Autonomous guidance and control of a solar electric propulsion spacecraft

Abstract

The New Millennium Deep Space Mission 1 (DS 1 ), a NASA designed advanced technology demonstration mission to flyby an asteroid and a comet, is the first deep space solar electric propulsion spacecraft (S/C). Several new challenges are presented in autonomous guidance and control of this spacecraft. The New Millennium DS1 onboard guidance and control (G&C) system has accommodated these challenges in a simple yet robust architecture. The DS 1 G&C system will implement trajectory correction maneuvers autonomously to support onboard optical navigation. This capability will be implemented for the traditional chemical propulsion system and the new ion propulsion system, both available onboard DS 1. A thrust vector controller has been designed to control the ion engine using 2-axis engine gimbal actuators. A solar panel controller has been designed to keep the large solar panels to within 2 degrees of total pointing control with respect to the Sun. An onboard autonomous pointing capability ensures that the solar panels remain sun pointed during basebody turns. Solar panel flexibility has been studied and modeled for the DS 1 spacecraft, and all controllers have been designed to be robust to the flexible modes. Additionally, all S/C attitude adjustments are implemented autonomously with onboard constraint checking. The G&C autonomous architecture incorporates the low level control components, the “traditional G&C”, with high level interfaces to autonomous attitude planning. An earlier description of the DS 1 Autonomous Guidance and Control System is available in Reference [1].