Neutron albedo measurements on polar orbiting satellites

An experiment to measure the earth's neutron albedo was flown on three polar orbiting Agena satellites in 1962. The detector, a BF3 counter within a moderator, was surrounded by a ring of charged-particle proportional counters to discriminate against neutrons produced by protons in the detector assembly. The results show an albedo flux of 0.085±0.03 n/cm2 sec at the equator at 300-km altitude, in agreement with the rocket measurements of Bame et al. and the calculations of Lingenfelter. However, at high latitudes we find 0.24±0.06 n/cm2 sec, a factor of 4 below the calculations of Lingenfelter. The appendix outlines calculations that have been used to estimate the neutron production by primary cosmic-ray protons on the detector assembly and the vehicle itself. These calculations are compared with the experimental measurements of production in the detector assembly.