IRF logo
Student project work (Examensarbete, 20 p)
The Solar UV (Ly-alpha) intensity from Langmuir probe sweep data around Saturn

Student: Robert Isaksson
Supervisor: Jan-Erik Wahlund

Swedish Institute of Space Physics, Uppsala
Department of Astronomy and Space Physics, Uppsala University

March - November 2005


The Cassini/Huygens spacecraft entered the Saturn system and passed its ring plane during the summer 2004, 7 years after launch from Earth. We have an instrument onboard, a Langmuir probe, which is part of the Radio & Plasma Wave Science (RPWS) investigation. Its a European-American collaborative project. The spacecraft will orbit Saturn for an additional 4-6 years. The Langmuir probe will continously sample data during this period, which will include close encounters by icy moons and the large mysterious moon Titan. A Langmuir probe is like a weather station for electrically charged gas, and can give estimates of a number of basic physical parameters like for example density and temperatures. An important parameter to estimate from so called Langmuir probe sweeps are the solar UV intensity with time. It is important for the on board instruments, since it determines the number of photoielectrons around the spacecraft and in the instruments, but also for determine the solar ionization degree of e.g. the upper atmosphere of Titan and on Saturn. This in turn effects radio propagation and detection from e.g. lightning in these bodies atmospheres.


From several months of Cassini RPWS Langmuir probe potential sweep operations around Saturn, this project estimated a calibrated value of the Ly- alpha intensity with time. In detail, this included reading large amounts of LP data, estimating the photoelectron flux, relating this flux to solar UV intensity through various theory, and making graphic output and routines for continued easy access of this parameter.


Jan-Erik Walhund.
last modified onMonday, 28-Aug-2006 15:40:38 CEST