A Numerical Method for Determining the Relative Spectral Response of the Vidicons in a Nimbus Satellite System

The calibration of the television cameras to be carried in the Nimbus meteorological satellites requires that the relative spectral responses of the vidicon systems be known. In the method developed for this purpose, a series of carefully selected optical filters was interposed between a known constant source and the camera lenses. From the measured outputs of the vidicons, the relative spectral responses were derived as the solution of an integral equation of the first kind. This solution, however, is generally highly unstable, but a physically acceptable solution may be obtained by imposing an appropriate smoothing condition on it. This technique was tested successfully with measurements by a brightness meter, and with simulated outputs by Tiros vidicons of known spectral responses. The spectral responses of two Nimbus vidicons, derived from measurements, are shown.