Synthetic Aperture Technic in Astronomy Using Slit Aperture Telescope

The interest in a Rotating Slit-Aperture Telescope (RSAT) among other synthetic aperture telescopes is its capability of being easily coupled with a spectrograph, in order to give reconstructed images of an astronomical object as a function of the light wavelength. Each colored image is comparable with the others for fruitful astrophysical applications. The principle of image reconstruction is well known: it consists of the inversion of the set of projections (Radon transform) given by the telescope during its rotation around its optical axis. A full coverage of the two dimensional Fourier plane can be obtained by rotating the SAT. This problem has led to intense developments for medical imaging (tomography). One of the main difficulties in the reconstruction process in space may come from the jitter of the rotation axis of the RSAT. A set of projections uncorrected for this jitter produces very fuzzy reconstructed images. An elegant solution to the necessary phasing between successive projections is proposed which makes use of a small auxilliary telescope, and some numerical simulations are presented.