HEAO attitude reference design

The paper deals with the precision onboard attitude reference implemented as part of the attitude control and determination subsystem for the three High Energy Astronomy Observatories (HEAO-A, HEAO-B, and HEAO-C) in the HEAO scientific spacecraft program. The first observatory (HEAO-A, designated HEAO-1 when in orbit) was launched successfully into near-earth orbit on August 12, 1977. The HEAO attitude reference, analysis techniques for performance prediction, and flight results from the HEAO-1 observatory during its first months of operation. The HEAO-B design is specifically described and analyzed in terms of gyro processing, kinematic integration, ground update algorithm, and star tracker update algorithm. Attitude reference performance estimates are also discussed. It is shown that the orbital performance of the attitude reference correlates very well with the developmental predictions, thereby validating the analytical techniques used during the development. This validation provides a firm basis from which to extrapolate to other applications and related design concepts.