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30 September 1999 Projection registration in reflective tomography
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The Air Force Research Laboratory, Directed Energy Directorate, is in the process of demonstrating an advanced space surveillance capability with a heterodyne laser radar system to be used for range-resolved imaging of orbiting satellites. This system, called HI-CLASS (High Performance CO2 Ladar Surveillance Sensor), uses a CO2 laser in a modelocked configuration to generate approximately 10 microsecond(s) bursts of approximately 1 ns pulses repeated at a 30 Hz rate. When reflected from an orbiting satellite, these pulses contain information about the range-resolved reflectivities and the Doppler spectrum of the target. For earth-stabilized satellites, cross-range motion is insufficient to produce Doppler-resolved images from the range-resolved data for the HI-CLASS system parameters. However, an image reconstruction method called reflection tomography can be used to reconstruct satellite images by using a tomographic reconstruction approach. An important issue in tomographic image reconstruction is correct registration of the individual projections. For accurate image reconstruction, all projections must be aligned to the target center of rotation. Due to typical system alignment uncertainties, atmospheric fluctuations, and random satellite displacements, range cannot be measured accurately enough to determine the satellite center of rotation. Therefore, this information must be inferred from the projection data itself. Here, we present an algorithm that uses a phase-retrieval approach to determine the required center of rotation from the projection data. We demonstrate the effectiveness of this algorithm using computer-simulated data. We also discuss the future application of this algorithm to actual ladar data.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Stephen D. Ford and Charles L. Matson "Projection registration in reflective tomography", Proc. SPIE 3815, Digital Image Recovery and Synthesis IV, (30 September 1999);

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