Comet Halley dust environment from SP-2 detector measurements

Abstract

The SP-2 experiment carried by the Vega spacecraft during their encounter with comet Halley was designed to determine the spatial distribution of cometary dust particles and their mass distribution over the range ∼10−16–10−6 g. The first infrequent dust particle impacts recorded by the SP-2 sensors indicated that Vega 1 entered the cometary dust coma at a distance of ∼280,000 km from the nucleus. Although the subsequent rapid and even spectacular developments were not unexpected and the results of the in situ measurements agree well with the general predictions of cometary dust environment models1,2, a number of remarkable features were revealed, such as the high density of sub-micrometre-sized particles, considerable variations in the particle mass distribution observed in different regions of the coma and particularly in jets, and the asymmetry relative to the comet–Sun line.