Solar and Heliospheric Observatory (SoHO) Spacecraft
Image of the Sun by SoHO
Solar and Heliospheric Observatory (SoHO) Spacecraft

Solar and Heliospheric Observatory (SoHO) Spacecraft

Courtesy of NASA

The spacecraft, a joint effort by the European Space Agency and NASA, is orbiting the Sun near the L1 equilibrium point. Although it was originally planned as a two-year mission, it continues to operate more than 15 years later. Besides its mission goals to study the sun, it also reports on space weather.

December 2, 1995

May, 1996 (began operating)

End of Mission
Still operating

SOHO was designed to answer the following three fundamental scientific questions about the Sun:

  1. What is the structure and dynamics of the solar interior?
  2. Why does the solar corona exist and how is it heated to such an extremely high temperature?
  3. Where is the solar wind produced and how is it accelerated?

SoHO has observed the changing Sun during its 11-year solar cycle, from quiet to stormy, and back again. On January 4, 2008, a reversed-polarity sunspot appeared, signaling the start of Solar Cycle 24. SoHO data are being used to try to predict, in real-time, the approach and intensity of solar particles that would threaten astronauts and technology in space. SoHO data shows that solar flares drive global oscillations (starquakes) in the Sun, confirming a prediction made more than 30 years ago. A similar phenomenon is known on Earth after large earthquakes. SoHO also discovered more than 2,100 comets that flew close to the Sun.