum of real numbers as opposed to the sequence of discrete integers, as the background continuum of a spectrogram due to thermal radiation.
2. = continuous spectrum.
continuum flow
   (NASA SP-7, 1965)
See rarefied gas dynamics.
continuum radiation
   (NASA SP-7, 1965)
= continuous spectrum.
contour
   (Global Land Information System Glossary - USGS)
Imaginary line on the ground, all points of which are at the same elevation above or below a specified datum.
contour sensors
   (NASA Thesaurus)
The sensing of image coincidences by means of optical processing techniques.
contrail
   (NASA SP-7, 1965)
= condensation trail.
contrails
   (NASA Thesaurus)
Condensation trails. Artificial clouds made by the exhaust of jet aircraft.
contrarotating propellers
   (NASA Thesaurus)
Two propellers mounted on concentric shafts having a common drive and rotating in opposite directions.
contrast
   (NASA Thesaurus / NASA SP-7, 1965)
1. In general, the degree of differentiation between different tones in an image.
Where the degree is slight, the image is said to be flat. Where the difference is marked, it is said to be contrasty.
2. The difference in luminance between two portions of the visual field usually expressed as:

c = (background - test field)/background * 100%


Since this ratio can be negative for nearly black targets at close range, and since the sign of the contrast has no psycho-physical significance, it is conventional to use only its absolute value. See threshold contrast.
contrast threshold
   (NASA SP-7, 1965)
= threshold contrast.
contravane
   (NASA SP-7, 1965)
A vane that reverses or neutralizes rotation of a flow. Also called a countervane.
control
   (NASA SP-7, 1965)
1. A lever, switch, cable, knob, push-button, or other device or apparatus by means of which direction, regulation, or restraint is exercised over something.
2. In plural (a) A system or assembly of levers, gears, wheels, cables, boosters, valves, etc., used to control the attitude, direction movement, power, and speed of an aircraft, rocket spacecraft, etc. (b) Control surfaces or devices.
3. Sometimes capitalized. An activity or organization that directs or regulates an activity. See central control.
4. Specifically, to direct the movements of an aircraft or rocket with particular references to changes in attitude and speed. Compare guidance.
control feel
   (NASA SP-7, 1965)
The impression of the stability and control of an aircraft that a pilot receives through the cockpit controls, either from the aerodynamic forces acting on the control surfaces or from forces simulating these aerodynamic forces. See artificial feel, feel.
control points
   (Glossary of Hydrologic Terms - NOAA)
Small monuments securely embedded in the surface of the dam. Any movement of the monument indicates a movement in the dam itself. Movements in the dam are detected by comparing control points location to location of fixed monuments located off the dam using accurate survey techniques.
control rocket
   (NASA Thesaurus / NASA SP-7, 1965)
A vernier engine, retro-rocket, or other such rocket, used to change the attitude of, guide, or make small changes in the speed of a rocket, spacecraft, or the like.
control unit
   (NASA SP-7, 1965)
The part of a computer which causes the arithmetic unit, storage, and transfer of a computer to operate in proper sequence.
control units (computers)
   (NASA Thesaurus)
Those parts of computers that cause the arithmetic unit, storage, and transfer of a computer to operate in proper sequence.
control vane
   (NASA SP-7, 1965)
A movable vane used for control, especially a movable air vane or jet vane on a rocket, used to control flight attitude.
controllability
   (NASA Thesaurus / NASA SP-7, 1965)
The capability of an aircraft, rocket, or other vehicle to respond to control, especially in direction or attitude.
controlled environment
   (NASA SP-7, 1965)
The environment of any object, such as an instrument, a man, or an unlaunched rocket, in which effects such as humidity, pressure, temperature, etc., are maintained at predetermined levels.
controlled fusion
   (Plasma Physics and Fusion Energy Glossary)
Controlled Thermonuclear Fusion: The process in which light nuclei, heated to a high temperature in a confined region, undergo fusion reactions under controlled conditions, with associated release of energy which may be harnessed for useful purposes.
controlled-leakage system
   (NASA SP-7, 1965)
A system that provides for the maintenance of life in an aircraft or spacecraft cabin by a controlled escape of carbon dioxide and other waste from the cabin, with replenishment provided by stored oxygen and food. Compare closed ecological system.
convection
   (NASA Thesaurus / NASA SP-7, 1965)
1. In general, mass motions within a fluid resulting in transport and mixing of the properties of that fluid. Compare conduction, radiation.
2. Specifically, in meteorology, atmospheric motions that are predominantly vertical. Compare advection.
convection
   (AS&T Dictionary)
In meteorology, the term is used specifically to describe vertical transport of heat and moisture, especially by updrafts and downdrafts in an unstable atmosphere.
convection
   (Galileo Project Glossary - JPL)
The transfer of heat from a region of high temperature to a region of lower temperature by the displacement of the cooler molecules by the warmer molecules.
convection zone
   (SOHO Glossary - GSFC)
A layer in a star in which convection currents are the main mechanism by which energy is transported outward. In the Sun, a convection zone extends from just below the photosphere to about seventy percent of the solar radius.
convection-diffusion equation
   (NASA Thesaurus)
An equation for convection and diffusion, in which the rate of change with respect to time of the density (concentration) of the convecting/diffusing substance at a fixed point in space plus the product of the divergence of the velocity field and the density of the convecting/diffusing substance equals the product of the diffusion coefficient and the differential of the density of the convecting/diffusing substance.
convective atmosphere
   (NASA SP-7, 1965)
= adiabatic atmosphere.
convergence
   (Glossary of Weather Terms for Storm Spotters - NOAA)
A contraction of a vector field; the opposite of divergence. Convergence in a horizontal wind field indicates that more air is entering a given area than is leaving at that level. To compensate for the resulting "excess," vertical motion may result: upward forcing if convergence is at low levels, or downward forcing (subsidence) if convergence is at high levels. Upward forcing from low-level convergence increases the potential for thunderstorm development (when other factors, such as instability, are favorable).
convergence
   (NASA Thesaurus)
Approach to a limit, e.g., by an infinite sequence.
convergence
   (NASA SP-7, 1965)
1. The contraction of a vector field; also, a precise measure thereof. Compare confluence.
Mathematically, convergence is negative divergence, and the latter term is used for both. (For mathematical treatment, see divergence.)
2. The property of a sequence or series of numbers or functions which ensures that it will approach a definite finite limit.
A series representation of a mathematical function exhibits convergence if the sum of the terms of the series approaches the value of the function more closely as more terms of the series are taken, the two agreeing in the limit of an infinite number of terms.
3. Decrease in area or volume.
