Wide-band white light sparse-aperture Fizeau imaging interferometer testbed for a distributed small-satellites...

Under the background of astronomical observation by a distributed small-satellites constellation, a Fizeau imaging interferometer testbed (FIIT) was designed and constructed at National Astronomical Observatories of the Chinese Academy of Sciences in the past four years that achieved wide-band white light (400-700 nm) phased imaging at laboratory with a field of view (FOV) ∼2  arcmin. This study presents the design of FIIT, which is mainly composed of a light source module for simulating infinite objects, three sub-telescopes in a Golay-3 distribution (i.e., equilateral triangle), three tip/tilt correction modules and optical path delay modules, as well as three detecting telescopes and one beam-combining telescope for phased imaging. The three detecting telescopes could determine the piston and tip/tilt errors, which could be compensated for by optical path delay modules and fast steering mirrors in a close-loop mode. The performance of FIIT is also derived analytically and simulated by a ray-tracing model. The tolerance analysis of the pupil geometry and magnification matching are also performed for achieving a better FOV. The optical test of each module could efficiently validate them to achieve diffraction limit imaging. The preliminary experimental results for both point source and extend scene could sufficiently demonstrate the phased mode imaging of FIIT, thus validating the good prospects of this technique in the future.