A Digital Closed-Loop Calibration System for Space-Borne Particle Spectrometers

The operation of a closed-loop, in-flight calibration system is described. This system utilizes a Cesium Iodide crystal with a grown-in Am241 source as the calibration reference and a programmable photomultiplier dynode supply as the gain-change element. Through the use of this system, the overall gain of a particle spectrometer is expected to be kept accurate to within 3% throughout the changing orbital environment. Approximate power consumption of the system, including the dynode supply, analog section and digital sectoring and control is 415 milliwatts.