Image quality assessment of sparse aperture designs

Increasing the available imaging time of a remote sensing satellite over a specified ground area can be accomplished by placing the satellite in a higher, more elliptical orbit. This, however, will also require the satellite to be farther away from the Earth, thus reducing the resolution of the images. If the aperture size of the optics can be increased proportional to the increase in the satellite´s altitude, then the resolution can be maintained. Remote sensing satellites with a single, large, monolithic telescope are difficult to manufacture and costly to launch. Several smaller telescopes can be used together to capture the resolution of a single large telescope. Collectively, these small telescopes generate a sparse aperture because they do not fill the entire aperture area that they synthesize. The fill factor of the aperture is the total area of the telescopes divided by the effective aperture size. Reducing the fill factor decreases the weight, but also reduces the signal-to-noise ratio and system modulation transfer function. Image simulations are used to assess the image quality of different sparse aperture designs