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O

  
OB
   (Space Flight Glossary - JPL)
Observatory phase in flyby mission operations encounter period.
Oberon
   (NASA SP-7, 1965)
A satellite of Uranus orbiting at a mean distance of 587,000 kilometers.
object glass
   (NASA SP-7, 1965)
= objective.
object-oriented programming
   (NASA Thesaurus)
The use of a programming language consisting of a sequence of commands directed at objects.
objective
   (NASA SP-7, 1965)
The lens or combination of lenses which receives light rays from an object and refracts them to form an image in the focal plane of the eyepiece of an optical instrument, such as a telescope. Also called object glass.
oblate spheroid
   (NASA Thesaurus / NASA SP-7, 1965)
An ellipsoid of revolution, the shorter axis of which is the axis of revolution.
An ellipsoid of revolution, the longer axis of which is the axis of revolution, is called a prolate spheroid. The earth is approximately an oblate spheroid.
oblique
   (Global Land Information System Glossary - USGS)
An image taken with a camera or sensor with the axis intentionally directed between the vertical and horizontal planes. A high oblique image includes the horizon in the field of view, while a low oblique shows only the Earth's surface.
oblique
   (NASA SP-7, 1965)
Pertaining to, or measured on, an oblique projection, as oblique equator, oblique pole, oblique latitude.
oblique coordinates
   (NASA Thesaurus / NASA SP-7, 1965)
Magnitudes defining a point relative to two intersecting nonperpendicular lines, called axes. See Cartesian coordinates.
The magnitude indicate the distance from each axis, measured along a parallel to the other side. The horizontal distance is called the abscissa and the other distance, the ordinate.
oblique projection
   (NASA SP-7, 1965)
A map projection with an axis inclined at an oblique angle to the plane of the equator.
oblique shock
   (NASA SP-7, 1965)
= oblique shock wave.
oblique shock wave
   (NASA SP-7, 1965)
A shock wave inclined at an oblique angle to the direction of flow in a supersonic flow field. Sometimes shortened to oblique shock. Compare normal shock.
oblique shock waves
   (NASA Thesaurus)
Shock waves attached to the bow and tail of an aerodynamic vehicle moving faster than the speed of sound. The sides of the oblique shock waves form the Mach cone.
obliqueness
   (NASA Thesaurus)
The state of being neither perpendicular nor horizontal.
obliquity
   (Solar System Dynamics Glossary - JPL)
The angle between the equatorial and orbital planes (or the rotational and orbital poles) of a body. The obliquity of the ecliptic for the Earth is the angle between the equatorial and ecliptic planes.
obliquity of the ecliptic
   (NASA SP-7, 1965)
(symbol epsilon)
The angle between the plane of the ecliptic (the plane of the earth's orbit) and the plane of the celestial equator.
The obliquity of the ecliptic is computed from the following formula: 23 degrees 27 minutes 08.26 seconds - 0.4684 (t - 1900) seconds, where t is the year for which the obliquity is desired.
observability (systems)
   (NASA Thesaurus)
The property of a system for which observations of the output variables always is sufficient to determine the initial values of all state variables.
observed
   (NASA SP-7, 1965)
In astronomy and navigation, pertaining to a value which has been measured in contrast to one which is computed.
observed altitude
   (NASA SP-7, 1965)
= true altitude.
observed magnitude
   (Comet Glossary - JPL)
The observed magnitude of the comet represents the integrated brightness of the comet's coma or head as seen from Earth. This is normally obtained by comparing the comet's average surface brightness with that of defocused stars (matching the comet's size) of known brightness. Because comets have size (in contrast to stars which are pinpoints of light), a comet of a given brightness will appear less obvious than a star of the same brightness.
obsidian
   (Photoglossary of Volcanic Terms - USGS)
A dense volcanic glass, usually rhyolite in composition and typically black in color. Compared with window glass, obsidian is rich in iron and magnesium; tiny (<.005 mm) crystals of iron oxide within the glass cause its dark color. Obsidian is often formed in rhyolite lava flows where the lava cools so fast that crystals do not have time to grow. Glass, unlike crystals, has no regular structure and therefore fractures in smooth conchoidal (curved) shapes. The intersections of these fractures can form edges sharper than the finest steel blades.
obstacle avoidance
   (NASA Thesaurus)
The use of sensors utilizing laser triangulation as means of preventing collisions, especially in the operation of roving vehicles on planetary surfaces.
occlusion
   (NASA Thesaurus / NASA SP-7, 1965)
Specifically, the trapping of undisolved gas in a solid during solidification.
occultation
   (NASA Thesaurus / NASA SP-7, 1965)
The disappearance of a body behind another body of larger apparent size.
