<title>Wavelength-dependent radiometric modeling for an active geosynchronous satellite imaging system</title>

Recent interest in imaging satellites in geo-synchronous earth orbit has led to the design of a ground-based active imaging system using a concept known as Fourier Telescopy. Fourier Telescopy systems use active laser illumination, aperture synthesis, and extensive computer processing to minimize atmospheric turbulence effects and form high-resolution images of distant stationary objects. Three laser transmitters of slightly different frequency illuminate the object with varying baseline separations to temporally encode object spatial frequency information in the energy backscattered from the object. Detection and demodulation of the temporal signals and processing using phase closure and wavefront reconstruction techniques yield measurements of the object's incoherent Fourier amplitude and phase distribution. We have developed a detailed wave optics simulation to analyze and optimize the performance of this system. Wavelength dependent renderings of 3-D satellite models and the statistical variations of object illumination determine the radiometric returns received for a given scenario and the effect on imaging system performance. This work uses the simulation to examine system performance for three different illumination laser wavelengths and for realistic system design limitations. System design trade-offs based on the wavelength dependence of satellite optical cross-section, atmospheric propagation, and diffraction are discussed. Our results indicate that a near infra-red (IR) wavelength may be most suitable for this system.