Space Engineering Research Center Research Articles

Initial safety posture investigations for earth regime rendezvous and proximity operations

Next-generation space activities, where companies and organizations begin to provide services for each others space assets, are real and coming on-line. The Consortium for Execution of Rendezvous and Servicing Operations (CONFERS) is an industry-led initiative meant to help enable new companies and industries in pursuit of on-orbit servicing (OOS) through metrics and standard developments. The University of Southern California’s (USC) Space Engineering Research Center (SERC) is chartered to examine past and present activities related to this new domain and uncover elements that might benefit from the application of standards or practices for the industry as a whole. This paper will 1) review and update USC’s initial technical rendezvous metrics, and 2) introduce OOS functional evaluations and an initial ontology for consideration.

On-orbit servicing ontology applied to recommended standards for satellites in earth orbit

The Consortium for Execution of Rendezvous and Servicing Operations (CONFERS) is an industry-led initiative with initial seed funding provided by the Defense Advanced Research Projects Agency (DARPA) that aims to leverage best practices from government and industry to research, develop, and publish non-binding, consensus-derived technical and operations standards for On-Orbit Servicing (OOS) and Rendezvous and Proximity Operations (RPO). As part of the CONFERS effort, the University of Southern California’s (USC) Space Engineering Research Center (SERC) conducted research into existing RPO methodologies and practices and OOS methodologies through literature review and interviews with practitioners. Following the first year of analytical input focused solely on RPO, the second year’s activities have focused further into the full extent of attributes for satellite servicing and in-space docking (OOS). USC’s focus was to develop a taxonomy of functions and attributes related to all aspects of technical elements and techniques required for past/current/anticipated OOS missions. A taxonomy database was created that allowed various key elements to be broken down into quantifiable data within common categories. Following the taxonomy creation, working with the Space Infrastructure Foundation (SIF) a review of existing standards in space along with other industries were analyzed and compared for possible matches. This standards gap analysis focused primarily from the end of the RPO maneuver to the point of physical contact or action between two spacecraft. These comparisons were then used to recommend where gaps in standards exist and where it might be most beneficial to create new ones, enabling spacecraft of various shapes and sizes to safely execute various OOS operations, and spur the industry between customers and providers. The field of space servicing is a rapidly growing field, with governments and numerous private entities developing robotic systems for mission extension vehicles and satellite repair. With an increased number of servicing missions forthcoming, a system of guidelines and standards on how to effectively and safely design on-orbit servicing activities is a next natural step to enable the expansion of this burgeoning industry.

Broadband control of flexible structures using statistical energy analysis concepts

An approach is described for designing optimal broadband controllers for flexible structures with collocated sensors and actuators. The statistical energy analysis assumptions of equipartition and incoherence, together with conservation of energy, are used to express the average value of a global 3^ performance metric in terms of the power dissipation of the compensator. This power dissipation can be represented using a dereverberated model, which is an experimentally determined local structural model that ignores the effect of the reverberant field. Minimizing the resulting cost yields controllers with good performance that are guaranteed to be stabilizing. The approach is demonstrated experimentally on the Massachusetts Institute of Technology Space Engineering Research Center interferometer testbed. This approach achieved a performance reduction that was approximately 30% greater than that obtained with a constant gain rate feedback approach.

Dynamics and control of multipayload platforms: The middeck active control experiment (MACE)

A flight experiment entitled the Middeck Active Control Experiment (MACE) proposed by the Space Engineering Research Center (SERC) at the Massachusetts Institute of Technology is described. The objective of this program is to investigate and validate the modeling of the dynamics of an actively controlled flexible, articulating, multibody platform free floating in zero gravity. A rationale and experimental approach for the program are presented. The rationale shows that on-orbit testing, coupled with ground testing and a strong analytical program, is necessary in order to fully understand both how flexibility of the platform affects the pointing problem, as well as how gravity perturbs this structural flexibility causing deviations between 1-and 0-gravity behavior. The experimental approach captures the essential physics of multibody platforms, by identifying the appropriate attributes, tests, and performance metrics of the test article, and defines the tests required to successfully validate the analytical framework.