GMAT is aspace trajectory optimization and mission analysis system
Editor: The General Mission Analysis Tool (GMAT) is a space trajectory optimization and mission analysis system developed by NASA and private industry in the Spirit of the NASA Vision. GMAT contains new technology and is a testbed for future technology development. To satisfy NASAs mandate and maximize technology transfer, GMAT is an open source software system licensed under the NASA Open Source Agreement.
Put simply, the goal of the GMAT project is to develop new space trajectory optimization and mission design technology by working inclusively with ordinary people, universities, businesses, and other government organizations, and to share that technology in an open and unhindered way. GMAT is a free and open source software system: free for anyone to use in development of new mission concepts or to Improve current missions, freely available in source code form for enhancement or further technology development. you can free download GMAT 2007-12-10 Beta now.