past Mission


Space Telescope


Aug. 30, 1991




Study the high-energy radiations from solar flares (hard and soft X-rays and energetic neutrons) as well as quiet structures and pre-flare conditions

Yohkoh (“Sunbeam”), a Japanese solar mission in partnership with the U.S. and Great Britain, provided valuable data about the Sun’s corona, solar flares, and gamma-ray emissions. In December 2001, it lost the ability to point toward the Sun, and the batteries discharged.

Orbit: Low-Earth Orbit

Yohkoh (“Sunbeam”) was a Japanese solar mission with USA and UK collaborators. It was launched into Earth orbit in August 1991 from the Kagoshima Space Center in Southern Japan, and provided valuable data about the sun’s corona and solar flares. Its mission was to observe in X-ray radiation the energetic phenomena occurring in the solar atmosphere or corona, such as solar flares and gamma-ray emissions. To meet the task, the satellite carried four instruments: a Soft X-ray Telescope, Hard X-ray Telescope, Bragg Crystal Spectrometer, and Wide Band Spectrometer.

In December 2001, a fatal spacecraft failure ended Yohkoh’s mission. During an annular solar eclipse on December 14, the spacecraft lost pointing and the batteries discharged. Spacecraft operators were unable to command the satellite to point towards the sun. Yohkoh re-entered Earth’s atmosphere on September 12, 2005.

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