When the moon passes between the observer and a star, the star is said to be occulted. The three associated terms, occultation, eclipse, and transit, are exemplified by the motions of the satellites of Jupiter. An eclipse occurs when a satellite passes into the shadow cast by the planet; an occultation occurs when a satellite passes directly behind the planet; so that it could not be seen even if it were illuminated; and a transit occurs when a satellite passes between the observer and the planet, showing against the disk of the planet.
ocean color scanner
   (NASA Thesaurus)
A multispectral scanning radiometer which is geared to observe ocean features such as chlorophyll, sediments, and topography in the invisible and thermal ranges of radiation.
ocean dynamics
   (NASA Thesaurus)
The study of the controlling forces in different ocean phenomena.
ocean temperature
   (NASA Thesaurus)
Surface or subsurface temperature of an entire or specific region of an ocean.
oceanography
   (NASA Thesaurus)
The science that deals with the study and exploration of seas and oceans.
oceans
   (NASA Thesaurus)
The continuous salt water bodies that surround the continents and fill the Earth's great depressions.
Oct, Octn
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Octans. See constellation.
octal notation
   (NASA SP-7, 1965)
Notation of numbers in the scale of eight. The octal digits can be represented by the eight possible combinations of three binary digits.
octant
   (NASA SP-7, 1965)
See sextant.
octave
   (NASA Thesaurus / NASA SP-7, 1965)
The interval between any two frequencies having the ratio of 1:2.
The interval in octaves between any two frequencies is the logarithm to the base 2 (or 3.322 times the logarithm to the base 10) of the frequency ratio.
Octn
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Octans. See constellation.
ocular
   (NASA SP-7, 1965)
Pertaining to or in relation with the eye.
oculogravic illusion
   (NASA SP-7, 1965)
= agravic illusion.
oculogyral illusion
   (NASA SP-7, 1965)
The apparent movement of an image in space in the same direction as that in which one seems to be turning when the semicircular canals are stimulated.
oculogyric
   (NASA SP-7, 1965)
Referring to movements of the eyes.
oersted
   (NASA SP-7, 1965)
The centimeter-gram-second electromagnetic unit of magnetic intensity. See gauss.
off-center plan position indicator
   (NASA SP-7, 1965)
See plan position indicator.
off-on control
   (NASA Thesaurus)
Flicker control, especially as applied to rockets. Used for bang-bang control.
offgassing
   (NASA Thesaurus)
The relative high mass loss characteristic of many nonmetallic materials upon initial vacuum exposure.
ogive
   (NASA Thesaurus / NASA SP-7, 1965)
A body of revolution formed by rotating a circular arc about an axis that intersects the arc; the shape of this body; also, a nose of a projectile or the like so shaped.
Typically, an ogive has the outline of a Gothic arch, although by definition it may be rounded rather than pointed. See tangent ogive.
ohm
   (NASA SP-7, 1965)
(abbr capital omega)
The unit of electrical resistance; the resistance between two points of a conductor when a constant difference of potential of 1 volt, applied between these two points, produces in the conductor a current of 1 ampere (the conductor not being the source of any electromotive force).
ohmic heating
   (Plasma Physics and Fusion Energy Glossary)
Heating that results from the flow of current through a medium with electrical resistance. In plasmas subjected to ohmic heating, ions are heated almost entirely by transfer of energy from the hotter, more mobile electrons.
ohmic heating
   (NASA SP-7, 1965)
In plasma physics, the energy imparted to charged particles as they respond to an electric field and make collisions with other particles.
The name was chosen for its similarity to the heat generated in an ohmic resistance due to the collisions of the charge carriers in their medium.
ohmmeters
   (NASA Thesaurus)
Direct-reading instruments for measuring electrical resistance. They are provided with a scale, usually graduated in either ohms, megohms, or both. If the scale is graduated in megohms, the instrument is usually called a megohmmeter.
Ohms law
   (NASA Thesaurus)
The current in an electric circuit is inversely proportional to the resistance of the circuit and is directly proportional to the electromotive force in the circuit. Ohm's law applies, strictly speaking, only to linear constant-current circuits.
oil fields
   (NASA Thesaurus)
Surface boundary of an area from which petroleum is obtained; may correspond to an oil pool or may be circumscribed by political or legal limits.
oilcan
   (NASA SP-7, 1965)
Of a sheet-metal skin or of other covering, to snap in and out between rows of rivets or between other places of support in a fashion like that of the bottom of an oilcan.
