Demonstrating predictive wavefront control with the Keck II near-infrared pyramid wavefront sensor
Abstract
The success of ground-based instruments for high contrast exoplanet imaging depends on the degree to which adaptive optics (AO) systems can mitigate atmospheric turbulence. While modern AO systems typically suffer from millisecond time lags between wavefront measurement and control, predictive wavefront control (pWFC) is a means of compensating for those time lags using previous wavefront measurements, thereby improving the raw contrast in the post-coronagraphic science focal plane. A method of predictive control based on Empirical Orthogonal Functions (EOF) has previously been proposed and demonstrated on Subaru/SCExAO. In this paper we present initial tests of this method for application to the near-infrared pyramid wavefront sensor (PYWFS) recently installed in the Keck II AO system. We demonstrate the expected root-mean-square (RMS) wavefront error and contrast benefits of pWFC based on simulations, applying pWFC to on-sky telemetry data saved during commissioning of the PYWFS. We discuss how the performance varies as different temporal and spatial scales are included in the computation of the predictive filter. We further describe the implementation of EOF pWFC within the PYWFS dedicated real-time controller (RTC), and, via daytime testing at the observatory, we demonstrate the performance of pWFC in real time when pre-computed phase screens are applied to the deformable mirror (DM).
Additional Information
© 2019 Society of Photo-Optical Instrumentation Engineers (SPIE). The predictive wavefront control demonstration is funded by the Heising-Simons Foundation. The authors would like to thank Marcos van Dam (Flat Wavefronts) for his suggestion to use the regularized least-squares inversion method to compute the predictive filter. The W. M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The near-infrared pyramid wavefront sensor is supported by the National Science Foundation under Grant No. AST-1611623. The PYWS camera was provided by Don Hall as part of his National Science Foundation funding under Grant No. AST 1106391. Support for R. J. -C. was provided by the Miller Institute for Basic Research in the Sciences. This work benefited from the NASA Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by the NASA Science Mission Directorate. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.Attached Files
Published - 111170W.pdf
Accepted Version - 1909.05302.pdf
Files
Name | Size | Download all |
---|---|---|
md5:fcae68fbef8f47a46a1c24e5e962c4ec
|
2.2 MB | Preview Download |
md5:2293137e7826f2ef84f09a944be482b7
|
2.1 MB | Preview Download |
Additional details
- Eprint ID
- 98619
- Resolver ID
- CaltechAUTHORS:20190912-140620297
- Heising-Simons Foundation
- W. M. Keck Foundation
- AST-1611623
- NSF
- AST-1106391
- NSF
- Miller Institute for Basic Research in Science
- Created
-
2019-09-12Created from EPrint's datestamp field
- Updated
-
2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Astronomy Department
- Series Name
- Proceedings of SPIE
- Series Volume or Issue Number
- 11117