Polarization aberrations in next-generation giant segmented mirror telescopes (GSMTs)

Astronomy and Astrophysics, vol. 672, pp. A121

Abstract

Context. Next-generation large segmented mirror telescopes are expected to perform direct imaging and characterization of Earth-like rocky planets, which requires contrast limits of 10 −7 to 10 −8 at wavelengths from I to J band. One critical aspect affecting the raw on-sky contrast are polarization aberrations (i.e., polarization-dependent phase and amplitude patterns in the pupil) arising from the reflection from the telescope’s mirror surfaces and instrument optics. These polarization aberrations induce false signals for polarimetry that can be calibrated to a certain degree, but they can also fundamentally limit the achievable contrast of coronagraphic systems. Aims. We simulate the polarization aberrations and estimate their effect on the achievable contrast for three next-generation ground-based large segmented mirror telescopes. Methods. We performed ray-tracing in Zemax ® and computed the polarization aberrations and Jones pupil maps using the polarization ray-tracing algorithm. The impact of these aberrations on the contrast is estimated by propagating the Jones pupil maps through a set of idealized coronagraphs using hcipy, a physical optics-based simulation framework. Results. The optical modeling of the giant segmented mirror telescopes (GSMTs) shows that polarization aberrations create significant leakage through a coronagraphic system. The dominant aberration is retardance defocus, which originates from the steep angles on the primary and secondary mirrors. The retardance defocus limits the contrast to 10 −5 to 10 −4 at 1 λ / D at visible wavelengths, and 10 −5 to 10 −6 at infrared wavelengths. The simulations also show that the coating plays a major role in determining the strength of the aberrations. Conclusions. Polarization aberrations will need to be considered during the design of high-contrast imaging instruments for the next generation of extremely large telescopes. This can be achieved either through compensation optics, robust coronagraphs, specialized coatings, calibration, and data analysis approaches, or by incorporating polarimetry with high-contrast imaging to measure these effects.

Authors 11

1. Ramya M. Anche corresponding

   University of Arizona

   Affiliation as printed

   Steward Observatory , University of Arizona , 933N Cherry Avenue , Tucson , AZ 85721 , USA

   Steward Observatory, University of Arizona, 933N Cherry Avenue, Tucson, AZ 85721, USA

2. Jaren Nicholas Ashcraft

   University of Arizona

   Affiliation as printed

   James C. Wyant College of Optical Sciences , University of Arizona , 933N Cherry Avenue , Tucson , AZ 85721 , USA

   Steward Observatory , University of Arizona , 933N Cherry Avenue , Tucson , AZ 85721 , USA

   College of Optical Sciences, University of Arizona, 933N Cherry Avenue, Tucson, AZ 85721, USA

   Steward Observatory, University of Arizona, 933N Cherry Avenue, Tucson, AZ 85721, USA

3. Sebastiaan Y. Haffert

   University of Arizona

   Affiliation as printed

   Steward Observatory , University of Arizona , 933N Cherry Avenue , Tucson , AZ 85721 , USA

   Steward Observatory, University of Arizona, 933N Cherry Avenue, Tucson, AZ 85721, USA

4. Maxwell A. Millar‐Blanchaer

   University of California, Santa Barbara

   Affiliation as printed

   Department of Physics , University of California , Santa Barbara , CA 93106 , USA

   Department of Physics, University of California, Santa Barbara, CA 93106, USA

5. Ewan S. Douglas
6. Frans Snik Aachen

   Leiden University

   Affiliation as printed

   Leiden University , Niels Bohrweg 2 , 2333 CA Leiden , The Netherlands

   Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands

7. G. Grant Williams

   University of Arizona

   Affiliation as printed

   Steward Observatory , University of Arizona , 933N Cherry Avenue , Tucson , AZ 85721 , USA

   Steward Observatory, University of Arizona, 933N Cherry Avenue, Tucson, AZ 85721, USA

8. R. G. van Holstein

   European Southern Observatory · European Southern Observatory

   Affiliation as printed

   European Southern Observatory (ESO) , Alonso de Córdova 3107 , Vitacura , Casilla 19001 , Santiago de Chile , Chile

   European Southern Observatory (ESO), Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago de Chile, Chile

9. David S. Doelman Aachen

   Leiden University

   Affiliation as printed

   Leiden University , Niels Bohrweg 2 , 2333 CA Leiden , The Netherlands

   Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands

10. Kyle Van Gorkom

    University of Arizona

    Affiliation as printed

    Steward Observatory, University of Arizona, 933N Cherry Avenue, Tucson, AZ 85721, USA

11. Warren Skidmore

    TMT Observatory

    Affiliation as printed

    TMT International Observatory LLC , 100 W. Walnut St. , Suite 300 , Pasadena , CA 91124 , USA

    TMT International Observatory LLC, 100 W. Walnut St., Suite 300, Pasadena, CA 91124, USA