Artist's concept of Ulysses spacecraft.

Artist's concept of Ulysses spacecraft.

Goals

NASA and the European Space Agency joined forces to send Ulysses to study the heliosphere - the region of space influenced by the Sun and its magnetic field - from a unique polar orbit. The spacecraft's 10 instruments on board measured the Sun's fields and particles, ultraviolet, X-rays and gamma rays.

Accomplishments

Ulysses was the first mission to survey the space environment above and below the poles of our Sun. The spacecraft used an unprecedented gravity assist maneuver at Jupiter to hurl itself out of the plane of the ecliptic and into its solar polar orbit.

During its 18-year mission, 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 solar orbiter's unique orbit and long lifespan produced three unexpected encounters with comet tails and a chance for bonus science.

The spacecraft's six-year orbits over the Sun's poles allowed scientists to observe our star from an unprecedented angle during both calm and turbulent periods. Ulysses also made the first direct measurements of interstellar dust particles and interstellar helium atoms in the solar system and the discovery that the magnetic field leaving the Sun is balanced across latitudes.

The spacecraft's May 1996 encounter with comet Hyakutake revealed comet tails are far longer than expected. The tail extended half a billion kilometers (more than 300 million miles)—more than three times the distance from the Earth to the Sun. The discovery marked the longest comet tail—streams of ions, gas and dust extending away from the Sun - recorded at the time.

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

References:

Ulysses NASA Homepage, http://ulysses.jpl.nasa.gov/
Ulysses ESA Homepage, http://sci.esa.int/science-e/www/area/index.cfm?fareaid=11
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, http://nssdc.gsfc.nasa.gov/nmc/


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.

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