Since 1959, the United States has launched many satellites to observe the Sun, including NASA's Orbiting Solar Observatories (OSO) of the 1960s and early 1970s, the 1980 Solar Maximum Mission, the European Space Agency/NASA Ulysses probe in 1990 and the Solar and Heliospheric Observatory (SOHO) in 1995, as well as more recent efforts, such as the Transition Region and Coronal Explorer (TRACE) in 1998 and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) in 2002.