Applications Programs The United States has conducted many applications programs and scientific projects in Earth orbit, which are discussed in numerous individual articles. Of ongoing programs that have become firmly integrated into everyday life, the two leading types involve communications satellites and Synchronous Meteorological Satellites. Dozens of the former type of satellite exist, built and operated by a number of different corporations. Of the latterÑbeyond the two past satellites of that specific nameÑthe most important is the Geostationary Operational Environmental Satellite (see GOES) operated by the National Oceanic and Atmospheric Administration (NOAA). Low-orbit weather satellites are also administered by NOAA and are launched into polar orbit under code names such as NOAA 9 and NOAA 10. By 1995, NASA had completed the space deployment of the revolutionary Tracking and Data Relay Satellite System, or TDRSS (see tracking station). This network of six satellites (three operational and three older ones acting as spares) in 24-hour orbit provides near-continuous communications with Space Shuttle missions, with many NASA science satellites, and with Department of Defense space assets. The Long Duration Exposure Facility, or LDEF, had been left in space in 1985 for a one-year mission, but the Challenger disaster delayed its retrieval several more years. Its experiments provided detailed data on the space environment's effect on materials to be used in building the space station, as well as some surprising finds on space radiation, space dust, space biology, and other scientific questions. In 1989 the Shuttle carried two major probes into space, the Magellan probe to Venus and the Galileo probe to Jupiter. In 1990 the Hubble Space Telescope was deployed, and an error in the optical system was corrected by a repair mission in 1994. Shuttle operations in 1995 were marked by the beginning of regular dockings with Russia's Mir space station and of lengthy stays there by astronauts. Improved life-support systems made flights of up to 18 days possible, and an improved jet backpack enabled astronauts to fly free of the Shuttle. In 1996, NASA signed a contract with a private contractor, United Space Alliance, the purpose of which was to reduce NASA's role in overseeing routine operations of the Shuttle fleet. NASA also began its development program for the Venture Star, a spacecraft that eventually is to replace the Shuttles.
Its nine powerful engines are designed to lift astronauts directly into space and return them to Earth, eliminating the need for booster rockets that separate from the ship during launch. With respect to military programs, by the late 1980s the Defense Department space budget well exceeded that of NASA. Expenditures were primarily for applications such as communications, tactical meteorology, navigation, missile warning, and reconnaissance. Military satellites are controlled from Onizuka Air Force Station in Sunnyvale, Calif., and from Falcon Air Force Station in Colorado Springs, Colo. Reconnaissance satellites, developed under the designation Keyhole (KH), perform an invaluable monitoring role by allowing detection of weapons buildups and providing verification for arms-control treaties. Satellites in the older KH 9, or Big Bird, series sent film back in small capsules, but the KH 11 satellites that have been operating since 1976 can transmit observations directly to ground stations. Each of them can operate for up to two years in orbit. Other military activities in space include the antisatellite (ASAT) missile being developed by the air force for launch from high-flying aircraft against targets in low orbits. Testing on ASAT was suspended, however, in response to a Soviet moratorium on its own so-called killer satellite. The highly controversial Strategic Defense Initiative nuclear-defense program (often referred to as "Star Wars") that had begun research and development in the 1980s was renamed scaled back in 1993. Space-based assets were no longer planned, but the program continued to conduct research on antimissile defense. Several scientific spin-offs of the program include many high-quality mirrors turned over to astronomical observatories for telescopes, and a series of space probes.