Cosmic-Ray Charging Advanced Example

High-energy proton interaction in LISA spacecraft

Henrique Araújo & Peter Wass
Imperial College London
April 2004

This Geant4 example was derived from an application aimed at simulating the electrostatic charging of isolated test masses in the LISA mission by galactic cosmic ray protons and helium nuclei. This work was supported by the European Space Agency through the SEPTIMESS project under Contract No. 16339/02/NL/FM.

 

The LISA constellation

LISA, the Laser Interferometer Space Antenna for the detection of gravitational waves, is a joint ESA/NASA mission composed of three identical spacecraft orbiting the Sun in a triangular formation, each containing two cubic test masses in pure geodesic (drag free) motion. The interferometric measurements between different spacecraft are affected by the accrual of charge in the test masses caused by the interaction of energetic cosmic rays.

Cubic test mass (gold) at the centre of the inertial sensor

With this example we intend to demonstrate an application of Geant4 to space environment simulations, using an extensive set of physics models spanning from TeV energies down to a few hundred eV. This code retains most (but not all) of the complex spacecraft and sensor geometry implemented for the original purpose. In particular, some complex elements of the inertial sensor surrounding the test masses have not been included. Differential energy spectra for protons, He-4 and He-3 nuclei at solar minimum conditions are the only input macros provided. The remaining application classes have been kept unchanged.

A Software Users' Manual suitable for Geant4 users of all levels is distributed here. Technical descriptions of the original software package, including further software documentation, Physics analysis and a similar effort for the precursor ESA mission LISA Pathfinder are available here.

Any queries regarding this example can be directed to h.araujo@imperial.ac.uk.


Last modified 06 July 2004