Inflight Calibration of the NEAR Multispectral Imager 1

The multispectral imager on the Near-Earth Asteroid Rendezvous spacecraft has been subjected to a comprehensive series of inflight tests to validate its radiometric characteristics measured onground and to characterize instrument stability, pointing, geometric distortion, coalignment with other instruments, 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 ∼5%, with no evident systematic change with time; validation of the focal length with an inflight measurement of 166.85 mm, compared 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.