First Halley Multicolour Camera imaging results from Giotto

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.