With increasing threats to satellites and signal denial methods becoming cheap and effective, GPS failure is a reality and critical risk for navigation, localization, and targeting applications. Inspired by nature, the SkyPASS polarimeter developed by Polaris Sensor Technologies exploits the atmospheric polarization pattern to find highly accurate heading in situations when a typical sun/star sensor would fail to operate. It provides improved availability under cloud cover, under canopy, in urban environments, in civil and nautical twilight, and during sunrise and sunset. Unpolarized sunlight (or moonlight) becomes partially polarized when scattered by atmospheric molecules. Rayleigh scattering creates a polarization pattern, or map, that is unique, depending upon the date, time, and the position of the observer. This natural phenomenon is the scientific basis for SkyPASS operation, and it can be predicted to first order using Rayleigh scattering theory. This paper provides an overview of the SkyPASS polarimeter design, the method to calculate heading from sky polarization information, and the performance of the polarimeter in different environments. The third generation of SkyPASS processes data in real-time and has small enough SWaP to fit almost any platform.
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