High Energy Astrophysics Group

OSO-3

Orbiting Solar Observatory-3

Spacecraft

The OSO-3 spacecraft consisted of a nine-compartment, 22 inch radius wheel from which three 24 inch arms extended, and a 22 inch radius sail structure. The UCSD X-ray Telescope occupied half of a wheel compartment. The wheel section spun at about 30 RPM to provide a stable platform for the sail. During the sunlit portion of the orbit, a motor drove the sail against the wheel so that the sail locked on the solar direction. Ground commanded firing of gas from the extended arms or energizing of a magnetic torque coil kept the wheel plane within 3 degrees of the sun. Thus, as the earth moved about the sun, the spin axis position changed an average of 1 degree per day, and in six months the great circle cut by the rotating wheel swept out almost the entire sky. The telescope missed about 10 degrees around the celestial poles, since the spin axis oscillated between -15 degrees and -35° declination, instead of precessing along a great circle.

OSO-3 Information

Mission Objectives
Spacecraft
X-Ray Telescope
Scientific Results
Publications