Hubble’s vision problem
The earliest test images from the Hubble Space Telescope alert ground-based astronomers to a serious problem: the telescope’s huge mirror has been ground to an incorrect shape, leaving the $2,000,000,000 telescope with a vision problem resulting in blurry pictures. Though they’re still an improvement over ground-based telescopes, the telescope’s main selling point – high-resolution images of distant objects – is moot. With the public considering the expensive satellite a failure (oblivious to the fact that it can be serviced via Space Shuttle), NASA begins an extensive investigation into the problem, arriving at a possible repair that can’t be applied until the first shuttle servicing mission to Hubble in 1993. In the meantime, attempts to correct the problem with Earthbound computer image processing yield some usable images.
Encouraged by the public interest in 
Launched via space shuttle in May 1989, the long-delayed Magellan space probe reaches the planet Venus after an unusually long voyage (15 months) and begins an orbital insertion maneuver. Where most missions to Venus have reached the planet in only a few months, Magellan has had to make do without the more powerful Centaur liquid-fueled booster stage, resulting in a journey of a year and three months. (The Centaur upper stage had been cancelled after the Challenger disaster because it was felt that carrying an additional liquid-fueled rocket in a shuttle cargo bay was too risky.) Magellan is placed into an elliptical orbit, completely circling Venus every three hours, where it will conduct high-resolution radar mapping of the surface at the closest point in its orbit, and transmitting the resulting data to Earth while furthest from Venus. The first phase of the mapping mission will last through 1991.
NASA’s Magellan space probe, orbiting the planet Venus, has completed a checkout phase and begins its primary mapping mission, intended to gather data of the Venusian surface as high resolution as one kilometer per pixel. Rather than using visible light – which would yield only images of Venus’ dense clouds – Magellan uses radar to map the planet’s blistering hot surface. Launched in May 1989 via space shuttle, Magellan will continue mapping the surface of Venus through May 1991.
NASA/JPL’s Galileo space probe reaches the second destination on the lengthy “
Launched in 1989 via Space Shuttle, the unmanned Galileo probe reveals a significant technical problem during its first flyby of Earth: the umbrella-like high-gain antenna, allowing it to send its observations of Jupiter and its moons back to Earth at high speed, is stuck in a partly-open, partly-closed configuration that prevents its use. Ground engineers at JPL have to devise data compression schemes, and a tight record/playback schedule, that will allow Galileo to take all of its planned observations and send them back to Earth at a lower bit rate than planned. It is theorized that the long delays in Galileo’s launch – the probe was ready for launch in 1982 but had to wait through delays in the early shuttle program and was then kept in storage in the aftermath of the Challenger disaster – allowed the antenna’s lubricant to dry up. Galileo won’t reach its target planet, Jupiter, until 1995.
NASA’s Magellan space probe, which has been mapping the planet Venus from orbit since September 1990, completes the first phase of its map-making mission, completing radar imaging of more than 80% of the planet’s surface. NASA authorizes an extended mission, lasting into 1992, which will yield a more complete map of the Venusian surface, including its polar regions.
NASA/JPL’s Galileo space probe, looping repeatedly through the inner solar system to gain a speed boost from a series of gravity assists from Earth and Venus, passes the asteroid 951 Gaspra, the first human-made spacecraft to visit such a body. Where humanity’s previous knowledge of asteroids was limited at best, Galileo’s findings are startling, with photos showing a small rocky body pummeled by ancient impacts, almost to the point of shattering it. Also discovered is a magnetic field generated by the core of the asteroid itself, something planetary scientists did not expect to find at all. Galileo will loop back toward Earth, picking up a critical speed boost to Jupiter from one last flyby of its home planet.
The third phase of data gathering begins for NASA’s Magellan unmanned space probe, launched via space shuttle in 1989 and currently orbiting the heavily-clouded planet Venus. Using radar to peer through the planet’s dense clouds, Magellan has now mapped 96% of the planet’s surface, and will now spend much of the remainder of 1992 filling in details in regions it has missed, as well as re-scanning some regions of Venus stereoscopically, allowing for three-dimensional terrain reconstruction.
A tech demonstration at the Jet Propulsion Laboratory leads to a rethink of the upcoming Mars Environmental Survey mission (MESUR). A self-contained “rover” named Rocky IV convinces mission planners to include a similar rover on an upcoming Mars mission; although the rest of MESUR is eventually scrapped due to budget cuts, the one portion of it to be salvaged is the Mars Pathfinder lander, which will deliver the rover (later to be named Sojourner in a nationwide contest) to the Martian surface sometime in the late ’90s.
