Synthetic-Images From Simulations Of Long-Base-Line 2d Optical Interferometers

We present computer simulations of variable baseline 2D imaging optical interferometers operating at visible and infrared wavelengths. Sparse apertures of fewer than 10 receivers, baselines up to 400 m and aperture size from 1 to 2 m are considered. SNR limitations pose significant problems with dilute apertures observing faint sources; we explore various ways to address this problem. We simulate pupil plane visibility measurements under perfect conditions and in the presence of wavefront aberrations due to atmospheric distortion. A variety of ideal sources are studied, including stellar photospheres with features and artificial satellites. Earth rotation aperture synthesis over extended periods improves spatial frequency coverage of astronomical sources, while observation at multiple wavelengths improves coverage for geosynchronous satellites. We introduce a hybrid technique for performing a fast analytic pixel transform, similar to the fast discrete Fourier transform, which allows complex sources to be represented in pixel form but which admits the full floating point accuracy of analytic calculation. We study image deconvolution techniques to enhance the final image. An algorithm is presented for improvement of images formed from pupil plane interferometric data. Values are added to the frequency domain with the dominant constraint being an image taken with a small filled aperture instrument. A deconvolution technique using the entropy function is developed to enhance reconstruction of the truth image. Examples of image improvement obtained by the algorithm are presented.