The temporal characteristics of the terrestrial radiation belt

The terrestrial radiation belt effects on the detectors in the Wisconsin equipment are considered. The lowest dark count rate observed in orbit, compared with that measured in the thermal vacuum test on the ground, shows no measurable difference for the solar blind ASCOP 541-F photomultiplier tubes while the EMI-6256B tubes show an increase in minimum dark count of a factor of from 20 to 150 times that observed on the ground. All instruments are perturbed when in the South Atlantic anomaly, but the EMI tubes are by far the most sensitive to it. Indeed, the effect never goes away.