Simulated measurements of 67P/Churyumov–Gerasimenko dust coma at 3 AU by the Rosetta GIADA instrument using the GIPSI tool

GIADA (Grain Impact Analyzer and Dust Accumulator) is an in situ instrument, on board the Rosetta spacecraft, designed to measure the dynamical properties of the dust grains emitted by the comet 67P/Churiumov–Gerasimenko (hereafter 67P/C–G). It consists of three subsystems able to measure the mass and speed of single dust grain and dust mass flux. Once the orbit and the attitude of a spacecraft are defined, it is needed to simulate the performances of an in situ instrument. We present simulated GIADA performances to evaluate its capability in fulfilling its scientific objectives along specific orbits. In order to perform these simulations, because of the lack of real data on near-nucleus cometary environment, it is necessary to use a modeled dust coma along the spacecraft (S/CS/C) orbits. We developed GIPSI (GIADA Performance Simulator), a simulation tool conceived to replicate the GIADA capability in detecting coma dust features through the dust abundances, mass and velocity dust distributions measurements. Using state-of-the-art coma modeling, we evaluated three different Rosetta orbit mission scenarios. We outline the optimal S/CS/C orbit for GIADA by means of achievable dust coma evolution description, number of collected particles and grain velocity measurements. The quasi circular orbit with a 5 km peri-center radius and a 10 km apo-center radius, during the pre-landing close observation phase is the best suited for the GIADA instrument.