Launch delay impact on the Galileo attitude control system

Abstract

The Galileo spacecraft was launched from the Space Shuttle in October 1989, using a two-stage inertial upper stage. The trajectory included flybys of Venus and earth for gravity assists. The mission duration increased to a total of 8 years rather than the original 4.5 years. The major impact of this new mission plan was on the thermal control design. A viable design was achieved, with one major attitude control constraint: the spacecraft antenna boresight must be pointed to within 14 deg of the sun whenever the spacecrat is within 1 AU of the sun, even in the presence of faults. Changes to hardware, software and operations strategies had to be made to handle the new and longer mission.