Ulysses probe

Ulysses

Artist rendering of Ulysses spacecraft in the inner Solar System
Operator	NASA / ESA
COSPAR ID	1990-090B
SATCAT no.	20842
Website	NASA Page ESA Page
Mission duration	18 years, 8 months and 24 days
Spacecraft properties
Launch mass	370 kg (820 lb)
Power	285 W
Start of mission
Launch date	11:47:16, October 6, 1990 (1990-10-06T11:47:16)
Rocket	Space Shuttle Discovery (STS-41) with Inertial Upper Stage and PAM-S
Launch site	KSC Launch Complex 39B
End of mission
Disposal	Decommissioned
Deactivated	June 30, 2009 (2009-06-30)
Orbital parameters
Reference system	Heliocentric
Eccentricity	0.60262
Perihelion	1.35 AU
Apohelion	5.4 AU
Inclination	79.11°
Period	2,264.26 days
Epoch	12:00:00, February 24, 1992
Flyby of Jupiter (gravity assist)
Closest approach	February 08, 1992
Distance	6.3 Jupiter Radii
ESA solar system insignia for the Ulysses mission

Ulysses is a decommissioned robotic space probe whose primary mission was to orbit the Sun and study it at all latitudes. It was launched in 1990, made three "fast latitude scans" of the Sun in 1994/1995, 2000/2001, and 2007/2008. In addition, the probe studied several comets. Ulysses was a joint venture of NASA and the European Space Agency (ESA) with participation from Canada's National Research Council. The last day for mission operations on Ulysses was June 30, 2009.

To study the Sun at all latitudes the probe needed to change its orbital inclination and leave the plane of the Solar System – to change the orbital inclination of a spacecraft a large change in heliocentric velocity is needed. However the necessary amount of velocity change to achieve a high inclination orbit of about 80° far exceeded the capabilities of any launch vehicle. Therefore, to reach the desired orbit around the Sun a gravity assist manoeuvre around Jupiter was chosen, but this Jupiter encounter meant that Ulysses could not be powered by solar cells – the probe instead was powered by a radioisotope thermoelectric generator (RTG).

The spacecraft was originally named Odysseus, because of its lengthy and indirect trajectory to study the solar poles. It was renamed Ulysses, the Latin translation of "Odysseus", at ESA's request in honour not only of Homer's mythological hero but also with reference to Dante's description in Dante's Inferno.Ulysses was originally scheduled for launch in May 1986 aboard the Space Shuttle Challenger on STS-61-F. Due to the loss of Challenger, the launch of Ulysses was delayed until October 6, 1990 aboard Discovery (mission STS-41).