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Mission Type: Orbiter
Launch Vehicle: Space Shuttle Discovery, STS-41
Launch Site: Cape Canaveral, Fla., USA (launch complex 39B)
NASA Center: Jet Propulsion Laboratory
Spacecraft Mass: 371 kg
Spacecraft 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
Maximum Power: 285 W
Ulysses NASA Homepage,

Ulysses ESA Homepage,

Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, by Asif A. Siddiqi, NASA Monographs in Aerospace History No. 24

NSSDC Master Catalog,

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.

When space shuttle Discovery launched Ulysses on 6 Oct. 6 1990, it had an expected lifetime of five years. The mission gathered unique information about the heliosphere, the bubble in space carved by the solar wind, for nearly four times longer than expected.

Ulysses made nearly three complete orbits of the sun. The probe revealed for the first time the three-dimensional character of galactic cosmic radiation, energetic particles produced in solar storms and the solar wind. Not only has Ulysses allowed scientists to map constituents of the heliosphere in space, its longevity enabled them to observe the sun over a longer period of time than ever before.

The sun's activity varies with an 11-year cycle. Ulysses provided measurements covering almost two complete cycles. The long observation led to one of the mission's key discoveries: the solar wind has grown progressively weaker during the mission and is currently at its weakest since the start of the Space Age.

In addition to measuring the solar wind and charged particles, Ulysses instruments measured small dust particles and neutral gases from local interstellar space that penetrate into the heliosphere. Ulysses had an unprecedented three chance encounters with comet tails, registered more than 1,800 cosmic gamma-ray bursts, and provided findings for more than 1,000 scientific articles and two books.

"The breadth of science addressed by Ulysses is truly astonishing," said Ed Smith, Ulysses project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "The data acquired during the long lifetime of this mission have provided an unprecedented view of the solar activity cycle and its consequences and will continue to keep scientists busy for many years to come."

Ulysses' successes have not been confined to scientific data. The extended mission presented significant challenges to the NASA-European operations team. In particular, critical parts of the spacecraft became progressively colder with time. In recent years, a major effort was needed to prevent the onboard hydrazine fuel from freezing. The operations team continually created methods to allow the aging space probe to continue its scientific mission.

The Ulysses orbital path is carrying the spacecraft away from Earth. The ever-widening gap has progressively limited the amount of data transmitted. Ulysses project managers, with the concurrence of ESA and NASA, decided it was an appropriate time to end this epic scientific adventure. Ulysses was commanded to switch off its transmitter at 20:15 UTC on 30 June 2009.

After the spacecraft was placed into low Earth orbit in 1990, a combination of solid fuel motors propelled Ulysses toward Jupiter. Ulysses swung by Jupiter on Feb. 8, 1992. The giant planet's gravity bent the spacecraft's flight path southward and away from the ecliptic plane, putting the probe into a final orbit that would take it over the sun's south and north poles.

The European Space Agency's European Space Research and Technology Centre and European Space Operations Centre managed the mission in coordination with the Jet Propulsion Laboratory. Ulysses is tracked by NASA's Deep Space Network. A joint ESA/NASA team at JPL oversaw spacecraft operations and data management. Teams from universities and research institutes in Europe and the United States provided the 10 instruments on board.

Key Dates
6 Oct 1990:  Launch (11:47:16 UT)
8 Feb 1992:  Jupiter Gravity Assist
26 Jun 1994 - 5 Nov 1994:  1st South Polar Pass
13 Mar 1995:  1st Ecliptic Crossing
19 Jun 1995 - 29 Sep 1995:  1st North Polar Pass
1 May 1996:  Comet Hyakutake Encounter
30 Jun 2009:  End of Mission
Status: Successful
Fast Facts
Ulysses Facts Ulysses was the first spacecraft to study our Sun's poles.

Ulysses was launched aboard the Space Shuttle Discovery STS-41 mission (right).

The spacecraft used Jupiter's powerful gravity to hurl it into an orbit that couldn't be reached with conventional rocket power.

Ulysses was the first spacecraft to fly by the Sun's polar regions.

Ulysses was launched by the Space Shuttle Discovery.

Ulysses was built by the European Space Agency, which managed it in cooperation with NASA.
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