In 1999, the U.S. launched 11 civil science spacecraft, up three from the previous year. This growth has become a trend because since 1995 NASA has markedly increased the number of civil satellites it develops and launches. The main reason and guiding force behind this trend is the switch in development strategy, shortly after the loss, in August 1993, of the Mars Observer, from large, expensive satellites to smaller and more numerous ones. Such new probe classes as Discovery, New Millennium, Small Explorer, and Medium Explorer will produce over 20 civil satellites during the next few years.

As in the previous year, in 1999 several automated and remotely-controlled research and exploration missions continued to add a remarkable range of significant and, in part, revolutionary discoveries to our growing body of knowledge about the universe.

Hubble Space Telescope. Nine years after it was placed in orbit, the Hubble Space Telescope (HST) continues to probe far beyond the Solar System, producing imagery and data useful across a range of astronomical disciplines.

The resulting data, in 1999, were used in one of the space telescope's most important projects to date - to determine more accurately the expansion rate of the universe and to give astronomers an extragalactic distance scale for their measurements. Using the unmatched resolution and photometry of the HST, astronomers reduced the uncertainties of the Hubble Constant that tells how rapidly the universe is expanding, by measuring the change in relative velocity of astronomical objects with distance, based on the Big Bang theory. The new estimate of the age of the cosmos is 12-13.5 billion years, and the reduction in uncertainty also showed that the universe will not collapse due to gravity but continue to expand indefinitely.

Among the stunning images from the HST are supermassive star clouds in the center of our Milky Way galaxy which give new clues of how stellar clusters are born, pictures of differing evolutionary paths of galaxies by peering deep inside the centers of star clusters and galaxies to resolve structures, bulges and bars of bright stars, the unusual bipolar shape of the Butterfly Nebula in the Large Magellanic Cloud, seen for the first time, and a dying star in the process of turning from a normal red giant into a planetary nebula, indicative of the likely future of our own Sun. Closer to Earth, Hubble's Wide Field and Planetary Camera, between April 27 and May 6, took pictures of the entire planet Mars, as it rotated, when it was only 87 million kilometers from Earth, the closest it has been in eight years.

When problems developed with the telescope's critical attitude control gyroscopes, leaving only two of its six gyros functioning and temporarily disabling the 12.5 ton, $3 billion facility, which went into a dormant "safe mode" stage, NASA quickly prepared an emergency repair and servicing mission with the space shuttle Discovery by dividing the regular maintenance and service mission scheduled for mid-2000 in two flights and launching the first one in December (see STS-103, above). The highly successful mission, during which the crew installed thirteen electronic systems and new protective blankets for the telescope, left it with a major increase in computer and data storage capability, new battery components, an upgraded guidance system and six new attitude gyros, laying the foundation for significant increases in observing capability as HST began its second decade in space.

Chandra. After several postponements during its development, testing, assembly and shipping, NASA's third "Great Observatory" (after Compton and Hubble), the massive Chandra X-ray Observatory was carried to orbit on 7/23 by the space shuttle Columbia (see STS-93, above). Named in honor of the late Indian-American astrophysicist and Nobel laureate Subrahmanyan Chandrasekhar, Chandra was formerly known as the Advanced X-ray Astronomy Facility (AXAF). With a total launch mass of 12,930 lbs. (5,870 kg), it is the largest satellite ever deployed by the space shuttle and the world's most powerful x-ray telescope. It uses a high-resolution camera, high-resolution mirrors and a charge-coupled detector (CCD) imaging spectrometer to observe, via x-rays, some of the most violent phenomena in the universe which cannot be seen by the Hubble's visual-range telescope. After barely two months in space, Chandra had already delivered a stunning image of the Crab Nebula, the spectacular remains of a stellar explosion, revealing something never seen before: a brilliant ring around the nebula's heart. Chandra also found long-sought "power lines" in the Crab, the most studied object in the sky, which connect the powerful spinning collapsed star with the luminous gas remnants around it. By the end of 1999, Chandra was well into its program of providing scientists with views of the high-energy universe never seen before which promise to revolutionize astronomical and cosmological concepts.

SOHO. In November, NASA engineers struggled to regain control of the European-U.S. Solar and Heliospheric Observatory (SOHO) after briefly losing contact with it. Cause was a "glitch" in the software which allows SOHO to operate without its gyroscopes. All three gyros had failed previously, and the new software was intended to enable the spacecraft to continue its science mission without them. A software patch returned the probe to normal operations.

