Imagery In Astronomy By Inverse Radon Transformation, Using A Rotating Slit Aperture Telescope (SAT)

A telescope with a long thin pupil, called SAT appears to be a promising alternative to the classical telescope for high resolution astronomical imagery. For such application a SAT must be able to rotate around its optical axis. The problem is to faithfully reconstruct the two-dimensional image of an observed object, from the one-dimensional data set (Radon transform) provided by the SAT during its rotation. This problem of image reconstruction from projections has been investigated in the field of medical imagery. The proposed algorithm, illustrated in this paper, for the reconstruction of astronomical images, is based upon the use of Fast Fourier Transforms (FFT). Although the reconstruction is accurate for unperturbed images, ground based observations are strongly affected by atmospheric turbulence ; under such conditions, we propose the use of phase closure, thus enabling unperturbed astronomical images to be retrieved. Image reconstruction entered radioastronomy in the 1950's in response to a need for high angular resolution in the mapping of radio emission from celestial objects. The technique used was that of aperture synthesis.