Astronomy & Telescopes

The High-contrast Performance of the Keck Planet Imager and Characterizer

By Keith Cowing

Status Report

astro-ph.IM

June 24, 2024

Filed under astro-ph.IM, astronomy, coronagraph, exoplanet, GPI, high-resolution spectrograph, imaging, Keck II Adaptive Optics System and Instrument Suite, Keck Observatory, Keck Planet Imager and Characterizer, KPIC, Spectroscopy, SPHERE, telescope

The High-contrast Performance of the Keck Planet Imager and Characterizer — The Keck Planet Imager and Characterizer (KPIC) connects the Keck II AO system and the Keck/NIRSPEC high-resolution infrared spectrograph (https://www2.keck.hawaii.edu/inst/nirspec/) via a linear bundle of four single-mode fibers spaced by ~800 mas on the sky. Single-mode fibers provide a more stable quasi-Gaussian line spread function. Their small angular size, matched to the diffraction limit (FWHM~50 mas in K band), also provides excellent sky background rejection, as well as reduces the off-axis starlight injection into the single mode fibers. Currently, KPIC uses the Shack-Hartmann Wavefront Sensors for AO. Larger image

The Keck Planet Imager and Characterizer (KPIC), a series of upgrades to the Keck II Adaptive Optics System and Instrument Suite, aims to demonstrate high-resolution spectroscopy of faint exoplanets that are spatially resolved from their host stars.

In this paper, we measure KPIC’s sensitivity to companions as a function of separation (i.e., the contrast curve) using on-sky data collected over four years of operation. We show that KPIC is able to reach contrasts of 1.3×10⁻⁴ at 90 mas and 9.2×10⁻⁶ at 420 mas separation from the star, and that KPIC can reach planet-level sensitivities at angular separations within the inner working angle of coronagraphic instruments such as GPI and SPHERE.

KPIC is also able to achieve more extreme contrasts than other medium-/high-resolution spectrographs that are not as optimized for high-contrast performance. We decompose the KPIC performance budget into individual noise terms and discuss limiting factors. The fringing that results from combining a high-contrast imaging system with a high-resolution spectrograph is identified as an important source of systematic noise.

After mitigation and correction, KPIC is able to reach within a factor of 2 of the photon noise limit at separations < 200 mas. At large separations, KPIC is limited by the background noise performance of NIRSPEC.

Jason J. Wang, Dimitri Mawet, Jerry W. Xuan, Chih-Chun Hsu, Jean-Baptiste Ruffio, Katelyn Horstman, Yinzi Xin, Jacques-Robert Delorme, Nemanja Jovanovic, Yapeng Zhang, Luke Finnerty, Ashley Baker, Randall Bartos, Geoffrey A. Blake, Benjamin Calvin, Sylvain Cetre, Gregory W. Doppmann, Daniel Echeverri, Michael P. Fitzgerald, Joshua Liberman, Ronald Lopez, Evan Morris, Jacklyn Pezzato-Rovner, Ben Sappey, Tobias Schofield, Andrew Skemer, J. Kent Wallace, Ji Wang

Comments: 16 pages, 6 figures, submitted to the proceedings of SPIE Astronomical Telescopes + Instrumentation 2024, 13096-69
Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2406.15028 [astro-ph.IM] (or arXiv:2406.15028v1 [astro-ph.IM] for this version)
Submission history
From: Jason Wang
[v1] Fri, 21 Jun 2024 10:11:39 UTC (1,902 KB)
https://arxiv.org/abs/2406.15028
Astrobiology, Astronomy,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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