Current issues in the use of the global positioning system aboard satellites

The Global Positioning System (GPS) was originally intended to provide prec ise navigation service for Earth-based users, however, the ability to use G PS aboard satellites has also been demonstrated. There is great promise in this application but before its full benefits can be fully realized there m ust be confidence that GPS can provide the same level of performance and re liability that current satellite tracking systems provide. This paper will overview the demonstrated utility of satellite-based GPS applications and i dentify the key issues that must be addressed before its use for satellite tracking can become common practice. Some of the ongoing work to address th e issues will be described. In addition, how planned improvements to the GP S constellations and it augmentations could help remedy some of the issue a reas will be overviewed. (C) 2000 American Institute of Aeronautics and Ast ronautics, Inc. published by Elsevier Science Ltd.