SBIR-STTR Award

The goal of the proposed Phase I work is to demonstrate the feasibility of the coordination and control of a low cardinality (n=12) swarm of smallsats that realizes a distributed Synthetic Aperture Radar (SAR) in low Earth orbit. Preliminary mission and spacecraft design work has shown that the swarm can support SAR imaging in the L-band (1.35 GHz) with a ground range resolution finer than 10 m with a revisit period of eight days. The spacecraft in the swarm are pre-programmed to rendezvous in a region, say a sphere or box of certain dimensions, centered at a specified set of (absolute) orbital elements. After deployment from the launcher each satellite maneuvers to bring itself into the rendezvous sphere while monitoring its surroundings with on-board means, such as the star tracker capable of taking still images while attempting to close inter-spacecraft radio communications (ISRC) links with its neighbors. Both (passive) optical or ISRC-based relative navigation are then used to determine the relative position and velocity vectors between spacecraft while they maneuver to aggregate the swarm in its nominal operations configuration. During swarm aggregation and nominal operations, algorithms developed in the framework of evolving systems ensure the stability of the swarm. Failure of one swarm member will also be simulated to analyze the swarm reconfiguration and recovery of nominal operations after reconfiguration. Formal proofs of feedback control system properties such as controllability-observability, stability, detectabililty, and robustness will be pursued to establish a solid theoretical foundation for the proposed algorithms. The Phase I feasibility demonstration will meet most of the technical objectives identified in the solicitation for the corresponding modes of swarm operations. Potential NASA Applications The evolving system algorithms proposed have a “common core” which can be applied to swarms of dynamic devices ranging from spacecraft to atmospheric and surface vehicles that cooperate to fulfill tasks beyond the capabilities of member. Swarm members can operate at a distance, without physical contact, such as the distributed SAR swarm proposed, or with physical contact such as in-orbit assembly of orbital solar power stations and commercial infrastructure. Potential Non-NASA Applications Near-term applications of the algorithms are to autonomous road or off-road vehicles or ships. For example, the rendezvous between swarm members, of the distributed SAR mission, followed by swarm aggregation to acquire its configuration for nominal operations is quite similar to convoy formation and deployment for surface vehicles performing (re)supply operations for either defense or commercial use.

The goal of Phase II work is to further advance the TRL of the swarm coordination and control algorithms from the current estimated TRL 3 to a TRL 4-5. The technical objectives proposed for Phase II are divided into two broad categories that support the goal. One category includes continuation and refinement of the work performed in Phase I and the other category includes new work, some of which has already been initiated. Continuation work: C1) update the MATLAB/Simulink simulator to include dynamic closing and opening of inter-SV communications links and sensor noise; C2) simulate the loose swarm aggregation for the entire swarm using the maneuvers and control algorithms designed in Phase I; C3) simulate the transition from a loose swarm to a coordinated swarm configuration; C4) simulate orbit maneuvering of the coordinated swarm orbit to acquire its nominal orbit; C5) simulate the transition between a coordinated swarm to a nominal formation; and C6) simulate nominal operations to determine control and coordination strategies during the off and on duty cycles of the radar payloads. Nota bene: the simulation work also includes further controller development and upgrades, identification of new TPMs for swarm operations, and tracking the swarm performance with the TPMs described in the previous sections. New work: N1) develop methods for and investigate swarm stability in the context of an ad hoc network between swarm members; N2) develop methods for and analyze swarm stability with nonlinear dynamics in the context of ESF; N3) design, implement, and test an ADCS for the SVs of the SSSASAfRaS swarm; N4) design optimal orbit maintenance maneuvers to keep the swarm operating in vLEO; and N5) implement select algorithms on a network of resource limited, commercial SBCs, and perform tests to verify their performance. In addition to the objectives described above the SV design will be updated as informed by the results of the simulations described above. Potential NASA Applications (Limit 1500 characters, approximately 150 words) Soil moisture and data products with 10m ground range resolution generated by the SSSASAfRaS mission are of high interest to NASA scientists performing research in hydrology and solid Earth processes. The proposed evolving systems framework algorithms, coordination with low SV resources and dynamical/ad hoc inter-spacecraft communications network, distributed fault detection and mitigation, and graceful degradation of performance, can be applied to a multitude of NASA missions ranging from Earth observation to small body exploration to drones. Potential Non-NASA Applications (Limit 1500 characters, approximately 150 words) Precision agriculture practitioners and farm consultants can benefit from from the soil moisture data products of the SSSASAfRaS mission.The evolving systems theory and algorithms can be used in terrestrial sensor nets Relative localization and collision avoidance algorithms can be applied to air traffic decongestion for UAS and to driverless car traffic management.