DIFFUSING SCREEN FOR ON-BOARD RADIOMETRIC CALIBRATION OF THE STEREO-SPECTRAL-IMAGING SYSTEM ARGUS FOR MARS 94 96 MISSION/

A new stereo-spectral-imaging system, ARGUS, has been developed for th e Mars 94/96 mission and consists of three videospectrometers with a w ide field-of-view covering the spectral range 320 nm to 5200 nm. The o n-board radiometric calibration is based on a diffusing target illumin ated by the Sun's radiation. The provision for a common target for all the videospectrometers of the ARGUS system allows an intercomparison of instruments to be carried out in addition to individual calibration verification. The development and testing of the target for on-board radiometric calibration is described and techniques for preparing the target surface are given. A brief description of the setup for measure ments of the spectral and angular response of the target reflectivity is presented, together with results of the spectral and angular respon se of the target reflectivity, for an angle of incidence of -70 degree s (relative to the normal) and at viewing angles from 0 degrees to +60 degrees at 2 degrees intervals. The bidirectional reflectance factor of the target is reported for the spectral range 320 nm to 5200 nm at an angle of incidence of -70 degrees and at a viewing angle of +20 deg rees.