# A charging model for the Rosetta spacecraft

Fredrik Leffe Johansson, Anders Eriksson, Nicolas Gilet, Pierre Henri, Gaëtan Wattieaux, Matt Taylor, Christian Imhof, Fabrice Cipriani

<figure><img src="image_1.png" /></figure>

## To cite this version:

Fredrik Leffe Johansson, Anders Eriksson, Nicolas Gilet, Pierre Henri, Gaëtan Wattieaux, et al. A charging model for the Rosetta spacecraft. vEGU21, 2021, Online, France. 10.5194/egusphere-egu21-9508. insu-03559304

HAL Id: insu-03559304

https://insu.hal.science/insu-03559304

Submitted on 7 Feb 2022

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_2.png" /></figure>
<figure><img src="image_3.png" /></figure>

# A charging model for the Rosetta spacecraft

Fredrik Leffe Johansson<fnref n="1" />, Anders Eriksson<fnref n="1" />, Nicolas Gilet<fnref n="2" />, Pierre Henri<fnref n="2" />,<fnref n="3" />, Gaëtan Wattiaux<fnref n="4" />, Matt Taylor<fnref n="5" />, Christian Imhof<fnref n="6" />, and Fabrice Cipriani<fnref n="5" />

Context. The electrostatic potential of a spacecraft, $V_s$, is important for the capabilities of in situ plasma measurements. Rosetta has been found to be negatively charged during most of the comet mission and even more so in denser plasmas.

Aims. Our goal is to investigate how the negative $V_s$ correlates with electron density and temperature and to understand the physics of the observed correlation.

Methods. We applied full mission comparative statistics of $V_s$, electron temperature, and electron density to establish $V_s$ dependence on cold and warm plasma density and electron temperature. We also used Spacecraft-Plasma Interaction System (SPIS) simulations and an analytical vacuum model to investigate if positively biased elements covering a fraction of the solar array surface can explain the observed correlations.

Results. Here, the $V_s$ was found to depend more on electron density, particularly with regard to the cold part of the electrons, and less on electron temperature than was expected for the high flux of thermal (cometary) ionospheric electrons. This behaviour was reproduced by an analytical model which is consistent with numerical simulations.

Conclusions. Rosetta is negatively driven mainly by positively biased elements on the borders of the front side of the solar panels as these can efficiently collect cold plasma electrons. Biased elements distributed elsewhere on the front side of the panels are less efficient at collecting electrons apart from locally produced electrons (photoelectrons). To avoid significant charging, future spacecraft may minimise the area of exposed bias conductors or use a positive ground power system.

<footnote n="1">¹Swedish Institute of Space Physics, Uppsala, Uppsala, Sweden (frejon@irfu.se)</footnote>

<footnote n="2">²LPC2E, CNRS, Orléans, France</footnote>

<footnote n="3">³Laboratoire Lagrange, OCA, CNRS, Nice, France</footnote>

<footnote n="4">⁴University Paul Sabatier Toulouse III, Toulouse, France</footnote>

<footnote n="5">⁵ESA/ESTEC, Noordwijk, The Netherlands</footnote>

<footnote n="6">⁶Airbus Defence and Space GmbH, Friedrichshafen, Germany</footnote>
<figure><img src="image_4.png" /></figure>