THE NEAR GUIDANCE AND CONTROL-SYSTEM

The Near Earth Asteroid Rendezvous (NEAR) spacecraft guidance and cont rol system supports all modes of pointing and control for the mission, including routine control during the long cruise to the asteroid Eros , high-frequency control of the propulsion subsystem thrusters during orbital corrections, precise pointing for science data collection, and spacecraft safety in emergencies. The attitude determination and cont rol algorithms have been structured to provide the necessary capabilit y, autonomy, high throughput, and relatively easy transitions among mo des. The guidance and control system includes very few attitude sensor s but achieves at least one level of redundancy for all reasonable fai lure modes. Its functions are divided between two redundant computers that are cross-strapped for maximum flexibility.