The HEAO Experience – Design Through operations

Abstract

Hardware go-ahead for the series of three High Energy Astronomy Observatory spacecraft was authorized in July 1974. Un-orbit operations were initiated in August 1977 with the successful launch of HEAO-1 and continued through May 1981 with the depletion of expendibles on HEAO-3. Incorporation of modular design and equipment commonality, minimization of non-flight hardware, and effective allocation of weight/power margins to effect costs savings were employed during the design phase. These techniques, coupled with sound initial conceptual designs, were used to implement a cost conscious development. Scientific data returns consisting of nearly an order of magnitude increase in the number of cataloged X-ray sources and factors of 3-5 improvements in source locations are two of the major benefits derived from the orbital operations of the observatories. Verification of attitude control performance predicted by analysis and simulation during the development phase was demonstrated by on-orbit operation. Reprogrammability of the on-board digital computer was found to provide significant enhancements in operations and expendible extensions as well as providing a means for working around hardware anomalies/ malfunctions. Lessons learned in this contemporary scientific spacecraft program provide an experience base and programmatic perspective which have application to future developments.