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Paper: Wide Field Imaging: Fourier and Fresnel
Volume: 345, From Clark Lake to the Long Wavelength Array: Bill Erickson's Radio Science
Page: 350
Authors: Cornwell, T.J.; Golap, K.; Bhatnagar, S.
Abstract: Wide field imaging with low frequency synthesis arrays is limited by a number of troublesome effects. First amongst these is the “non-coplanar baselines” distortion whereby the integral relationship between sky brightness and measured visibility function is not a simple Fourier transform. A piece wise approximation to the integrals can be used and forms the basis of the facet approaches used for the last 15 years. These approaches are difficult to program and perform relatively poorly. We have developed a novel, high performance algorithm based upon convolution of the visibility samples with a Fresnel kernel. We interpret the Fresnel kernel as being required to propagate the electric field to a common reference plane. The role of Fresnel diffraction in radio inteferometry seems to have been unrecognized previously.
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