Omega Navigation System
   (NASA Thesaurus)
A very long distance navigation system operating at approximately 10 kHz (kilohertz), in which hyperbolic lines of position are determined by measurement of the difference in travel time of continuous wave signals from two transmitters separated by 5000 nmi (nautical miles) to 6000 nmi (9000 km {kilometers} to 11000 km) or in which changes in distances from the transmitters are measured by counting RF (radio frequency) wavelengths in the space of lanes as the vehicle moves from a known position, the lanes being counted by phase comparison with a stable oscillator aboard the vehicle.
omni
   (NASA SP-7, 1965)
1. A prefix meaning all , as in omnidirectional.
2. Short for omnirange.
omnidirectional range
   (NASA SP-7, 1965)
= omnirange.
omnirange
   (NASA SP-7, 1965)
A radio navigation system providing a direct indication of the bearing of the omnirange facility from the vehicle. Usually used in combination with distance measuring equipment. Also called omnidirectional range.
on-line systems
   (NASA Thesaurus)
Systems where the input data enters the computer directly from the point of origin and/or in which output data is transmitted directly to where it is used.
onboard data processing
   (NASA Thesaurus)
Processing of acquired data aboard an aircraft, satellite, etc., rather than transmission to ground stations for processing.
one-way
   (Space Flight Glossary - JPL)
Communications mode consisting only of downlink received from a spacecraft.
Oort cloud
   (NASA Thesaurus)
A region of millions of comets between 30,000 and 100,000 A.U. from the sun. Comets are perturbed out of the Oort cloud by passing stars and fall into the inner solar system. The Oort cloud was named after the Dutch astronomer, Jan Hendrik Oort.
opacity
   (Imagine the Universe Dictionary - NASA GSFC)
A property of matter that prevents light from passing through it; non-transparent. The opacity or opaqueness of something depends on the frequency of the light.
opacity
   (NASA Thesaurus / NASA SP-7, 1965)
Of an optical path, the reciprocal of transmission. See transmittance.
opaque plasma
   (NASA SP-7, 1965)
A plasma through which an electromagnetic wave cannot propagate and is either absorbed or reflected.
In general, a plasma is opaque for frequencies below the plasma frequency. The fact that a plasma is opaque over a certain frequency range will change the radiation properties within that frequency range. Any radiation emitted within the volume of the plasma is quickly absorbed. In this opaque region, therefore, the plasma can only radiate from its surface.
OPCT
   (Space Flight Glossary - JPL)
Operations Planning and Control Team, "OPSCON."
open circuit voltage
   (NASA Thesaurus)
The steady state or equilibrium potential of an electrode in absence of external current flow to or from the electrode.
open loop
   (NASA SP-7, 1965)
A system operating without feedback, or with only partial feedback. See closed loop system.
OPEN Project
   (NASA Thesaurus)
A former NASA project now absorbed by the International Solar Terrestrial Physics Project. It proposed a simultaneous study of plasmas in the Earth's magnetosphere and neighborhood using the following four instrumented spacecraft: interplanetary physics laboratory (IPL), geomagnetic tail laboratory (GTL), polar plasma laboratory (PPL), and equatorial magnetosphere laboratory (EML). Used for Origin of Plasmas in Earth Neighborhood.
open system
   (NASA SP-7, 1965)
A system that provides for the body's metabolism in an aircraft or spacecraft cabin by removal of respiratory products and of waste from the cabin and by use of stored food and oxygen. Compare closed system.
open-center plan position indicator
   (NASA SP-7, 1965)
See plan position indicator.
operand
   (NASA SP-7, 1965)
In computer operations, a word on which an operation is to be performed.
operating costs
   (NASA Thesaurus)
The price for operating a system exclusive of the cost of the system itself.
operating ratio
   (NASA SP-7, 1965)
= computing efficiency.
operating systems (computers)
   (NASA Thesaurus)
Computer programs for expediting, controlling and/or recording computer use by other programs. Used for executive systems (computers).
operative temperature
   (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. It is equal to the temperature at which a specified hypothetical environment would support the same heat loss from an unclothed, reclining human body as the actual environment. In the hypothetical environment, the wall and air temperatures are equal and the air movement is 7.6 centimeters per second. From experiment it has been found that the operative temperature

T sub o equals 0.48 t sub r plus 0.19 open bracket square root of nu t sub a minus open parens square root of nu minus 2.76 close parens t sub s close bracket

where tr is the mean radiant temperature; ta is the mean air temperature; ts is the mean skin temperature (all in degrees C); and v is the airspeed in centimeters per second.
Oph, Ophi
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Ophiuchus. See constellation.
Ophiuchi clouds
   (NASA Thesaurus)
Dense concentrations of interstellar gas near the stars Rho Ophiuchi and Zeta Ophiuchi.
