Experimental study of a low-order wavefront sensor for a high-contrast coronagraphic imager at 1.2 λ/D

Julien Lozi, Ruslan Belikov, Glenn Schneider, Olivier Guyon, Eugene Pluzhnik, Sandrine J. Thomas, Frantz Martinache

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

High-contrast imaging will be a challenge for future ELTs, because their vibrations create low-order aberrations - mostly tip/tilt - that reduce coronagraphic performances at 1.2 λ/D and above. A Low-Order WaveFront Sensor (LOWFS) is essential to measure and control those aberrations. An experiment simulating a starlight suppression system is currently developed at NASA Ames Research Center, and includes a LOWFS controlling tip/tilt modes in real-time at 500 Hz. The LOWFS allowed us to reduce the tip/tilt disturbances to 10-3 λ/D rms, enhancing the previous contrast by a decade, to 8×10-7 between 1.2 and 2 λ/D. A Linear Quadratic Gaussian (LQG) controller is currently implemented to improve even more that result by reducing residual vibrations. This testbed is developed for the mission EXCEDE (EXoplanetary Circumstellar Environments and Disk Explorer), selected by NASA for technology development, and designed to study the formation, evolution and architectures of exoplanetary systems and characterize circumstellar environments into stellar habitable zones. It is composed of a 0.7 m telescope equipped with a Phase-Induced Amplitude Apodization Coronagraph (PIAA-C) and a 2000-element MEMS deformable mirror, capable of raw contrasts of 10-6 at 1.2 λ/D and 10-7 above 2 λ/D. Although the testbed simulates space conditions, its LOWFS has the same design than on the SCExAO instrument at Subaru telescope, with whom it shares the same kind of problematic. Experimental results show that a good knowledge of the low-order disturbances is a key asset for high contrast imaging, whether for real-time control or for post processing, both in space and on ground telescopes.

Original languageEnglish (US)
Title of host publication3rd AO4ELT Conference - Adaptive Optics for Extremely Large Telescopes
PublisherINAF - Osservatorio Astrofisico di Arcetri Largo Enrico Fermi
ISBN (Print)9788890887604
DOIs
StatePublished - Jan 1 2013
Event3rd Conference on Adaptive Optics for Extremely Large Telescopes, AO4ELT 2013 - Florence, Italy
Duration: May 26 2013May 31 2013

Publication series

Name3rd AO4ELT Conference - Adaptive Optics for Extremely Large Telescopes

Other

Other3rd Conference on Adaptive Optics for Extremely Large Telescopes, AO4ELT 2013
CountryItaly
CityFlorence
Period5/26/135/31/13

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics

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