Calculation of Optimized Apodizers for a Terrestrial Planet Finder Coronagraphic Telescope

Abstract

One of two approaches to implementing NASA's Terrestrial Planet Finder is to build a space telescope that utilizes the techniques of coronagraphy and apodization to suppress diffraction and image exo-planets. We present a method for calculation of a telescope's apodizer which suppresses the side lobes of the image of a star so as to optimally detect an Earth-like planet. Given the shape of a telescope's aperture and given a search region for a detector, we solve an integral equation to determine an amplitude modulation (an apodizer) which suppresses the star's energy in the focal plane search region. The method is quite general and yields as special cases the product apodizer reported by Nisenson and Papaliolios (2001) and the Prolate spheroidal apodizer of Kasdin et al (2002), and Aime et al (2002). We show computer simulations of the apodizers and the corresponding point spread functions for various aperture-detector configurations.