For nearly 19 years, the ULYSSES probe studied the heliosphere, the huge bubble of gas enveloping our Sun generated by the solar wind, mapping it in 3D and bringing new insights into its composition.

Launched by the U.S. space shuttle Discovery from Cape Canaveral on 6 October 1990, ULYSSES was a joint U.S.-European space probe. After launch, it got a gravity assist from Jupiter to boost it on its way to a polar heliocentric orbit between Earth and Jupiter. From this vantage point, it was able to closely observe the stream of particles responsible for the heliosphere, measuring the solar wind, the Sun’s magnetic field and the local interstellar medium.

After three full orbits of the Sun, ULYSSES was able not only to construct a 3D map of its magnetic field and the solar wind, but also to ascertain where they originate and how they are organized. The probe also measured the amount of interstellar dust in the heliosphere, which proved to be 30 times more abundant than astronomers had predicted. Another bonus of the mission was that ULYSSES flew through the tail of three comets and analysed them in situ.

ULYSSES carried 12 instruments, including the VHM/FGM magnetometer, SWOOPS, URAP and ISCALE, to which the LPP (Laboratoire de Physique des Plasmas, ex-CETP) and the LESIA (Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique) at the Paris Observatory contributed.