Spacecraft Missions (cont.) Ulysses – The Space Shuttle Discovery launched the Ulysses spacecraft on October 6, 1990. The primary mission of the Ulysses spacecraft was to characterize the heliosphere as a function of solar latitude. (The heliosphere is the vast region of interplanetary space occupied by the Sun's atmosphere and dominated by the outflow of the solar wind.) Ulysses studies the complex forces at work in the Sun's outer atmosphere (the corona) from high latitudes. The mission has enabled us, for the first time, to view our solar system from far above the ecliptic plane. After more than 12 years in flight, Ulysses has returned a wealth of data that has led to a much broader understanding of the global structure of the heliosphere. Key results to date include the first detailed measurements of the solar wind from the Sun's polar regions at solar minimum and solar maximum, the discovery that the magnetic flux leaving the Sun is the same at all latitudes, the discovery of energetic particle "reservoirs" surrounding the Sun, the discovery of interstellar dust in the solar system, and the first direct measurements of interstellar helium atoms in the solar system.