Ulysses probes solar wind, interstellar gas

The Ulysses mission, a joint collaboration of the European Space Agency and NASA, was successfully launched on October 6, 1990, to investigate the regions of interplanetary space at high solar latitudes. Much has been learned by spacecraft at low solar latitudes, but the heliosphere (the region dominated by the Sun and the solar wind) is still unexplored at latitudes above 30°. As the properties of the corona and solar wind vary with latitude, important advances in our understanding of the solar corona and the interplanetary environment are anticipated. To reach these high latitudes, Ulysses will use the gravitational force of Jupiter to deflect the spacecraft out of the ecliptic into a highly inclined orbit that cannot be provided by conventional rockets. The Jupiter flyby will occur on February 8, 1992; the high‐latitude passes over the solar poles will occur in mid‐1994 and mid‐1995 at a distance of about 2.3 astronomical units. (One AU is the distance from the Earth to the Sun.)