HERCULES attitude processor: gyro data processing system for real-time geolocation of images captured by astronauts

The HERCULES (hand held, earth oriented, real-time, cooperative, user friendly, location, targeting, and environmental system) attitude processor (HAP), a microprocessor-based gyro attitude data processing system used in the geolocation process, is described. The HAP software and hardware structures are discussed. A worst-case analysis of the design shows that there are no design flaws. The HERCULES HAP and attitude reference unit (ARU) are able to track the Earth rate to within 0.005 degrees per hour in some cases, and always within 0.05 degrees per hour. ARU alignment methods have been verified. Typical alignment errors are less than 0.03 degrees.<
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