General Mission Analysis Tool (GMAT) is open-source space mission analysis software developed by NASA and private industry.

[2] It has been used for several missions, including LCROSS, the Lunar Reconnaissance Orbiter, OSIRIS-REx, the Magnetospheric Multiscale Mission, and the Transiting Exoplanet Survey Satellite (TESS) mission.

[2][3] GMAT is an open-source alternative to software like Systems Tool Kit and FreeFlyer.