- Aeronautics and Astronautics
Top 3 Areas of Expertise:
Expected date of graduation:
There is growing interest in multi-satellite architectures owing to the increasing desire for on-orbit servicing, assembly, and active debris removal. These three mission scenarios each have separate objectives, though there is a common set of technologies pertaining to the need for autonomous proximity operations that enable the rendezvous and docking of a chaser satellite to a target object. These missions are associated with inherent risks, since the target may not be fully cooperative, and it may be tumbling in its orbit. The chaser must safely approach the target for all mission scenarios using a combination of a priori knowledge and information gained from sensors aboard the chaser satellite itself. Each target object may be defined by a set of physical parameters and state variables, and each of which has an associated uncertainty in its true value. Spent rocket bodies are prime examples of target objects because they represent a large category of resident space objects: rigid, tumbling, uncooperative, and demand careful handling on orbit. Because of their large mass and the remnant volatiles, rocket bodies pose an urgent threat to the Earth orbital environment. Removing them from orbit, however, requires that the chaser satellite soft dock with low contact forces and torques regardless of their angular velocity or axis of rotation. This objective, though, may be met with technologies that are extensible to the other proximity operation mission scenarios, so the research conducted for the active removal of rocket body debris may be applied well beyond this scope.
Existing research has provided safe trajectories and control algorithms for conducting rendezvous and docking missions to rotating targets. The prior work has enabled demonstrations of autonomous, on-orbit docking, but the targets have been cooperative or designed to facilitate the docking. Additionally, there have not been studies to optimize the chaser satellite and its trajectory together, especially when optimized with respect to properties of the target satellite. Similarly, there have not been sensitivity analyses performed to determine how changing target properties affect the mission. These studies require the use of simulations to provide a large number of trials with varying parameters, and these simulations need to be validated. To date, numerous hardware facilities have been developed to provide validation data, but there has not been an assessment of how well constrained degree of freedom testbeds can validate unconstrained degree of freedom simulations.
This research proposal presents a method of determining how the target satellite affects the design of both the chaser satellite and the trajectory to be followed. A definition is provided for a satellite feasibility space to encompass both the properties of the chaser satellite and its trajectory options in order to assess whether a mission scenario may be carried out successfully. Additionally, a methodology for mapping this space is presented for visualizing the options available for a mission given the properties of the target object. A microgravity simulation is used to determine the feasibility space and to predict on-orbit chaser satellite performance; the process for tuning this simulation using the Synchronized Position Hold Engage Reorient Experimental Satellites (SPHERES) satellites in the 1g laboratory environment and validating it with on-orbit tests aboard the International Space Station is described. The simulation is used to conduct a sensitivity analysis to determine the properties of the target which most affect the requirements on the chaser and rendezvous trajectory. Results-to-date are presented which show how the newly defined feasibility space may be mapped using nondimensionalized parameters and how Monte Carlo trials may be used to perform the sensitivity analysis. Future work and an expected schedule are also presented.
Top 5 Awards and honors (name of award, date received):
5 Recent Papers:
Yoon, H. Sternberg, D., and Cahoy, K., (2016), “A General Solution for Update with Out-of-Sequence Measurements: The Augmented Fixed-Lag Smoother”, Journal of Guidance Control, and Dynamics.
Sternberg, D., Miller, D., Jewison, C., James, J., Hilton, A., McCarthy, B., Roascio, D., and Saenz-Otero, A., (2016), “Reconfigurable Ground and Flight Testing Facility for Robotic Servicing, Capture, and Assembly”, IEEE Aerospace Conference.
Karlow, B., Jewison, C., Sternberg, D., Hall, S., and Golkar, A., (2015) “Tradespace Investigation of Strategic Factors in the Design of Large Space Telescopes”, Journal of Astronomical Telescopes, Instruments, and Systems, 1(2), 1-22
Sternberg, D., Sheerin, T., and Urbain, G., (2015), “INSPECT Sensor Suite for On-Orbit Inspection and Characterization with Extravehicular Activity Spacecraft”, ICES Conference.
Sternberg, D., Chodas, M., Jewison, C., and Jones, M., (2015), “Multidisciplinary System Design Optimization of On-Orbit Satellite Assembly Architectures”, IEEE Aerospace Conference.