Estimating low-order aberrations through a Lyot coronagraph with a Zernike wavefront sensor for exoplanet imaging

Space Telescopes and Instrumentation: Optical, Infrared, and Millimeter Wave, pp. 186

Abstract

Imaging exo-Earths is an exciting but challenging task because of the 10-10 contrast ratio between these planets and their host star at separations narrower than 100 mas. Large segmented aperture space telescopes enable the sensitivity needed to observe a large number of planets. Combined with coronagraphs with wavefront control, they present a promising avenue to generate a high-contrast region in the image of an observed star. Another key aspect is the required stability in telescope pointing, focusing, and co-phasing of the segments of the telescope primary mirror for long-exposure observations of rocky planets for several hours to a few days. These wavefront errors should be stable down to a few tens of picometers RMS, requiring a permanent active correction of these errors during the observing sequence. To calibrate these pointing errors and other critical low-order aberrations, we propose a wavefront sensing path based on Zernike phase-contrast methods to analyze the starlight that is filtered out by the coronagraph at the telescope focus. In this work we present the analytical retrieval of the incoming low order aberrations in the starlight beam that is filtered out by an Apodized Pupil Lyot Coronagraph, one of the leading coronagraph types for starlight suppression. We implement this approach numerically for the active control of these aberrations and present an application with our first experimental results on the High-contrast imager for Complex Aperture Telescopes (HiCAT) testbed, the STScI testbed for Earth-twin observations with future large space observatories, such as LUVOIR and HabEx, two NASA flagship mission concepts.

Authors 16

1. Raphaël Pourcelot

   Centre National de la Recherche Scientifique · Lagrange Laboratory · Observatoire de la Côte d’Azur

   Affiliation as printed

   Univ. Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Lab. Lagrange (France)

2. Mamadou N’Diaye

   Centre National de la Recherche Scientifique · Lagrange Laboratory · Observatoire de la Côte d’Azur

   Affiliation as printed

   Univ. Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Lab. Lagrange (France)

3. Gregory R. Brady

   Space Telescope Science Institute

   Affiliation as printed

   Space Telescope Science Institute (United States)

4. Marcel Carbillet

   Centre National de la Recherche Scientifique · Lagrange Laboratory · Observatoire de la Côte d’Azur

   Affiliation as printed

   Univ. Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, Lab. Lagrange (France)

5. Kjetil Dohlen

   Centre National de la Recherche Scientifique · Aix-Marseille Université

   Affiliation as printed

   Aix Marseille Univ., CNRS, CNES, LAM (France)

6. J. Fowler

   Space Telescope Science Institute

   Affiliation as printed

   Space Telescope Science Institute (United States)

7. Iva Laginja

   Centre National de la Recherche Scientifique · Space Telescope Science Institute · Aix-Marseille Université · Office National d'Études et de Recherches Aérospatiales · Département Optique et Techniques Associées

   Affiliation as printed

   Aix Marseille Univ., CNRS, CNES, LAM (France)

   DOTA, ONERA, Univ. Paris Saclay (France)

   Space Telescope Science Institute (United States)

8. Matthew T. Maclay

   Space Telescope Science Institute

   Affiliation as printed

   Space Telescope Science Institute (United States)

9. James Noss

   Space Telescope Science Institute

   Affiliation as printed

   Space Telescope Science Institute (United States)

10. Marshall D. Perrin

    Space Telescope Science Institute

    Affiliation as printed

    Space Telescope Science Institute (United States)

11. Peter Petrone

    Space Telescope Science Institute · Sigma Space (United States)

    Affiliation as printed

    Sigma Space Corp. (United States)

    Space Telescope Science Institute (United States)

12. Emiel H. Por Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden Univ. (Netherlands)

13. Jean-François Sauvage

    Centre National de la Recherche Scientifique · Aix-Marseille Université · Office National d'Études et de Recherches Aérospatiales · Département Optique et Techniques Associées

    Affiliation as printed

    Aix Marseille Univ., CNRS, CNES, LAM (France)

    DOTA, ONERA, Univ. Paris Saclay (France)

14. Rémi Soummer

    Space Telescope Science Institute

    Affiliation as printed

    Space Telescope Science Institute (United States)

15. A. Vigan

    Centre National de la Recherche Scientifique · Aix-Marseille Université

    Affiliation as printed

    Aix Marseille Univ., CNRS, CNES, LAM (France)

16. Scott D. Will

    Space Telescope Science Institute · Goddard Space Flight Center · University of Rochester

    Affiliation as printed

    Institute of Optics, Univ. of Rochester (United States)

    NASA Goddard Space Flight Ctr. (United States)

    Space Telescope Science Institute (United States)