SUGGESTIONS FOR RADIOMETRIC CALIBRATION COEFFICIENT GENERATION

The great emphasis that studies of global change have placed on accura te absolute radiometric calibration of satellite sensors has led to th e development of many new onboard and vicarious calibration techniques . With the launch in 1998 of the first Earth Observing System sensors, calibration scientists will, for the first time, be confronted by a l arge number of calibration coefficients for each band of each sensor o btained using these different techniques. The question that arises is, what is the best way to combine these coefficients to maximize the ac curacy of sensor calibration as a function of time? This paper discuss es the problem and suggests procedural criteria followed by a procedur e for calibration coefficient generation. Emphasis is placed on the us e of onboard results in an on-line production of calibration coefficie nts and the modification of these coefficients, at perhaps 3-month int ervals, by reference to vicarious calibration results obtained during that period. Reference is made to the calibration of SPOT as a first s imple example of such an approach.