conversion device
   (NASA SP-7, 1965)
In computer terminology, any device for changing the manner of representing information. Also called a converter.
convert
   (NASA SP-7, 1965)
In computer terminology, (a) to change the manner of representing information, e.g., from analog to digital; (b) to translate the medium of conveying or storing information, e.g., from punched cards to magnetic tape; (c) to change numeric information from one notation to another.
converter
   (NASA SP-7, 1965)
1. A rotary device for changing alternating current to direct current.
A static device for this purpose is called a rectifier. A device for changing direct current to alternating current is called an inverter.
2. A transducer whose output is a different frequency from its input.
3. In computer terminology = conversion device.
converters
   (NASA Thesaurus)
Rotary devices for changing alternating current to direct current. Transducers whose output is a different frequency from its input.
convertiplane
   (NASA SP-7, 1965)
A hybrid form of heavier-than-air aircraft that is capable, by virtue of one or more horizontal rotors or units acting as rotors, of taking off, hovering, and landing as, or in a fashion similar to, a helicopter, and once aloft, and moving forward, capable, by means of a mechanical conversion of one sort or another, of flying purely as a fixed-wing aircraft, especially in its higher speed ranges.
coolant
   (NASA SP-7, 1965)
( symbol c used as subscript )
A liquid or gas used to cool something, as a rocket combustion chamber.
This word is used in many self-explanatory compounds, which include: coolant chamber, coolant gallery, coolant hose, coolant jacket, coolant passage, coolant pump, coolant radiator.
coolants
   (NASA Thesaurus)
Liquids of gases used to cool something, as a rocket combustion chamber.
cooled-tube pyrometer
   (NASA SP-7, 1965)
A thermometer for high-temperature flowing gases that uses a liquid-cooled tube inserted in the flowing gas; gas temperature is deduced from the law of convective heat transfer to the outside of the tube and from measurement of the mass flow rate and temperature rise of the cooling liquid.
cooler
   (NASA SP-7, 1965)
See radiator, note.
cooling power
   (NASA SP-7, 1965)
In the study of human bioclimatology, one of several parameters devised to measure the air's cooling effect upon a human body.
cooperative observer
   (Glossary of Hydrologic Terms - NOAA)
An individual (or institution) who takes precipitation and temperature observations -- and in some cases other observations such as river stage, soil temperature, and evaporation -- at or near their home, or place of business. Many observers transmit their reports by touch-tone telephone to an NWS computer, and nearly all observers mail monthly reports to the National Climatic Data Center to be archived and published.
coordinate
   (NASA SP-7, 1965)
One of a set of measures defining a point in space.
If the point is know to be on a given line, only one coordinate is needed; if on a surface, two are required; if in space, three. Cartesian coordinates define a point relative to two intersecting lines, called axes. If the axes are perpendicular, the coordinates are rectangular; if not perpendicular, they are oblique coordinates. A three-dimensional system of Cartesian coordinates is called space coordinates. Polar coordinates define a point by its distance and direction from a fixed point called the pole. Direction is given as the angle between a reference radius vector and a radius vector to the point. If three dimensions are involved, two angles are used to locate the radius vector. Space-polar coordinates define a point on the surface of a sphere by (1) its distance from a fixed point at the center, the pole; (2) the colatitude or angle between the polar axis (a reference line through the pole) and the radius vector (a straight line connecting the pole and the point); and (3) the longitude or angle between a reference plane through the polar axis and a plane through the radius vector and the polar axis. Spherical coordinates define a point on a sphere or spheroid by its angular distances from a primary great circle and from a reference secondary great circle. Geographical or terrestrial coordinates define a point on the surface of the earth. Celestial coordinates define a point on the celestial sphere.
Table VI summarizes the terms used in four geocentric celestial coordinate systems and the terrestrial (geographic) coordinate system and indicates the analogous terms under each system.
coordinate axes
   (NASA SP-7, 1965)
See Cartesian coordinates.
coordinate line
   (NASA SP-7, 1965)
See curvilinear coordinates.
coordinate planes
   (NASA SP-7, 1965)
See Cartesian coordinates.
coordinate surface
   (NASA SP-7, 1965)
See curvilinear coordinates.
coordinate system
   (NASA SP-7, 1965)
Any scheme for the unique identification of each point of a given continuum. The geometry of the system is a matter of convenience determined by the boundaries of the continuum or by other considerations. Also called reference frame.
coordinates
   (NASA Thesaurus)
Sets of measures defining points in space. Used for axes (coordinates) and coordinate systems.
Copernican system
   (From Stargazers to Starships Glossary - GSFC)
A theory of planetary motions, proposed by the Polish astronomer Copernicus, according to which all planets move in circular orbits around the Sun, with those closer to the Sun moving faster, and with the Earth itself a planet orbiting between Venus and Mars.
copolymers
   (NASA Thesaurus)
Polymers formed from two or more types of monomers.
copy
   (NASA SP-7, 1965)
To reproduce information without changing it.
Cor A
   (NASA SP-7, 1965)
International Astronomical Union abbreviation for Corona Austrina. See constellation.
Cor B
   (NASA SP-7, 1965)
International Astronomical Union abbreviation for Corona Borealis. See constellation.
Cordelia
   (NASA Thesaurus)
A natural satellite of Uranus orbiting at a mean distance of 49,750 kilometers.
core
   (SOHO Glossary - GSFC)
In solar astronomy, the innermost part of the Sun, where energy is generated by nuclear reactions.
coriolis acceleration
   (NASA SP-7, 1965)
An acceleration of a particle moving in a relative coordinate system. The total acceleration of the particle, as measured in an inertial coordinate system, may be expressed as the sum of the acceleration within the relative system, the acceleration of the relative system itself, and the coriolis acceleration.
Physically, coriolis acceleration may be considered as coming from the conservation of momentum in a body moving in a direction not parallel to the axis of rotation of the relative system.
Mathematically, coriolis acceleration comes from the differentiation of terms containing the angular velocity in the expression for the absolute velocity of the particle.
In the case of the earth, moving with angular velocity , a particle moving relative to the earth with velocity v has the coriolis acceleration 2 * v. If Newton laws are to be applied in the relative system, the coriolis acceleration and the acceleration of the relative system must be treated as forces. See apparent force, coriolis force, inertial force, gravity.
coriolis correction
   (NASA SP-7, 1965)
A correction applied to an assumed position, celestial line of position, celestial fix, or to a computed or observed altitude to allow for apparent acceleration due to coriolis acceleration.
Coriolis effect
   (NASA Thesaurus)
