||Kirtland Air Force Base, NM 871175776
|Lovell, Thomas Alan
The Air Force has a pressing need to better understand and utilize the dynamics of relative satellite motion (i.e., the motion of one satellite with respect to one or more other satellites) for close-proximity missions. These missions include both cluster/formation missions and rendezvous/proximity operations missions. The former missions typically involve multiple satellites with maneuvering capability and communication links (both with the ground and one another) performing some cooperative task (e.g., remote sensing), whereas the latter missions typically involve a lesser degree of maneuverability, connectivity, and cooperation among the satellites. Areas of relevant research include:
(1) Modeling of Relative Orbit Dynamics. The relative motion between two or more satellites in close proximity can be modeled in unique ways. The governing equations for such motion can account for a variety of physical phenomena and maybe either linear or nonlinear, time-varying, or time-invariant. We are particularly interested in the formulation of relative dynamics in such a way that it can be characterized geometrically (as opposed to using Cartesian coordinates), as well as in ways that lend themselves to the applications below. A separate area involves the analysis of natural revisit opportunities for proximity operations between satellites, using concepts such as synodic period.
(2) Relative Navigation for Satellite Systems. Satellites flying in close proximity have tight navigation requirements that may exceed the state-of-the-art in relative and autonomous navigation. These requirements include accurate estimation of both the position/velocity and attitude of the satellites. Sensing schemes include differential GPS and intersatellite ranging, using vision sensors such as radar and LIDAR. In addition to sensing, the navigation task requires accurate estimation techniques. We are particularly interested in improved filter design that may involve maximum on-board autonomy (i.e., minimum interaction from the ground), faster computation methods, use of new or unique propagation models, the ability to handle a wide variety of observation types from multiple satellites, and/or applicability over a wide range of orbital regimes.
(3) Guidance/Control Algorithms for Relative Satellite Motion. Satellites flying in close proximity have unique control requirements. Guidance algorithms must be designed taking into account both mission requirements/constraints and the natural orbital dynamics of the system. In addition, control of the satellites must often be accomplished in an optimal fashion, where trajectory time and/or fuel expenditure are of concern. The versatility of satellite cluster missions allows for reconfiguration of the satellites to perform different missions or to account for the addition or deletion of members to the cluster. Such reconfiguration will require sophisticated guidance and control algorithms. Ware particularly interested in the development of open- and/or closed-loop control algorithms for relative satellite trajectories and optimization of these trajectories. The former area may involve both centralized and decentralized control, as well as hierarchical control; while the latter area may involve both conventional (e.g., LQR, gradient-based) and modern (e.g., genetic algorithm) optimization schemes. In addition to the close-proximity maneuvering described above, we would also like to study orbit transfer techniques to achieve rendezvous, whether based on conventional methods (e.g., Lambert transfer) or lesser known methods (e.g., hodograph theory).
Lovell TA, et al: AIAA Journal of Guidance, Control, & Dynamics 32(3): 2009
Thompson, et al: AIAA Journal of Guidance, Control, & Dynamics 33(5): 2010