Simultaneous ultra-high contrast imaging and determination of time-dependent, non-common path aberrations in the presence of detector noise

Abstract

Ground-based ultra-high contrast imaging, as required for direct imaging of exoplanets and other solar systems, is limited by difficulty of separating the planetary emission from the effects of optical aberrations that are not compensated by the adaptive optics (AO) system, so-called "non-common path aberrations" (NCPAs). Simultaneous ($\sim$ millisecond) exposures by the science camera and the AO system enable the use of "phase diversity" to estimate both the NCPAs and the scene via a processing procedure first described by the author (R. Frazin 2013, ApJ, 767, article id. 21). This method is fully compatible with more standard concepts used in long-exposure high-contrast imaging, such as angular differential imaging and spectral deconvolution. Long-exposure methods find time-dependent NCPAs, such as those caused by vibrations, particularly challenging. Here, an NCPA of the form of $\alpha \cos (k\cdot r-\omega t+\vartheta )$ is considered. It is shown that, when sampled at millisecond time-scales, the image plane data are sensitive to $\mbox{arg}(α)$, $\vartheta$ and $\omega$, and, therefore such NCPAs can be simultaneously estimated with the scene. Simulations of observations with ms exposure times are reported. These simulations include substantial detector noise and a sinusoidal NCPA that places a speckle exactly at the location of a planet. Simulations show that the effects of detector noise can be mitigated by mixing exposures of various lengths, allowing estimation of the planet's brightness.

arXiv comment7 pages, 3 figures, to be published in Proc. SPIE

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Cited by in corpus (5)

• A Statistical Framework for the Utilization of Simultaneous Pupil Plane and Focal Plane Telemetry for Exoplanet Imaging, Part I: Accounting for Aberrations in Multiple Planes
• Speckle Space-Time Covariance in High-Contrast Imaging
• Empirical Green's Function Approach for Utilizing Millisecond Focal and Pupil Plane Telemetry in Exoplanet Imaging
• Millisecond Exoplanet Imaging, II: Regression Equations and Technical Discussion
• A Statistical Framework for Utilization of Simultaneous Pupil Plane and Focal Plane Telemetry for Exoplanet Imaging, Part II: The Science Camera Image as a Function of the Wavefront Sensor Field