The ability to simulate and analyze satellite or spacecraft missions before they ever leave the ground is one of the most powerful tools in modern aerospace engineering. Among the most accessible and capable tools for this purpose is NASA’s GMAT — the General Mission Analysis Tool. Developed by NASA’s Goddard Space Flight Center, GMAT is a free and open-source platform for designing and simulating space missions. It has been used in real-world missions such as LCROSS (Lunar Crater Observation and Sensing Satellite) and the Lunar Reconnaissance Orbiter. This article offers a high-level overview of what GMAT can do, followed by a hands-on walkthrough of a simple satellite orbit simulation. The aim is to introduce the software's utility in a way that is accessible even to those without prior experience. What is GMAT? GMAT is a space mission analysis and trajectory optimization tool. It allows users to simulate spacecraft motion under a variety of physical forces including gravity...