A 3-D method for autonomously controlling multiple spacecraft orbits

The need for innovative technical approaches for achieving and maintaining formations of spacecraft has come to the forefront as scientific objectives for Earth observation programs become more ambitious and spacecraft become more autonomous. The trend to develop small low-cost spacecraft has led many scientists to recognize the advantage of flying several spacecraft in formation to achieve the correlated instrument measurements formerly possible only by flying many instruments on a single large platform. Yet, formation flying imposes additional complications on orbit maintenance, especially when each spacecraft has its own orbit requirements. Advances in automation and technology by the Goddard Space Flight Center (GSFC) allow the burden in manoeuvre planning and execution to be placed onboard the spacecraft, mitigating some of the associated operational concerns while increasing autonomy. This paper presents GSFC´s Guidance, Navigation, and Control Center´s (GNCC) 3-D operational control theory for formation maintenance of multiple Low Earth Orbit (LEO) spacecraft and an algorithm for formation flying of the low earth orbiting spacecraft that are part of the New Millennium Program (NMP). This system will be implemented as a closed-loop flight code onboard the NMP Earth Orbiter-1 (EO-1) spacecraft. This paper describes the orbital dynamics necessary to quantify proposed methods for the guidance and control of spacecraft required to fly in formation with either a reference spacecraft or a predicted orbit. Simulation results from an integrated autonomous “fuzzy logic” control system called AutoCon^TM are presented which use an autonomous closed-loop three-axis navigation control system