Ophiuchus
   (NASA SP-7, 1965)
(abbr Oph, Ophi)
See constellation.
opposition
   (Galileo Project Glossary - JPL)
A configuration in which a celestial body is in the opposite direction (180 degrees) from the sun as seen from another body located along the line between them. (e.g. when Mars, Earth and the Sun are located along a straight line, Mars is in opposition as seen from Earth.)
opposition
   (NASA SP-7, 1965)
1. The situation of two celestial bodies having either celestial longitudes or sidereal hour angles differing by 180 degrees. The term is usually used only in relation to the position of a planet or the moon from the sun. Compare conjunction.
2. The situation of two periodic quantities differing by half a cycle.
opposition surge
   (Galileo Project Glossary - JPL)
An increase in brightness as an observer approaches the line between the sun and a target. The strength of the surge is an indicator of small-scale surface texture.
optical activity
   (NASA Thesaurus)
Ability to rotate the plane of vibration of polarized light to the right or left.
optical air mass
   (NASA SP-7, 1965)
(symbol m)
A measure of the length of the path through the atmosphere to seal level traversed by light rays from a celestial body, expressed as a multiple of the path length for a light source at the zenith. Originally called, simply, air mass. Also called airpath.
optical axis
   (NASA SP-7, 1965)
Of an antenna, a line parallel to, but offset from, the electrical axis of an antenna.
This axis is offset by the distance necessary to have the optical sighting device removed from the electrical center of the antenna.
optical bistability
   (NASA Thesaurus)
A property of certain materials in which a nonlinear response is exhibited when under the influence of an external driving coherent light, thereby allowing these materials to behave like optical switches.
optical computers
   (NASA Thesaurus)
Computers which use light rather than electricity for all or part of their operation. They perform multiple tasks in parallel as opposed to electronic computers which would perform those tasks sequentially. Such increased processing capability makes them suited for aerospace problems which involve systems that have a large number of degrees of freedom, i.e., large space structures, pattern recognition activity, and robotics.
optical control
   (NASA Thesaurus)
The control of light sensitive devices by means optical radiation.
optical countermeasures
   (NASA Thesaurus)
Equipment for exploiting the vulnerability of laser guided weapon systems.
optical density
   (NASA Thesaurus)
The image intensity or density in terms of, or measured by, a reflectance densitometer.
optical density
   (NASA SP-7, 1965)
= photographic transmission density.
optical depth
   (Planetary Rings Glossary - ARC)
Optical depth is a measure of the transparency of a ring system. When a ring is "optically thick" (i.e., the optical depth is large), the ring is nearly opaque and very little light passes through. When a ring is "optically thin" (i.e., the optical depth is small), very little material is present and most of the light passes through.
optical depth
   (NASA SP-7, 1965)
= optical thickness.
optical double star
   (NASA SP-7, 1965)
Two stars in nearly the same line of sight but differing greatly in distance from the observer, as distinguished from a physical double star.
optical haze
   (NASA SP-7, 1965)
= terrestrial scintillation.
optical line of sight
   (NASA SP-7, 1965)
The generally curved path of visible light through the atmosphere.
Often used erroneously for geometrical line of sight.
optical mass
   (NASA SP-7, 1965)
= laser.
optical path
   (NASA SP-7, 1965)
1. = line of sight.
2. The path followed by a ray of light through an optical system.
optical pumping
   (Plasma Physics and Fusion Energy Glossary)
In laser physics, this denotes the process in which absorbed light is stored in the laser medium. If the absorption & storage process creates a population inversion, laser action can occur (and extract the energy stored by optical pumping in the form of laser emission).
optical pyrometer
   (NASA SP-7, 1965)
A device for measuring the temperature of an incandescent radiating body by comparing its brightness for a selected wavelength interval within the visible spectrum with that of a standard source; a monochromatic radiation pyrometer.
Temperatures measured by optical pyrometers are known as brightness temperatures and except for black bodies are less than the true temperatures.
optical relay systems
   (NASA Thesaurus)
Systems using photocouplers in which the output device is a light sensitive switch that provides the same on and off operations as the contacts of a relay.
optical scanners
   (NASA Thesaurus)
A light source and phototube combined as a single unit for scanning moving strips of paper or other materials in photoelectric side-register control systems.
optical slant range
   (NASA Thesaurus / NASA SP-7, 1965)
The horizontal distance in a homogeneous atmosphere for which the attenuation is the same as that actually encountered along the true oblique path.
optical thickness
   (NASA Thesaurus)
A measure of the cumulative attenuation of electromagnetic radiation in transit through a medium. In calculations of the transfer of radiant energy, the mass of a given absorbing or emitting material lying in a vertical column of unit cross sectional area and extending between two specific levels. Used for optical depth.
optical thickness
   (NASA SP-7, 1965)
Specifically, in calculations of the transfer of radiant energy, the mass of a given absorbing or emitting material lying in a vertical column of unit cross-sectional area and extending between two specific levels. Also called optical depth.
