POWER SUBSYSTEM DESIGN AND EARLY MISSION PERFORMANCE

The power subsystem for the Near Earth Asteroid Rendezvous (NEAR) spac ecraft is a direct energy transfer system with an Eagle Picher Industr ies Super nickel-cadmium battery and fixed solar panels populated with solar cells of gallium arsenide on germanium. Power is controlled by digital and analog sequential shunts. During the mission the distance from the Sun varies significantly, causing large variations in solar a rray power and temperature. To minimize solar array size, the solar ar ray and power system electronics were designed to allow operation at v oltages both greater than and less than the array's maximum power volt age. The power system design emphasizes reliability with low weight an d volume. Analyses verified subsystem capabilities over the varied mis sion environment, and early mission flight data indicate that performa nce is consistent with analysis models.