The physiological effect felt by a person moving radially in a rotating system, as a rotating space station resulting in nausea, vertigo, dizziness, etc. Named after Gaspard G. Coriolis (d 1843), French civil engineer.
coriolis effects
   (NASA SP-7, 1965)
The physiological effects (nausea, vertigo, dizziness, etc.) felt by a person moving radially in a rotating system, as a rotating space station.
Coriolis force
   (From Stargazers to Starships Glossary - GSFC)
In meteorology, a force which must be included in the calculation of motion in a rotating frame of reference, if the body moves in such a way that its rotation velocity changes. In general, it tends to preserve that part of its velocity. The Coriolis force is responsible for the swirling of hurricanes and large weather systems--for air flowing into a region of low pressure, counterclockwise north of the equator, clockwise south of the equator.
coriolis force
   (NASA SP-7, 1965)
An inertial force on a moving body, or particles, produced by the movement of the masses involved, perpendicular to the axis of the primary rotating system. Also called compound centrifugal force, deflecting force. See inertial force, coriolis acceleration.
Such a force is required if Newton Laws are to be applied in the system.
coriolis parameter
   (NASA SP-7, 1965)
Twice the component of the earth's angular velocity about the local vertical, 2 lower case omega sin lower case phi, where lower case omega is the angular speed of the earth and lower case phi is the latitude.
corner reflector
   (NASA SP-7, 1965)
In radar, three conducting surfaces mutually intersecting at right angles designed to return electromagnetic radiations toward their sources and used to render a position more conspicuous to radar observations.
corona
   (From Stargazers to Starships Glossary - GSFC)
The outermost layer of the Sun´s atmosphere, visible to the eye during a total solar eclipse; it can also be observed through special filters and best of all, by X-ray cameras aboard satellites. The corona is very hot, up to 1-1.5 million degrees centigrade, and is the source of the solar wind
corona
   (High Energy Astrophysics Dictionary- GSFC)
The uppermost level of the solar atmosphere, characterized by low densities and high temperatures (> 1,000,000 degrees K).
corona
   (NASA SP-7, 1965)
1. The outer visible envelope of the sun. Also called solar corona.
It is observed at solar eclipse or with the coronagraph. The shape of the corona varies during the sunspot cycle. At sunspot minimum the corona has large extensions along the sun's equator, with short brushlike tufts near the poles. At sunspot maximum the equatorial extensions are much smaller and the corona is more regular in shape. The temperature of the corona appears to be in the vicinity of 1,000,000° K.
2. The extremely tenuous outer atmosphere of the sun now known to extend past the earth's orbit.
3. A set of one or more prismatically colored rings of small radii, concentrically surrounding the disk of the sun, moon, or other luminary when veiled by a thin cloud.
The corona is due to diffraction by numerous water drops. It can be distinguished from the relatively common halo of 22° by the much smaller angular diameter of the corona, which is often only a few degrees, and by its color sequence, which is from blue inside to red outside, the reverse of that in the 22° halo.
4. See corona discharge.
5. See aurora.
6. See geocorona.
Corona Australis
   (NASA SP-7, 1965)
= Corona Austrina
Corona Borealis
   (NASA SP-7, 1965)
(abbr CrB, Cor B)
See constellation.
corona discharge
   (NASA SP-7, 1965)
A luminous, and often audible, electric discharge the is intermediate in nature between a spark discharge (with, usually, its single discharge channel) and a point discharge (with its diffuse, quiescent, and nonluminous character). Also called brush discharge, St. Elmo's fire, corposant.
coronagraph
   (NASA SP-7, 1965)
An instrument for photographing the corona and prominences of the sun at times other than at solar eclipse. An occulting disk is used to block out the image of the body of the sun in the focal plane of the objective lens. The light of the corona passes the occulting disk and is focused on a photographic film.
Great care must be taken to avoid light scattered from the atmosphere and the lenses, and from reflections in the tube of the instrument. The coronograph is used with a narrow-band polarizing filter or with a spectroscope.
coronagraphs
   (SOHO Glossary - GSFC)
Telescope for observing the corona. Often contains an occulting disk which covers the disk of the Sun so that the corona may be more easily observed.
coronal holes
   (NASA Thesaurus)
Solar areas where exteme UV and x ray coronal emission is abnormally low or absent. These are coronal regions apparently associated with diverging magnetic fields.
coronal loops
   (NASA Thesaurus)
Loop like structures revealed in soft x ray images of the solar limb and believed to evolve from the introduction of energy and density perturbations at the top of an arched, cylindrical magnetic flux tube initially in equilibrium in the coronal plasma.
coronal mass ejection
   (From Stargazers to Starships Glossary - GSFC)
A huge cloud of hot plasma, occasionally expelled from the Sun. It may accelerate ions and electrons and may travel through interplanetary space as far as the Earth´s orbit and beyond it, often preceded by a shock front. When the shock reaches Earth, a magnetic storm may result.
coronal streamer
   (SOHO Glossary - GSFC)
large scale magnetic structures observed in the Sun's corona.
corposant
   (NASA SP-7, 1965)
= corona discharge.
corpuscular
   (NASA SP-7, 1965)
Consisting of particles, specifically atomic particles.
corpuscular cosmic rays
   (NASA SP-7, 1965)
Primary cosmic rays from outer space which consist mainly of protons with energies of 2-20 billion electron volts (Bev).
For 1000 protons there are about 80 helium nuclei, about 3 nuclei in the carbon-nitrogen-oxygen range, and 1 or 2 heavier nuclei. The proton energy may be as high as 105 Bev, and the other nuclei show an energy distribution similar to that of the protons.
corpuscular radiation
   (NASA Thesaurus)
Nonelectromagnetic radiation consisting of energetic charged or neutral particles. Used for penetrating particles.
corpuscular theory of light
   (NASA SP-7, 1965)
The hypothesis, by Sir Isaac Newton, that light consists of a stream of minute particles emitted by luminous bodies at very high velocities, and that the sensation of light, is due to the bombardment of the retina of the eye by these particles.
Although this theory was later replaced by the wave theory of light, the concept of photons in the modern quantum theory is reminiscent of Newton theory.
correction
   (NASA Thesaurus / NASA SP-7, 1965)
A quantity, equal in absolute magnitude to the error, added to a calculated or observed value to obtain the true value.
correlation
   (NASA Thesaurus / NASA SP-7, 1965)
1. In statistics, a relationship between two occurrences which is expressed as number between minus one (-1) and plus one (+1).
2. When used without further qualification, the statistical term correlation usually refers to simple, linear correlation between two variables x and y and is measured by the product-moment coefficient of correlation rho or its sample estimate r defined as follows, where the respective population mean values of x and y are denoted by xi and zeta, the respective standard deviations by sigma( x ) and sigma( y ), and where E is the expected value:
 

