Satellite-borne high-resolution Ge(Li) gamma-ray spectrometer system. Part 1. Description of the instrument and gamma-ray backgrounds in earth orbit

Gamma radiation from terrestrial and extraterrestrial sources has been investigated for the first time with a high-resolution lithium-drifted germanium spectrometer-cryogen system flown on board a low-altitude, spin-stabilized, polar-orbiting satellite (1972-076B) launched on October 2, 1972. Gamma-ray pulses corresponding to energies between 40 keV and ~ 2.8 MeV are analyzed by a 4096-channel pulse-height analyzer with an overall system resolution of 3.5 - 4.0 keV FWHM (1.33 MeV Co60). A description of the instrument, its performance in earth orbit and preliminary results of the gamma-ray backgrounds are presented.