The U.S.-European spacecraft has been suffering from a decline in its plutonium power (read: nuclear) for some time. Despite conservation measures by ground controllers, the power has dwindled to the point where thruster fuel soon will freeze up.Launched in Oct. 1990 from the space shuttle Discovery, Ulysses is a joint mission of the European Space Agency and NASA. Unlike other spacecraft, Ulysses is able to fly over the sun's poles, looking down on regions that are difficult to see from Earth. (see diagram)
"Just as Earth's poles are crucial to studies of terrestrial climate change, the sun's poles may be crucial to studies of the solar cycle," explains Ed Smith, Ulysses project scientist at NASA's Jet Propulsion Laboratory.
Many researchers believe the sun's poles are central to the ebb and flow of the solar cycle (which, in turn, dramatically effects the Earth's weather). Consider the following: When sunspots break up, their decaying magnetic fields are carried toward the poles by vast currents of plasma. This makes the poles a sort of "graveyard for sunspots." Old magnetic fields sink beneath the polar surface two hundred thousand kilometers deep, all the way down to the sun's inner magnetic dynamo. There, dynamo action amplifies the fields for use in future solar cycles.
"When the last bits of data finally arrive, it surely will be tough to say goodbye," European Space Agency mission operations manager Nigel Angold said in a statement.