If z1 and z2 are the lower and upper limits, respectively, of a layer in which the variation of a density rho of some absorbing or emitting substance is given as a function of height z, then the quantity

the integral of z sub one to z sub two, rho of z, d z

is called the optical thickness of that substance within that particular layer.
optical turbulence
   (NASA SP-7, 1965)
Irregular and fluctuating gradients of optical refractive index in the atmosphere.
Optical turbulence is caused mainly by mixing of air of different temperatures, and particularly by thermal gradients which are sufficient to reverse the normal decrease in density with altitude, so that convection occurs.
optical waveguides
   (NASA Thesaurus)
Any device or component that guides optical energy.
optically effective atmosphere
   (NASA SP-7, 1965)
That portion of the atmosphere lying below the altitude from which scattered light at twilight still reaches the observer with sufficient intensity to be discerned. Also called effective atmosphere.
The top of this region lies between 50 and 60 kilometers.
optics
   (NASA Thesaurus)
Branch of physical science concerned with the transmission, generation, manipulation, and detection of electromagnetic radiation in the wavelength range from vacuum ultraviolet to the far infrared.
optics
   (NASA SP-7, 1965)
See atmospheric optics.
optimal
   (NASA SP-7, 1965)
Pertaining to a trajectory, path, or control motion, one that minimizes or maximizes some quantity or combination of quantities such as fuel, time, energy, distance, heat transfer, etc. This optimum condition, or path, is commonly calculated by a type of mathematics known as calculus of variations.
optimization
   (NASA Thesaurus)
The procedure used in the design of a system to maximize or minimize some performance index. May entail the selection of a component, a principle of operation, or a technique.
optoelectronic devices
   (NASA Thesaurus)
Electronic devices combining optic and electric ports.
optogalvanic spectroscopy
   (NASA Thesaurus)
A method of obtaining absorption spectra of atomic and molecular species in flames and electrical discharges by measuring voltage and current changes upon laser irradiation.
OR
   (NASA SP-7, 1965)
1. The logical operator which has the property that A or B is true if either A is true or B is true.
2. In Boolean algebra, the operation of union.
OR-circuit
   (NASA SP-7, 1965)
= OR-gate.
OR-gate
   (NASA SP-7, 1965)
A gate whose output is energized when any one or more of the inputs is in its prescribed state. An OR-gate performs the function of the logical inclusive-OR , of Boolean algebra.
orbit
   (NASA SP-7, 1965)
1. The path of a body or particle under the influence of a gravitational or other force. For instance, the orbit of a celestial body is its path relative to another body around which it revolves.
Orbit is commonly used to designate a closed path and trajectory to denote a path which is not closed. Thus, the trajectory of a sounding rocket, the orbit of a satellite.
2. To go around the earth or other body in an orbit, sense 1.
orbit insertion
   (NASA Thesaurus)
The process by which a spacecraft enters into a desired orbit around a celestial body.
orbit spectrum utilization
   (NASA Thesaurus)
Telecommunication techniques in spectrum conservation for reducing user costs.
orbit transfer vehicles
   (NASA Thesaurus)
Concept of propulsive (velocity producing) rockets or stages for use with crew transfer modules, manned sortie modules, or other payloads. Used for OTV.
orbital
   (NASA SP-7, 1965)
Taking place in orbit, as orbital refueling , orbital launch , or pertaining to an orbit as orbital plane.
orbital elements
   (NASA Thesaurus / NASA SP-7, 1965)
A set of seven parameters defining the orbit of a body attracted by a central, inverse-square force.
Several different sets of parameters have been used. For artificial satellites the elements usually given are: longitude of the ascending node, capital omega; inclination of the orbit plane, i; argument of perigee, lower case omega; eccentricity, e; semimajor axis, a; mean anomaly, M; and epoch, t0 .
orbital glider
   (NASA SP-7, 1965)
See hypersonic glider.
orbital lifetime
   (NASA Thesaurus)
The predicted lifetime of a satellite in orbit, usually based on such criteria as solar flux density, atmospheric density, the lessening of the eccentricity of elliptical orbits, or the gravitational effects of the sun or the moon.
orbital motion
   (NASA SP-7, 1965)
Continuous motion in a closed path such as a circle or an ellipse.
orbital period
   (Solar System Dynamics Glossary - JPL)
The time required for an object to make a complete revolution along its orbit. For example, the orbital period for a typical main-belt asteroid is about 4 years.
orbital period
   (NASA SP-7, 1965)
The interval between successive passages of a satellite through the same point in its orbit. Often called period. See anomalistic period, nodical period, sidereal period.
orbital resonances (celestial mechanics)
   (NASA Thesaurus)
Systems of two or more satellites (including planets) that orbit the same primary and whose orbital mean motions are in a ratio of small whole numbers.
orbital servicing
   (NASA Thesaurus)
The replenishing of propellants, pressurants, coolants, and the replacement of modules and experiments, during some phase of a spacecraft flight to extend the mission and lifetime, or change the payloads.
orbital velocity
   (NASA Thesaurus / NASA SP-7, 1965)
1. The average velocity at which an earth satellite or other orbiting body travels around its primary. Compare separation velocity.
