ESA Science & Technology - Summary

Mission technology

Ulysses is equipped with a comprehensive range of scientific instruments. These are able to detect and measure solar wind ions and electrons, magnetic fields, energetic particles, cosmic rays, natural radio and plasma waves, cosmic dust, interstellar neutral gas, solar X-rays and cosmic gamma-ray bursts. This combination of experiments is helping scientists to understand the Sun and its heliosphere. Because Ulysses travels far from the Sun (aphelion is at ~5.4 AU), solar power can't be used to provide electricity to the spacecraft. Instead, a Radio-isotope Thermoelectric Generator (RTG) is used.

Mission status

After more than 17.5 years the mission has come to an end. The spacecraft finally succumbed to the cold conditions in space as the result of the continually declining power output from the RTG and because the onboard heaters were no longer able to prevent the freezing of fuel lines.

At the end of the mission Ulysses was in its third orbit around the Sun and had completed its third north polar pass (in March 2008; polar passes are defined to be the periods when the spacecraft is within 20° of either of the Sun's poles). Science operations continued to the very end of the mission.

Mission History

Ulysses was launched by the Space Shuttle Discovery on 6 October, 1990. It headed out to Jupiter, arriving in February 1992 for a gravity-assist manoeuvre that swung the craft into its unique solar polar orbit. This highly elliptical operational orbit takes the spacecraft from Jupiter's orbit to within ~1.4 AU from the Sun and back out again, with a period of 6.2 years. Around each perihelion, Ulysses performs two passes of the Sun's poles. Three sets of polar passes were completed during its operational lifetime: in 1994/1995, 2000/2001 and 2007/2008.