Suspected Plume Impingement Influence on Board Calibration System of Terra/aster/vnir Investigated through Trend Analysis on Board Calibration Data

Trend analysis of Terra/ASTER/VNIR calibration data is made for finding possible causes for degradation of radiometric calibrat ion coefficients. Two sets of photometers are equipped at just after the onboard calibration lamp and at just in front of optics en trance of the mission instrument, VNIR. Unfortunately, the later was malfunctioned 300 days after the launch so that degradation of calibration optics which is situated in between calibration lamp and VNIR optics entrance is not monitored after that. The trends of calibration lamp response of VNIR within 300 days after the launch is very resemble to that of degradation of the later calibra tion lamp so that it might be possible to say that one of the possible causes of degradation VNIR response would be common. That might be a contamination at the optics entrance of VNIR which is later photo monitor is equipped due to plume impingement. From the spectral dependency, particle size of plume impingement is estimated. Also, it is confirmed that extrapolated trend is very similar to the onborad calibration data trend.