2. The velocity of such a body at any given point in its orbit, as in its orbital velocity at the apogee is less than at the perigee.
3. = circular velocity.
orbiting
   (NASA SP-7, 1965)
Of a spacecraft, in orbit about the earth or other spatial body, as in an orbiting astronomical laboratory.
orbits
   (NASA Thesaurus)
The paths of bodies or particles under the influence of a gravitational or other force. Used for orbital motion and periodic orbits.
order of magnitude
   (NASA SP-7, 1965)
A factor of 10. Compare octave, magnitude.
Two quantities of the same kind which differ by less than a factor of 10 are said to be of the same order of magnitude. Order of magnitude is used loosely by many writers to mean a pronounced difference in quantity but the difference may be much less or much more than a factor of 10.
order of reflection
   (NASA SP-7, 1965)
The number of hops, or trips, to the ionsphere and back to earth, that a radio wave makes in traveling from one point to another.
ordinary ray
   (NASA SP-7, 1965)
That magnetoionic wave component deviating the least, in most of its propagation characteristics, relative to those expected for a wave in the absence of the earth's magnetic field. More exactly, if at fixed electron density, the direction of the earth's magnetic field were rotated until its direction is transverse to the direction of phase propagation, the wave component whose propagation is then independent of the magnitude of the earth's magnetic field. Also called ordinary-wave component. See magnetic double refraction, magnetoionic theory.
ordinary wave component
   (NASA SP-7, 1965)
= ordinary ray.
organ
   (NASA SP-7, 1965)
A portion or subassembly of a computer which constitutes the means of accomplishing some inclusive operation or function (e.g., arithmetic organ).
organic charge transfer salts
   (NASA Thesaurus)
Organic compounds exhibiting temperature-dependent electrical, magnetic, and heat transfer properties.
organic chemistry
   (NASA Thesaurus)
The study of the composition, properties, structure, and reactions of carbon-based compounds, specifically hydrocarbons and their derivatives, and normally excluding carbon oxides, metallic carbonates, carbides, and carbon-sulfur and carbon-nitrogen compounds.
organic compounds
   (Galileo Project Glossary - JPL)
Complex chemical compounds that contain carbon
organic peroxides
   (NASA Thesaurus)
Organic compounds containing radical groups combined with oxides in which two atoms of oxygen are linked together, e.g., diethyl peroxide.
organic solids
   (NASA Thesaurus)
Solid materials composed of organic materials.
Ori, Orio
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Orion. See constellation.
origin
   (NASA SP-7, 1965)
The reference from which measurement begins.
Orio
   (NASA SP-7, 1965)
International Astronomical Union abbreviations for Orion. See constellation
Orion
   (NASA SP-7, 1965)
(abbr Ori, Orio)
See constellation.
Orion (radio interferometry network)
   (NASA Thesaurus)
An operational radio interferometry observational network.
Orion nebula
   (NASA Thesaurus)
An H 11 region about 500 pc distant and barely visible to the naked eye in the center of Orion's sword.
ortho-correction
   (Global Land Information System Glossary - USGS)
Correction applied to satellite imagery to account for terrain-induced distortion.
orthochromatic
   (NASA SP-7, 1965)
See color sensitive, note.
orthodrome
   (NASA SP-7, 1965)
= great circle.
orthogonal
   (NASA SP-7, 1965)
Originally, at right angles; later generalized to mean the vanishing of a sum (or integral) of products.
The cosine of the angle between two vectors V1 and V2 with the respective components x1, y1, z1, and x2, y2, z2 is proportional to the sum of products x1x2 + y1y2 + z1z2. Hence, if the vectors are perpendicular, the latter sum equals zero. For this reason any two series of numbers (x1, x2, ... Xn) and (y1, y2, ...yn) is said to be orthogonal if

summation symbol x sub I y sub I equals zero

.
orthogonal antennas
   (NASA SP-7, 1965)
In radar, a pair of transmitting and receiving antennas, or a single transmitting-receiving antenna, designed for the detection of a difference in polarization between the transmitted energy and the energy returned from the target.
orthogonal curvilinear coordinates
   (NASA SP-7, 1965)
See curvilinear coordinates.
orthogonal functions
   (NASA SP-7, 1965)
A set of functions, any two of which, by analogy to orthogonal vectors, vanish if their product is summed by integration over a specified interval.
