Using mission analysis software GMAT to develop skills in astrodynamics

Learning about the geometry and kinematics of orbital motion (or 'astrodynamics') is challenging due to its 3D nature. To address this, the University of Bristol have developed 3D orbit visualization exercises using a free NASA tool called 'General Mission Analysis Tool' (GMAT). The aims are to develop skills in manipulation of orbits and to focus on areas subject to common misconceptions. The skills targeted include: varying orbital elements and observing the effect, interpreting ground tracks, exploring features of sun-synchronous, Molniya and geostationary orbits, adding pro and retrograde burns and seeing the effects, performing inclination changes and Hohmann transfers. Common misconceptions include: confusing the orbital elements, thinking that satellites move faster in their orbits with increasing altitude, thinking that geostationary satellites are not moving (relative to stars), forgetting that Earth rotates when considering ground tracks, thinking that a Hohmann transfer is composed of one burn only, thinking that for a chaser spacecraft to catch up with a target in orbit, it must accelerate. Feedback from students is discussed, along with proposals for further work to assess the extent to which misconceptions have been addressed. Overall, GMAT exercises offer a promising way to visualise orbits and improve conceptual understanding of astrodynamics.