The two spacecraft used for the ANDE mission are the Mock ANDE Active (MAA) sphere (Navy-OSCAR 61) and the Fence Calibration (FCAL) sphere (OSCAR 62). These microsatellites, developed by the Naval Research Laboratory, will measure drag through the use of precision orbit determination. Ground-based lasers will be used to track the orbits of the sphere to with a couple centimeters of accuracy. Perturbations caused by density gradients and winds will be backed out from these measurements. The two ANDE satellites are nearly perfect spheres; this was done to make the drag on the satellites independent of their orientation, and because the drag coefficient, optical cross-sections, and radar cross sections of spheres are well understood.