Joe Warren

The landing of the NEAR-Shoemaker spacecraft on asteroid 433 Eros.

The NEAR-Shoemaker spacecraft was designed to provide a comprehensive characterization of the S-type asteroid 433 Eros (refs 1,2,3), an irregularly shaped body with approximate dimensions of 34 × 13 × 13 km. Following the completion of its year-long investigation, the mission was terminated with a controlled descent to its surface, in order to provide extremely high resolution images. Here we report the results of the descent on 12 February 2001, during which 70 images were obtained. The landing area is marked by a paucity of small craters and an abundance of ‘ejecta blocks’. The properties and distribution of ejecta blocks are discussed in a companion paper. The last sequence of images reveals a transition from the blocky surface to a smooth area, which we interpret as a ‘pond’. Properties of the ‘ponds’ are discussed in a second companion paper. The closest image, from an altitude of 129 m, shows the interior of a 100-m-diameter crater at 1-cm resolution.

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

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 asteroids geochemical evolution. On approach to Eros, a search will be made for satellites: objects as small as 12 m (some 100 times smaller than Idas Dactyl) could be detected.