Unmanned Passive Navigation without GPS

The success and ubiquity of the Global Positioning System (GPS) have created a single point of failure for applications requiring precise time and position. While inertial measurement unit (IMU) technology continues to improve, the performance of even navigation-grade instruments can be insufficient for extended autonomous missions. Vision-based navigation aiding offers an attractive alternative to GPS that is immune to both jamming and accidental interference. However, surface vessels are not able to employ traditional approaches to vision-based navigation aiding that rely on extraction and matching of keypoints between image frames or on computation of optical flow. Instead, we propose the use of alternative, upward-looking vision-based techniques, including calculating heading (and, with sufficient movement of the vessel, position) directly from skylight polarization during the daytime, and attaining attitude and position fixes during the nighttime from the stars themselves, as well as observed transits of man-made Resident Space Objects (RSOs). Finally, because vision alone simply cannot provide an all-weather solution like GPS, we additionally discuss non-cooperative exploitation of signals-of-opportunity (SoOp) as an important component of our solution. These alternative vision-based approaches – along with information gleaned from SoOp – are optimally combined in a multi-sensor fusion framework to maintain the accuracy of the navigation solution.