General Mission Analysis Tool

General Mission Analysis Tool is an open-source space mission analysis software developed by NASA and private industry. GMAT is currently under development. It is an open source alternative to Systems Tool Kit.  

Software details and download. (Software Reference Number: GSC-18094-1, link could be changed by software update) 
Download (Sourceforge)

References

External links
Spaceref.com
Youtube videos

Category:Aerospace engineering
Category:3D graphics software
Category:Astronomy software
Category:Mathematical software
Category:Physics software