The heart of the NASA programs has remained its shuttle fleet of four manned orbiters (COLUMBIA, DISCOVERY, ATLANTIS, ENDEAVOUR). By the end of the decade, the fleet will be almost 20 years old, and have flown over 150 missions. Although the shuttle was never able to meet it planned expectations of low cost and ready access to space, it was and is a marvelous manned technological machine that proved that a vehicle could be reusable and is laying the ground work for follow on manned spacecraft. The building blocks to space have always been a reusable shuttle, a Space Station, and manned expeditions to the Moon, Mars and beyond. NASA was finally able to initiate, design, build and start assembly of its International Space Station.
Part of the agreement with Congress over beginning the Station program was to bring in the international community to help defray costs, and this NASA was able to do. There are almost a dozen international partners on the program including Japan, ESA and Russia. In fact, Russia is supplying two of the first three major components of the station based on MIR designs and technology and the country's experience in operating Salyut and MIR for over 20 years. Russia will also supply Soyuz spacecraft to act as emergency escape vehicles for the station early on in the program. Assembly began in 1998 with the launch of the first component from Russia, and then in 1999 with the first American component. Anticipating the international Space Station, the United States began sending American astronauts to the MIR Space Station complex.
Interplanetary exploration had a mild resurgence in the 1990s. Two probes launched in 1989, Magellan to Venus and Galileo to Jupiter, reached their destinations in the 90s. Magellan arrived at Venus 1990 and began radar mapping operations soon thereafter. Magellan showed that Venus was more geologically active than previous thought. Galileo arrived at Jupiter in 1995, and began exploration of the Jovian system. This included release of a probe into Jupiter's atmosphere and with precise orbital maneuvers, exploration of the many moons of this large planet. In 1992, NASA launched its first probe to Mars in over 15 years, the Mars Observer. Unfortunately, two days before reaching Mars, the Observer went dead when controllers at the Jet Propulsion Lab (JPL) attempted some pressurization tests for the propulsion and attitude control systems. NASA also sent the last great interplanetary probe Cassini to Saturn in 1997. It will reach Saturn in the next century. Two new probes were designed and launched in 1996 on Delta expendable boosters, the Mars Pathfinder and the Mars Global Surveyor. The country watched with delight when the Mars Pathfinder successfully landed on the Red Planet, and released its Mars Rover to roam over the Martian terrain. Finally in 1997, NASA returned to the Moon with its Lunar Prospector.
NASA maintained a healthy space science and earth applications programs during this time period. These satellites include: the Combined Release and Radiation Effects Satellite (CCRES) launched to perform a one-to-three year study of the earth's magnetic field; The Gamma Ray Observatory (GRO), the second in a series of four NASA Great Observatories, is a platform hosting four experiments that detect the gamma ray emissions of cataclysmic cosmic events (black holes, pulsars, quasars) during a 15-month sky survey mission; the Upper Atmosphere Research Satellite (UARS) was the first in a series of NASA environmental monitoring satellites; Extreme Ultraviolet Explorer (EUVE) was designed to study the heavens through the extreme ultraviolet (EUV) region of the electromagnetic spectrum; and Geotail was a scientific mission to explore the earth's geomagnetic tail and was cosponsored by NASA and the Japanese Institute of Space and Astronautical Science (ISAS). NASA also continued its advances in spacecraft technology with the Advanced Communications Technology Satellites (ACTS) which was a joint NASA, Defense Department and private industry venture.