Description: To solve the problem of autonomous navigation on small satellite platforms less than 20 kg, we propose to develop an onboard orbit determination receiver for small LEO satellites which lack stable Attitude Determination and Control System (ADCS), continuous GPS coverage, or ground tracking. The system is a refinement of existing spaceborne receiver technology built around a new, innovative collective detection and direct positioning algorithm developed by Dr. Penny Axelrad, a reduced set of GPS hardware, and a compact orbit propagator. The small satellite collective orbit determination receiver (SCOR) brings together efficient reference orbit representations, snapshot GPS sampling, collective detection and direct positioning, and modular orbit propagation methods, to produce an effective new approach for onboard support of small satellites. Since the collective detection algorithm does not require continuous GPS tracking to generate navigation solutions, portions of the receiver can be duty cycled to reduce power consumption between measurements. Additionally, this approach allows for satellites without pointing capabilities to obtain sufficient measurements to generate solutions by taking multiple snapshots when the spacecraft attitude is in a favorable orientation with respect to the GPS constellation.

Benefits: NASA is currently fueling the development of cutting edge technology demonstrations, each being a potential candidate for our innovative solution. The current small satellite missions FASTSAT and Nanosail-D are missions which would have been ideal platforms for the receiver. In February of 2012 NASA issued a call for proposals under the Edison Small Satellite demonstration program. The SCOR is ideally suited for the size and power requirements of small satellites. A secondary application for this technology can be part of a Fault Detection Isolation and Recovery (FDIR) system for GPS receivers on larger, mission critical satellites. The state solutions generated by the collective detection receiver could be compared with the solutions from the traditional on-board GPS receiver to ensure the estimated states are correct. This would be a low cost, low power solution for autonomously ensuring the onboard state solution is accurate and robust.

Several universities are developing small satellites to advance the current state-of-the-art and demonstrate technologies for larger missions. Georgia Tech is developing PROX-1, a mission to demonstrate autonomous proximity operations. The University of Maryland is demonstrating technologies that could be used for satellite servicing missions with DYMAFLEX satellite. The University of Colorado recently launched and is operating the 3U cubesat CSSWE (Colorado Student Space Weather Experiment), and is working on AllStar, a small satellite bus that is designed to inspire and develop America's future technological workforce and provide students hands-on-experience in applying science, technology, engineering and mathematics. Along the same lines, the MicroMAS satellites being developed by MIT and the NEMO-HD proposed by the University of Toronto would also make ideal platforms for implementation of the SCOR. All of these projects typically require low cost, robust instruments; a category that would be serviced by the proposed receiver.