Progress on optical verification for occulter-based high contrast imaging

Abstract

An external occulter is a specially-shaped spacecraft flown in formation with a telescope. It enables high-contrast imaging of the dim planetary companions of the neighboring solar system by blocking starlight before it reaches the entrance pupil. Occulters have to be designed via optimization methods that account for diffraction to most effectively block starlight. To predict occulter performance, we must verify the fidelity of the optical propagation models under scaled conditions. In this paper, we measure the contrast of a scaled occulter. The validity of the contrast calibration is determined using a baseline circular occulter. We verify contrast better than 10-10, however the measurements do not perform as well as the prediction from theoretical modelling. We attribute this difference to glint scattering off mask edges. © 2013 SPIE.