| Charging and arcing experiment|
B. MUSCAT (MUltility Spacecraft Charging Analysis Tool)
In order to prevent power system failure due to charging like what occurred on ADEOS-II, quantitative analysis from the viewpoint of charging-arcing issues from the early stage of satellite designing phase is necessary.
Electric potential of satellite body with respect to ambient plasma and differential voltage of each surface component with respect to the satellite body potential are the most important elements to consider in charging-arcing problems.
A spacecraft potential analysis tool available from the satellite designing phase is indispensable to make the satellite operations on PEO secure. (Fig. 1)
PEO satellites are exposed to an unique plasma environment where the low energy ionosphere plasma (0.1~0.2 eV) and particles of auroral zone (>1 keV) are mixed.
In LEO with a low inclination angle low energy particles are dominant. In GEO, on the other hand, high-energy particles are dominant. Therefore, an analyzing tool developed for PEO can be used both for LEO and GEO with minor modification.
It will be available for charging analysis of LEO spacecrafts such as science satellites or ISS, and for large telecommunication satellites or broadcasting satellites such as ETS-VIII.
At present, NASACAP/GEO and NASCAP/LEO, which were developed in 1970’s, have been introduced to the world satellite development as spacecraft charging analyzing tools. Nowadays, they are de facto standard in the world.
To analyze charging status of a polar satellite, POLAR which was developed in 1980’s is necessary. NASCAP/GEO, NASCAP/LEO and POLAR were all developed with technologies in 70’s and 80’s and their usability like user interface are not so good and satellite modeling functions are limited.<.p>
Although, a new version of NASCAP, NASCAP-2k, has been developed in the U.S for GEO, LEO and PEO, it is not available in Japan because of export restriction.
In Europe, software called SPIS is under development since 2002 funded by ESA (European Space Agency). SPIS is going to complete in 2005.
It was also presented at an international symposium in 2003 that ALCATEL Co. a satellite manufacturer is developing its own charging analysis tool.
In Japan, Space Plasma Simulation Group promotes “Geospace Environment Simulator (GES)” project using the Earth Simulator, one of the fastest computer at present in the world. As a component of GES, a computer code for simulating plasma environment surrounding a satellite is under construction.
As GES uses Particle-in-Cell (PIC) method for computation of environment around spacecraft and includes all plasma process from unsteady to steady, it requires long computation time even for the Earth Simulator. Even GES needs long computation time to simulate the whole spacecraft charging processes with the time scale of the order of seconds or minutes. Therefore, although GES is very powerful, it is not useful for easy use like parametric runs in spacecraft designing phase.
The objective of the project was the development of Multi-Utility Spacecraft Charging Analysis Tool (MUSCAT). MUSCAT will be used to evaluate the risk of charging in spacecraft design phase, to determine appropriate parameter settings of ground tests by calculating the worst-case charging potential, and to determine whether a given satellite failure is due to charging or not.
The development is going to make MUSCAT able to provide users the solution corresponding to a computation condition in half a day with commercial-type 4 or 8 CPU server.
The basic specifications of MUSCAT is as follows:
i) Users can carry out satellite modeling, execution of computation and visualization of the computation result through graphical user interface.
The development of MUSCAT started in November 2004 as funded research by JAXA.The principal actor of the development is Kyushu Institute of Technology (KIT). KIT conducted development of the GUI and the solver, parallelization and speeding up, code validation experiment and so on.
In addition to the tasks above, building up of space environment database, code validation experiment, validation of in-situ data and cross validation with GES results are done as collaboration of KIT, JAXA, Kyoto university, National Institute of Polar Research (NIPR) and National Institute of Information and Communications Technology (NICT).
We plan to release the beta version of MUSCAT by the end of the period, March, 2006. The final version of MUSCAT will be released by the end of the period, April 2007.
| Charging and arcing experiment |