Space Probe Ulysses Reaches End of Odyssey

June 13, 2008 -- European and American scientists will bid a fond farewell on July 1 to the space probe Ulysses, which has circled the sun gathering data for 17 years, almost four times its expected lifetime.

The first major collaboration between NASA and the European Space Agency (ESA), launched in 1990, "changed forever the way we view the sun and its effect on the surrounding space," David Southwood, ESA's director of science, said in announcing the end of mission.

Stuffed with 10 observational instruments, the 814-pound probe is the only satellite to have circled the sun's poles.

Its principle objective was to explore the boundaries and impact of the sun's sphere of influence, called the heliosphere.

One of its many findings was that the sun's magnetic fields, thrust outward by solar wind, extends into the solar system in ways that were previously not suspected.

"This is very important because regions of the sun not previously considered as potential sources of hazardous particles for astronauts and satellites must now be taken into account," noted the Paris-based ESA's Richard Marsden.

Scientists originally thought that the speed of solar wind -- a constant stream of particles emitted by the sun -- was about 250 miles per second.

But Ulysses proved that during much of the Sun's 11-year solar cycle, wind travels at nearly double that speed.