rho equals E open bracket open parens chi minus xi close parens open parens gamma minus zeta close parens close bracket over sigma of chi sigma of gamma

r equals summation symbol open parens x sub i minus x bar close parens open parens y sub I minus y bar close parens over square root of summation symbol open parens x sub i minus x bar close parens squared summation symbol open parens y sub i minus y bar close parens squared

The product-moment E[(x - xi)(y - zeta)] is usually called the covariance of x and y. See autocorrelation, partial correlation.
In connection with correlation, the word simple is used in contradistinction to other qualifiers such as multiple or partial. The word linear refers to a linear relationship between the two variables, or more precisely, to a linear approximation of the regression function of either variable with respect to the other.

correlation coefficient
   (NASA SP-7, 1965)
1. See correlation, sense 2.
2. A measure of the persistence of eddy velocity as a function of time and space.
correlation detection
   (NASA Thesaurus / NASA SP-7, 1965)
A method of detection in which a signal is compared, point-to-point, with an internally generated reference. Also called cross correlation detection.
The output of such a detector is a measure of the degree of similarity of the input and reference signals. The reference signal is constructed in such a way that it is at all times a prediction, or best guess, of what the input signal should be at that time.
correlation tracking and ranging
   (NASA SP-7, 1965)
(abbr Cotar)
A nonambiguous trajectory-measuring system using short-baseline, single-station, continuous-wave phase-comparison measuring two direction cosines and a slant range.
correlation tracking and triangulation
   (NASA SP-7, 1965)
(abbr Cotat)
A trajectory measuring system composed of several antenna baselines, each separated by large distances, used to measure direction cosines to an object.
From these measurements its space position is computed by triangulation.
correlation tracking system
   (NASA SP-7, 1965)
A trajectory measuring system utilizing correlation techniques where signals derived from the same source are correlated to derive the phase difference between the signals. This phase difference contains the system data.
correlators
   (NASA Thesaurus)
Devices that detect weak signals in noise by performing an electronic operation. Used for synchronous detectors.
corrosion
   (NASA Thesaurus / NASA SP-7, 1965)
The deterioration of a metal by chemical or electrochemical reaction with its environment.
Corv
   (NASA SP-7, 1965)
International Astronomical Union abbreviation for Corvus. See constellation.
Corvus
   (NASA SP-7, 1965)
(abbr Crv, Corv)
See constellation.
cosine law of illumination
   (NASA SP-7, 1965)
A purely geometric relationship between the illuminance of a surface and the angle of incidence of the illuminating rays. Mathematically, the illuminance I of the surface illuminated by a beam of flux density F incident at angle theta is I = F cos theta
The marked latitudinal variation in insolation on the earth is largely a consequence of this simple relationship. Compare Lambert law.
cosmic
   (NASA SP-7, 1965)
Of or pertaining to the universe, especially that part of it outside the earth's atmosphere. Used by the USSR as equivalent to space, as in cosmic rocket, cosmic ship.
Cosmic Background Explorer satellite
   (NASA Thesaurus)
A NASA satellite launched on November 18, 1989 on a Delta I expendable launch vehicle. It is designed to measure backgound radiation in order to confirm or deny the big bang theory. Used for COBE.
cosmic background radiation
   (High Energy Astrophysics Dictionary- GSFC)
The background of radiation mostly in the frequency range 3 × 10[superscript]8 to 3 × 10[superscript]11 Hz discovered in space in 1965. It is believed to be the cosmologically redshifted radiation released by the Big Bang itself
cosmic dust
   (NASA Thesaurus / NASA SP-7, 1965)
Finely divided solid matter with particle sizes smaller than a micrometeorite, thus with diameters much smaller than a millimeter, moving in interplanetary space. See dust.
Cosmic dust in the solar system is thought to be concentrated in the plane of the ecliptic, thus causing the zodiacal light.
cosmic noise
   (NASA Thesaurus / NASA SP-7, 1965)
Interference caused by cosmic radio waves.
cosmic radiation
   (NASA SP-7, 1965)
= cosmic rays.
cosmic radio waves
   (NASA SP-7, 1965)
Radio waves emanating from extraterrestrial sources.
They are galactic radio waves if their origin is within our galaxy and extragalactic radio waves if their origin is outside our galaxy. Solar radio waves emanate from the sun.
cosmic rays
   (NASA Thesaurus / NASA SP-7, 1965)
The aggregate of extremely high energy subatomic particles which travel the solar system and bombard the earth from all directions. Cosmic-ray primaries seem to be mostly protons, hydrogen nuclei, but also contain heavier nuclei. On colliding with atmospheric particles they produce many different kinds of lower energy secondary cosmic radiation (see cascade shower). Also called cosmic radiation.
Cosmic rays thought to originate outside the solar system are called galactic cosmic rays. Those thought to originate in the sun are called solar cosmic rays.
In the earth's atmosphere, the maximum flux of cosmic rays, both primary and secondary, is at an altitude of 20 km, and below this the absorption of the atmosphere reduces the flux, though the rays are still readily detectable at sea level. Intensity of cosmic-ray showers has also been observed to vary with latitude, being more intense at the poles. See cosmic-ray knee, corpuscular cosmic rays.
cosmic-ray burst
   (NASA SP-7, 1965)
An extensive production of ionization from a common origin by cosmic rays in a recording device such as a cloud chamber.
cosmic-ray knee
   (NASA SP-7, 1965)
The point of sudden drop-off in the intensity of recorded cosmic rays at about 40 degrees geomagnetic latitude.
The drop-off is due to the shield effect of the earth's magnetic field.
cosmochemistry
   (NASA Thesaurus)
The branch of chemistry that deals with the chemical composition and changes in the universe.
cosmological constant
   (High Energy Astrophysics Dictionary- GSFC)
The constant introduced to the Einstein field equation, intended to admit static cosmological solutions. At the time the current philosophical view was the steady-state model of the Universe, where the Universe has been around for infinite time. Early analysis of the field equation indicated that general relativity allowed dynamic cosmological models only (ones that are either contracting or expanding), but no static models. Einstein introduced the most natural abberation to the field equation that he could think of: the addition of a term proportional to the spacetime metric tensor, g, with the constant of proportionality being the cosmological constant:

G + Lambda g = 8 pi T.

Hubble's later discovery of the expansion of the Universe indicated that the introduction of the cosmological constant was unnecessary; had Einstein believed what his field equation was telling him, he could have claimed the expansion of the Universe as perhaps the greatest and most convincing prediction of general relativity; he called this the "greatest blunder of my life."

cosmological distance
   (High Energy Astrophysics Dictionary- GSFC)
A distance far beyond the boundaries of our Galaxy. When viewing objects at cosmological distances, the curved nature of spacetime could become apparent. Possible cosmological effects include time dilation and red shift.
cosmological redshift
   (High Energy Astrophysics Dictionary- GSFC)
An effect where light emitted from a distant source appears redshifted because of the expansion of spacetime itself. Compare Doppler effect.
cosmology
   (Imagine the Universe Dictionary - NASA GSFC)
The astrophysical study of the history, structure, and constituent dynamics of the universe.
cosmonaut
   (NASA SP-7, 1965)
A Soviet astronaut, sense 1.
Cosmos 1129 satellite
   (NASA Thesaurus)
Soviet VOSTOK biological spacecraft launched on September 25, 1979 carrying experiments from several nations. NASA contributed 13 experiments.
Cosmos 782 satellite
   (NASA Thesaurus)
One in a series of satellites launched by the USSR reportedly for geophysical observations.
Cosmos 936 satellite
   (NASA Thesaurus)
One in a series of satellites launched by the USSR reportedly for geophysical observations.
Cosmos 954 satellite
   (NASA Thesaurus)
A Russian ocean surveillance satellite which reentered over Canada spreading radioactive debris.
COSPAR (abbr)
   (NASA SP-7, 1965)
= Committee on Space Research, International Council of Scientific Unions.
COSPAS
   (NASA Thesaurus)
The USSR satellite of the COSPAS-SarSat project which is a satellite-aided project for the search and rescue of distressed vehicles, administered by USSR, US, French, and Canadian agencies.
Cotar
   (NASA SP-7, 1965)
= correlation tracking and ranging.
Cotat
   (NASA SP-7, 1965)
= correlation tracking and triangulation.
Couette flow
   (NASA SP-7, 1965)
The shearing flow of a fluid between two parallel surfaces in relative motion. A two-dimensional steady flow without pressure gradient in the direction of flow and caused by the tangential movement of the bounding surfaces. The only practical type is the flow between concentric rotating cylinders (as of the oil in a cylindrical bearing).
coulomb
   (NASA SP-7, 1965)
(abbr C)
The unit of quantity of electricity; the quantity of electricity transported in 1 second by a current of 1 ampere. Expression in terms of SI base units: s * A.

See the WWW version of the National Institute of Standards and Technology: Physics Laboratory's International System of Units (SI)

Coulomb collision
   (NASA Thesaurus / NASA SP-7, 1965)
The collision of two particles both of which are charged.
In this case the collision cross section is considerably larger than when one of the particles is neutral because the electric field of the two particles can interact at much larger distances. Since the collisions are distant ones, however, the particles will suffer only a small angular deviation.
Coulomb damping
   (NASA SP-7, 1965)
The dissipation of energy that occurs when a particle in a vibrating system is resisted by a force whose magnitude is a constant independent of displacement and velocity, and whose direction is opposite to the direction of the velocity of the particle. Also called dry friction damping.
Coulomb ionization
   (Plasma Physics and Fusion Energy Glossary)
Ionization produced by Coulomb forces between a moving particle ("projectile") and another particle it interacts/collides with ("target").
Coulomb's law
   (Plasma Physics and Fusion Energy Glossary)
Force law governing the electrical interaction between charged particles. Force is proportional to (charge of first particle) * (charge of second particle) / (square of separation between particles).
coulometers
   (NASA Thesaurus)
Electrolytic cells or electronic devices arranged to measure the quantity of electricity by the chemical action produced in accordance with Faraday's law.
count
   (NASA SP-7, 1965)
1. To proceed from one point to another in a countdown or plus count, normally by calling a number to signify the point reached; to proceed in a countdown, as in T minus 90 and counting. Compare hold.
2. In radiation counters, a single response of the counting system.
countdown
   (NASA Thesaurus / NASA SP-7, 1965)
1. A step-by-step process that culminates in a climactic event, each step being performed in accordance with a schedule marked by a count in inverse numerical order; specifically, this process is used in leading up to the launch of a large or complicated rocket vehicle, or in leading up to a captive test, a readiness firing, a mock firing, or other firing test.
2. The act of counting inversely during this process.
In sense 2, the countdown ends with T-time; thus, T minus 60 minutes indicates there are 60 minutes to go, excepting for holds and recycling. The countdown may by hours, minutes, or seconds. At the end, it narrows down to seconds, 4-3-2-1-0. See plus count.
counter
   (NASA SP-7, 1965)

