The American Galileo spacecraft makes its closest approach to 951 Gaspra, becoming the first probe to visit an asteroid.
951 Gaspra is an S-type asteroid that orbits very close to the inner edge of the asteroid belt. Gaspra was discovered by Russian astronomer G. N. Neujmin in 1916. Neujmin named it after Gaspra, a Black Sea retreat that was visited by his contemporaries, such as Gorky and Tolstoy.
Gaspra was the first asteroid ever to be closely approached when it was visited by the Galileo spacecraft, which flew by on its way to Jupiter on 29 October 1991.
Galileo was an American robotic space probe that studied the planet Jupiter and its moons, as well as the asteroids Gaspra and Ida. Named after the Italian astronomer Galileo Galilei, it consisted of an orbiter and an entry probe. It was delivered into Earth orbit on October 18, 1989 by Space Shuttle Atlantis. Galileo arrived at Jupiter on December 7, 1995, after gravitational assist flybys of Venus and Earth, and became the first spacecraft to orbit an outer planet.The Jet Propulsion Laboratory built the Galileo spacecraft and managed the Galileo program for NASA. West Germany's Messerschmitt-Bölkow-Blohm supplied the propulsion module. NASA's Ames Research Center managed the atmospheric probe, which was built by Hughes Aircraft Company. At launch, the orbiter and probe together had a mass of 2,562 kg (5,648 lb) and stood 6.15 m (20.2 ft) tall.
Spacecraft are normally stabilized either by spinning around a fixed axis or by maintaining a fixed orientation with reference to the Sun and a star. Galileo did both. One section of the spacecraft rotated at 3 revolutions per minute, keeping Galileo stable and holding six instruments that gathered data from many different directions, including the fields and particles instruments.
Galileo was intentionally destroyed in Jupiter's atmosphere on September 21, 2003. The next orbiter to be sent to Jupiter was Juno, which arrived on July 5, 2016.