Yesterday (June 30), the Ulysses mission finally ended today when ground controllers sent commands to shut down the spacecraft's communications. The event marks the conclusion of one of the longest and most successful space missions ever conducted (and also the very first mission that your author ever worked on, back in 1983 when it was known as the International Solar Polar Mission).From launch in 1990 the 18-year, 8-month mission has returned a wealth of scientific data on the space environment above and below the poles of the Sun (each orbit taking aound six years). The spacecraft and its suite of nine instruments had to be highly sensitive yet robust enough to withstand some of the most extreme conditions in the Solar System, including a close fly-by of the giant planet Jupiter.
The end of the mission had been predicted for July 2008, at which time the satellite's depleted radioisotope power supply was expected to fall below the minimum required to keep fuel lines from freezing. However, mission controllers determined they could keep this from happening by firing the thrusters briefly every few hours. The final decision to end the mission was taken because the unavailability of ground station time to communicate with Ulysses in the future.