A device capable of changing from one to the next of a sequence of distinguishable states upon each receipt of an input signal. Also called accumulator.
counter rotation
   (NASA Thesaurus)
Movement of sets of bodies or fluids around a common axis where movement in own rotational direction is opposed by movement in the opposite direction.
counterclockwise polarized wave
   (NASA SP-7, 1965)
= left-handed polarized wave.
counterglow
   (NASA SP-7, 1965)
= gegenschein.
counterpressure
   (NASA SP-7, 1965)
A pressure applied to the exterior of the human body to counteract a pressure introduced inside during pressure breathing.
counterradiation
   (NASA SP-7, 1965)
The downward flux of atmospheric radiation passing through a given level surface, usually taken as the earth's surface. Also called back radiation.
This result of infrared (long-wave) absorption and reemission by the atmosphere is the principal factor in the greenhouse effect.
countervane
   (NASA SP-7, 1965)
= contravane.
coupled modes
   (NASA Thesaurus / NASA SP-7, 1965)
Modes of vibration that are not independent but which influence one another because of energy transfer from one mode to the other.
coupling
   (NASA Thesaurus / NASA SP-7, 1965)
1. A device or contrivance for joining adjacent ends or parts of anything.
2. A device permitting transfer of energy from one electrical circuit to another, or from one mechanical device to another.
course
   (NASA SP-7, 1965)
1. A predetermined or intended route or direction to be followed, measured with respect to a geographic reference direction; a line on a chart representing a course.
2. A line of flight taken by an aircraft, rocket, etc.
3. A radio beam in a radio range.
course line
   (NASA SP-7, 1965)
1. A line of position plotted on a chart, parallel or substantially parallel to the intended course of a craft, showing whether the craft is to the right or the left of its course.
2. Any line representing a course.
covariance matrix
   (Global Land Information System Glossary - USGS)
A matrix containing the expected values derived from the products of the deviations of pairs of random variables from their means. Covariance measures the extent to which two random numbers vary together (i.e., varying at the same rate in the same direction).
Cowell method
   (NASA SP-7, 1965)
A method of orbit computation using direct step-by-step integration in rectangular coordinates of the total acceleration of the orbiting body.
The Cowell method is a special perturbations method.
cowlings
   (AS&T Dictionary)
A streamlined metal housing or removable covering for an engine, esp. an aircraft or spacecraft engine, often part of or forming a continuous line with the fuselage or wing.
CPES--Control Point Extraction System
   (Global Land Information System Glossary - USGS)
CPES is software used to produce and process a single-band (Band 4) Landsat chip.
CPT--Control Point
   (Global Land Information System Glossary - USGS)
CPTs are features of known ground location that can be accurately located on imagery.
CrA, Cor A
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Corona Australis. See constellation.
Crab nebula
   (From Stargazers to Starships Glossary - GSFC)
A cloud-like nebula observed in the Crab constellation, the remnant of a supernova explosion observed in China in 1054. It contains a very rapidly rotating (and hence, young) pulsar, which is probably the remnant of the supernova. The emissions of radio waves and light from this nebula suggest the presence of high energy particles.
crack bridging
   (NASA Thesaurus)
The occurence of unbroken material grains or reinforcing elements extending across the surfaces of a crack. A common occurrence in fiber composites and some ceramic materials, it contributes to improved crack growth resistance.
crack closure
   (NASA Thesaurus)
Phenomenon which occurs when the cyclic plasticity of a material gives rise to the development of residual plastic deformations in the vicinity of a crack tip, causing the fatigue crack to close at positive load.
crack geometry
   (NASA Thesaurus)
The shape and size of partial fractures or flaws in materials.
crack opening displacement
   (NASA Thesaurus)
The displacement at the mouth of a crack in a material. Used for COD (cracks).
crack tips
   (NASA Thesaurus)
The boundaries between cracked and uncracked material.
cracking
   (NASA SP-7, 1965)
Presence of relatively large cracks extending into the interior of a structure, usually produced by overstressing the structural material. Compare checking.
cracking (chemical engineering)
   (NASA Thesaurus)
A process used to reduce the molecular weight of hydrocarbons by breaking molecular bonds by thermal, catalytic, or hydrocracking methods.
CRAF
   (Space Flight Glossary - JPL)
Comet Rendezvous / Asteroid Flyby mission, cancelled.
craft
   (NASA SP-7, 1965)
1. An aircraft, or aircraft collectively.
2. Any vehicle or machine designed to fly through air or space.
Crank-Nicholson method
   (NASA Thesaurus)
A method for solving parabolic partial differential equations, whose main feature is an implicit method which avoids the need for using very small time steps.
crashworthiness
   (NASA Thesaurus)
The ability of a vehicle to withstand a crash.
Crat
   (NASA SP-7, 1965)
International Astronomical Union abbreviation for Crater. See constellation.
crater
   (NASA SP-7, 1965)
1. = lunar crater.
2. The depression resulting from high speed solid particle impacts on a rigid material as a meteoroid impact on the skin of a spacecraft.
Crater
   (NASA SP-7, 1965)
(abbr Crt, Crat)
See constellation.
crater density
   (Galileo Project Glossary - JPL)
The number of craters on a surface per unit area.
crater size distribution
   (Galileo Project Glossary - JPL)
The relative numbers of craters of given sizes on a surface.
craterlets
   (NASA SP-7, 1965)
See lunar crater, note.
craters
   (Galileo Project Glossary - JPL)
A typically bowl-shaped pit, depression, cavity or hole, generally of considerable size and with steep slopes, formed on a surface or in the ground by the explosive release of chemical or kinetic energy.
Cray computers
   (NASA Thesaurus)
Supercomputers built by Cray Research Inc. that require the supporting services of another front-end general purpose computer for operation. They incorporate very fast scalar and vector hardware, are used primarily for the simulation of physical phenomena, and are programmed in FORTRAN.
CrB, Cor B
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Corona Borealis. See constellation.
creep
   (NASA SP-7, 1965)
The slow but continuous deformation of a material under constant load or prolonged stress (usually critically encountered at elevated temperatures).
creep strength
   (NASA Thesaurus / NASA SP-7, 1965)
The constant nominal stress that will cause a specified quantity of creep in a given time at constant temperature.
crescent
   (NASA SP-7, 1965)
See phases of the moon.
crest
   (Glossary of Hydrologic Terms - NOAA)
The highest stage or level of a flood wave as it passes a point.
crew procedures (inflight)
   (NASA Thesaurus)
Operations performed by crews aboard aircraft or spacecraft during flight. Includes flight operations as well as spaceborne experiment procedures.
crew procedures (preflight)
   (NASA Thesaurus)
Operations performed by crews aboard aircraft or spacecraft and by ground support crews before flight or launching.
crew size
   (NASA Thesaurus)
The number of people in a crew.
crippled leapfrog test
   (NASA SP-7, 1965)
In computer operations, a modified leapfrog test in which tests are repeated from a single set of storage locations and do not leap to another set of storage locations.
criteria
   (NASA Thesaurus)
The minimum standards or limits on which judgments may be based.
critical
   (NASA SP-7, 1965)
In reactor theory, capable of sustaining a chain reaction. See critical reactor.
critical circumference
   (Spacetime Wrinkles Glossary)
The circumference below which an object of given mass would collapse to form a black hole. This circumference depends on the mass of the object in question. For example, a collapsing star equal to 10 suns will have a critical circumference of 198 kilometers or 118 miles. See also Schwarschild Radius
critical current
   (NASA Thesaurus)
A current value in a superconductive material, at a particular constant temperature and in the absence of a magnetic field, below which the material is superconducting and above which the material behaves normally.
critical damping
   (NASA SP-7, 1965)
The minimum damping that will allow a displaced system to return to its initial position without oscillation.
critical frequency
   (NASA SP-7, 1965)
The limiting frequency below which a magnetoionic wave component is reflected by, and above which it penetrates through, an ionized medium (plasma) at vertical incidence.
critical level
   (NASA SP-7, 1965)
= critical level of escape.
critical level of escape
   (NASA SP-7, 1965)
That level, in the atmosphere, at which a particle moving rapidly upwards will have a probability of 1/e, where e is base of natural logarithm, of colliding with another particle on its way out of the atmosphere. It is also the level at which the horizontal mean free path of atmospheric particle equals the scale height of the atmosphere. The critical level of escape is the base of the exosphere. Also called level of escape, critical level. See cone of escape, fringe region.
Estimates of the height of the critical level of escape range from about 500 to 1000 kilometers. This large range of estimated values is due primarily to the general uncertainty about the temperature distribution in the ionosphere.
critical Mach number
   (NASA SP-7, 1965)
The free-stream Mach number at which a local Mach number of 1.0 is attained at any point on the body under consideration.
For example, an airplane traveling at a Mach number of 0.8 with respect to the undisturbed flow might attain Mach number of 1 in the flow about the wing; the critical Mach number would thus be 0.8.
critical mass
   (NASA Thesaurus / NASA SP-7, 1965)
The amount of concentrated fissionable material that can just support a self-sustaining fission reaction.
critical point
   (NASA Thesaurus / NASA SP-7, 1965)
The thermodynamic state in which liquid and gas phases of a substance coexist in equilibrium at the highest possible temperature. At higher temperatures than the critical no liquid phase can exist. For water substance the critical point is

