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A. S. Rivkin, R. P. Binzel (MIT), S. J. Bus (IRTF)
Albedo is one of the fundamental physical properties for asteroids, knowledge of which is important for interpreting spectra and determining sizes. This is particularly true for near-Earth asteroids, which show a large range of albedos in a number of spectral types (Harris and Lagerros 2001). For near-Earth asteroids, however, albedo measurements are often not available due to the short periods for which these objects are available and the "catch as catch can" nature of observations.
Because NEAs are close to the sun, and their temperatures are warm (relative to their main-belt cousins), observations in the 1-2.5 \mum region can constrain albedos for NEAs. For some objects, thermal emission can in fact be detected and measured at 2.5 \mum, allowing a model fit to determine or constrain the albedo value. For example: an object at 1.2 AU with an albedo of 0.1 will have an "excess" flux of roughly 10 others, a lower limit for albedo can be calculated based on the lack of thermal emission.
We will present a set of NEA albedos determined from 1-2.5 \mum spectra taken with SpeX on the IRTF. We will also present a graphical means of roughly constraining the albedos of new NEAs observed in the 1-2.5 \mum region, based on phase angle and solar distance.
This work was partially supported through grants by the NASA PGG and Planetary Astronomy programs.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.