Relative navigation of spacecraft has been an area of active research since the Apollo era. Optical sensor systems offer a distinct advantage for spacecraft relative navigation applications by collecting passive data to be used as measurement updates; however, these systems often require large databases of feature locations on the deputy spacecraft and a communication link to retrieve IMU data from the deputy spacecraft. The central objective of the proposed technology is the development of a spacecraft relative navigation system that is capable of using an arbitrary non-cooperative object as the deputy spacecraft without the need of training trials. The technology consists of a novel sensor, called VISNAV, an IMU and computational hardware. During Phase I, the actual relative navigation algorithms will be developed. The algorithms will consist of extracting feature information from the images collected by the optical sensor. This feature information will be utilized for determining rate information of the deputy vehicle through an optical flow technique. It will also be used for measurement updates in a newly derived filter, called the geometric extended Kalman filter, which provides physically consistent estimates, unlike all existing filter formulations. Finally, a multiple hypothesis tracking algorithm will be used to compare the expected feature locations from the filter to the ones measured in the images. This will ensure that the features are accurately tracked over time, thus eliminating the need to train the system or rely on a communication datalink. It is expected that at the completion of Phase I the navigation algorithms will be derived and verified through simulation testing as well as hardware in the loop testing within a realistic test environment. This initial testing and hardware configuration will be used to expedite prototyping and system tests to be conducted during Phase II. Potential NASA Applications (Limit 1500 characters, approximately 150 words) NASA has flown several formation flying missions, such A-Train and Cluster. Also, applications involving proximity operations are of great interest to NASA. The proposed technology can further advance current navigation applications related to formation missions since it provides a robust solution for non-cooperative objects. Furthermore, no data links are required, thus reducing costs and failure points. Finally, the application is based on rigorously derived error definitions, so that physically correct uncertainty bounds are provided. Potential Non-NASA Applications (Limit 1500 characters, approximately 150 words) Non-NASA applications, especially DoD ones, are heavily focusing on anti-jamming communication and navigation systems, such as GPS-less navigation. The proposed technology can significantly advance these focus areas because it is self-contained and decreases the susceptibility to outside attacks.