Ps = 2.21 X 10 5 millibars
T = 647° K
v = 3.10 grams/cubic centimeter

where Ps is the saturation vapor pressure of the water vapor; T is the Kelvin temperature; and v is the specific volume.

critical pressure
   (NASA Thesaurus / NASA SP-7, 1965)
1. In rocketry, the pressure in the nozzle throat for which the isentropic weight flow rate is a maximum.
2. The pressure of a gas at critical point, which is the highest pressure under which a liquid can exist in equilibrium with its vapor.
critical reactor
   (NASA SP-7, 1965)
The steady-state condition of a reactor in which the neutron fission process is self-sustaining without the aid of external neutron sources. A critical reactor has a criticality factor of one (ke = 1).
critical Reynolds number
   (NASA SP-7, 1965)
The Reynolds number at which some significant change occurs, e.g., the Reynolds number at which a transition from laminar to turbulent flow begins, or at which the drag of a cylinder or sphere drops sharply.
critical speed
   (NASA SP-7, 1965)
A speed of a rotating system that corresponds to a resonance frequency of the system.
critical temperature
   (NASA Thesaurus / NASA SP-7, 1965)
1. The temperature above which a substance cannot exist in the liquid state, regardless of the pressure.
2. As applied to reactor overheat or afterheat, the temperature at which the least resistant component of the reactor core begins to melt down.
3. As applied to materials, the temperature at which a change in phase takes place causing an appreciable change in the properties of the material.
critical throat velocity
   (NASA SP-7, 1965)
= critical velocity.
critical velocity
   (NASA Thesaurus / NASA SP-7, 1965)
In rocketry, the speed of sound at the conditions prevailing at the nozzle throat. Also called throat velocity, critical throat velocity.
criticality factor
   (NASA SP-7, 1965)
As applied to a reactor, the numerical value of the effective multiplication factor (ke), denoting the degree to which the reactor has achieved a self-sustaining chain reaction.
crop calendars
   (NASA Thesaurus)
Schedules for the maturation and harvesting of seasonal crops.
crop dusting
   (NASA Thesaurus)
The application of fungicides or insecticides in powder form to a crop, usually from a low flying aircraft.
crop inventories
   (NASA Thesaurus)
Numerical estimates of vegetable, fruit, and other commercial farm products based on the analysis of photography or imagery from aircraft or satellites made during periodic passes during the growth cycle.
cross correlation detection
   (NASA SP-7, 1965)
= correlation detection.
cross flow
   (NASA Thesaurus)
A flow going across another flow, as a spanwise flow over a wing.
cross modulation
   (NASA SP-7, 1965)
In general, modulation of a desired signal by an undesired signal.
cross polarization
   (NASA Thesaurus)
The component of the electric field vector normal to the desired polarization component.
cross product
   (NASA SP-7, 1965)
= vector product.
cross section
   (Plasma Physics and Fusion Energy Glossary)
In physics this usually refers to the (apparent) area presented. by a target particle to an oncoming particle (or electromagnetic wave).
cross sections
   (NASA Thesaurus / NASA SP-7, 1965)
1. Measures of the effectiveness of a particular processes expressed either as areas (geometric cross sections) which would produce the observed result, or as ratios. See absorption cross sections, scattering cross sections.
2. = nuclear cross section.
cross sensitivity
   (NASA SP-7, 1965)
The ratio of change in output to an incremental change in a given stimulus along any axis perpendicular to the sensitive axis.
In accelerometers it refers to the change in the transducer output at zero acceleration and at some other acceleration value applied along a plane perpendicular to the sensitive axis.
cross-cut (principle of cross-cutting relationships)
   (Galileo Project Glossary - JPL)
An interruption of a geologic feature by another, which can give an indication of the relative ages of these geologic features/events. (e.g. a fault cutting across an impact crater would be younger than the crater.)
crossflow
   (NASA SP-7, 1965)
A flow going across another flow, as a spanwise flow over a wing.
crossflow plane
   (NASA SP-7, 1965)
In aerodynamics, a plane at right angles to the free-stream velocity. Compare crossflow.
crosshair
   (NASA SP-7, 1965)
A hair, thread, or wire constituting part of a reticle.
crosspatching
   (NASA SP-7, 1965)
See supercommutation.
crosstalk
   (NASA Thesaurus / NASA SP-7, 1965)
Electrical disturbances in a communication channel as a result of coupling with other communication channels.
crosswind
   (NASA SP-7, 1965)
That wind vector component which is perpendicular to the course of an exposed moving object. Compare range wind.
CRT
   (Space Flight Glossary - JPL)
Cathode ray tube video display device.
CRT (abbr)
   (NASA SP-7, 1965)
Cathode-ray tube.
Crt, Crat
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Crater. See constellation.
Cruc
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Crux. See constellation.
cruise missiles
   (NASA Thesaurus)
Guided missiles, the major portion of whose flight path to its target is conducted a approximately constant velocity - depends on the dynamic reaction of air for lift, and upon propulsive forces to balance drag.
crusts
   (Galileo Project Glossary - JPL)
The outermost layers of a planet, composed of relatively low-density materials.
Crux
   (NASA SP-7, 1965)
(abbr Cru, Cruc)
See constellation.
Crv, Corv
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Corvus. See constellation
cryochemistry
   (NASA Thesaurus)
The study of chemical phenomena in very low temperature environment.
cryogenic cooling
   (NASA Thesaurus)
Use of cryogenic fluids to reach temperatures near absolute zero.
cryogenic materials
   (NASA SP-7, 1965)
Those metals and alloys which are usable in structures operating at very low temperature, and usually possess improved strength properties at these temperatures.
cryogenic propellant
   (NASA SP-7, 1965)
A rocket fuel, oxidizer, or propulsion fluid which is liquid only at very low temperatures.
cryogenic pump
   (NASA SP-7, 1965)
A type of pump which uses cryopumping to attain a vacuum.
cryogenic rocket propellants
   (NASA Thesaurus)
Rocket fuels, oxidizers, or propulsion fluids which are liquid only at very low temperatures.
cryogenic temperature
   (NASA SP-7, 1965)
In general, a temperature range below the boiling point of nitrogen (-195° C); more particularly, temperatures within a few degrees of absolute zero.
cryogenic wind tunnels
   (NASA Thesaurus)
Wind tunnels employing a cryogenic environment and utilizing independent control over Mach number, Reynolds number, aeroelastic effects, and model-tunnel interactions.
cryogenics
   (NASA Thesaurus / NASA SP-7, 1965)
1. The study of the methods of producing very low temperatures.
2. The study of the behavior of materials and processes at cryogenic temperatures.
cryopump
   (NASA SP-7, 1965)
1. An exposed surface refrigerated to cryogenic temperature for the purpose of pumping gases in a vacuum chamber by condensing the gas and maintaining the condensate at a temperature such that the equilibrium vapor pressure is equal to or less than the desired ultimate pressure in the chamber.
2. The act of removing gases from an enclosure by condensing the gases on surfaces at cryogenic temperature.
