When
Where
Dissertation Title: Development of a High-Contrast Adaptive Optics Phasing Testbed for the Giant Magellan Telescope
Abstract:
Our galaxy hosts ~ 300 billion stars. Ever since the first exoplanet was discovered in 1992, over 5,000 more exoplanet discoveries have been confirmed, and the number is still counting. As each new exoplanet is discovered, the case seems more and more likely that each star in our Milky Way galaxy has at least one exoplanet orbiting around it, many of which fall into the “potentially habitable, terrestrial size” category, meaning they are just the right distance from their host star to potentially harbor life. Hence, there could be billions of earth-like planets waiting to be discovered.
If we hope to discover life outside of our solar system, it has been shown that directly imaging these potentially habitable earth-like planets in reflected light (visible light reflected from its host star) is optimal. This is very possible, however difficult, since it requires Extremely Large Telescopes (~ 30 meters in diameter) to achieve high angular resolutions and contrasts, extreme adaptive optics (ExAO) to suppress the effects of atmospheric seeing, and coronagraphy to block the starlight. These three technologies could coexist once the 25.4-m Giant Magellan Telescope (GMT) is completed in 2029. With the combined power of ExAO and the future GMT, the discovery of life outside of our solar system may become a reality. However, the GMT’s unique seven segmented mirror design raises a challenge to keep the telescope segments aligned and co-phased—a task which is critical for the direct imaging of exo-earths and any other diffraction-limited science with the GMT.
This dissertation addresses the challenge of co-phasing a giant segmented telescope for exoplanet imaging and describes the development of a High-Contrast Adaptive optics phasing Testbed (HCAT) which simulates the GMT with real optics in a lab environment with six piston, tip, and tilt actuators and a working concept for a “parallel deformable mirror” to optically redistribute the GMT pupil onto seven commercially available 3,000 actuator deformable mirrors. HCAT also leverages an existing ExAO system called MagAO-X to test and demonstrate segment phase sensing and AO-control with a real ExAO system’s hardware. The design and build of MagAO-X will be discussed, along with an introduction to adaptive optics. I will then discuss the developments that were made with an early stage GMT testbed which evolved into a prototype version of HCAT (p-HCAT). P-HCAT led to the invention of a new phasing method for co-phasing the GMT using a novel optic called the “Holographic Dispersed Fringe Sensor” (HDFS). The success of the demonstrations performed with p-HCAT and the novel HDFS will be discussed. Lastly, the final design and build of the full-scale HCAT testbed will be described with a demonstration of the fully phased “parallel DM" working in the lab to co-phase all seven GMT segments at the nanometer level.