IMAGING OF ASTEROID 4179-TOUTATIS WITH THE HUBBLE-SPACE-TELESCOPE

We obtained four images of the asteroid 4179 Toutatis during its close approach to the Earth on 10 December 1992 with the planetary camera o f the Hubble Space Telescope. The distance between the Earth and Touta tis at the time of our observations was 0.0291 AU (4.35 x 10(6) km); a single planetary camera pixel width subtends a distance of 996 meters at this distance. The solar phase angle was 91.3 degrees. Analysis of both raw and deconvolved images indicate that Toutatis was marginally resolved by the HST. There is evidence for an extended object with a projected illuminated dimension less than 2.8 km while the best fit sy mmetric model has a maximum illuminated size of 2.0 km and deconvoluti ons suggest an irregular object with a maximum dimension of 1.7 km, Ou r size determination is in good agreement with groundbased infrared ra diometric size estimates. Our observations occurred near a local peak in the lightcurve and photometric points extracted from our images sho w that there were no rapid changes in brightness during the time we ob served. The combination of a local peak in the lightcurve and our deri ved upper limit on the size places some constraints on possible shape models of Toutatis. (C) 1995 Academic Press, Inc.