Overview and status of the fiber delivery subsystem (FIB) of Keck/HISPEC, the diffraction-limited y-K band spectrograph for exoplanet characterization

Nemanja Jovanovic; Greg Sercel; Takayuki Kotani; John I. Bailey III; Ashley Baker; Svarun Soda; Aoi Takahashi; Jonathan Lin; Yoo Jung Kim; Michael P. Fitzgerald; Sebastien Vievard; Chris Betters; Sergio Leon-Saval; Jocelyn Ferrara; Truman Wold; Jonathan Steiner; Jim Thorne; Marc Kassis; Motohide Tamura; Dimitri Mawet

doi:10.1117/12.3020499

18 July 2024 Overview and status of the fiber delivery subsystem (FIB) of Keck/HISPEC, the diffraction-limited y-K band spectrograph for exoplanet characterization

Nemanja Jovanovic, Greg Sercel, Takayuki Kotani, John I. Bailey III, Ashley Baker, Svarun Soda, Aoi Takahashi, Jonathan Lin, Yoo Jung Kim, Michael P. Fitzgerald, Sebastien Vievard, Chris Betters, Sergio Leon-Saval, Jocelyn Ferrara, Truman Wold, Jonathan Steiner, Jim Thorne, Marc Kassis, Motohide Tamura, Dimitri Mawet

Author Affiliations +

Proceedings Volume 13096, Ground-based and Airborne Instrumentation for Astronomy X; 130966I (2024) https://doi.org/10.1117/12.3020499
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Conference Poster

Abstract

The High-Resolution Infrared Spectrograph for Exoplanet Characterization (HISPEC) is a new instrument for the W. M. Keck Observatory that enables R∼100,000 spectroscopy simultaneously across the y, J, H, and K astronomical bands (0.98-2.5 μm). The fiber delivery subsystem of HISPEC is responsible for routing science and calibration light throughout the observatory efficiently. It consists of high-performance single mode fibers, a photonic lantern, mechanical and MEMS-based fiber switchers that allow for the reconfiguration of light paths. To efficiently cover this large wavelength range, a silica fiber is used for the y&J bands and the 1×3 photonic lantern while a ZBLAN fiber is used for the H&K bands. The HK fiber is a custom design by Le Verre Fluore. The fibers route the science light from the focal point of the adaptive optics system to spectrographs in the basement ∼65 m away, hence, the fibers must be very efficient. To calibrate the instrument, several mechanical fiber switchers can be used to direct calibration light to the spectrograph or the front of the optical train. Some switchers must make over 800 cycles annually, while maintaining sub-3% coupling losses between fibers with core sizes of 4.4 μm. To achieve this, extensive testing was conducted, in which throughput and dust accumulation were monitored to determine how these parameters are impacted by switch preparation procedures and ambient environmental conditions. We developed systems to automatically and remotely clean and image fiber end faces in situ. We have created a protocol that allows us to achieve thousands of switch connections reliably. Additionally, through the 25,000+ switch cycles ran during testing, we identified shortcomings in the design of these mechanical fiber switchers which will be remedied for the final instrument.

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

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Nemanja Jovanovic, Greg Sercel, Takayuki Kotani, John I. Bailey III, Ashley Baker, Svarun Soda, Aoi Takahashi, Jonathan Lin, Yoo Jung Kim, Michael P. Fitzgerald, Sebastien Vievard, Chris Betters, Sergio Leon-Saval, Jocelyn Ferrara, Truman Wold, Jonathan Steiner, Jim Thorne, Marc Kassis, Motohide Tamura, and Dimitri Mawet "Overview and status of the fiber delivery subsystem (FIB) of Keck/HISPEC, the diffraction-limited y-K band spectrograph for exoplanet characterization", Proc. SPIE 13096, Ground-based and Airborne Instrumentation for Astronomy X, 130966I (18 July 2024); https://doi.org/10.1117/12.3020499

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