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| INSTITUTET FÖR RYMDFYSIK | UPPSALA |
 |
|
| Swedish Institute of Space Physics | (59°50.272′N, 17°38.786′E) |
Project work /
Examensarbete (30 hp)
The electrostatic
potential of the Rosetta spacecraft
Student: Jonny
Jansson,
Uppsala UniversitySupervisor: Anders Eriksson
Period: Autumn 2007
Background
Rosetta is an ESA spacecraft launched in 2004, presently en route to comet Churyomov-Gerasimenko, which it will reach in 2014. The Swedish Institute of Space Physics in Uppsala has contributed a Langmuir probe instrument (LAP) to Rosetta, for measurement of plasma parameters like density and electron temperature. Until reaching the fully developed cometary coma, the plasma environment for most Rosetta operations is the solar wind, characterized by densities in the range of a few to a few tens of particles per cm3. The potentially best method for LAP to measure these low densities is by measurement of the spacecraft potential, which is related to the plasma density, usually by an exponential relation. However, as Rosetta has solar panels with large exposed areas at varying positive potential, the exact form of the relation relevant for Rosetta is not known. This is the topic for the present investigation.Project
Construct an analytical model for the density-potential relation, n = f(V). Compare predictions from this model to data available from Rosetta's Earth and Mars swing-by maneouvres, and to solar wind data. Investigate the relation between the potential measured by the LAP probes and the spacecraft potential to infinity. A possible extension could be the use of numerical modelling, using the SPIS software package (www.spis.org), for investigations of how the potential measured by LAP relates to the true spacecraft potential for different attitudes, in vacuum (due to solar panel orientation) and possibly in a plasma (including the spaceraft photoelectron cloud).![[Rosetta]](../../rosetta/fig/rosetta1_sm.jpg)
The Rosetta spacecraft, with LAP probes mounted at the tips of the two solid booms and the large (32 m wing span) solar panels clearly visible.