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R.J. Whiteley, D.J. Tholen (University of Hawaii, IfA)
We present an update on our spectrophotometric survey of the Near-Earth asteroids. From 1985 to 1992, approximately 100 NEA's were observed in the 8-color photometric scheme using a photomultiplier system. From 1996 to 1999, we observed another 100 NEAs, again in the 8-color photometric system, this time using CCD technology. The basic end result of our survey will be a catalogue of NEA taxonomies and whatever rotational information can be discerned from our data. But the driving purpose behind gathering such a large data set is to do statistically meaningful checks on possible correlations between the spectral properties and the dynamical state of the NEA's. For example, several researchers have reported color variations with absolute magnitude [1,2,3].
We are interested in testing this assertion, of course, as well as the potential correlation between the optical principal components and perihelion distances of the NEA's. If there is a temporal weathering sequence among the chondrite/silicate NEA's, evidence for it may be found in such a relationship. At the very least a lack of correlation between perihelion distance and colors should allow us to set lower limits on the time scales over which any weathering process must occur. By the time of the Padua DPS meeting, we should have on hand and available for review spectral data on about 50 objects out of our total sample of 200. This will allow us to make some preliminary statistical analysis of this idea, as well to check on the absolute magnitude vs. color correlation.
[1] Binzel, et al., 1998, Size dependence of asteroid spectral properties: SMASS results for Near-Earth and main belt asteroids, LPSC 29 [2] Hicks, et al. 1998, The unusual spectra of 15 near-Earth asteroids and extinct comet candidates, Icarus 133,69. [3] Rabinowitz and Hicks, 1998, The Table Mountain Photometric Survey of the Near-Earth Asteroids, Bull. Am. Astron. Soc., 30, 1042