Extreme Wavefront Control for Ground and Space Observatories

Abstract

Large segmented aperture ground and space based telescopes are undergoing development to enable direct imaging of extrasolar planets. The ground-based GMT (Giant Magellan Telescope) is planned for first light in the mid-2020’s. Future space-based segmented aperture telescope missions, such as LUVOIR (Large UV Optical Infrared Surveyor), will have picometer-level observatory stability requirements for detecting Earth-like planets within the habitable zone. The challenges of high contrast imaging (HCI) for both ground and space applications can be met with extreme adaptive optics (ExAO), a high-order (>=1000 degrees of freedom) adaptive optics (AO) system which performs wavefront sensing and correction at high speed (>=1KHz). In this dissertation, I will describe two ExAO projects, one each for ground and space telescopes, focused on exoplanet detection using HCI. MagAO-X is an NSF-funded ExAO system for the Magellan Clay 6.5-meter telescope at Las Campanas Observatory in Chile which is helping push the limits of HCI. Additionally, MagAO-X is a pathfinder for ExAO instruments on the GMT. I constructed a comprehensive end-to-end (E2E) simulation using Fresnel propagation to characterize the static performance of MagAO-X. The E2E model utilizes both directly measured surfaces and simulated wavefront error maps based on the power spectral density models of the optical surface measurements. For space-based segmented aperture observatories, I will describe a laser guide star (LGS) companion satellite spacecraft which uses a remote beacon to increase the signal available for wavefront sensing and control (WFSC) of the primary segments to help achieve the stringent picometer-stability requirement for the primary mirror segments. I will present a segment cophasing testbed demonstration of correcting the on-axis target point spread function using WFSC on the off-axis LGS source. I will show how these projects push the limits of HCI to enable detecting earth-like exoplanets and ultimately the presence of life in the universe.