First Halley Multicolour Camera imaging results from Giotto
Wilhelm, K.; Keller, H. U.; Barbieri, C.; Reitsema, H. J.; Delamere, W. A.; Huebner, W. F.; Arpigny, C.; Schmidt, H. U.; Hughes, D. W.; Jamar, C.; Cosmovici, C. B.; Coradini, M.; Bonnet, R. M.; Cazes, S.; Whipple, F. L.; Malaise, D.; Schmidt, W. K. H.; Seige, P.
Germany, Belgium, Italy, France
Abstract
The first imaging results from the Halley Multicolour Camera (HMC) during the Giotto fly-by of comet Halley provide images centred on the brightest part of the inner coma which show the silhouette of a large, solid and irregularly shaped cometary nucleus and jet-like dust activity visible in reflected sunlight. A first assessment of the data yields information on the dimensions and shape of the nucleus and dust emission activity. The nucleus is at least 15 km long and ~10 km wide; its geometrical albedo is very low (<4%). Only minor parts of the surface are active, most of it beirig covered by non-volatile material. Dust jets dominate the inner coma and are restricted to the sub-solar hemisphere. Preliminary interpretations of these observations are presented. The parameters of the fly-by trajectory relative to the nucleus are given.