Rosetta spacecraft potential and electron temperature in the coma of comet 67P

Elias Odelstad , Gabriella Stenberg-Wieser , Martin Wieser , Anders Eriksson , Hans Nilsson , Pierre Henri (1)

1 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace

We present and compare measurements of the spacecraft potential (VS/C) of ESA's Rosetta spacecraft during its ∼2 year stay in the inner coma of comet 67P/Churyumov-Gerasimenko, by the Rosetta Langmuir probe (RPC-LAP) and Ion Composition Analyzer (RPC-ICA) instruments. VS/C was mostly negative, driven so by the high (∼5-10 eV) electron temperature of the coma photoelectrons. LAP only picks up a portion of the full VS/C since the two probes, mounted on booms of length 2.2 and 1.6 m, respectively, are generally inside the potential field of the negatively charged spacecraft. Comparison of the minimum energy of positive ions collected by ICA shows that this portion varies between 0.7 and 1 VS/C, with generally good correspondence between the two instruments except when local ion production is weak and accelerated ions dominate the flux. We map VS/C and its evolution during the mission and use it to constrain the electron density ne and temperature Te in the inner coma. Comparison of VS/C measurements to electron density measurements by the Mutual Impedance Probe (RPC-MIP) allows more accurate estimates of the electron temperature and a cross-calibration of the neand Te measurements by the different instruments.

Domains: Sciences of the Universe [physics]

Elias Odelstad, Gabriella Stenberg-Wieser, Martin Wieser, Anders Eriksson, Hans Nilsson, et al.. Rosetta spacecraft potential and electron temperature in the coma of comet 67P. 19th EGU General Assembly, Apr 2017, Vienne, Austria. pp.9258. ⟨insu-03568143⟩