SOHO stands for the Solar and Heliospheric Observatory and spends all of its time staring at the Sun.

Why was SOHO launched?

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

  • What is the structure and dynamics of the solar interior?
  • Why does the solar corona exist and how is it heated to the extremely high temperature of about 1 000 000°C?
  • Where is the solar wind produced and how is it accelerated?

SOHO has done more than answer these three basic questions. Some of the things it has managed to do for science includes

  • Revealing the first images ever of a star’s convection zone (its turbulent outer shell) and of the structure of sunspots below the surface.
  • Providing the most detailed and precise measurements of the temperature structure, the interior rotation, and gas flows in the solar interior.
  • Measuring the acceleration of the slow and fast solar wind.
  • Identifying the source regions and acceleration mechanism of the fast solar wind in the magnetically “open” regions at the Sun’s poles.
  • Discovering new dynamic solar phenomena such as coronal waves and solar tornadoes.
  • Revolutionising our ability to forecast space weather, by giving up to three days notice of Earth-directed disturbances, and playing a lead role in the early warning system for space weather.
  • Monitoring the total solar irradiance (the ‘solar constant’) as well as variations in the extreme ultra violet flux, both of which are important to understand the impact of solar variability on Earth’s climate.

Besides watching the Sun, SOHO has become the most prolific discoverer of comets in astronomical history: as of May 2003, more than 620 comets had been found by SOHO.

Finding Comets

The below video showcases a secondary task that SOHO was able to cover off that was never part of the original plan and that was to detect and track Comets being pulled in by the Sun’s gravitations pull.

SOHO Images

Latest Realtime Image of the Sun from SOHO

Mission Timeline

SOHO Launch

The SOHO probe was launched on an Atlas II-AS rocket (AC-121) from the Cape Canaveral Air Station (Florida, United States)


Beginning normal operations

Beginning normal operations
in may 1996 SOHO began normal operations.


Lost Contact

Contact lost during maintenance operations.


Spacecraft Recovered

Spacecraft recovered and back in normal mode