An overview of the NEAR multispectral imager‐near‐infrared spectrometer investigation

Abstract

The combined MSI‐NIS investigation on NEAR consists of a Multi‐Spectral Imager (MSI) and a Near‐Infrared Spectrometer (NIS). MSI covers the spectral range from 0.4 to 1.1 μm in seven narrow passbands and one broad filter. MSI has a field of view of 2.25° by 2.90° and will achieve an image scale of about 3 m/pixel at the surface of Eros. NIS covers the spectral interval from 0.8 to 2.6 μm: the range between 0.804 and 1.506 μm is measured by a 32‐element Germanium detector; a 32‐element Indium‐Gallium‐Arsenide detector observes wavelengths between 1.348 and 2.600 μm. The instrument has a selectable field of view of either 0.38°×0.76° or 0.76°×0.76°. A spatial resolution of about 300 m (100 times coarser than MSI) can be achieved at Eros. A major goal of the MSI‐NIS investigation is to determine the fundamental global properties of Eros, including spin state, size, and shape. Precise size and shape measurements are necessary to determine an accurate volume and thereby a mean density from mass measurements. MSI‐NIS spectral data will be combined with abundance determinations of key rock‐forming elements obtained by the X ray/gamma ray spectrometers (XGRS) to infer the distribution of minerals on Eros and constrain models of the asteroid's geochemical evolution. On approach to Eros, a search will be made for satellites: objects as small as 12 m (some 100 times smaller than Ida's Dactyl) could be detected.