Also referred to as a cryogenic pump and not to be confused with cryogenic fluid pump for circulating cryogenic propellants.
cryopumping
   (NASA Thesaurus / NASA SP-7, 1965)
The process of removing gas from a system by condensing it on a surface maintained at very low temperatures.
cryotron
   (NASA Thesaurus / NASA SP-7, 1965)
A device based upon the principle that superconductivity established at temperatures near absolute zero is destroyed by the application of a magnetic field.
cryptography
   (NASA Thesaurus)
The science of preparing messages in a form which cannot be read by those not privy to the secrets of the form.
crystal defects
   (NASA Thesaurus)
Departure from the regular arrangment of atoms in the ideal crystal lattice.
crystal dislocations
   (NASA Thesaurus)
Types of lattice imperfections whose existence in metals is postulated in order to account for the phenomenon of crystal growth and of slip, particularly for the low value of shear stress required to initiate slip.
crystal lattice
   (NASA Thesaurus / NASA SP-7, 1965)
The three-dimensional, recurring pattern in which the atoms of a crystal are arranged.
crystal transducer
   (NASA SP-7, 1965)
A transducer in which the method of transduction is accomplished by means of the piezoelectric properties of certain crystals or salts. Also called crystal.
cubic convolution
   (Global Land Information System Glossary - USGS)
A high order resampling technique in which the brightness value of a pixel in a corrected image is interpolated from the brightness values of the 16 nearest pixels around the location of the corrected pixel.
culmination
   (NASA SP-7, 1965)
= transit (sense 1), specifically upper transit.
cultural resources
   (NASA Thesaurus)
Archaeological and historical sites.
cumulonimbus clouds
   (NASA Thesaurus)
A cumuliform cloud type: heavy and dense, with considerable vertical extent in the form of massive towers. This form frequently exhibits tops in the shape of an anvil or massive plume. It is frequently accompanied by lightning, thunder, and sometimes hail; occasionally producing a tornado or a watersprout.
cumulus clouds
   (NASA Thesaurus)
Clouds in the form of individual detached domes or towers which are usually dense and well defined. These clouds develop vertically in the form of rising mounds. The sunlit parts are mostly brilliantly white; their bases are relatively dark and nearly horizontal.
curie
   (NASA SP-7, 1965)
(abbr C)
The unit of the rate of radioactive decay; the quantity of any radioactive nuclide which undergoes 3.70 X 1010 disintegrations per second.
Curie point
   (NASA SP-7, 1965)
The temperature in a ferromagnetic material above which the material becomes substantially nonmagnetic.
Curie temperature
   (NASA Thesaurus / NASA SP-7, 1965)
= Curie point.
curl
   (NASA SP-7, 1965)
A vector operation upon a vector field which represents the rotation of the field, related to the circulation of the field at each point. The curl is invariant with respect to coordinate transformations and is usually written "curl F" of " nabla del (down pointing triangle) * F" where nabla del (down pointing triangle) is the del-operator. In Cartesian coordinates, if F has the components Fx, Fy, Fz the curl is r equals summation symbol open parens x sub i minus x bar close parens open parens y sub I minus y bar close parens over square root of summation symbol open parens x sub i minus x bar close parens squared summation symbol open parens y sub i minus y bar close parens squared Expansions in other coordinate systems may be found in any text on vector analysis.
The curl of a two-dimensional vector field is always in a field of solid rotation it is equal to twice the angular velocity. Occasionally the vorticity is defined as one-half the curl.
The curl of a two dimensional vector field is always normal to the vectors of the field; this is not necessarily true in three dimensions. Compare divergence.
curl (vectors)
   (NASA Thesaurus)
A vector operation upon a vector field which represents the rotation of the field, related to the circulation of the field at each point.
current density
   (Plasma Physics and Fusion Energy Glossary)
Amount of current flowing through a substance, per unit area perpendicular to the direction of current flow.
current drive
   (Plasma Physics and Fusion Energy Glossary)
Any of a variety of techniques used to cause current flow in a plasma.
cursor
   (NASA SP-7, 1965)
A device used with an instrument to provide a movable reference, as the runner of a slide rule or a ratable plastic disk with inscribed crosslines, used in reading bearings on a plan position indicator.
Curtis turbine
   (NASA SP-7, 1965)
A turbine in which a stationary set of blades is used to change the direction of the fluid flow as the fluid travels between two sets of rotating blades.
curve of growth
   (NASA SP-7, 1965)
In spectroscopy, the relationship between the amount of radiant energy removed by an absorption line and the number of atoms or molecules of the absorbing gas in the light path.
If the logarithm of energy absorbed is plotted against the logarithm of amount of gas in the path, the resulting curve of growth usually has two straight-line segments. The first, for small absorption and small amounts of gas, has a slope of 1; the second, for large absorption and large amounts of gas, has a slope of 1/2. Thus, initially absorption is directly proportional to the number of atoms or molecules, but as the line becomes more intense, absorption becomes proportional to the square root of the number of atoms or molecules. Between these two straight-line segments there is often a portion in which an increase in the amount of gas in the path produces very little increase in total absorption. All of this discussion applies in the case of gaseous emission as well as absorption.
curve of regression
   (NASA SP-7, 1965)
A realistic curve having a least-squares fit to the data points.
There are an infinity of least-squares curves to fit a set of data points (one curve of which touches every point). Therefore, the regression curve must be the best least-squares estimate (of the true curve of the phenomenon observed) that can be made in light of the data and prior knowledge of the physics of the phenomenon observed. Note that a regression curve is offset from the true curve by the amount of any bias error and of most systematic errors.
curved-path error
   (NASA SP-7, 1965)
The difference between the length of a ray refracted by the atmosphere and the straight-line distance between the ends of the ray.
curvilinear coordinates
   (NASA SP-7, 1965)
Any linear coordinates which are not Cartesian coordinates. Examples of frequently used curvilinear coordinates are polar coordinates and cylindrical coordinates. See natural coordinates, spherical coordinates.
cutoff
   (NASA Thesaurus / NASA SP-7, 1965)
(or cut-off) 1. An act or instance of shutting something off; specifically, in rocketry, an act or instance of shutting off the propellant flow in a rocket, or of stopping the combustion of the propellant. Compare burnout.
2. Something that shuts off, or is used to shut off. See fuel shutoff.
3. Limiting or bounding as in cutoff frequency.
Cvn, C Ven
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Canes Venatici. See constellation.
CW radar
   (NASA SP-7, 1965)
= continuous-wave radar.
