Farewell Ulysses

ESA/NASA Ulysses

After nearly 19 years observing the Sun, together with a fascinating flyby of Jupiter in 1992, the joint European Space Agency/NASA Ulysses mission has come to an end. The satellite is this evening being put into a deep electronic coma, and no further contact with the spacecraft is planned.

Ulysses has been a hugely successful space science mission, and during nearly two decades of operations has revealed a great deal about our neighbourhood star. What occurs in the Sun’s outer layers and interplanetary magnetic field has a direct impact on Earth’s local space environment and upper atmosphere. Results published last year show that the solar wind – a fast stream of charged particles moving away from the Sun in a garden hose pattern – is at its weakest for 50 years.

“Ulysses has taught us far more than we ever expected about the Sun and the way it interacts with the space surrounding it,” says Richard Marsden, ESA’s Ulysses Project Scientist.

It was never envisaged that Ulysses would survive this long. In fact, the mission has been extended four times over the years, and is only being shut down as its ageing, failing hardware means that the now small return of science data cannot justify the considerable running costs.

“We expected the spacecraft to cease functioning much earlier. Its longevity is a tribute to Ulysses’s builders and the people involved in operations over the years,” says Paolo Ferri of ESA’s operations centre in Darmstadt. “Although it is always hard to take the decision to terminate a mission, we have to accept that the satellite is running out of resources and a controlled switch-off is the best ending.”

Ulysses will continue orbiting the Sun as a man-made comet.