The spatial resolution of a conventional imaging laser radar system is constrained by the diffraction limit of the telescope's aperture. We investigate a technique known as synthetic-aperture imaging laser radar (SAIL), which employs aperture synthesis with coherent laser radar to overcome the diffraction limit and achieve fine-resolution, long-range, two-dimensional imaging with modest aperture diameters. We detail our laboratory-scale SAIL testbed, digital signal-processing techniques, and image results. In particular, we report what we believe to be the first optical synthetic-aperture image of a fixed, diffusely scattering target with a moving aperture. A number of fine-resolution, well-focused SAIL images are shown, including both retroreflecting and diffuse scattering targets, with a comparison of resolution between real-aperture imaging and synthetic-aperture imaging. A general digital signal-processing solution to the laser waveform instability problem is described and demonstrated, involving both new algorithms and hardware elements. These algorithms are primarily data driven, without a priori knowledge of waveform and sensor position, representing a crucial step in developing a robust imaging system.

Starting in late 2007 and continuing through the present, NFIRE (Near-Field Infrared Experiment), a Missile Defense Agency (MDA) experimental satellite and TerraSAR-X, a German commercial SAR satellite have been conducting mutual crosslink experiments utilizing a secondary laser communication payload built by Tesat-Spacecom. The narrow laser beam-widths and high relative inter-spacecraft velocities for the two low-earth-orbiting satellites imply strict pointing control and dynamics aboard both vehicles. The satellites have achieved rapid communication acquisition times and maintained communication for hundreds of seconds before losing line of sight to the counter satellite due to earth blockage. Through post-mission analysis and other related telemetry we will show results for pointing accuracy, disturbance environments and pre-engagement prediction requirements that support successful and reliable operations.

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