FLIGHT DYNAMICS ASPECTS OF THE GRACE FORMATION FLYING

Kurzfassung

Three key items have been studied at the mission control center (GSOC) for the build-up and control of the GRACE formation (along-track separation of about 220±50 km): 1. The safe ejection of both satellites from the upper stage and the intial acquistion of the nominal formation. 2. The control of the semi-major axes of both spacecrafts to maintain the inter-satellite separation within tolerable margins while minimizing any perturbations of the science operations. 3. The use of the SGP4 orbit model as on-board orbit propagator to allow a pery precise prediction of the relative position perpendicular of the line-of-sight vector.