NEAR Lightcurves of Asteroid 433 Eros

The NEAR spacecraft flew by Asteroid 433 Eros on December 23, 1998, and obtained images with a best angular resolution of about 400 m/pixel. These images were used to derive a shape model (Thomas et al. 2000, Icarus). In addition, images obtained at phase angles of 88° to 115° during the flyby were used to modify our photometric model of Eros. NEAR has continued to observe Eros in flight, taking a series of lightcurves. The multispectral imager (MSI) lightcurve data consist of six observations of one full rotation each and range in phase angle from 62° to 98°. With the post flyby shape and photometric models, we have predicted the lightcurve of Eros. We used viewing angles which corresponded to actual viewing angles of lightcurve data obtained in flight by the MSI. Comparisons between observed and modeled lightcurves reveal relative discrepancies of up to 0.3 magnitudes. Our analysis shows that these differences indicate significant albedo features located between longitudes 220° and 300°. These longitudes were imaged during the NEAR flyby of December 1998, and indeed they show that a bright facet, well constrained in the shape model, appears to have an anomalously high albedo.