Inflight calibration of the NEAR multispectral imager

The multispectral imager on the Near-Earth Asteroid Rendezvous spacecraft h as been subjected to a comprehensive series of inflight tests to validate i ts radiometric characteristics measured onground and to characterize instru ment stability, pointing, geometric distortion, coalignment with other inst ruments, and light-scattering characteristics under flight conditions. The results of these tests, described herein, support the conversion of images of 253 Mathilde and 433 Eros into scientifically valid products with known geometric and radiometric characteristics. Key results include stability of dark current during cruise to within 1 data number; stability of the flat field to within the limits of inflight detectability; absolute radiometric accuracy of similar to 5%, with no evident systematic change with time; val idation of the focal length with an inflight measurement of 166.85 mm, comp ared to 167.0 +/- 0.2 mm derived onground; measurement of coalignment with the near-infrared spectrometer under flight conditions; and quantification of the intensity and distribution of scattered light. (C) 1999 Academic Pre ss.