NASA and JPL announce a plan is in the works to launch small twin spacecraft toward the planet Pluto. The Pluto Fast Flyby mission would launch two vehicles in 1997 or 1998, much smaller than the Voyager spacecraft that have explored the larger outer planets, with the two vehicles possibly arriving at Pluto as early as 2005 or 2007. Pluto Fast Flyby has the support of NASA’s new administrator and the White House, both of whom are insisting that NASA embrace a “faster, better, cheaper” space exploration philosophy. To save weight and energy, the initial mission proposal calls for no instruments other than cameras. This meets with protests from scientists (and proponents of the earlier 
NASA’s unmanned Magellan space probe, having completed three extensive campaigns of mapping the surface of Venus from orbit with cloud-penetrating radar, begins a fourth mission phase, this time sending constant engineering telemetry to Earth, where measurements of Doppler shift in the signal received allows Earthbound scientists to map the gravitational field of Venus. Magellan’s map-making days are over, having achieved a 98% complete map of the cloud-shrouded planet that it has been orbiting since 1990.
The Pioneer Venus Orbiter, launched into orbit around Venus in 1978 and now the only surviving component of the Pioneer Venus mission, enters the cloudy planet’s dense, toxic atmosphere and disintegrates, its fuel supply too exhausted to keep it in orbit any longer. Originally intended to orbit Venus for only a year, Pioneer Venus has survived, fully functional, for nearly 14 years in Venusian orbit, continuing to study the planet and taking readings not only Venus but such objects as Halley’s Comet.
Catching the last gravity assist on its four-year “
To increase the accuracy of its gravity map of the planet Venus, NASA’s unmanned space probe Magellan conducts the first experimental aerobraking maneuvers to alter the shape its orbit to a near-circular shape. By dipping Magellan into the upper layers of the Venusian atmosphere, the spacecraft is slowed and its orbit is changed, but it is kept far enough from the denser lower layers of the atmosphere to avoid re-entry. Aerobraking will become more commonly used by future space probes at the planet Mars.
Bound for Jupiter, the NASA/JPL unmanned space probe Galileo swings past the asteroid Ida, discovering – for the first time – an asteroid with its own satellite, a tiny body orbiting Ida. The satellite is later named Dactyl. This is only the second asteroid to be visited by a spacecraft from Earth, and Ida also marks Galileo’s last visit to a body in the solar system before a two-year cruise toward Jupiter.
NASA launches Space Shuttle Endeavour on a ten-day mission to retrieve and repair the Hubble Space Telescope, which was launched in 1990 with flawed optics. With the $2,000,000,000 telescope held steady in the cargo bay, Endeavour astronauts conduct repairs during spacewalks totaling over 35 hours of the mission, before releasing Hubble back into orbit with new eyes. Aboard Endeavour for her history-making fifth flight are Commander Richard Covey, Pilot Kenneth Bowersox, Payload Commander Story Musgrave, and mission specialists Kathryn Thornton, Claude Nicollier, Jeffrey Hoffman and Tom Akers.
Following the Space Shuttle repair mission to the Hubble Space Telescope, the orbiting telescope’s new Wide Field and Planetary Camera 2 shows incredible improvement in image resolution. By determining the exact deformation of the telescope’s main mirror, the new camera is created almost like corrective glasses: it’s designed to compensate for that deformation at all times. The resulting improvement in image quality is remarkable, enabling Hubble to spot volcanic activity on Io, a moon of Jupiter whose volcanoes have only been visible from space probes making a close flyby. Hubble’s improved vision also arrives just in time to witness an unprecedented event: a cometary collision with Jupiter later in 1994.
NASA’s Clementine unmanned spacecraft is launched from Vandenberg Air Force Base toward Earth’s moon, the first American spacecraft to aim at that destination since the 1970s. Intended to map the moon with multispectral cameras and obtain a fresh gravity map, Clementine is a huge technological advance over NASA’s last lunar vehicle, featuring a 32-bit image processing system with solid state data storage. Clementine takes a leisurely trajectory to reach its destination, flying by Earth twice before reaching the moon a month after launch.
NOAA’s GOES-8 Geostationary Operational Environmental Satellite is launched from Cape Canaveral into a geosynchronous orbit now designated GOES-EAST to monitor weather patterns over the United States; its predecessor, GOES-7, takes up the GOES-WEST position. GOES-8 is a major design evolution in the GOES weather satellite series, incorporating new hardware, some of which proves to be less sturdy than is required for an extensive orbital tour of duty. GOES-8 will remain in the GOES-EAST orbit until it is retired from active weather-watching duty in 2003 and shut down in 2004.
