Ulysses Spacecraft

Ulysses Spacecraft

Courtesy of NASA


Ulysses was a joint mission between the European Space Agency and NASA to explore the Sun, including the little-known polar regions. Ulysses launched from the space shuttle Discovery, and instead of using solar cells for power, used a generator powered by radioactive plutonium-238.

October 6, 1990

February 8, 1992 (Jupiter for repositioning orbit)

1994 (southern solar pole)

1995 (northern solar pole)

End of Mission
June 30, 2009 (last communication)

Ulysses was put in polar orbit around the Sun. It would describe the heliosphere based on the solar latitude. The heliosphere is the vast region of interplanetary space occupied by the Sun’s atmosphere where there are strong solar winds.

In its first orbit, Ulysses charted the structured heliosphere of solar minimum. A very different second orbit revealed the complex solar maximum heliosphere where there is less structure and the Sun’s ejected energy is stored in coronal magnetic fields. Ulysses’ observations of these ejections are helping us to understand how space radiation is affected by the 3-dimensional magnetic field. It is also helping us to define the challenges we face in developing protective environments for human space exploration. Ulysses discovered that energetic particles change latitude more often than expected. This result is the same for cosmic rays, pickup ions, and dust. There are at least occasional direct magnetic field connections across latitude. A similar result has been found in Jupiter’s atmosphere, where Jovian electron and dust jets reach Ulysses.