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A brassboard demonstration system was fabricated, tested, and exercised to compile parametric data on the acquisition and tracking portions of a 1 Gbps laser communication subsystem. The demonstration system consists of three primary parts: the acquisition and tracking package, precision instrumentation equipment, and simulation equipment. The brassboard acquisition and tracking package utilizes three electrooptic detectors to sense the incoming signal from a cooperative beacon laser, a two axis gimbaled mirror for coarse pointing, and high frequency piezoelectric bender bimorph mirrors for fine pointing. The precision instrumentation equipment measures the pointing error of the brassboard acquisition and tracking package with an accuracy of 0.1 microradian. The simulation equipment provides beacon laser signals, background noise, realistic satellite limit cycles, satellite flexure effects, and orbital kinematic motions of the line-of-sight vector during acquisition and tracking. The brassboard system demonstrates the total automatic sequence of operations to verify the performance of all three stations: low altitude satellite, synchronous satellite, and ground. Engineering data is presented on the basic modes of operation, the optical detectors, the control system, and the satellite dynamical effects. Performance data showed a system acquisition sensitivity at 1.06 micrometer of 9 photoelectrons per pulse.

The objective of this study was to define the hardware design requirements of a brassboard acquisition and tracking subsystem, based on the preliminary subsystem design documented in SAMSO-TR-71-251. The work includes detailed design for the acquisition and tracking subsystem, simulation equipment, and precision instrumentation equipment; and detailed descriptions of the integration of components and experiment test plan. The brassboard acquisition and tracking package is configured to verify the performance for all three primary stations; low altitude satellite, synchronous satellite, and ground. It is capable of demonstrating the total automatic sequence of operations required to detect and sense initial errors as large as + or - 8.75 mrad, align the optical boresight and point a simulated communication laser to within + or - 50 micro-rad using 10 pps information, change modes from acquisition to tracking, and track and fine point with an error of less than 1 micro-rad. The precision instrumentation equipment is designed to measure the pointing capability of the brassboard acquisition and tracking subsystem to a fraction of the 1 micro-rad tracking error. The simulation equipment is configured to provide beacon laser signals, realistic satellite rotations, satellite flexure effects, and orbital kinematic motions of the line-of-sight during acquisition and tracking. (Author)