High-contrast imager for Complex Aperture Telescopes (HiCAT). 4. Status and wavefront control development

Segmented telescopes are a possible approach to enable large-aperture space telescopes for the direct imaging and spectroscopy of habitable worlds. However, the increased complexity of their aperture geometry, due to their central obstruction, support structures and segment gaps, makes high-contrast imaging very challenging. The High-contrast imager for Complex Aperture Telescopes (HiCAT) was designed to study and develop solutions for such telescope pupils using wavefront control and starlight suppression. The testbed design has the flexibility to enable studies with increasing complexity for telescope aperture geometries starting with off-axis telescopes, then on-axis telescopes with central obstruction and support structures (e.g. the Wide Field Infrared Survey Telescope [WFIRST]), up to on-axis segmented telescopes e.g. including various concepts for a Large UV, Optical, IR telescope (LUVOIR), such as the High Definition Space Telescope (HDST). We completed optical alignment in the summer of 2014 and a first deformable mirror was successfully integrated in the testbed, with a total wavefront error of 13nm RMS over a 18mm diameter circular pupil in open loop. HiCAT will also be provided with a segmented mirror conjugated with a shaped pupil representing the HDST configuration, to directly study wavefront control in the presence of segment gaps, central obstruction and spider. We recently applied a focal plane wavefront control method combined with a classical Lyot coronagraph on HiCAT, and we found limitations on contrast performance due to vibration effect. In this communication, we analyze this instability and study its impact on the performance of wavefront control algorithms. We present our Speckle Nulling code to control and correct for wavefront errors both in simulation mode and on testbed mode. This routine is first tested in simulation mode without instability to validate our code. We then add simulated vibrations to study the degradation of contrast performance in the presence of these effects.

[1]  P. Baudoz,et al.  High-contrast imaging in polychromatic light with the self-coherent camera , 2014, 1402.5914.

[2]  C. Burrows,et al.  On the feasibility of detecting extrasolar planets by reflected starlight using the hubble space telescope , 1990 .

[3]  Mamadou N'Diaye,et al.  APODIZED PUPIL LYOT CORONAGRAPHS FOR ARBITRARY APERTURES. V. HYBRID SHAPED PUPIL DESIGNS FOR IMAGING EARTH-LIKE PLANETS WITH FUTURE SPACE OBSERVATORIES , 2016, 1601.02614.

[4]  Amir Give'on,et al.  Pair-wise, deformable mirror, image plane-based diversity electric field estimation for high contrast coronagraphy , 2011, Optical Engineering + Applications.

[5]  L. Pueyo,et al.  HIGH-CONTRAST IMAGING WITH AN ARBITRARY APERTURE: ACTIVE COMPENSATION OF APERTURE DISCONTINUITIES , 2012, 1211.6112.

[6]  Kjetil Dohlen,et al.  Simultaneous phase and amplitude retrieval with COFFEE: from theory to laboratory results , 2014, Astronomical Telescopes and Instrumentation.

[7]  J. P. Laboratory,et al.  High-Contrast Imaging from Space: Speckle Nulling in a Low-Aberration Regime , 2005, astro-ph/0510597.

[8]  N. Jeremy Kasdin,et al.  Recursive starlight and bias estimation for high-contrast imaging with an extended Kalman filter , 2016, 1602.02044.

[9]  M. Shao,et al.  HIGH-DYNAMIC-RANGE IMAGING USING A DEFORMABLE MIRROR FOR SPACE CORONOGRAPHY , 1995, astro-ph/9502042.

[10]  Lee D. Feinberg,et al.  A cost-effective and serviceable ATLAST 9.2m telescope architecture , 2014, Astronomical Telescopes and Instrumentation.

[11]  Laurent Pueyo,et al.  Active compensation of aperture discontinuities for WFIRST-AFTA: analytical and numerical comparison of propagation methods and preliminary results with a WFIRST-AFTA-like pupil , 2015, 1511.01929.

[12]  Alexis Carlotti,et al.  High-contrast imager for complex aperture telescopes (HiCAT): 1. testbed design , 2013, Optics & Photonics - Optical Engineering + Applications.

[13]  S. Gezari,et al.  From Cosmic Birth to Living Earths: The Future of UVOIR Space Astronomy , 2015, 1507.04779.

[14]  Edward J. Wollack,et al.  Wide-Field InfrarRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST-AFTA 2015 Report , 2015, 1503.03757.

[15]  Emmanuel Hugot,et al.  High-contrast Imager for Complex Aperture Telescopes (HICAT): II. Design overview and first light results , 2014, Astronomical Telescopes and Instrumentation.

[16]  Dimitri Mawet,et al.  Correcting for the effects of pupil discontinuities with the ACAD method , 2016, Astronomical Telescopes + Instrumentation.

[17]  Joseph J. Green,et al.  Coronagraph contrast demonstrations with the high-contrast imaging testbed , 2004, SPIE Astronomical Telescopes + Instrumentation.

[18]  Olivier Guyon,et al.  High contrast internal and external coronagraph masks produced by various techniques , 2013, Optics & Photonics - Optical Engineering + Applications.

[19]  Wesley A. Traub,et al.  Advanced Technology Large-Aperture Space Telescope: science drivers and technology developments , 2012 .

[20]  Alexis Carlotti,et al.  High-contrast imager for complex aperture telescopes (HiCAT): 3. first lab results with wavefront control , 2015, SPIE Optical Engineering + Applications.

[21]  L. Pueyo,et al.  Optimal dark hole generation via two deformable mirrors with stroke minimization. , 2009, Applied optics.

[22]  Robert J. Vanderbei,et al.  Toward 1010 contrast for terrestrial exoplanet detection: demonstration of wavefront correction in a shaped-pupil coronagraph , 2006, SPIE Astronomical Telescopes + Instrumentation.

[23]  R. Soummer,et al.  APODIZED PUPIL LYOT CORONAGRAPHS FOR ARBITRARY APERTURES. IV. REDUCED INNER WORKING ANGLE AND INCREASED ROBUSTNESS TO LOW-ORDER ABERRATIONS , 2014, 1412.2751.