Viking orbiter attitude control analysis

Abstract

Two Viking orbiters are currently in Mars orbit. In the nearly two years since they were launched, the orbiters have successfully performed many functions including transportation of the Viking landers to Mars. The orbiters have for the last year provided relay links for lander-earth communications, and they have carried out from orbit their own scientific exploration of the planet. Crucial to the success of the orbiters has been the performance of the on-board attitude control system, which has provided the required orbiter stabilization and orientation throughout the missions. A comprehensive spacecraft and attitude control system dynamic analysis was necessary to certify the control system before launch and to evaluate its flight performance. This paper contains an outline of the analysis and of some of its results.