HEAO 1

Description

High-Energy Astronomy Observatory 1 (HEAO 1) was the first in a series of three satellite observatories designed to continue the X-ray and gamma-ray studies initiated by ANS, OAO 3, UK 5, the OSO series, the SAS series, and the gamma-ray burst discoveries of the Vela satellites. This mission was specifically designed to map and survey the celestial sphere for X-ray and gamma-ray sources in the energy range of 150 eV to 10 MeV, to establish the size and precise location of X-ray sources to determine the contribution of discrete sources to the X-ray background, and to measure time variations of X-ray sources. This observatory consisted of a common spacecraft equipment module (SEM), which carried most of the spacecraft operational equipment, and a unique experiment module (EM), which carried some elements of the electrical distribution system in addition to the four experiments: Large Area X-ray Survey, Cosmic X-ray Background Experiment, Scanning Modulation Collimator, and Hard X-ray and Low Energy Gamma-Ray Experiment. Continuous celestial scans were made perpendicular to the satellite-sun vector during the initial phase of the mission. Scan rate was 0.03 rpm. The entire celestial sphere would be scanned in 6 months. When passing over the South Atlantic Anomaly (SAA) of the inner Van Allen Belt, high-voltage supplies were turned off or reduced to prevent damage caused by saturation effects. The six-sided HEAO 1 was 5.68 m high and 2.67 2.67 m in diameter, and weighed 2552 kg, which included 1220-kg experiments. Downlink telemetry was at a data rate of 6.5 kb/s for real-time data and 128 kb/s for either of the two tape recorder systems. The mission lifetime was August 12, 1977, to January 9, 1979. For more details, see New Instrumentation for Space Astronomy, edited by K. A. van der Hucht and G. Vaiana, pp. 101-113, "HEAO-A," H. Friedman, l968.