Autonomous Formation Flying Control of Earth Observing (EO)-1

NASA’s first-ever autonomous formation flying mission was an unqualified success with significant contributions from the NMDB. GSFC continued to demonstrate the capability of satellites to continuously fly in formation, to react to each other, and to maintain close proximity without human intervention. This unique advancement highlighted in Aviation Weekly and Space Technology allows satellites to autonomously react to each other’s orbit changes quickly and efficiently. It permits scientists to obtain unique measurements by combining data from several satellites rather than flying all the instruments on one costly satellite. It also enables the collection of different types of scientific data unavailable from a single satellite, such as stereo views or simultaneously collecting data of the same ground scene at different angles.

On EO-1, formation flying was required to calibrate and compare technological advances made in ground observing instruments that are smaller, less costly, and more powerful. Onboard EO-1, an advanced technological controller called AutoCon provides the capability of autonomously planning, executing, and calibrating satellite orbit maneuvers. On EO-1 it was used for the computation of maneuvers to maintain the separation between the two satellites (EO-1 and Landsat-7). The maneuver algorithm was designed by the NMDB as a universal three-dimensional method for controlling the relative motion of multiple satellites in any orbit. This was then combined with new flight software that is the commercial predecessor of a GSFC sponsored commercial software package called FreeFlyer produced by a.i.-solutions, inc., in Lanham, Maryland.

There are many benefits of this onboard formation flying system. Because maneuver calculations and decisions can be performed onboard the satellite, the lengthy period of ground-based planning currently required prior to maneuver execution will eventually be eliminated. The system is also modular so that it can be easily extended to other mission objectives such as simple orbit maintenance for both formation and non-formation flying missions. Furthermore, the flight controller is designed to be compatible with various onboard navigation systems. Onboard formation control enables a large number of satellites to be managed with a minimum of ground support. The result will be a group of satellites with the ability to detect errors and cooperatively agree on the appropriate maneuver to maintain the desired positions and orientations. The formation flying technology flown onboard EO-1 will make distributing scientific instruments over many separate satellites routine and cost effective.