NASA
NASA/GSFC/SED/HSD/SPL/SOHO
The ESA-sponsored Solar and Heliospheric Observatory (SOHO) carries twelve scientific instruments to study the solar atmosphere, helioseismology, and solar wind. Information from the mission allows scientists to learn more about the Sun?s internal structure and dynamics, the chromosphere, the corona, and solar particles. The SOHO and Cluster missions, part of ESA?s Solar Terrestrial Science Programme (STSP), are ESA?s contributions to the Inter-Agency Solar Terrestrial Physics (IASTP) program. NASA contributed three instruments on SOHO as well as launch and flight operations support. About two months after launch, on 14 February 1996, SOHO was placed at a distance of 1.5 million kilometers from Earth at the L1 Libration Point. The spacecraft returned its first image on 19 December 1995 and was fully commissioned for operations by 16 April 1996. SOHO finished its planned two-year study of the Sun?s atmosphere, surface, and interior in April 1998. Communications with the spacecraft were interrupted for four months beginning on 24 June 1998, but, after intensive search efforts, controllers managed to regain full control by 16 September. Barring three instruments, the spacecraft was functional and was declared fully operational once again by mid-October 1998. SOHO?s original lifetime was three years (to 1998), but ESA and NASA jointly decided to prolong the mission, enabling the spacecraft to compare the Sun?s behavior during low dark sunspot activity (1996) to the peak (around 2000). Summary provided by http://solarsystem.nasa.gov/missions/profile.cfm?Sort=Chron&MCode=SOHO&StartYear=1990&EndYear=1999&Display=ReadMore