The electron distribution in the Earth's radiation belts during July 1962 as measured by Telstar

Results obtained from the electron detector on Telstar between July 10 and 31, 1962, are presented. The principal sensitivity of the detector is to electrons of energies between 0.25 and 1.0 Mev. Flux maps have been drawn for days 193–197, 203–207, and 208–212, 1962. Maximum omnidirectional electron fluxes of approximately 109/cm2 sec were encountered with energies in excess of 200 kev near the magnetic equator at L's of about 1.25 and 1.8Re. The intensity decreased exponentially with a time constant of about 4.5 days between L values of 2.2 and 3.0, and with a time constant of about 15 days at L = 2.0 and 3.5, creating a slot be tween the inner and outer electron belts that had become pronounced by the end of July. The energy spectrum encountered seems to contain a substantial number of electrons with energies of about a Mev or more and is not inconsistent with the fission β spectrum above 400 kev. At lower energies the spectrum is steeper. Within the sensitivity of the measurement no spectral changes with either position or time were observed. Because of Telstar's launch date it is not possible to conclude what fraction of the electrons measured were produced by the high-altitude nuclear test of July 9. In spite of the high flux of electrons encountered, electrons are not the major source of radiation damage to the Telstar solar power plant.