Suggestions for radiometric calibration coefficient generation

The great emphasis that studies of global change have placed on accurate absolute radiometric calibration of satellite sensors has led to the 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 large number of calibration coefficients for each band of each sensor obtained using these different techniques. The question that arises is, what is the way to combine these coefficients to maximize the accuracy of sensor calibration as a function of time? This paper discusses the problem and suggests procedural criteria followed by a procedure for calibration coefficient generation. Emphasis is placed on the use of onboard results in an on-line production of calibration coefficients and the modification of these coefficients, at perhaps 3-month intervals, by reference to vicarious calibration results obtained during that period. Reference is made to the calibration SPOT as a first simple example of such an approach.