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E. S. Howell, M. C. Nolan (Arecibo Obs.), L. DeRemer (Wellesley College), J.-L. Margot (Caltech)
In April of 2000 and again in April of 2001 radar images of near-Earth asteroid 2000 EE104 were obtained with the Arecibo Observatory planetary radar. Most of the images show a double-lobed object. However, other images clearly show that the two components are not separated. The asteroid appears to be in rigid body rotation with a period of approximately 8 hours.
The pole orientation was significantly different between the two apparitions, and it is likely that the geometry is well determined from the two sets of images. The radar-determined size can be combined with the visual brightness (H=20.50) to determine an optical albedo of 0.18 ±0.05. However, this assumes that G=0.15, and there are indications that the scattering phase function of this object could be very unusual.
The asteroid is elongated, approximately 240m in length. The axial ratio appears to be at least 2:1, although a detailed shape model has not yet been determined. The echo in the expected (opposite circular, or OC) polarization is nearly the same as in the same-circular (SC) sense: The SC/OC polarization ratio is typically 0.1--0.3 for NEAs, but is 1.1 ± 0.3 for 2000 EE104, and varies with rotational phase. This value was confirmed in the April 2001 observations. This high ratio is very unusual, and indicates some interesting surface material properties. Additional analyses will be presented and the implications explored.
The author(s) of this abstract have provided an email address for comments about the abstract: ehowell@naic.edu