Giotto observations of Comet Halley dust

Abstract

Measurements of the dust environment of Comet P/Halley by the dust experiments on the Giotto and Vega spacecraft are discussed, as well as some aspects of the dust modelling that was carried out before the spacecraft encounters with the comet. These data have highlighted certain shortcomings in the models. For example, significant fluxes of grains ( m < 10 -17 kg) smaller than allowed by the models have been detected, as well as a far higher ratio than predicted of light to dark side emission from the cometary nucleus. The mass-loss rate is determined and implications for the past history of the comet are discussed. It is also shown how the dust-impact data from the spacecraft experiments can be used to derive information on the distribution of emission over the surface of the nucleus.