The radial brightness dependence in the dust coma of comet P/Grigg-Skjellerup

In a previous paper (Fülle et al. 1993a) we have obtained a three-dimensional coma model of the short period comet P/Grigg-Skjellerup, by fitting ground-based images taken in coincidence with the fly-by of the GIOTTO spacecraft (GEM mission). Concerning the cometary dust environment, we confirmed the excess of large grains measured by the in-situ experiment GEM-DIDSY (McDonnell et al. 1993). In this letter we extend the comparison with space-born data by considering the results provided by the GEM-OPE experiment (Levasseur-Regourd 1993). The same model, once projected along the line of sight of GEM-OPE, is able to produce radial brightness slopes in quite good agreement with those obtained from the in-situ experiment. This result confirms the physical reliability of the proposed dust environment.