GPI 2.0: Upgrading the Gemini Planet Imager
ABSTRACT
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 years 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.
1. INTRODUCTION
Since the discovery of 51 Pegasi in 1995,1 the search for and discovery of extrasolar planets has dramatically changed our understanding of planetary formation and the place where our solar system stands with respect to other solar systems in the galaxy. While thousands of exoplanets have now been discovered only a few of the most massive or widest separation ones have been observed spectroscopically. Direct imaging is expected to play an increasingly significant role in the future.2 Direct imaging allows for the discovery of planets on solar system-scale orbits, provides new insight into the formation and characteristics of extrasolar systems, and enables direct spectroscopic observations of their atmospheres.
The Gemini Planet Imager (GPI) is a facility class instrument designed to address the fundamental goal of directly detecting and observing exoplanets (Figure 1). GPI was designed and built to directly image and spectroscopically characterize young, Jupiter-sized, self-luminous extrasolar planets and search for circumstellar debris disks that are sculpted by planetary systems. The primary motivation for creating GPI was to measure the frequency and distribution of wide-orbit, giant planets. While designed for either Gemini North or Gemini South, GPI was installed at Gemini South in the fall of 2013.
1.1 Overview of exoplanet science with GPI
The original GPI consisted of an adaptive optics (AO) system, apodized-pupil Lyot coronograph (APLC), a precision infrared wavefront sensor (CAL), and a near-IR integral field spectrograph (IFS). The AO system consists of a 4096-acuator microelectro-mechanical (MEMS) deformable mirror, a CILAS 11 actuator diameter piezoelectric DM in a woofer-tweeter configuration, and a Shack-Hartmann WFS design with a Lincoln Labs CCID-66 sensor.3, 4 GPI uses an APLC to suppress coherent light from the central star.5 GPI’s science instrument is an IFS with 192x192 spatial pixels dispersed through a prism to provide a resolving power of R=∼30-100 depending upon the band. The GPI IFS has 5 individual filters in Y, J, H, and 2 in K-band (split into overlapping segments). The IFS further incorporates a Wollaston prism to allow for polarization measurements but only in broad band.
