Grain impact analyser and dust accumulator (Giada) experiment for the Rosetta mission: Design, performances and first results

The Grain Impact Analyser and Dust Accumulator (GIADA) onboard the ROSETTA mission to comet 67P/Churyumov-Gerasimenko is devoted to study the cometary dust environment. Thanks to the rendezvous configuration of the mission, GIADA will be plunged in the dust environment of the coma and will be able to explore dust flux evolution and grain dynamic properties with position and time. This will represent a unique opportunity to perform measurements on key parameters that no ground-based observation or fly-by mission is able to obtain and that no tail or coma model elaborated so far has been able to properly simulate. The coma and nucleus properties shall be, then, clarified with consequent improvement of models describing inner and outer coma evolution, but also of models about nucleus emission during different phases of its evolution. GIADA shall be capable to measure mass/size of single particles larger than about 15 mu m together with momentum in the range 6.5 x 10(-10) / 4.0 x 10(-4) kg in s(-1) for velocities up to about 300 m s(-1). For micron/submicron particles the cumulative mass shall be detected with sensitivity 10(-10) g. These performances are suitable to provide a statistically relevant set of data about dust physical and dynamic properties in the dust environment expected for the target comet 67P/Churyumov-Gerasimenko. Pre-flight measurements and post-launch checkouts demonstrate that GIADA is behaving as expected according to the design specifications.