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A number of tracking and pointing applications require extremely precise referencing of the optical line of sight (LOS) relative to some small portion of the vehicle to be tracked. Since the referencing must be performed in a vehicle fixed coordinate system and the optical image is degraded due to disturbances such as atmospheric blurring, sensor noise, and diffraction, the referencing becomes quite difficult. These degradations, along with potentially coarse spatial quantization of the optical image [large pixel size driven by signal-to-noise ratio (SNR) considerations], also limit the ability of a human operator to interact with the optical system in real time to control the LOS. Several concepts to determine the real-time LOS control (vehicle intensity moments, neural networks, optical correlators, etc.) have been suggested in past studies, but generally have proven insufficiently sensitive or too complex to implement in a real-time system. The preliminary concept presented here centers on using a correlation tracker combined with a precomputed image sequence as a straightforward means to maintain a precision LOS. The concept employs the high SNR image within the correlation tracker reference map to make the relatively low bandwidth LOS corrections required. The corrections are determined by correlation of the tracker reference map imagery with a precomputed image sequence and thus provide the accuracy associated with the high SNR map image and high SNR precomputed image sequences. [The satellite tracking problem provides the tracker with viewing/aspect angle geometry, which is generally deterministic, within the uncertainty bounds of ephemeris and satellite attitude information, and thus stimulates the use of precomputed (simulated) imagery.] The precomputed image sequence provides the LOS control through registration of the desired vehicle fixed coordinate on the image with a fiducial point on the image array. We will discuss the theoretical basis, potential advantages, implementation, and performance [as determined by Time-Domain Analysis Simulation for Advanced Tracking (TASAT)] of the concept.
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