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Proceedings Paper

Extreme precision photometry from the ground with beam-shaping diffusers for K2, TESS, and beyond
Author(s): Gudmundur Stefansson; Suvrath Mahadevan; John Wisniewski; Yiting Li; Leslie Hebb; Brett Morris; Samuel Halverson; Andrew Monson; Paul Robertson
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Paper Abstract

The Transiting Exoplanet Survey Satellite (TESS, launched early 2018) is expected to find a multitude of new transiting planet candidates around the nearest and brightest stars. Timely high-precision follow-up observations from the ground are essential in confirming and further characterizing the planet candidates that TESS will find. However, achieving extreme photometric precisions from the ground is challenging, as ground-based telescopes are subject to numerous deleterious atmospheric effects. Beam-shaping diffusers are emerging as a low-cost technology to achieve hitherto unachievable differential photometric precisions from the ground. These diffusers mold the focal plane image of a star into a broad and stable top-hat shape, minimizing photometric errors due to non-uniform pixel response, atmospheric seeing effects, imperfect guiding, and telescope-induced variable aberrations seen in defocusing. In this paper, we expand on our previous work (Stefansson et al. 2017; Stefansson et al. 2018), providing a further detailed discussion of key guidelines when sizing a diffuser for use on a telescope. Furthermore, we present our open source Python package iDiffuse which can calculate the expected PSF size of a diffuser in a telescope system, along with its expected on-sky diffuser-assisted photometric precision for a host star of a given magnitude. We use iDiffuse to show that most (~80%) of the planet hosts that TESS will find will be scintillation limited in transit observations from the ground. Although iDiffuse has primarily been developed to plan challenging transit observations using the diffuser on the ARCTIC imager on the ARC 3.5m Telescope at Apache Point observatory, iDiffuse is modular and can be easily extended to calculate the expected diffuser-assisted photometric precisions on other telescopes.

Paper Details

Date Published: 2 August 2018
PDF: 16 pages
Proc. SPIE 10702, Ground-based and Airborne Instrumentation for Astronomy VII, 1070250 (2 August 2018); doi: 10.1117/12.2312833
Show Author Affiliations
Gudmundur Stefansson, The Pennsylvania State Univ. (United States)
Suvrath Mahadevan, The Pennsylvania State Univ. (United States)
John Wisniewski, The Univ. of Oklahoma (United States)
Yiting Li, The Pennsylvania State Univ. (United States)
Univ. of California, Santa Barbara (United States)
Leslie Hebb, Hobart and William Smith Colleges (United States)
Brett Morris, Univ. of Washington (United States)
Samuel Halverson, The Pennsylvania State Univ. (United States)
Massachusetts Institute of Technology (United States)
Andrew Monson, The Pennsylvania State Univ. (United States)
Paul Robertson, Univ. of California, Irvine (United States)


Published in SPIE Proceedings Vol. 10702:
Ground-based and Airborne Instrumentation for Astronomy VII
Christopher J. Evans; Luc Simard; Hideki Takami, Editor(s)

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