Fast Coherent Differential Imaging on Ground-Based Telescopes using the Self-Coherent Camera

TL;DR

This paper introduces FAST, a novel method using the self-coherent camera for rapid wavefront correction in ground-based telescopes, significantly improving exoplanet imaging contrast by reducing speckle noise.

Contribution

The paper develops a new framework for fast atmospheric speckle correction using SCC, enabling near photon-noise limited contrast in short exposures for ground-based exoplanet imaging.

Findings

Achieves contrast close to photon noise limit after 30 seconds.

Provides about 110 times better raw contrast for 5th magnitude stars compared to current methods.

Demonstrates potential for detecting lower mass exoplanets with improved sensitivity.

Abstract

Direct imaging and spectral characterization of exoplanets using extreme adaptive optics (ExAO) is a key science goal of future extremely large telescopes and space observatories. However, quasi-static wavefront errors will limit the sensitivity of this endeavor. Additional limitations for ground-based telescopes arise from residual AO-corrected atmospheric wavefront errors, generating millisecond-lifetime speckles that average into a halo over a long exposure. A solution to both of these problems is to use the science camera of an ExAO system as a wavefront sensor to perform a fast measurement and correction method to minimize these aberrations as soon as they are detected. We develop the framework for one such method based on the self-coherent camera (SCC) to be applied to ground-based telescopes, called Fast Atmospheric SCC Technique (FAST). We show that with the use of a specially designed coronagraph and coherent differential imaging algorithm, recording images every few milliseconds allows for a subtraction of atmospheric and static speckles while maintaining a close to unity algorithmic exoplanet throughput. Detailed simulations reach a contrast close to the photon noise limit after 30 seconds for a 1 % bandpass in H band on both 0$^\text{th}$ and 5$^\text{th}$ magnitude stars. For the 5th magnitude case, this is about 110 times better in raw contrast than what is currently achieved from ExAO instruments if we extrapolate for an hour of observing time, illustrating that sensitivity improvement from this method could play an essential role in the future detection and characterization of lower mass exoplanets.