Systems for calibration of optical instrument on satellite with reference light source

摘要

A calibration system for periodically calibrating an optical instrument on board a satellite with reference light. In the disclosed system, a calibration unit has two photodetectors one of which is positioned near the light source which radiates reference light and the other near the aperture from which the reference light emerges toward optics of the instrument. Therefore, it is possible to discriminate between contamination or degradation of the optical instrument and contamination of the calibration unit. Two identical and independent calibration units are employed to provide redundancy and enhance the accuracy of calibration.