Numerical images applied to the spatial technics: the discovery of the Halley's comet nucleus

For the first time, the solide nucleus of a comet was observed by the 2 soviet spacecraft VEGA on 6 and 9 March 1986. They were followed by the european spacecraft GIOTTO on 14 march. The numerical images transmitted by the 3 spacecraft have been corrected from instrumental degradations and allowed a unique description of the shape and the movement of Halley's comet nucleus. Thus the contours become clearly apparent. Its volume can be described by an ellipsoid which principal axis are equal to 16, 8.2 and 7.5 km: it has an oblate rugby balloon shape. Its rational movement is complicated, but we are able to analyse it with the identification of details seen on the surface at three different moments. The nucleus is greater than expected in the past. It is made of a mixture of water ice and dust, and is covered by a dust dark mantle: it is one of the darkest objects in the solar system. This mantle is not uniform, as shown by the images sent by the 3 spacecraft. They display a spectacular distribution of dust jets emitted by very active regions on the nucleus surface