Identification and adaptive control of a high-contrast focal plane wavefront correction system

He Sun, N. Jeremy Kasdin, Robert Vanderbei

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

All coronagraphic instruments for exoplanet high-contrast imaging need wavefront correction systems to reject optical aberrations and create sufficiently dark holes. Since the most efficient wavefront correction algorithms (controllers and estimators) are usually model-based, the modeling accuracy of the system influences the ultimate wavefront correction performance. Currently, wavefront correction systems are typically approximated as linear systems using Fourier optics. However, the Fourier optics model is usually biased due to inaccuracies in the layout measurements, the imperfect diagnoses of inherent optical aberrations, and a lack of knowledge of the deformable mirrors (actuator gains and influence functions). Moreover, the telescope optical system varies over time because of instrument instabilities and environmental effects. We present an expectation-maximization (E-M) approach for identifying and real-Time adapting the linear telescope model from data. By iterating between the E-step (a Kalman filter and a Rauch smoother) and the M-step (analytical or gradient-based optimization), the algorithm is able to recover the system even if the model depends on the electric fields, which are unmeasurable hidden variables. Simulations and experiments in Princeton's High Contrast Imaging Lab demonstrate that this algorithm improves the model accuracy and increases the efficiency and speed of the wavefront correction.

Original languageEnglish (US)
Article number049006
JournalJournal of Astronomical Telescopes, Instruments, and Systems
Volume4
Issue number4
DOIs
StatePublished - Oct 1 2018

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Control and Systems Engineering
  • Instrumentation
  • Astronomy and Astrophysics
  • Mechanical Engineering
  • Space and Planetary Science

Keywords

  • E-M algorithm
  • adaptive control
  • coronagraph
  • exoplanet direct imaging
  • reinforcement learning
  • system identification
  • wavefront correction

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