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N. R. Izenberg (Johns Hopkins University Applied Physics Laboratory), J. F. III Bell, B. E. Clark (Cornell Univ.), S. L. Murchie, L. Prockter, D. Domingue (JHU/APL), S. M. Robinson (Northwestern Univ.), L. K. McFadden, D. Wellnitz (Univ. of Maryland), M. J. Gaffey (Rensselaer Polytechnic Inst.), P. Lucey (Univ. of Hawaii), C. Chapman (Southwest Research Inst.), J. Veverka (Cornell Univ.), NEAR MSI/NIS Team
Color and spectral comparison of Multispectral Imager (MSI) and Near Infrared Spectrometer data were performed for a number of locations on Eros. Such a comparison provides an essential cross-calibration of the two optical instruments, and is intended to enable utilization of the full VIS-IR spectrum from 450 to 2500 nm for the characterization of Eros's surface composition.
High-resolution (400x800 meters per spectrum and better) NIS spectra taken April and May of 2000 were co-located on co-registered MSI 4- and 7-color datasets from April and June (200 and 50 km orbits respectively). Initial observations include the rim and interior of Psyche crater (the "paw"), Himeros (the "saddle"), and Shoemaker Regio as well as more average surfaces of Eros. The non-contemporaneous NIS data observed at different incidence, emission, and phase angles from the MSI images were adjusted to MSI observation geometry using a Hapke-derived photometric correction (Clark et al, this meeting). MSI color data agree with photometrically corrected NIS data, with radiance factor (I/F) systematically higher by 6% on average at 950 nm in most locations. Contributors to the NIS-MSI differences include different viewing geometries in the non-contemporaneous data resulting in different degrees of shadowing within the respective fields of view, and may include aspects of the photometric correction and/or remnant calibration imperfections in either MSI or NIS.
Global comparisons of MSI color ratios and NIS spectra across the Northern hemisphere of Eros show correlation of slight variations near 1000 nm. Joint NIS and MSI spectra of target spots provisionally confirm the synoptic observations.