We introduce and raise awareness of NASA’s GMAT (General Mission-design and Analysis Tool) software system tool for spacecraft trajectory optimization and mission design, navigation and orbit analysis. GMAT is developed by NASA Goddard Space Flight Center (GSFC) in collaboration with private industry, public developers and various national space agencies. The tool has applications in all orbital regimes (mission to libration points, LEOs, landing scenarios, gravity-assist fly-by’s). GMAT is fully tested and certified for operational use and was chosen as the primary operational tool for NASA’s ACE (Advanced Composition Explorer) mission for maneuver planning, orbit determination. Various spacecraft models (various thruster models, impulse burn, etc), numerical propagators (Prince-Dormand, Adams-Bashford) and force models (atmospheric drag, solar pressure, etc.) are implemented. GMAT was selected as the primary mission design tool for NASA’s TESS space telescope mission and was used for mission design for the James Webb Space Telescope. At SDU/SDU-Galaxy we have embarked on weekly workshop-like meetings to gradually gain experience with this tool aiming to apply gained knowledge to the Århus University-led “STEP-A” space telescope mission (2025/2026) and optimal geolocation-planning of ground stations (based on predicted TLE’s) for effective Earth-spacecraft communication and data telemetry. This tool can also be used for science communication, STEM outreach activities raising awareness of space science, spacecraft control and astrodynamics.