Nulling interferometers for space-based high-contrast visible imaging and measurement of exoplanetary environments

• Main Author: Hicks, Brian Andrew
• Language: en_US
• Published: Boston University 2018
• Subjects: Exoplanets; Telescopes; Astronomy
• Online Access: https://hdl.handle.net/2144/32883

Thesis (Ph.D.)--Boston University === PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at [e-mail]. Thank you. === This dissertation presents the legacy, theory, design, characterization, and application prospects of a fully symmetric monolithic nulling interferometer (nuller). A nuller's function is to destructively interfere light originating from a bright, on-axis, unresolved source in order to lower its contrast with faint, off-axis sources of light in the field of view. The primary application lies in astronomical instrumentation, serving as an enabling technology for directly imaging exoplanets and measuring exozodiacal dust and debris disks, the planetary system evolutionary components around nearby stars. Typical on-sky planet/star flux ratios are 1:109 or less in the visible. Mitigating this contrast is key to spectroscopic study of exoplanets, which aims to characterize exoplanetary atmospheres and potentially locate biosignatures on exo-Earths. Within the past decade, adaptive optics-equipped breadboard demonstrations of nullers and other coronagraphs have shown the capability to image nearby (< 30 lightyears) extrasolar analogs to Jupiter with a 0.5 meter diameter telescope in the visible. The quiet laboratory environments that have been produced to demonstrate this capability do not reflect those of typical ground-based observatories where thermal drifts perturb optical alignment and atmospheric turbulence perturbs the source wavefront. Space-based platforms circumvent the atmosphere problem, but are still subjected to thermal instabilities and their associated risks. Robust optical systems must be designed and flight-tested in order to address such risks and provide grounds for their inclusion in the design of future exo-Earth imaging satellites. Sub-orbital platforms such as sounding rockets and high-altitude balloons provide a rapid, lowcost means of providing heritage for such optical systems while also delivering significant scientific results. The primary risk inherent with these platforms are harsh transient environmental conditions, for which, similar to an orbital platform, robust optical systems are necessary. A novel feature of the nuller described in this work is its monolithic design, which greatly enhances optical stability, the primary obstacle plaguing all high-contrast imaging efforts. Additional design benefits include theoretical achromatic performance and an inner working angle that is 2-4 times smaller than other coronagraph designs, enabling its use with proportionally smaller telescopes. === 2031-01-01