Improved Contrast in Images of Exoplanets using Direct SNR Optimization

Abstract

Direct imaging of exoplanets is usually limited by quasi-static speckles. These uncorrected aberrations in a star's point spread function (PSF) obscure faint companions and limit the sensitivity of high-contrast imaging instruments. Most current approaches to processing differential imaging sequences like angular differential imaging (ADI) and spectral differential imaging (SDI) produce a self-calibrating dataset that are combined in a linear least squares solution to minimize the noise. Due to temporal and chromatic evolution of a telescope's PSF, the best correlated reference images are usually the most contaminated by the planet, leading to self-subtraction and reducing the planet throughput. In this paper, we present an algorithm that directly optimizes the non-linear equation for planet signal to noise ratio (SNR). This new algorithm does not require us to reject adjacent reference images and optimally balances noise reduction with self-subtraction. We then show how this algorithm can be applied to multiple images simultaneously for a further reduction in correlated noise, directly maximizing the SNR of the final combined image. Finally, we demonstrate the technique on an illustrative sequence of HR8799 using the new Julia-based Signal to Noise Analysis Pipeline (SNAP). We show that SNR optimization can provide up to a $5\times$ improvement in contrast close to the star. Applicable to both new and archival data, this technique will allow for the detection of lower mass, and closer in companions, or achieve the same sensitivity with less telescope time.

arXiv comment14 pages, 9 figures. Accepted for publication in AJ

References in corpus (18)

• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• Angular Differential Imaging: a Powerful High-Contrast Imaging Technique
• Images of a fourth planet orbiting HR 8799
• Detection and Characterization of Exoplanets and Disks using Projections on Karhunen-Loeve Eigenimages
• The Gemini Planet Imager: First Light
• SPHERE: the exoplanet imager for the Very Large Telescope
• A new algorithm for point spread function subtraction in high-contrast imaging: a demonstration with angular differential imaging
• Hints for a Turnover at the Snow Line in the Giant Planet Occurrence Rate
• Improving and Assessing Planet Sensitivity of the GPI Exoplanet Survey with a Forward Model Matched Filter
• Astrometry and Photometry with Coronagraphs
• Application of a damped Locally Optimized Combination of Images method to the spectral characterization of faint companions using an Integral Field Spectrograph
• Accurate Astrometry and Photometry of Saturated and Coronagraphic Point Spread Functions
• Direct Detection and Orbit Analysis of the Exoplanets HR 8799 bcd from Archival 2005 Keck/NIRC2 Data
• The Gemini Planet Imager Exoplanet Survey: Dynamical Mass of the Exoplanet beta Pictoris b from Combined Direct Imaging and Astrometry
• Optimized Principal Component Analysis on Coronagraphic Images of the Fomalhaut System
• Effects of Quasi-Static Aberrations in Faint Companion Searches
• Convex Optimization in Julia
• Shades of Black: Searching for Brown Dwarfs & Giant Planets

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• Half-sibling regression meets exoplanet imaging: PSF modeling and subtraction using a flexible, domain knowledge-driven, causal framework
• Use the 4S (Signal-Safe Speckle Subtraction): Explainable Machine Learning reveals the Giant Exoplanet AF Lep b in High-Contrast Imaging Data from 2011
• Auto-RSM: an automated parameter-selection algorithm for the RSM map exoplanet detection algorithm
• Speckle Space-Time Covariance in High-Contrast Imaging
• An Alternating Minimization Algorithm with Trajectory for Direct Exoplanet Detection -- The AMAT Algorithm