spacetoday.net: Ulysses mission ends

Posted: Tue, Jul 7, 2009, 6:16 AM ET (1016 GMT)
Ulysses illustration (ESA)

Spacecraft controllers shut down the ESA/NASA Ulysses spacecraft last week, ending a nearly 18-year mission to study the Sun. The spacecraft, launched by the space shuttle in October 1990, provided scientists with the first observations of the polar regions of the Sun and lasted far longer than originally planned. Project officials had expected the mission to end a year earlier as the power output of the spacecraft's RTG dropped to the point where heaters would no longer be able to keep the spacecraft's fuel lines from freezing. However, occasional use of the spacecraft's thrusters kept the fuel lines open, allowing scientists to eke out an additional year's worth of data. Project officials decided to shut down the spacecraft now as power levels dropped further and time on ground stations became more difficult to obtain.