Organization/Nation: ESA and U.S. (1)
Objective(s): heliocentric orbit
Spacecraft: Ulysses
Spacecraft Mass: 371 kg
Mission Design and Management: ESA and NASA JPL
Launch Vehicle: STS-41 Atlantis
Launch Date and Time: 6 October 1990 / 11:47:16 UT
Launch Site: ETR / launch complex 39B

Scientific Instruments:
1) BAM solar wind plasma experiment
2) GLG solar wind ion composition experiment
3) HED magnetic fields experiment
4) KEP energetic-particle composition/ neutral gas experiment
5) LAN low-energy charged-particle composition/anisotropy experiment
6) SIM cosmic rays and solar particles experiment
7) STO radio/plasma waves experiment
8) HUS solar x-rays and cosmic gamma-ray bursts experiment
9) GRU cosmic dust experiment

Results: The Ulysses mission was an outgrowth of the abandoned International Solar Polar Mission (ISPM) that involved two spacecraft flying over opposite solar poles to investigate the Sun in three dimensions.

Eventually, ESA built a single spacecraft for launch on the Space Shuttle. The vehicle was designed to fly a unique trajectory that would use a gravity-assist from Jupiter to take it below the elliptic plane, past the solar south pole, and then above the elliptic to fly over the north pole.

Eventually, thirteen years after ESA's science council had originally approved the mission, Ulysses was sent on its way via a Shuttle/PAM-S motor combination. Escape velocity was 15.4 kilometers per second, higher than had been achieved by either of the Voyagers or Pioneers, and the fastest velocity ever achieved by a humanmade object.

After a midcourse correction on 8 July 1991, Ulysses passed within 378,400 kilometers of Jupiter at 12:02 UT on 8 February 1992. After a seventeen-day period passing through and studying the Jovian system, the spacecraft headed downwards and back to the Sun.

From about mid-1993 on, Ulysses was constantly in the region of space dominated by the Sun's southern pole, as indicated by the constant negative polarity measured by the magnetometer. South polar observations extended from 26 June to 6 November 1994, when the vehicle was above 70ýý solar latitude. It reached a maximum of 80.2ýý in September 1994. Its instruments found that the solar wind blows faster at the south pole than at the equatorial regions.

Flying up above the solar equator on 5 March 1995, Ulysses passed over the north polar regions between 19 June and 30 September 1995 (maximum latitude of 80.2ýý). The closest approach to the Sun was on 12 March 1995 at a range of 200 million kilometers. ESA officially extended Ulysses's mission on 1 October 1995, renaming this portion as the Second Solar Orbit. The spacecraft made a second pass over the south pole between September 2000 and January 2001, and it made a pass over the northern pole in October 2001.

In October 2000, ESA announced that Ulysses had discovered the most distant gamma-ray burst yet recorded, about 11 billion light years from Earth.

ESA's Science Programme Committee extended the Ulysses mission from the end of 2001 to 1 September 2008.

Editor's Note: This mission profile was originally published in Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, by Asif A. Siddiqi, NASA Monographs in Aerospace History No. 24.