Reports

Observations of Nuclear Reactors on Satellites with a Balloon-Borne Gamma-Ray Telescope

Science  28 Apr 1989:
Vol. 244, Issue 4903, pp. 451-454
DOI: 10.1126/science.244.4903.451

Abstract

Gamma rays at energies of 0.3 to 8 megaelectron volts (MeV) were detected on 15 April 1988 from four nuclear-powered satellites including Cosmos 1900 and Cosmos 1932 as they flew over a double Compton gamma-ray telescope. The observations occurred as the telescope, flown from a balloon at an altitude of 35 kilometers from Alice Springs, Australia, searched for celestial gamma-ray sources. The four transient signals were detected in 30 hours of data. Their time profiles show maxima with durations of (21 ± 1) and (27 ± 1) seconds (half-width at half maximum) for the lower two satellites and (85 ± 5) and (113 ± 7) seconds for the remaining two. Their durations place the origin of the two shorter signals at orbital radii of 260+40-60 and 260 ± 60 km above the earth and the two longer at 800+100-300 and 800+250-300 kilometers. Their luminosities for energies >0.3 MeV are then (6.1 ± 1.5) x 1015, (3.9 ± 1.0) x 1015, (1.10 ± 0.28) x 1016, and (1.30 ± 0.32) x 1016 photons per second. The imaging of the strongest signal indicates a southeastern direction passing nearly overhead. The energy spectrum can be fit to an exponential with index 2.4 ± 1.4. These transient events add to the already large backgrounds for celestial gamma ray sources.

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