Early Observations with the Rosetta Langmuir Probe Instrument at the Target Comet

Thursday, 18 December 2014
Anders I Eriksson1, Niklas J. T. Edberg1, Reine Gill1, Fredrik Johansson1, Elias Odelstad1, Jan-Erik Wahlund1, Erik Vigren1, Tomas Karlsson2, Per-Arne Lindqvist2, Riku Jarvinen3, Bjorn Lybekk4, Wojciech Miloch4, Arne Pedersen4, Jean-Pierre Lebreton5, Chris Carr6 and Emanuele Cupido6, (1)IRF Swedish Institute of Space Physics Uppsala, Uppsala, Sweden, (2)KTH Royal Institute of Technology, Stockholm, Sweden, (3)Finnish Meteorological Inst, Helsinki, Finland, (4)University of Oslo, Department of Physics, Oslo, Norway, (5)University of Orleans, Orleans, France, (6)Imperial College London, London, United Kingdom
Rosetta provides an unprecedented opportunity to follow the evolution of the plasma environment close to a comet as activity grows and recedes from 4 AU to perihelion and out again. Like the rest of the Rosetta Plasma Consortium (RPC), the Langmuir probe instrument (RPC-LAP) has been operating from early summer 2014 to cover also the approach of Rosetta toward comet 67P/Churyumov-Gerasimenko. The instrument uses two spherical probes mounted on short (few meters) solid booms protruding from the spacecraft body. The probes can be used as classical Langmuir probes, as electric field probes with bias current and for wave observations up to 8 kHz. In the low density solar wind, probe bias sweeps are dominated by spacecraft photoelectrons, but plasma density variations can still be accessed through the spacecraft potential. As the density of the comet plasma increases with growing comet activity, direct plasma measurements become possible. We present initial data and first results on the comet plasma environment.