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M. L. Urquhart, B. M. Jakosky (U. Colorado)
The NEAR rendezvous with the asteroid Eros is scheduled to begin in February 1999. Understanding the thermal regime of Eros is necessary for the proper interpretation of band shape from NEAR's Near-Infrared Spectrograph (NIS). In support of such analysis, we have used a standard numerical thermal diffusion model to calculate theoretical surface temperatures for the asteroid. Our model has been modified to allow for the temperature dependence of thermal inertia. The determination of surface temperatures requires knowledge of the rotation, orbit, albedo, and thermal inertia of the body of interest. However, the thermal inertia of Eros's surface layer is currently unknown. To allow for this uncertainty, we have adopted thermal inertias based on a reasonable range of values for fines on airless bodies. Temperatures are derived over both diurnal and seasonal cycles for a variety of planetographic latitudes. Understanding the seasonal thermal behavior of Eros, in addition to diurnal temperatures, is especially important because of the length of the rendezvous (approximately one year), the high eccentricity of Eros's orbit, and its obliquity of nearly 90 degrees. We have designed our model to generate surface temperatures for any planetographic latitude on any given day during the rendezvous or for an entire orbit. This model can also be quickly adapted for predicting surface temperatures on other minor planets with simple rotation.