Speckle Suppression with the Project 1640 Integral Field Spectrograph

TL;DR

This paper presents advanced speckle suppression techniques for the Project 1640 instrument, significantly improving its ability to detect faint exoplanets and circumstellar material by reducing residual noise close to stars.

Contribution

The paper introduces a novel speckle suppression pipeline combining the IFS's chromatic diversity with the LOCI algorithm, achieving over an order of magnitude noise reduction in high-contrast imaging.

Findings

Achieved $5\sigma$ contrast of $2.1\times10^{-5}$ at 1 arcsecond in 20 minutes.

Demonstrated suppression factors of at least tenfold in on-sky data.

Projected near-infrared contrast levels of about $10^{-7}$ at subarcsecond separations.

Abstract

Project 1640 is a high-contrast imaging instrument recently commissioned at Palomar observatory. A combination of a coronagraph with an integral field spectrograph (IFS), Project 1640 is designed to detect and characterize extrasolar planets, brown dwarfs, and circumstellar material orbiting nearby stars. In this paper, we present our data processing techniques for improving upon instrument raw sensitivity via the removal of quasi-static speckles. Our approach utilizes the chromatic image diversity provided by the IFS in combination with the locally-optimized combination of images (LOCI) algorithm to suppress the intensity of residual contaminating light in close angular proximity to target stars. We describe the Project 1640 speckle suppression pipeline (PSSP) and demonstrate the ability to detect companions with brightness comparable to and below that of initial speckle intensities using on-sky commissioning data. Our preliminary results indicate that suppression factors of at least one order of magnitude are consistently possible, reaching $5\sigma$ contrast levels of $2.1\times10^{-5}$ at $1\arcsec$ in the H-band in 20 minutes of on-source integration time when non-common-path errors are reasonably well-calibrated. These results suggest that near-infrared contrast levels of order $\approx10^{-7}$ at subarcsecond separations will soon be possible for Project 1640 and similarly designed instruments that receive a diffraction-limited beam corrected by adaptive optics (AO) systems employing deformable mirrors with high actuator-density.