The National Aeronautics and Space Administration is planning high data rate optical communications for future deep space missions. The Johns Hopkins University Applied Physics Laboratory (JHU/APL) is responding by developing concepts for implementing optical communications terminals that are more compact and lightweight than heretofore. An essential requirement for these long-range optical links is a high-precision pointing and tracking system. Focal plane array (FPA)-based star trackers that enable open-loop pointing and tracking are necessary. Spacecraft attitude instabilities, emphemeris errors, tracking sensor noise, clock errors, and mechanical misalignments are among the error sources that must be minimized and compensated for. To achieve this JHU/APL has developed an imaging star tracker concept using redundant multi-aperture FPA's symmetrically disposed about the laser downlink. Centroid estimation and pattern matching techniques account for aberration and motion errors. Robustness, sensitivity to detection thresholds, field-of-view sizing, number of stars per frame, missed detections, false alarms, and position biases, as well as stellar catalog size and star selection, will be described. Finally the conceptual design of a frame-to-frame integration method and sensor fusion algorithm (such as a Kalman filter) will be considered. The goal is to achieve a system pointing and tracking error significantly less than 1 μrad.
The Low Cost Gun Launched Seeker is a component of the Navy's effort to develop effective weapons for surface fire support missions by enhancing the performance of projectiles like the Extended Range Guided Munitions with low-cost, uncooled infrared (IR) staring focal plane array terminal seekers. IR target images for validating target detection algorithms were collected using a Merlin long wave camera from Indigo Systems. This paper characterizes the camera in order to develop performance parameters for simulating the seeker and to understand features in the imagery. These parameters include temperature response, temporal noise characteristics, fixed pattern noise, and the modulation transfer function.
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