27.01-P

Adaptive optics observations of solar system objects

F. Roddier (University of Hawaii), A. Brahic (University of Paris VII), C. Dumas, J. E. Graves, B. Han, M. J. Northcott, T. Owen, C. Roddier (University of Hawaii)

Diffraction-limited images can now be obtained from the ground using adaptive optics. We present here a number of results obtained with this technique by researchers at the Institute for Astronomy. These include:
1) Observations of the rings of Saturn as the Earth was crossing the ring plane in August 95. Evidence was found for a dozen of 20- to 40-km diameter objects, probably clumps, orbiting at the distance of the F-ring. Among these objects two of them have been identified with objects 1995 S5 and S7 observed by the Hubble Space Telescope. An eclipse of Epimetheus by the F ring was observed, putting new constraints on its orbit as well as the size and density of the F ring. Photometric profiles have been obtained along the rings, and their time evolution has been modeled.
2) Observations of Titan through narrowband filters in and out of the 1.6 micron methane window. The surface feature observed by Smith et al and Combes et al on the leading hemisphere has been detected as well, albeit with morphological differences. A program of adaptive-optics observations of Titan is under way.
3) K-band observations of Uranus and its rings. Puck has been detected.
4) K-band observations of Neptune, confirming that low-latitude cloud activity has shifted from the south to the north hemisphere since Voyager observations. For the first time Proteus was detected from Earth and its albedo was measured at 2.2 m.
5) Wide band observations of Pluto and Charon. A program of narrow band photometry of the individual components is under way.
6) Observations of asteroid 4 Vesta during its 1996 opposition through narrow band filters in and out the pyroxene bands. Its dimensions and shape as well as the nature of the geological units present on its surface, have been derived.