CW system
   (NASA SP-7, 1965)
A trajectory measuring system that utilizes a continuous wave signal to obtain information on the trajectory of a target.
cyanometer
   (NASA SP-7, 1965)
An instrument designed to measure or estimate the blueness of the sky.
The type in most common use is the Linke scale.
cyanometry
   (NASA SP-7, 1965)
The study and measurement of the blueness of the sky.
The characteristic blue color of clear skies is due to preferential scattering of the short wavelength components of visible sunlight by air molecules. Presence of foreign particles in the atmosphere alters the scattering processes in such a way as to reduce the blueness. Hence spectral analysis of diffuse sky radiation provides useful information concerning the scattering particles.
cybernetics
   (NASA Thesaurus)
The study of methods of control and communication which are common to living organisms and machines.
cybernetics
   (NASA SP-7, 1965)
The study of methods of control and communication which are common to living organisms and machines.
cycle
   (NASA SP-7, 1965)
(symbol c)
1. The complete sequence of values of a periodic quantity that occur during a period.
2. One complete wave, a frequency of 1 wave per second.
3. Any repetitive series of operations or events.
cycle efficiency
   (NASA SP-7, 1965)
The efficiency of a given cycle in an internal combustion engine, in producing work, expressed as the useful work output divided by the work input. For a gas-turbine engine, the cycle efficiency is the useful work energy less the work required for compression divided by the heat energy in the fuel used; for a reciprocating engine, it is the energy of the indicated horsepower divided by the heat energy of the fuel.
cycles
   (NASA Thesaurus)
The complete sequences of values of a periodic quantity that occur during a period. Used for cycling and periodic processes.
cyclic
   (NASA SP-7, 1965)
Of or pertaining to a cycle or cycles.
cyclic AMP
   (NASA Thesaurus)
A nucleotide which is implicated as an intracellular messenger in a wide variety of cellular processes. Prototypically it acts as a molecular transducer of nonsteroid signals from outside the cell to relevant cellular enzymes by a series of reactions. Used for cyclic adenosine monophosphate.
cyclic code
   (NASA SP-7, 1965)
In computer operations, a positional notation, not necessarily binary, in which quantities differing by one unit are represented by expressions which are identical except for one place or column, and the digits in that place or column differ by only one unit. Also called reflected code. See Gray code.
cyclic compounds
   (NASA Thesaurus)
In organic chemistry, compounds containing a ring of atoms.
cycloaddition
   (NASA Thesaurus)
Pericyclic chemical reaction in which unsaturated molecules combine to form a cyclic compound under the influence of heat or light.
cyclones
   (NASA Thesaurus)
Atmospheric closed circulation, synoptic-scale weather features associated with rising air and lower atmospheric pressure, and whose relative direction of rotation is counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
cyclonic
   (NASA SP-7, 1965)
Having a sense of rotation about the local vertical the same as that of the earth's rotation: that is, as viewed from above, counterclockwise in the Northern Hemisphere, clockwise in the Southern Hemisphere, undefined at the equator; the opposite of anticyclonic.
cyclophon
   (NASA SP-7, 1965)
A name given to a generic type of vacuum tube utilizing a beam of electrons as a switching or commutating element.
cyclotron
   (NASA SP-7, 1965)
A device for accelerating charged particles to high energies by giving particles traveling in a spiral path successive increments of energy from an alternating electric field between electrodes placed in a constant magnetic field. The path radius increases as energy increases.
cyclotron frequency
   (NASA Thesaurus / NASA SP-7, 1965)
The frequency at which a charged particle orbits in a uniform magnetic field. It depends on the charge to mass ratio of the particle times the magnetic field. While the frequency is independent of the particle energy, the Larmor orbit increases with energy. Sometimes called the Larmor frequency.
In a magnetic field of 1 gauss, the electron cyclotron frequency is 2.8 megacycles per second and the proton cyclotron frequency is 1.5 kilocycles per second.
cyclotron radiation
   (NASA Thesaurus / NASA SP-7, 1965)
The electromagnetic radiation emitted by charged particles as they orbit in a magnetic field. The radiation arises from the centripetal acceleration of the particle as it moves in a circular orbit. See Larmor orbit.
When the velocity is small, the radiation is concentrated in a single spectral line, at the cyclotron frequency. The spectral line is spread into a band of frequencies, however, from the effects of Doppler, Stark, and collision broadening. In addition, as the speed of the particles approaches the velocity of light, higher harmonics of the cyclotron radiation occur at multiples of the cyclotron frequency.
cyclotron resonance
   (NASA Thesaurus / NASA SP-7, 1965)
Energy transfer to charged particles in a magnetic field from an alternating-current electric field whose frequency is equal to the cyclotron frequency.
An analogous physical situation is the large increase in the motion of a pendulum if it is given a little push in every period of its natural oscillation. Such a technique is useful in heating either the electrons or ions.
cyclotron resonance devices
   (NASA Thesaurus)
Microwave amplifiers based on the interaction between electromagnetic waves and transverse electron streams moving along helical trajectories. Used for gyrotrons.
cyclotrons
   (Plasma Physics and Fusion Energy Glossary)
Particle accelerator in which a magnetic field cause particles to orbit in circles, and an oscillating electric field accelerates the particles.
Cyg, Cygn
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Cygnus. See constellation.
Cygnus
   (NASA SP-7, 1965)
(abbr Cyg, Cygn)
See constellation.
cylindrical coordinates
   (NASA SP-7, 1965)
A system of curvilinear coordinates in which the position of a point in space is determined by (a) its perpendicular distance from a given line, (b) its distance from a selected reference plane perpendicular to this line, and (c) its angular distance from a selected reference line when projected onto this plane. The coordinates thus form the elements of a cylinder, and, in the usual notation, are written, r, theta, and z where r is the radial distance from the cylinder's axis z, and theta is the angular position from a reference line in a cylindrical cross section normal to z. Also called cylindrical polar coordinates, circular cylindrical coordinates. See polar coordinates.
The relations between the cylindrical coordinates and the rectangular Cartesian coordinates (x, y, z) are x = r cos , y = r sin , z = z.
cylindrical plasmas
   (NASA Thesaurus)
Magnetic self-attraction of parallel electric currents causing constriction of a conducting plasma through which a large current is flowing.
cylindrical polar coordinates
   (NASA SP-7, 1965)
= cylindrical coordinates.
cylindrical wave
   (NASA SP-7, 1965)
A wave in which the wave fronts are coaxial cylinders.
Czechoslovakian spacecraft
   (NASA Thesaurus)
Spacecraft of Czechosolovakia.
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