For example, f(x) and g(x) are orthogonal in the interval x = a to x = b if the integral of a to b f of x g of x d x equals zero



The functions are also said to be normal if

the integral of a to b open bracket f of x close bracket squared d x equals the integral a to b open bracket g of x close bracket squared d x equals one

The most familiar examples of such functions, many of which have great importance in mathematical physics, are the sine and cosine functions between zero and 2pi.
orthogonic
   (NASA SP-7, 1965)
Pertaining to a state in which the spatial variations of a quantity have two planes of symmetry at right angles to each other.
osciducer
   (NASA SP-7, 1965)
A transducer in which information pertaining to the stimulus is provided in the form of deviation from the center frequency of an oscillator.
oscillation
   (NASA Thesaurus / NASA SP-7, 1965)
1. Fluctuation or vibration on each side of a mean value or position.
2. Half an oscillatory cycle, consisting of a fluctuation or vibration in one direction; half a vibration.
3. The variation, usually with time, of the magnitude of a quantity with respect to a specified reference when the magnitude is alternately greater and smaller than the reference.
oscillator
   (NASA Thesaurus / NASA SP-7, 1965)
A nonrotating device for producing alternating current.
oscillator strengths
   (NASA Thesaurus)
A quantum mechanical analog of the number of dispersion electrons having a given natural frequency in an atom, used in an equation for the absorption coefficient of a spectral line.
oscillatory wave
   (NASA SP-7, 1965)
A wave in which only the form advances, the individual particles moving in closed orbits, as ocean waves in deep water.
oscilloscope
   (NASA Thesaurus / NASA SP-7, 1965)
1. An instrument for producing a visual representation of oscillations or changes in an electric current.
2. Specifically, a cathode-ray oscilloscope.
The face of the cathode-ray tube used for this representation is called a scope or screen.
osculating elements
   (NASA SP-7, 1965)
The orbital elements of an osculating orbit.
osculating orbit
   (NASA SP-7, 1965)
The ellipse that a satellite would follow after a specific time t (the epoch of osculation) if all forces other than central inverse-square forces ceased to act from time t on.
An osculating orbit is tangent to the real, perturbed, orbit and has the same velocity at the point of tangency.
OSO
   (AS&T Dictionary)
Orbiting Solar Observatories-- A series of eight Sun observing satellites launched from 1962 to 1975.
OSO-8
   (NASA Thesaurus)
One of a series of NASA orbiting solar observatories developed mainly for solar research. Used for OSO-J.
OSR
   (Space Flight Glossary - JPL)
Optical Solar Reflector, thermal control component onboard a spacecraft.
OSS-1 payload
   (NASA Thesaurus)
Experiment package flown aboard the Space Shuttle STS-3 in 1982 which was sponsored by the NASA Office of Space Sciences from which the acronym is derived.
OSSA
   (Space Flight Glossary - JPL)
Office Of Space Science and Applications, NASA.
OSTA-1 payload
   (NASA Thesaurus)
Spaceborne experiments flown aboard the Space Shuttle STS-2 in 1981 which was sponsored by the NASA Office of Space & Terrestrial Applications from which the acronym is derived. Used for Office of Space & Terrestr Applic Payloads.
OSTA-3 payload
   (NASA Thesaurus)
Spaceborne systems flown aboard the Space Shuttle STS-17, sponsored by the NASA Office of Space & Terrestrial Applications from which the acronym is derived. The systems included the feature identification and location experiment-1 (FILE-1), the measurement of atmospheric pollution from satellite (MAPS), the imaging camera-B, and the large format camera/attitude reference system (LFC/ARS). Used for Office of Space & Terrestr Applic Payloads.
osteoporosis
   (NASA Thesaurus)
A medical condition whose chief symptom is the loss of internal bone mass.
otitic barotrauma
   (NASA SP-7, 1965)
= aero-otitis media.
OTM
   (Space Flight Glossary - JPL)
Orbit Trim Maneuver, spacecraft propulsive maneuver.
otolith
   (NASA SP-7, 1965)
A small calcareous concretion located in the inner ear which plays a part in the mechanism or orientation.
otolith organs
   (NASA Thesaurus / NASA SP-7, 1965)
Structures of the inner ear (utricle and saccule) which responds to linear acceleration and tilting.
out of phase
   (NASA SP-7, 1965)
The condition of two or more cyclic motions which are not at the same part of their cycles at the same instant. Also called out of step. Compare in phase.
