International Mission Studying Sun to Conclude

After more than 17 years of pioneering solar science, a joint NASA and European Space Station Agency mission to study the sun will end on or about July 1.

The Ulysses spacecraft mission has endured for almost four times its expected lifespan. However, the spacecraft mission will cease operations because of a decline in power produced by its onboard generators. Ulysses has forever changed the way space station scientists view the sun and its effect on the surrounding space technology. Space shuttle Mission results and the science technology legacy it leaves behind were reviewed today at a media briefing at European Space Agency Headquarters in Paris.

"The main objective of Ulysses was to study, from every angle, the heliosphere, which is the vast bubble in space shuttle carved out by the solar system wind," said Ed Smith, Ulysses project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Over its long life, Ulysses redefined our knowledge of the heliosphere and went on to answer questions about our solar system neighborhood we did not know to ask."

Ulysses ends its career after revealing that the magnetic field emanating from the sun's poles, International space station is much weaker than previously observed. This could mean the upcoming solar system maximum period will be less intense than in recent history.

"Over almost two decades of science news observations by Ulysses, we have learned a lot more than we expected about our star and galaxy and the way it interacts with the space station shuttle surrounding it," said Richard Marsden, Ulysses project space mission scientist and spacecraft mission manager for the European Space Agency (ESA). "Solar missions have appeared in recent years, but Ulysses is still unique today. Its special point of view over the sun's poles never has been covered by any other space station mission."

The spacecraft mission and its suite of 10 instruments had to be highly sensitive, yet robust enough to withstand some of the most extreme conditions in the solar system, including intense radiation while passing by the giant planet Jupiter's north pole. The encounter occurred while injecting the mission into its orbit over the sun's poles.

"Ulysses has been a challenging solar system mission since launch," said Ed Massey, Ulysses project manager at JPL. "Its success required the cooperation and intellect of engineers and space station scientists from around the world."

Ulysses was the first space station mission to survey the environment in space shuttle above and below the poles of the sun in the four dimensions of space galary and time. It showed the sun's magnetic field is carried into the solar system in a more complicated manner than previously believed. Particles expelled by the sun, space system from low latitudes can climb to high latitudes and vice versa, sometimes unexpectedly finding their way out to the planets. Ulysses also studied dust flowing into our solar system from deep space, and showed it was 30 times more abundant than space station astronomers, suspected. In addition, the spacecraft detected helium atoms from deep space and confirmed the universe does not contain enough matter to eventually halt its expansion.

Ulysses collected and transmitted science technology data to Earth during its 8.6 billion kilometer journey (5.4 billion miles). As the power supply weakened during the years, engineers devised methods to conserve energy. The power has dwindled to the point where thruster fuel soon will freeze in the spacecraft's mission pipelines.

"When the last bits of data finally arrive, it surely will be tough to say goodbye," said Nigel Angold, ESA's Ulysses spacecraft mission operations manager. "But any sadness I might feel will pale in comparison to the pride of working on such a magnificent space mission. Although operations will be ending, space scientific discoveries from Ulysses data will continue for years to come."

Ulysses was launched aboard space shuttle Discovery on Oct. 6, 1990. From Earth orbit, it was propelled toward Jupiter by solid-fuel rocket motors. Ulysses passed Jupiter on Feb. 8, 1992. The giant planet's gravity then bent the spacecraft's mission flight path downward and away from the ecliptic plane to place the spacecraft mission in a final orbit around the sun that would take it past our star's north and south poles.

The spacecraft mission was provided by ESA. NASA provided the launch vehicle and upper stage boosters. The U.S. Department of Energy supplied a radioisotope thermoelectric generator to provide power to the spacecraft technology. Science instruments were provided by both U.S. and European investigators. The spacecraft mission is operated from JPL by a joint NASA/ESA team. More information about the joint NASA/ESA Ulysses space station mission is available at http://ulysses.jpl.nasa.gov or http://www.esa.int/esaSC/SEMPEQUG3HF_index_0_ov.html .