Dust particle impacts during the Giotto encounter with comet Grigg-Skjellerup
Colangeli, L.; Green, S. F.; Greenberg, J. M.; Eberhardt, P.; Bussoletti, E.; McBride, N.; McDonnell, J. A. M.; Beard, R.; Firth, J. G.; Grard, R.
United Kingdom, Italy, Switzerland, Netherlands
Abstract
IN the European Space Agency's 1992 Giotto Extended Mission, the Dust Impact Detection System operated successfully during a fly-by that took the spacecraft within about 200 km of the nucleus of comet Grigg-Skjellerup. During the encounter, three meteoroid impacts were detected on Giotto's front shield. The particle masses were found to be lOO+105-50 µg, 2+4-1 µg and 20+25-10 µg, suggesting that the mass distribution of the cometary dust was dominated by larger particles. This is supported by the independent detection of a very large meteoroid (14+40-4 mg) by the Giotto Radio-Science Experiment, and is consistent with data over the same mass range from the 1986 encounter with comet Halley. The results indicate a higher rate of mass loss from the nucleus than previously thought, and hence a higher dust-to-gas mass ratio.