By imaging strong ultraviolet reflections of sunspots on the far side of the Sun in the solar atmosphere, SOHO opened a way for scientists to study the backside of the Sun, out of view from Earth. This intriguing new discovery by French researchers could be used to predict solar storms threatening the Earth and future spacefarers much earlier than at present. New results from SOHO also indicate that the waves in the Sun's atmosphere are produced by vibrating solar magnetic field lines which give solar wind particles a push like an ocean wave pushes a surfer on a ride. In November, SOHO also tracked, along with NASA's Transition Region and Coronal Explorer (TRACE), a pass (transit) of the planet Mercury in front of the Sun for its entire duration of 51 minutes. The data will allow improved measuring of the Sun's outer atmosphere, or corona.

Galileo. Galileo in 1999 continued to return unprecedented data on Jupiter and its satellites, with several encounters with Jupiter's bizarre moons: one with Europa on 1/31, four with Callisto starting 5/5 and two with Io. The first one, on 10/11, was at 380 miles (612 km), yielding images 50 times better than the previous best picture of Io from Voyager 1 in 1979, and on 11/25, the probe flew by the colorful moon in a do-or-die effort at the extremely short range of only 187 miles (300 km) passage - and survived. Galileo, launched in October 1989, has revolutionized our knowledge about the mysterious, fascinating worlds of Jupiter's planetary system, offering tantalizing glimpses of possible life-supportive environments on some of the moons. On Europa, the probe in 1999 found sulfuric acid on the frozen surface, beneath which may lie a liquid ocean with bio-organic substances. This theory is supported by patterns of arc-shaped cracks in the surface, called cycloids, that are probably caused by tidal forces.

Cassini. Cassini, NASA's six-ton spacecraft heading to the planet Saturn on an epic 6.7-year, 3.2-billion-km journey, flew by the planet Venus on 6/24 and then made a close approach of Earth of 727 miles (1163 km) over the South Pacific on 8/17 (11:28pm EDT) on its last of three inner-planet flybys designed to accelerate the scientific probe toward its four-year mission at Saturn, beginning in 2004. During the Earth flyby it took a sequence of Moon photographs to calibrate its imaging science subsystem camera. In addition to the June and August flybys, Cassini has flown past Venus before in April 1998. The Earth passage gained the spacecraft a speed increase of 12,000 miles per hour (5.5 km/sec). A final planetary flyby, with Jupiter, will take place on 12/30/2000, boosting Cassini's velocity by 2.2 km/sec (5000 mph). The spacecraft remains in excellent health.

DS-1. NASA's Deep Space 1 (DS-1) technology test satellite on 7/29 undertook the closest encounter with an asteroid ever attempted when it flew within 10 miles (16 km) of the asteroid 1992 KD, newly named Braille. To alter its trajectory toward the rendezvous, DS-1 performed a six-week burn of its low-thrust xenon ion engine in March/April when it was more than 1.2 astronomical units (AU) from the Sun. With less than 70% of sunlight intensity of that at Earth available at that distance, the engine produced only about 0.14 ounces (40 milliNewtons) of thrust, but due to its extensive burn time it can effect trajectory changes while using little propellant (for example, a total of 9 kg of xenon gas have produced 545 m/s velocity change). DS-1 relied on its experimental autonomous navigation system AutoNav to guide itself past the asteroid. This system determines position by optically sighting on asteroids and stars, calculating the future trajectory, and devising and executing engine firings to meet the desired trajectory conditions. Launched on 10/24/98 on NASA's first Med-Lite version of the Boeing Delta 2 7326 booster (which uses only three solid strap-ons instead of nine) on its two-year voyage into a stretched-out elliptical orbit around the Sun, the spacecraft's mission is to test several advanced technologies for future interplanetary science missions, particularly the ion engine which uses electric power to accelerate ionized xenon fuel to over 18 miles per second (30 km/sec) for high-efficiency low-thrust (0.02 lbf, 9.4 grams). Other revolutionary technologies on board besides the AutoNav are testing power generation with concentrator solar arrays, Ka-band communications, and others.

If further tests go off as planned, DS-1 is tentatively scheduled for a flyby in January 2001 at the mysterious object Wilson-Harrington and, in September of the same year, at comet Borelly.

Lunar Prospector. By deliberately crashing the 660 lbs. (300 kg) spacecraft Lunar Prospector into the Moon at the end of its low-budget ($63 million) research mission in circumlunar orbit, NASA had hoped to get some evidence of whether there is hidden water ice on the Moon. The controlled crash of this third flight in NASA's Discovery Program of lower-cost, highly focused Solar System exploration, which had been launched on January 6, 1998, into a shadowed crater near the south pole did not produce any ultraviolet spectral lines of hydroxyl (OH) molecules in the cloud kicked up by the impact which would have been a water "signature".

