Numerical study of satellite images in the presence of fifth-order aberrations and tri-arm fractal sparse apertures.

We present simulation results of hypothetical satellite systems with fifth-order optical aberrations and various fractal apertures. On the image sensor side, we utilized novel metamaterial based image sensors (metaxels). Real physical systems always have some amount of optical aberrations even though electro-optical systems operating in space are generally idealized as diffraction limited in many simulations. Not only Seidel aberrations but also fifth-order aberrations are important in satellite image analyses and here we illustrate the effects of six aberration groups: spherical, linear coma, elliptical coma, oblique spherical, astigmatism-field curvature, and distortion. Our analyses yield optical diffraction and aberration effects all at once. Any combined form of aberrations could be investigated, which constitute an ample dimension for imaging chain and image quality studies. For a λ/2 aberration coefficient, quantitative comparison was provided, and for various fractal aperture cases image chain simulations are performed. Correlation coefficient values for the listed groups of aberration enabled us to quantify significance order of these fifth-order aberrations. Fifth-order distortion was the most dominant aberration affecting the image quality. In addition, we increased the fractal dimension of apertures and obtained smaller degradation in the images. The study ends with Wiener filter restoration results. Peak signal-to-noise ratio and correlation coefficient values for the restored images were higher than corresponding aperture cases as expected. [ABSTRACT FROM AUTHOR]