Survey of the Plasma Environment of a ComeT with RosettA – SPECTRA

We propose a 42-month project at the frontier between space physics and plasma physics, based on the scientific exploitation of in situ measurement from the ESA’s exploratory space mission Rosetta, to investigate the structure, evolution and dynamics of the ionised environment of a comet.

Rosetta is an exploratory space mission of the European Space Agency (ESA), launched in March 2014, which arrived in the vicinity of its target comet 67P/Churyumov-Gerasimenko (CG) in summer 2014. It is the first mission designed to orbit and escort a comet. Rosetta carries different experiments, among which a suit of sensors designed for plasma studies (charged particles, electromagnetic field, spacecraft potential), the Rosetta Plasma Consortium (RPC), that is monitoring in situ the ionized environment of comet CG. The LPC2E has the duty and privilege of carrying the technical and scientific responsibility of an experiment on board the ESA’s Rosetta spacecraft: the Mutual Impedance Probe, MIP, one of the five plasma sensors of the ROSETTA plasma consortium. The SPECTRA project is build around the scientific exploitation of this unique instrument, together with the other RPC sensors, which are operating almost continuously around comet CG/67P, the target comet of the ROSETTA mission.

In this context, the SPECTRA project addresses four fundamental issues in space science and plasma physics:
(1) the interaction between the Sun and an non-magnetised, primitive object of the solar system,
(2) the evolution and dynamics of a cometary ionosphere and its link to the cometary physico-chemistry,
(3) the effect of collisionality and the presence of dust in a partially ionised plasma and
(4) the influence of spacecraft – plasma interactions on the behaviour of space instruments.

To tackle those fundamental space plasma issues, the SPECTRA project will bring together necessary skills from complementary fields, from space instrumentation and operations to space data analysis, from space science to fundamental plasma physics, from theoretical to numerical modelling.

The SPECTRA project is structured in five interacting and complementary tasks focused on instrument modelling studies (Task 1) in order to produce the accurate electron density and temperature estimates in the cometary plasma. These in situ measurements, combined with complementary plasma measurement from the other RPC sensors, will be used to study both fundamental plasma physics effects (Task 2) and fundamental space science topics such as the characterization of Sun–comet (Task 3) and cometary coma (Task 4) interactions and associated dynamics. The modelling activity of instrumental behaviour in typical space plasma conditions will also enable to prepare the exploitation of future mutual impedance experiments on board future international space mission (Task 5).

The ANR will enable to hire a Ph.D. student and a post-doctoral researcher to strengthen this fundamental research project and to help building a new team in the laboratory through the building and development of new tools (instrumental response taking into account non-ideal plasma features and the presence of spacecraft-plasma interaction, data analysis software) to be used for future space missions as well. The deliverables of this project (codes, internal reports, scientific articles) will be key for the scientific exploitation of future European space missions, in particular BepiColombo and JUICE, that will carry an experiment similar to MIP onboard Rosetta.