TechSat 21: formation design, control, and simulation

The satellite cluster approach to space missions requires science and technology advances in several key areas. Among these challenges is understanding the dynamics of satellites in close proximity to each other so that a formation can be intelligently designed, controlled, and simulated. An overview of on-going research in this area under the TechSat 21 program along with preliminary findings is provided. Included in this overview is the recent progress made in the design of formations including designs for circular formations, projected circular formations, and J₂ invariant formations. Strategies for formation control are presented as well as the baseline design for the TechSat 21 propulsion system. Fuel expenditure is estimated for various formations using different control strategies. The TechSat 21 mission requires relative position knowledge between satellites to the millimeter level while the radar is transmitting and receiving; concepts for meeting this requirement are also presented. In order to facilitate mission planning and gain confidence in mission success, the Air Force Research Laboratory (AFRL) is building an end to end simulation testbed for the TechSat 21 mission. An overview of the testbed design and functionality is provided. Focus is centered on the dynamics and control module of the testbed. The dynamics and control module utilizes high fidelity orbit propagation as the basis of the simulation of the formation dynamics. Through this simulation control algorithms, relative navigation techniques, and the effects of errors in initial conditions and control forces are investigated