Solar and Heliospheric Observatory

Solar and Heliospheric Observatory (SOHO) A joint ESA–NASA spacecraft launched in 1995December, to observe the Sun in ultraviolet and visible light, study the solar wind, and measure small oscillations on the Sun's surface. Its twelve instruments included the Large Angle and Spectrometric Coronagraph (LASCO), a set of three coronagraphs that record white‐light images of the solar corona out to 30 solar radii. LASCO has returned spectacular views of coronal mass ejections and led to the discovery of over 1000 comets, including many Kreutz sungrazers and sunskirters. Other major instruments are the Extreme Ultraviolet Imaging Telescope (EIT), which images the solar transition region and inner corona at four wavelengths in the EUV, and the Michelson Doppler Imager (MDI), which studies solar oscillations. SOHO is in a halo orbit around the inner Lagrangian point (L₁) between the Sun and Earth, some 1.5 million km from the Earth in the sunward direction, so that the Sun can be observed without the interruption of eclipses by the Earth. http://sohowww.nascom.nasa.gov/