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L. C. DeRemer (Wellesley College), E. S. Howell, M. C. Nolan (Arecibo Obs.), J.-L. Margot (Caltech)
High-resolution radar images of near-Earth asteroids reveal their sizes, shapes and some surface properties. The radar-determined size can be combined with the apparent visual brightness to obtain a visual albedo. The radar reflectivity can be used to determine the radar albedo, which is related to the surface bulk density. In some cases, the rotation period and spin axis are also determined from a series of images. The range of variability of each of these properties is greatly increased among the smallest near-Earth asteroids, compared to those 350m diameter and larger.
We will present observations of three near-Earth asteroids, 2000 EE104, 2001 BF10, and 2001 GQ2. Asteroid 2000 EE104 shows a very high polarization ratio (SC/OC), which is difficult to explain simply on the basis of surface roughness. The value changes with rotation phase, ranging from SC/OC = 0.8--1.4. Typical values for larger NEAs are SC/OC = 0.1--0.3. Asteroid 2001 BF10 is a very rapid rotator, with a rotation period of no more than 12 minutes. This 100-m object must have some material strength and no loose regolith. Asteroid 2001 GQ2 is rounded in shape, and is consistent with being a rubble pile without material strength. The spin axis changed enough during the time it was imaged to constrain the viewing geometry. These results will be presented and placed into the context of the near-Earth asteroid population.
The author(s) of this abstract have provided an email address for comments about the abstract: lderemer@wellesley.edu