QuickSCAT. NASA's Quick Scatterometer (QuickSCAT) mission to measure wind speed and direction over the world's oceans from space was launched on a Titan 2 on June 20. The 1914-lbs. (870 kg) spacecraft, which replaced a critical NASA "SeaWinds" instrument lost when Japan's ADEOS satellite failed in 1997, was placed in a sun-synchronous orbit of 98 degrees inclination and 499 miles (803 km) altitude. As an example of its uses, in September the SeaWinds radar tracked a large iceberg over a lengthy period which could have posed a threat to international shipping. The iceberg, measuring 24 x 48 miles (38 x 77 km), had detached from Antarctica seven years earlier.

ACE & Wind. The two NASA spacecraft ACE (Advanced Composition Explorer) and Wind during May found that the density of the solar wind dropped by more than 98%. This gave physicists the unique opportunity to observe particles (electrons) flowing directly from the Sun's corona to Earth. The severe change in the solar wind also changed the shape of the Earth's magnetic field (magnetosphere) and produced an unusual auroral display at the North Pole.

Stardust. NASA's comet probe Stardust was launched on 2/3 on a Delta 2 to begin its mission to intercept a comet and return close-up imagery and a soil sample to Earth. On its trajectory to its rendezvous with Comet Wild-2 in 2004, the spacecraft went suddenly into a safing mode on March 18. The computer had determined that it was carrying out an excessive number of functions during testing of the Stardust navigation camera and the return of its images to Earth. Controllers quickly commanded the probe back to a normal operational mode.

WIRE. The Wide-Field Infrared Explorer (WIRE) was launched on 3/4 on a Pegasus XL air-launched booster to conduct extra-galactic science surveys in the deep infrared. After deployment in orbit, the spacecraft was observed, during its first pass over the Poker Flat, Alaska, ground station, to be initially tumbling at 60 revolutions per minute, a rate higher than expected. After significant recovery efforts, WIRE was declared a loss on 3/8 after all solid hydrogen on board, necessary for the instrument, had been lost by inadvertent venting when the telescope instrument cover was ejected three days earlier than planned.

FUSE. NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) was launched on June 24 from Cape Canaveral on a Delta 2 Med-Lite vehicle. Following the liftoff, the 3000-lbs. (1360-kg) spacecraft was successfully placed into the targeted 480 mi. (768 km) orbit inclined 25 degrees against the equator, despite a misalignment of 5.3 degrees during its installation on top of the Delta booster. The spacecraft's mission is to characterize relationships between the interstellar medium and star formation and determine how much mass in the Universe was created during the Big Bang. The mission, of about $215 million total including the launcher, was the first developed for NASA by a university (Johns Hopkins), and France and Canada are participating with critical hardware.

NEAR. Almost three years after its liftoff in February '96, the Near Earth Asteroid Rendezvous (NEAR) spacecraft, NASA's second Discovery program mission, fired its engine on 1/3 to gain a second chance to meet and orbit the asteroid 433 Eros after a failure of the first of several rendezvous maneuvers on 12/20/98 changed plans. Instead of meeting its rendezvous with Eros in January 1999, NEAR was now set on a course to fulfill its research mission in mid-February 2000.

Mars exploration. In 1999 Mars continued to be the focus of excitement, even if partly for spectacular failure rather than success. Mars Global Surveyor continued to produce the highest resolution images of Mars to date, after concluding aerobraking into an operational orbit using atmospheric drag. Intended to investigate Mars on a global scale, the Mars Climate Orbiter suffered a stunning failure instead, followed by the disappearance of Mars Polar Lander. As investigations into the basic designs of low-cost robotic Mars missions are continuing, new missions are anticipated for 2001 and beyond, set to be launched in synodic period intervals of 26 months, preparatory to human expeditions now expected to follow in about the second decade after 2000.

