Sun Sets on NASA's Solar Mission

By Roy Mark  |  Posted 2009-06-30 Print this article Print

After 18 years of reliable duty, engineers from NASA and the European Space Agency are pulling the plug on Ulysses, a nuclear-powered solar orbiter. Surviving almost six times longer than predictions, Ulysses has finally succumbed to the harsh space environment.

NASA and the ESA (European Space Agency) will communicate for the final time June 30 with Ulysses, the nuclear-powered solar orbiter that has been faithfully relaying data back to Earth for 18 years. Ulysses has charted the unexplored regions of space above the poles of the sun since it was launched in 1990.
Ulysses was originally scheduled for a five-year mission, but the robotic satellite just kept churning along until the spacecraft finally succumbed to the harsh environment of space. The spacecraft no longer can run all of its communications, heating and scientific equipment simultaneously.

The first signs of the end for Ulysses hit the satellite in 2008 when the power supply to the radio transmitter failed to turn back on. As a result, the spacecraft lost its ability to send large quantities of scientific data back to Earth and the gradual freezing of its fuel lines became inevitable.

"The data and science output of this mission truly deserves to be named after the legendary explorer in Greek mythology," Arik Posner, Ulysses program scientist at NASA Headquarters in Washington, said when the power supply failed. "My compliments go out to the international team of scientists and engineers who built a spaceship and instrument payload that is highly sensitive, yet durable enough that it withstood the most extreme conditions in the solar system, including a polar passage of the giant planet Jupiter."

The science findings and discoveries from the mission included taking 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.

Richard Marsden, ESA project scientist and mission manager, called Ulysses a "terrific old workhorse. It has produced great science and lasted much longer than we ever thought it would."

The space Shuttle Discovery launched Ulysses on Oct. 6, 1990. A combination of solid fuel motors propelled Ulysses out of low-Earth orbit and toward Jupiter. After swinging past Jupiter in 1992, the 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 Ulysses spacecraft was built by Dornier Systems of Germany for ESA. NASA provided the launch and the upper stage boosters. The U.S. Department of Energy supplied the generator that powered the spacecraft while science instruments were provided by both U.S. and European investigators. The spacecraft is operated from JPL by a joint NASA/ESA team and has employed NASA's Deep Space Network for communications. 


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