HEAO 3

The HEAO 3 (High-Energy Astronomy Observatory 3) mission performed a sky survey of gamma rays and cosmic rays in a manner similar to HEAO 1. It had a higher orbital inclination than the previous missions in this series, since the payload consisted primarily of cosmic-ray instrumentation; greater cosmic-ray flux occurs near the earth's magnetic poles. The scientific objectives of the mission were 

• to determine the isotopic composition of the most abundant components of the cosmic-ray flux with atomic mass between 7 and 56, and the flux of each element with atomic number (Z) between Z = 4 and Z = 50;
• to search for super-heavy nuclei up to Z = 120 and measure the composition of the nuclei with Z >20;
• to study intensity, spectrum, and time behavior of X-ray and gamma-ray sources between 0.06 and 10 MeV; measure isotropy of the diffuse X-ray and gamma-ray background; and perform an exploratory search for X-and gamma-ray line emissions.

The normal operating mode was a continuous celestial scan about the Z axis (which nominally pointed to the sun).

HEAO 3 featured a Gamma ray spectrometer with 4 cryogenically cooled germanium detectors, each with an energy range of 50 keV.to 10 MeV.

Experiments on board were:

• Gamma-Ray Line Spectrometer
• Heavy Nuclei
• Gamma-Ray Spectrometer Shield
• Isotopic Composition of Cosmic Rays