The Grain Detection System for the GIADA instrument: Design and expected performances

The Grain Detection System (GDS) is part of the instrument GIADA (Grain Impact Analyser and Dust Accumulator), included in the scientific payload of the ESA Rosetta mission towards comet 46P/Wirtanen. GIADA is aimed at analysing the grain dynamic properties and the dust flux evolution in the cometary environment. The GDS is devoted to the detection of single grains entering the instrument, to measure their velocity and to obtain information about their morphology and possibly composition. In this paper we describe the design of the GDS instrument and give some predictions on GDS performances at the comet. In particular, the simulation shows that the GDS will be able to count a total of 4.7 x 10(5) particle 'events' during all the GIADA operating phase and so satisfy scientific requirements for a statistically reliable analysis of cometary grains. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.