Two or more cycles motions which are at the same part of their cycles at the same instant are said to be in phase or in step.
out of step
   (NASA SP-7, 1965)
= out of phase.
outer atmosphere
   (NASA SP-7, 1965)
Very generally, the atmosphere at a great distance from the earth's surface; an approximate synonym for exosphere.
outer planets
   (NASA SP-7, 1965)
The planets with orbits larger than that of Mars: Jupiter, Saturn, Uranus, Neptune, and Pluto.
outer product
   (NASA SP-7, 1965)
= vector product.
outgassing
   (NASA Thesaurus / NASA SP-7, 1965)
The evolution of gas from a material in a vacuum.
outliers (landforms)
   (NASA Thesaurus)
Areas or groups of rocks surrounded by rocks of older age. Used for klippen.
outliers (statistics)
   (NASA Thesaurus)
In sets of data values so far removed from other values in the distribution that their presence cannot be attributed to the random combination of change causes.
output
   (NASA Thesaurus / NASA SP-7, 1965)
1. The yield or product of an activity furnished by man, machine, or a system.
2. Power or energy delivered by an engine, generator, etc.
3. The electrical signal which emanates from a transducer and which is a function of the applied stimulus. Compare input.
The quantity represented by the signal may be given in terms of electrical units, frequency, or time.
output unit
   (NASA SP-7, 1965)
In computer terminology, a unit which delivers information from the computer to an external device or from internal storage to external storage.
overall heat-transfer coefficient
   (NASA SP-7, 1965)
(symbol U ). The value U , in British thermal units per hour per square foot per degrees F in the equation Q = UA(t1 - t2) where Q is heat flow per unit time; A is area; and t is temperature.
overexpanding nozzle
   (NASA SP-7, 1965)
A nozzle in which the fluid is expanded to a lower pressure than the external pressure.
An overexpanding nozzle has an exit area larger than the optimum.
Overhauser effect
   (NASA Thesaurus)
In atomic physics, a radio frequency field applied to a substance in an external magnetic field, whose nuclei have spin 1/2 and which has unpaired electrons at the electron spin resonance frequency. This results in polarization of the nuclei as great as if the nuclei had the much larger electron magnetic moment.
overpressure
   (NASA Thesaurus)
(1) The pressure resulting from the blast wave of an explosion. It is referred to as positive when it exceeds atmospheric pressure and negative during the passage of the wave when resulting pressures are less than atmospheric pressure. (2) The transient pressure, usually expressed in pounds per square inch, exceeding existing atmospheric pressure manifested in the blast wave from an explosion. During some period of the passage of the wave past a point, the overpressure is negative.
overshoot
   (Global Land Information System Glossary - USGS)
That portion of an arc (line) digitized past its intersection with another arc.
OWLT
   (Space Flight Glossary - JPL)
One-Way Light Time, elapsed time between Earth and spacecraft or solar system body.
oxazole
   (NASA Thesaurus)
Compounds that contain a five-membered heterocyclic ring containing one nitrogen and one oxygen atom.
oxidant
   (NASA SP-7, 1965)
= oxidizer.
oxidation
   (NASA Thesaurus)
A reaction in which electrons are removed from a reactant. Sometimes, more specifically the combination of a reactant with oxygen.
oxidation-reduction reactions
   (NASA Thesaurus)
An oxidizing chemical change, where an element's positive valence is increased (electron loss), accompanied by a simultaneous reduction of an associated element (electron gain).
oxidizer
   (NASA Thesaurus / NASA SP-7, 1965)
(symbol o, used as subscript). Specifically, a substance (not necessarily containing oxygen) that supports the combustion of a fuel or propellant.
oximeter
   (NASA SP-7, 1965)
An instrument for measuring the oxygen saturation of the blood.
oxygen 17
   (NASA Thesaurus)
An isotope of oxygen.
oxygen bottle
   (NASA SP-7, 1965)
A small container for pressurized oxygen used in life-support systems. See bailout bottle.
oxygen mask
   (NASA SP-7, 1965)
A covering for the nose and lower face fitted with special attachments for breathing oxygen or a mixture of oxygen and other gases.
The oxygen mask has provision for separating the expired breath from the incoming oxygen.
oxygen paradox
   (NASA SP-7, 1965)
= posthypoxia paradox.
oxynitrides
   (NASA Thesaurus)
Base for a broad field of nitrogen ceramics utilizing silicon, aluminum, and other elements to produce high temperature refractory materials.
ozone
   (NASA Thesaurus)
A very active form of oxygen that may be produced by the corona, arcing, or ultra-violet rays.
ozone layer
   (NASA SP-7, 1965)
= ozonosphere.
ozonosphere
   (NASA Thesaurus / NASA SP-7, 1965)
The general stratum of the upper atmosphere in which there is an appreciable ozone concentration and in which ozone plays an important part in the radiation balance of the atmosphere. This region lies roughly between 10 and 50 kilometers, with maximum ozone concentration at about 20 to 25 kilometers. Also called ozone layer. See atmospheric shell.