Autonomy for SOHO Ground Operations

The SOLAR and HELIOSPHERIC OBSERVATORY (SOHO) project [1] is being carried out by the European Space Agency (ESA) and the US National Aeronautics and Space Administration (NASA) as a cooperative effort between the two agencies in the framework of the Solar Terrestrial Science Program (STSP) comprising SOHO and other missions. SOHO was launched on December 2, 1995. The SOHO spacecraft was built in Europe by an industry team led by Matra, and instruments were provided by European and American scientists. There are nine European Principal Investigators (PI’s) and three American ones. Large engineering teams and more than 200 coinvestigators from many institutions support the PI’s in the development of the instruments and in the preparation of their operations and data analysis. . NASA is responsible for the launch and mission operations. Large radio dishes around the world, which form NASA’s Deep Space Network (DSN), are used to track the spacecraft beyond the Earth’s orbit. Mission control is based at Goddard Space Flight Center in Maryland. SOHO is designed to study the internal structure of the Sun, its extensive outer atmosphere and the origin of the solar wind. That view of the Sun is achieved by operating SOHO from a permanent vantage point 1.5 million kilometers sunward of the Earth in a halo orbit. SOHO is commanded from NASA's Goddard Space Flight Center (GSFC) in Greenbelt, Maryland (USA). Its data is retrieved via the NASA Deep Space Network (DSN) and routed to the Experimenters' Operations Facility (EOF) located at GSFC. There the SOHO experimenters will be able to display on their workstations the images and measurements that are being produced by their instruments. From the EOF the experimenters will point the instruments aboard SOHO to a particular region of the Sun, or change the operating mode of the instruments. The SOHO scientists will use their instruments very much as an observer would at a ground-based observatory. SOHO instruments produce a data stream of 200 kilobits per second, that can be transmitted continuously to the DSN stations of Goldstone (USA), Canberra (Australia) and Madrid (Spain), when each is visible from SOHO due to the daily rotation of the Earth.