NASA’s Clementine lunar orbiter, its moon mapping mission complete, is directed to fire its engines to put it on a trajectory for asteroid 1620 Geographos, a near-Earth asteroid named for the National Geographic Society (which sponsored a sky survey that led to its discovery). But one of Clementine’s thrusters stays on too long, firing for 11 minutes and revving the vehicle up to an unrecoverable spin of 80 revolutions per minute, exhausting its entire fuel supply in the process. Clementine’s secondary mission to Geographos is abandoned, and its batteries are exhausted a month later.
Its collision with the solar system’s largest planet predicted over a year in advance, the fragments of Comet Shoemaker-Levy 9 begin impacting Jupiter’s atmosphere in an astronomical event lasting six days. With Earth-based telescopes watching, as well as cameras and instruments on the Hubble Space Telescope, Galileo and even Voyager 2, huge explosions are witnessed as the cometary chunks slam into Jupiter’s southern hemisphere at over 200,000 miles per hour, leaving dark “scars” larger than the diameter of Earth visible on the planet’s atmosphere and releasing more heat than the surface of the sun. Galileo is still over a year away from arriving at Jupiter.
NASA’s Magellan space probe, still orbiting Venus since 1990, enters a phase of slightly riskier experiments, dipping its solar panels into the upper reaches of the Venusian atmosphere and firing its reaction control engines to keep from spinning out of control. This allows for studies of the composition of Venus’ atmosphere, as well as studies of the vehicle’s behavior as it resists atmospheric friction. The results of the “windmill” experiment inform the design of future Mars probes which will need to aerobrake to slow down and enter the Martian atmosphere.
NASA’s Magellan space probe, orbiting Venus since 1990, is retired by entering the atmosphere of the planet whose surface it has mapped. With its power systems exhibiting signs of age and wear, Magellan has been intentionally dropped into an orbit low enough to allow its destruction in Venus’ dense atmosphere. Launched in 1989 via space shuttle, Magellan mapped the planet’s surface with cloud-penetrating radar, covering 98% of the Venusian surface, at least 1/5 of it with stereoscopic imaging allowing for accurate 3-D reconstruction of Venus’ surface features.
The Hubble Space Telescope, observing M16 (also known as the Eagle Nebula), takes what may be its most famous image: towering clouds of rapidly-evaporating interstellar gas which scientists theorize are the birthplace of new stars. The huge, light-years-long hydrogen clouds are dubbed evaporating gaseous globules, or EGGs; astronomers also call the structure a stellar nursery. The image quickly becomes a mainstay of the media, making appearances in Babylon 5 and the movie Contact.
After five months of independent flight, the Galileo atmospheric probe slams into the atmosphere of giant planet Jupiter at a speed over 100,000mph, burrowing over a hundred miles into the huge planet’s dense atmosphere before the heat of entry and the atmospheric pressure crush the probe. Deploying a parachute to slow its descent, the probe survives for nearly an hour, its sensors finding a surprisingly dry atmosphere. As it plummets toward the center of Jupiter, the Galileo probe registers 450mph winds, but never finds any hints of anything resembling a solid surface. The sum total of the probe’s sensor readings – the entirety of our data gathered directly within the atmosphere of Jupiter – tops out at 460 kilobytes of data.
The NEAR (Near Earth Asteroid Rendezvous) unmanned spacecraft, built and flown for NASA by John Hopkins University’s Applied Physics Lab, lifts off from Cape Canaveral on a mission to orbit and study asteroid 433 Eros, a target it won’t reach until 1998 at the earliest; it will fly by another asteroid in 1997. Other trajectories under consideration during mission planning included a combination of several asteroids and comets, before the limitations of NEAR’s chemical propulsion system forced those plans to be scaled back. (A more ambitious multi-asteroid mission, Dawn, will be launched in the 21st century.) NEAR will become the first human-made spacecraft to land on an asteroid.
After decades of the tiny object being seen only as a point of light in even the best telescopic images, the Hubble Space Telescope makes the first survey of the surface of Pluto. Even without the distortion introduced by Earth’s atmosphere, Hubble’s best shots of Pluto are vague due to the distance from Earth to Pluto, but they mark the first time that even blurry surface detail has been seen. The new images help NASA gain support for a Pluto flyby mission in the 21st century, which will eventually be named New Horizons.
With NASA/JPL’s Pluto Fast Flyby mission cancelled, a new mission is proposed by several scientists and engineers, including veterans of the Voyager program, to send a small spacecraft to Pluto. Originally named Pluto Express, and later Pluto-Kuiper Express, the unmanned spacecraft would be armed with a handful of scientific instruments (as opposed to Pluto Fast Flyby’s camera-only proposal). Plans call for launch via a Delta Heavy rocket or from the cargo bay of a Space Shuttle in 2004, a Jupiter gravity assist flyby in 2006, and a Pluto flyby in 2012. Though there are early talks with the Russian space program about including landers or penetrators, that element of the mission is dropped soon afterward.