Advances in edge diffraction algorithms.

Starshade external occulters are a leading technology that provide the starlight suppression needed to directly image and spectroscopically characterize Earth-sized exoplanets in the habitable zone of nearby stars. A high-priority technology area identified in need of development for a future starshade mission is the development and validation of high-fidelity optical models to predict the performance of a full-scale starshade. We present the generalization of an algorithm to formulate the Fresnel diffraction equation as a one-dimensional integral around the edge of an arbitrary binary diffraction screen.

Technology gap assessment for a future large-aperture ultraviolet-optical-infrared space telescope.

The Advanced Technology Large Aperture Space Telescope (ATLAST) team identified five key technology areas to enable candidate architectures for a future large-aperture ultraviolet/optical/infrared (LUVOIR) space observatory envisioned by the NASA Astrophysics 30-year roadmap, "Enduring Quests, Daring Visions." The science goals of ATLAST address a broad range of astrophysical questions from early galaxy and star formation to the processes that contributed to the formation of life on Earth, combining general astrophysics with direct-imaging and spectroscopy of habitable exoplanets. The key technology areas are internal coronagraphs, starshades (or external occulters), ultra-stable large-aperture telescope systems, detectors, and mirror coatings.

Propagation of aberrations through phase-induced amplitude apodization coronagraph.

The specification of polishing requirements for the optics in coronagraphs dedicated to exoplanet detection requires careful and accurate optical modeling. Numerical representations of propagated aberrations through the system as well as simulations of the broadband wavefront compensation system using multiple DMs are critical when one devises an error budget for such a class of instruments. In this communication, we introduce an analytical tool that serves this purpose for phase-induced amplitude apodization (PIAA) coronagraphs.

Designing asymmetric and branched petals for planet-finding occulters.

One of the proposed methods for finding small extrasolar planets is through use of an occulter, a spacecraft which flies in formation with a space-based telescope to block the light from a star, while leaving nearby planets unaffected. This is accomplished by placing the occulter far enough from the telescope to give it a small angular size, and by carefully choosing the shape to strongly suppress the starlight at the telescope aperture. For most designs, this shape takes the form of a number of bilaterally-symmetric structures called petals, arrayed about a circular central disk.

Closed loop, DM diversity-based, wavefront correction algorithm for high contrast imaging systems.

High contrast imaging from space relies on coronagraphs to limit diffraction and a wavefront control systems to compensate for imperfections in both the telescope optics and the coronagraph. The extreme contrast required (up to 10(-10) for terrestrial planets) puts severe requirements on the wavefront control system, as the achievable contrast is limited by the quality of the wavefront. This paper presents a general closed loop correction algorithm for high contrast imaging coronagraphs by minimizing the energy in a predefined region in the image where terrestrial planets could be found.

Reflectivity and optical surface height requirements in a broadband coronagraph. 1. Contrast floor due to controllable spatial frequencies.

We derive the broadband contrast floor in a coronagraphic telescope having nonideal optical surfaces. We consider only fundamental spatial frequencies within the control bandwidth of the coronagraph's deformable mirror. Cross terms arising from the beating of spatial frequencies beyond the deformable mirror control bandwidth will be considered in a second paper.