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Ulysses


Ulysses – the first and only planned mission to orbit over and around the Sun to explore and chart the unknown reaches of its polar regions – is, along with SOHO and Cluster, giving scientists their first close-up look at the Sun.

Named after the Greek hero, Ulysses is a joint NASA-ESA mission that was launched by Space Shuttle Discovery (STS-41) on October 6, 1990. On leaving Earth, the spacecraft, which is powered by a radioisotope thermoelectric generator (RTG), rocketed away at 9.5 miles/15.4 kilometers per second to become the fastest ever artificially-accelerated object, then in 1992 swung by Jupiter to gain the acceleration needed to send it out of the ecliptic plane and on toward its destination.

Ulysses is equipped with instruments to characterize fields, particles, and dust, to study the Sun's environment and understand how it works. In particular, the mission is studying the heliosphere, the huge bubble in which we live, and which is created by the solar wind blowing non-stop from the Sun. Ulysses was near perihelion in its observations of the Sun in 1995 and in 2001, recording the Sun near both a minimum (1995) in the solar cycle and near a maximum (2001). In 1996, Ulysses unexpectedly crossed the ion tail of Comet Hyakutake (C/1996 B2), revealing the tail to be at least 3.8 astronomical units (AU) in length. As it approached aphelion in 2003/2004, it made further distant observations of Jupiter. Its next perihelion is in mid-2007.

Ulysses was extended to at least March 2008, but in early 2005 NASA targeted it for cancellation, along with the legendary Voyager, because of budgetary woes.