KEYWORDS: Gemini Planet Imager, Analog to digital converters, Mathematical modeling, Humidity, Atmospheric corrections, Atmospheric modeling, Gemini Observatory, Relative humidity, Data modeling, Refractive index
The atmospheric dispersion corrector (ADC) of the Gemini Planet Imager (GPI) corrects the chromatic dispersion caused by differential atmospheric refraction (DAR), making it an important optic for exoplanet observation. Despite requiring <5 mas of residual DAR to avoid potentially affecting the coronagraph, the GPI ADC averages ∼7 and ∼11 mas of residual DAR in H and J band, respectively. We analyzed GPI data in those bands to find explanations for the underperformance. We found the model GPI uses to predict DAR underestimates humidity’s impact on incident DAR, causing on average a 0.54 mas increase in H band residual DAR. Additionally, the GPI ADC consistently undercorrects in H band by about 7 mas, causing almost all the H band residual DAR. J band does not have such an offset. Perpendicular dispersion induced by the GPI ADC, potentially from a misalignment in the prisms’ relative orientation, causes 86% of the residual DAR in J band. Correcting these issues could reduce residual DAR, thereby improving exoplanet detection. We also made an approximation for the index of refraction of air from 0.7 to 1.36 microns that more accurately accounts for the effects of humidity.
The Gemini Planet Imager (GPI) is a high-contrast imaging instrument designed to directly detect and characterize young, Jupiter-mass exoplanets. After six years of operation at Gemini South in Chile, the instrument is being upgraded and relocated to Gemini North in Hawaii as GPI 2.0. GPI helped establish that Jovian-mass planets have a higher occurrence rate at smaller separations, motivating several sub-system upgrades to obtain deeper contrasts (up to 20 times improvement to the current limit), particularly at small inner working angles. This enables access to additional science areas for GPI 2.0, including low-mass stars, young nearby stars, solar system objects, planet formation in disks, and planet variability. The necessary instrumental changes required toenable these new scientific goals are to (i) the adaptive optics system, by replacing the current Shack-Hartmann Wavefront Sensor (WFS) with a pyramid WFS and a custom EMCCD, (ii) the integral field spectrograph, by employing a new set of prisms to enable an additional broadband (Y-K band) low spectral resolution mode, as well as replacing the pupil viewer camera with a faster, lower noise C-RED2 camera (iii) the calibration interferometer, by upgrading the low-order WFS used for internal alignment and on-sky target tracking with a C-RED2 camera and replacing the calibration high-order WFS used for measuring and correcting non-common path aberrations with a self coherent camera, (iv) the apodized-pupil Lyot coronagraph designs and (v) the software, to enable high-efficiency queue operations at Gemini North. GPI 2.0 is expected to go on-sky in early 2024. Here I will present the new scientific goals, the key upgrades, the current status and the latest timeline for operations.
GPI is a facility instrument designed for the direct detection and characterization of young Jupiter mass exoplanets. GPI has helped establish that the occurrence rate of Jovian planets peaks near the snow line (~3 AU), and falls off toward larger separations. This motivates an upgrade of GPI to achieve deeper contrasts, especially at small inner working angles, to extend GPI’s operating range to fainter stars, and to broaden its scientific capabilities, all while leveraging its historical success. GPI was packed and shipped in 2022, and is undergoing a major science-driven upgrade. We present the status and purpose of the upgrades including an EMCCD-based pyramid wavefront sensor, broadband low spectral resolution prisms, new apodized-pupil Lyot coronagraph designs, upgrades of the calibration wavefront sensor and increased queue operability. We discuss the expected performance improvements and enhanced science capabilities to be made available in 2024.
High-contrast imaging instruments have advanced techniques to improve contrast, but they remain limited by uncorrected stellar speckles, often lacking a “second stage” correction to complement the Adaptive Optics (AO) correction. We are implementing a new second stage speckle-correction solution for the Gemini Planet Imager (GPI), replacing the instrument calibration unit (CAL) with the Fast Atmospheric Self coherent camera Technique (FAST), a new version of the self-coherent camera (SCC) concept. Our proposed upgrade (CAL2.0) will use a common-path interferometer design to enable speckle correction, through post-processing and/or by a feedback loop to the AO deformable mirror. FAST utilizes a new type of coronagraphic mask that will enable, for the first time, speckle correction down to millisecond timescales. The system's main goal is to improve the contrast by up to 100x in a halfdark hole to enable a new regime of science discoveries. Our team has been developing this new technology at the NRC's Extreme Wavefront control for Exoplanet and Adaptive optics Research Topics (NEW EARTH) laboratory over the past several years. The GPI CAL2.0 update is funded (November 2020), and the system’s first light is expected late 2023.
The Gemini Planet Imager (GPI) is a dedicated high-contrast imaging facility designed for the direct detection and characterization of young Jupiter mass exoplanets. After six yrs of operation at Gemini South, GPI has helped establish that Jovian planets are rare at wide separations, but have higher occurrence rates at small separations. This motivates an upgrade of GPI to achieve deeper contrasts, especially at small inner working angles, while leveraging its current capabilities. GPI has been funded to undergo a major science-driven upgrade as part of a relocation to Gemini North (GN). Gemini plans to remove GPI at the end of 2020A. We present the status of the proposed upgrades to GPI including a EMCCD-based pyramid wavefront sensor, broadband low spectral resolution prisms and new apodized-pupil Lyot coronagraph designs. We discuss the expected performance improvements in the context of GPI 2.0's enhanced science capabilities which are scheduled to be made available at GN in 2022.
The Gemini Planet Imager (GPI) is a high-contrast adaptive optics instrument designed to detect and characterize substellar companions and circumstellar debris disks around nearby young stars using infrared integral field spectroscopy and polarimetry. GPI has been in routine operations at Gemini South for the past six years. Because precise astrometry and photometry of exoplanets is critical to GPI's science, we undertook extensive efforts both in-lab and on-sky to refine the astrometric and photometric calibration of the instrument. We describe revisions to the GPI Data Reduction Pipeline (DRP) that account for these revised calibrations, and that fix several issues identified over the previous six years, including some subtle issues affecting astrometric calibrations caused by a drift of the instrument’s clock. These calibrations are critical for the interpretation of observations obtained with GPI, and for a comparison with measurements from other high-contrast imaging instruments.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.