IRF Uppsala
RPF programme
IRF-U Staff
PhD studies
Solar Orbiter
Swedish Institute of Space Physics (59o50.272'N, 17o38.786'E)
Student project at IRF Uppsala

Project work / Examensarbete (20 p)

Plasma parameters from the Rosetta LAP instrument

Student: Claes Engelhardt Weyde
Supervisor: Anders Eriksson
Period: 2005-2006


Rosetta is an ESA (European Space Agency) spacecraft, launched towards a comet in March 2, 2004. To be able to catch up with the comet, Rosetta has to take a long route through the planetary system, including three flybys of Earth and one of March. At the Swedish Institute of Space Physics in Uppsala, we have built an instrument called LAP (Langmuir probe) to study the ionized gas (plasma) close to the comet. We do not arrive at the comet until 2013, but have already collected data from the solar wind and close to the Earth (during the 1st Earth flyby in March 2005).


A Langmuir probe is a conceptually simple instrument, but deriving the plasma parameters from the measured data often requires some careful analysis. The topic of this project was to investigate and model some aspects of the performance of LAP in different plasma environments, based on data mainly from the 1st Earth flyby. We investigate the electron current produced by the photoelectric effect on the spacecraft and determine a model to use in describing it mathematically. We notice a small remnant current, which may be explained by a leak-current from the probe to the spacecraft (equivalent to a 10 Gohm resistance) or influence from the spacecraft body on the plasma being measured by the probes. We use the analysis routines on the LAP data from the first Earth fly-by performed by Rosetta. The physical parameters extracted are consistent with independent sources.

Screenshot of the software developed for data analysis.
last modified on Monday, 20-Aug-2007 09:19:18 CEST