Optical Aperture Synthesis for Airborne ISR Platforms

We propose to design an optical imaging system consisting of multiple transmit and receive apertures. This distributed aperture array can provide resolution capabilities similar to a large monolithic aperture without the associated volume, weight, and aircraft structural modifications. A key challenge of such a system is to accomplish the imaging function without requiring an elaborate optical relay system to bring all subaperture channels together on a single focal plane array. We propose a coherent heterodyne imaging scheme in which each of the subapertures measures the complex optical field. These field measurements can then be digitally combined to synthesize a high resolution image thereby removing the burden of physically matching subaperture optical paths to within a fraction of a wavelength and allowing for a modular design. In many tactical imaging scenarios, atmospheric turbulence limits the achievable resolution and the digital coherent image synthesis processing can compensate for atmospheric turbulence including anisoplanatic aberrations. This active system could increase platform standoff range and allow for nighttime operation. This effort will begin with an analysis of atmospheric paths and imaging geometries specific to Army airborne platforms. We will conduct wave-optics simulations to evaluate the performance of multiple array geometries under a variety of conditions.