Mars Global Surveyor. MGS was the first Surveyor-type Mars explorer of a series of probes planned for the next decade. After its arrival at Mars on 9/11/97, it started a long series of aerobrake passes around the planet. After reaching its operational orbit early in 1999, it began its mapping mission on 3/9. For the first three weeks, the mission proceeded with the spacecraft's 1.5-m (5 ft) high-gain antenna stowed due to concerns about the proper operation of its deployment mechanism. On 3/28, the antenna was successfully deployed. Since then, MGS has been transmitting a steady stream of high-resolution images of Mars. Overall, they showed that the red planet is a different place today than it was two years ago when the spacecraft arrived -- a world constantly reshaped by forces of nature including shifting sand dunes, monster dust devils, wind storms, frosts and polar ice caps that grow and retreat with the seasons. Today, Mars is a much more dynamic place than it was when the Viking spacecraft saw it in the late 1970s. In August, MGS' Mars Orbiter Camera succeeded in capturing images of the shadow of the Martian moon Phobos on the surface of the planet in western Xanthe Terras. Previously, MGS, for the first time in Mars exploration, mapped the full evolution of a Martian dust storm. Data from its Thermal Emission Spectrometer also supported the finding from Pathfinder that the red planet once had abundant water and thermal activity. Also for the first time, a three-dimensional picture of Mars' north pole was assembled from 2.6 million laser pulse measurements, with a spatial resolution of 0.6 miles (1 km) and a vertical accuracy of 15-90 ft (5-30 m). It allowed, for the first time, an estimate of the volume of the water ice cap with unprecedented precision, as well as study of surface variations and cloud heights in the region for the first time. MGS photographs of the Cydonia region, taken in 1998, also revealed the previously controversial "Face on Mars" to be an eroded mesa-like hill, as scientists had expected.

Mars Climate Orbiter. In September, NASA's Mars Climate Orbiter (MCO) prepared to enter orbit around Mars after a nine-months voyage from Earth where it had been launched on 12/11/98 on a Delta 2 rocket, for a nearly two-year study of the red planet's climate and the circulation of its atmosphere, and also, for the first several months after its arrival, to serve as a communications relay for the Mars Polar Lander. On 9/23, however, MCO failed to enter orbit due to navigation and maneuver errors caused by a mix-up in measurement units between two separate operations teams at Lockheed Martin and NASA's Jet Propulsion Laboratory (JPL). The numerical values used for trajectory modeling had been calculated in English units by spacecraft engineers and were mistakenly assumed, by spacecraft navigators calculating attitude control maneuvers, to be in metric units. As a result, MCO began its planned orbit insertion burn of 16m 23s duration at about 60 km (37.5 mi.) altitude, i.e., about 25 km (15.6 mi.) lower than what navigators had considered the minimal acceptable altitude for survival of the spacecraft, and thus was destroyed by atmospheric friction.

Mars Polar Lander. After the MCO loss, NASA's quickly established Mishap Investigation Board had about two months to investigate the cause of the failure and ensure that the Mars Polar Lander (MPL), due to arrive on 12/3, would not suffer a similar fate. Contact with MPL was lost as expected on 12/3 at 3:02 pm EST after the spacecraft had turned its antenna away from Earth by 75 degrees and shut off its transmitter in the process of assuming its proper entry attitude. Contact with the lander was never regained, and at the end of 1999 it remained unknown whether it had actually entered the Martian atmosphere and landed as planned at the so-called Mars Layered Deposits near the south pole, the first lander mission intended for a polar region of the planet. It is also not known whether its two Deep Space 2 (DS-2) penetrator microprobes, named Scott and Amundsen after Earth's famous south-pole explorers, had separated from the spacecraft before atmospheric entry and impacted on the surface. Despite intensive search efforts continuing at year's end no radio signals were received either from the lander nor the microprobes.

Pioneer 10. Launched from Cape Kennedy in 1972 aboard an Atlas/Centaur on a mission to Jupiter planned for only two years, the 570-lbs. (258-kg) Pioneer 10, the Earth's longest-lived interplanetary explorer, continues on its epic voyage to the stars as contact with it is still maintained by NASA's Deep Space Network. Currently at a distance of 11 billion kilometers (7 billion miles) from Earth, Pioneer 10 is passing through the transitional region between the farthest traces of the Sun's atmosphere, the heliosphere, still noticeable at that distance, and free intergalactic space. Signals transmitted by the little spacecraft today need 10 hours 10 minutes to reach Earth. Its course is pointed in the direction of the star Aldebaran, the "eye" of the constellation Taurus at a distance of 68 light-years (LY), which it will reach in two million years. But before that, at its current speed of 45,000 km/h (28,000 mph) the spacecraft will pass the red dwarf Proxima Centauri in 26,118 years, come within 3.2 LY of the red dwarf star Ross-248 in the Andromeda Nebula in 32,605 years, and fly by the white giant star Altair in 227,068 years.

Questions or comments? Send a message to Jesco von Puttkamer

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