IN-ORBIT PERFORMANCE OF THE ITOS IMPROVED ATTITUDE CONTROL SYSTEM WITH HALL GENERATOR BRUSHLESS MOTOR AND EARTH-SPLITTING TECHNIQUE

摘要

The National Aeronautics and Space Administration (NASA), Goddard Space Flight Center (GSFC), launched ITOS-D (NOAA-2)* with an im-proved attitude control system from the Air Force Western Test Range (AFWTR) at Vandenberg Air Force Base, California, on October 15, 1972. A Hall generator brushless dc torque motor replaced the brush dc torque motor on TIROS-M (ITOS-l)**and ITOS-A (NOAA-l). Two CO2 attitude horizon sensors and one mirror replaced the four wide¬band horizon sensors and two mirrors on ITOS-1 and NOAA-1. Re¬dundant pitch-control electronic boxes containing additional electronic circuitry for earth-splitting and brushless motor electronics were used. A new method of generating a spacecraft earth-facing side re¬ference for comparison to the time occurrence of the earth-splitting pulse was used for the first time to automatically correct pitch-atti¬tude error. A single rotating flywheel, supported by a single bear¬ing, provided gyroscopic stability and the required momentum inter¬change to keep one side of the satellite facing the earth. Magnetic torquing against the earth's magnetic field eliminated the requirement for expendable propellants which would limit satellite life in orbit.