Olivier Guyon/University of Arizona

Phase-Induced Amplitude Apodization (PIAA) is a high efficiency coronagraphy technique enabling high contrast imaging at a small inner working angle (within 2 λ/D). Direct imaging and characterization of potentially habitable exoplanets with a PIAA coronagraph is therefore possible with a medium-size space telescope at optical wavelength, and was explored for two of the NASA-funded medium class Astrophysics Strategic Missions Concept Studies (PECO and ACCESS). It is also a candidate for a smaller mission (the EXCEDE 0.5-m diameter mission concept) and for a larger ~4-m diameter Terrestrial Planet Finder Coronagraph mission. The potential of the PIAA is now widely recognized. As a recently developed technology, the realization of PIAA in future missions awaits proof of technical readiness.

We will develop Phase-Induced Amplitude Apodization technologies through a combination of laboratory development/validation and design/modeling efforts. We will carry out vacuum laboratory PIAA testing at the High Contrast Imaging Testbed (HCIT) at NASA JPL, with an optical architecture relevant to an actual flight mission. Our test will use a set of recently manufactured reflective PIAA optics. Two deformable mirrors will provide the agility required to address polychromatic wavefront error. A dedicated low order wavefront sensor will use light reflected by the focal plane mask for high accuracy high bandwidth pointing control. By measuring pointing error suppression, the laboratory test will allow an experimental verification of the pointing control architecture developed for the Pupil Mapping Exoplanet Coronagraphic Observer (PECO). A key goal of the effort will be a monochromatic demonstration at 10^-9 contrast at 2 λ/D. We will also measure performance in a 20% wide spectral band and develop a polychromatic contrast error budget.

Tests of components, subsystems and models which do not require vacuum will be performed at NASA Ames in an existing testbed dedicated to PIAA technologies. This stabilized air testbed will also test wavefront control algorithms and architectures prior to high contrast vacuum demonstration at HCIT.

Together, results from these laboratory tests and analysis will advance PIAA technological readiness level from currently 3 to between 4 and 5, and identify remaining technology challenges to meet requirements for a flight instrument aimed at direct imaging and spectroscopy of exoplanets in the habitable zones of nearby stars.