SOHO solar physics spacecraft. Technicians running tests on the Solar and Heliospheric Observatory (SOHO) spacecraft at the Matra-Marconi test centre in Cannes, France. SOHO will study the Sun's surface and atmosphere and the solar wind in order to increase our understanding of a variety of solar processes. The spacecraft will make observations from an orbit about the L1 Sun-Earth Lagrangian point. This is about 1.5 million km from Earth, and is the point between the Sun and Earth where their respective gravitational forces on the spacecraft cancel out. SOHO is part of the International Solar Terrestrial Physics (ISTP) project, and is due for launch in late 1995.