The description of dynamic spacecraft charging using modern computer tools

The peculiarity of spacecraft charging dynamic processes on GEO is determined by the mechanism of suppression of an secondary electron emission by a retarding electrical field and sharply differing timescales of charging processes, including fast change of external conditions (plasma, sunlight, spacecraft orientation). For numerical simulation of development of spacecraft charging processes in time the automatic multistep Gear method specially intended for the decision of "stiff' systems of the ordinary differential equations is used in this work. The increase of performance modern PC has allowed to use this method for spacecraft models with number of elements more than 1000. The tests show high stability and accuracy of the used methods even with the influence of spacecraft model sampling degree. This algorithm is realized in a new version of the spacecraft charging tool "Coulomb", constructed as the WWW client-server. The tools include the interactive builder of spacecraft models and 3D display system of the information and results of accounts, material properties, and space plasma parameter databases, tools for solution of electrostatic and dynamic problems, and scenario manager tool. The tool uses HTML browsers with VRML by plug-in, WWW Apache server with PHP, and mySQL extensions, which allows using it in local and remote access mode. The described technique is applied to the of spacecraft charging analysis on a GEO and HEO under various conditions: in the eclipse and in the sunlight, slow or fast rotation spacecraft in sunlight, movement of a shadow on the spacecraft surface, and also with time variation of plasma parameters. The results of spacecraft charging calculation are presented. (Author)