Since the start of science operations in 1993, the twin 10-meter W. M. Keck Observatory (WMKO) telescopes have continued to maximize their scientific impact to produce transformative discoveries that keep the U.S. observing community on the frontiers of astronomical research. Upgraded capabilities and new instrumentation are provided though collaborative partnerships primarily with the Caltech and University of California instrument development teams and through additional collaborations with the University of Notre Dame, the University of Hawaii, Swinburne University of Technology, industry, and other organizations. This paper summarizes the status and performance of observatory infrastructure projects, technology upgrades, and new additions to the suite of observatory instrumentation. We also provide a status of instrumentation projects in early and advanced stages of development that will achieve the goals and objectives summarized in the 2023 Keck Observatory strategic plan. Developed in collaboration with the WMKO science community, the Keck strategic plan sets our sites on 2035 and meets goals identified in the Astro2020 Decadal Survey.
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 (0.98-2.5μm). The Front-End Instrument (FEI) steers the adaptive optics corrected beam delivered by Keck to single-mode fibers used to route the light to the spectrographs. This paper shows the structural (static and dynamic scenarios) and thermal (cryogenic H2RG tracking camera) design of the Front-End Instrument (FEI).
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 front-end instrument steers the adaptive optics corrected beam delivered by Keck to single-mode fibers used to route the light to the spectrographs. The basic architecture of the front-end instrument leverages from the design from the Keck Planet Imager and Characterizer where a tracking camera is used to monitor the location of the target and send commands to a tip/tilt mirror mounted in a pupil plane, which aligns the beam with the fiber in the downstream focal plane. The system will have an atmospheric dispersion corrector to minimize chromatic smearing of the PSF, phase induced amplitude apodization optics to mitigate coupling limitations imposed by the pupil geometry, and vortex masks to enable vortex fiber nulling. The front-end instrument will utilize a Teledyne H2RG for tracking allowing for the ability to guide on targets as faint as 15th magnitude and for tip/tilt control up to 500 Hz on brighter targets. In this paper we provide an overview of the detailed design of the front-end instrument and elucidate the design choices driven by de-risking exercises. We will describe our plan to utilize the J-H gap for tracking which will allow for uninterrupted science for a large population of targets. We present how the front-end instrument will be integrated into the Keck adaptive optics bench to allow for easy removal and cable management. Finally, we provide an update on the project status and the timeline for the sub-system.
HISPEC (High-resolution Infrared Spectrograph for Exoplanet Characterization) is an infrared (0.98 to 2.46 microns) cross-dispersed, R=100,000 single-mode fiber-fed diffraction-limited echellette spectrograph for the Keck II telescope’s adaptive optics (AO) system. MODHIS (Multi-Objective Diffraction-limited High-resolution Infrared Spectrograph) shares similar specifications as HISPEC while being optimized for TMT’s first-light AO system NFIRAOS. Keck-HISPEC, currently in full-scale development and slated for first light in 2026, and TMTMODHIS, currently in conceptual design phase, will provide increasingly compelling science capabilities from exoplanet atmosphere characterization through both transit and direct high-contrast spectroscopy, to detection and mass measurements through infrared precision radial velocity (RV). The science cases include the precise RV measurements of stars orbiting the Galactic Center, Solar System studies, and the chemodynamical history of nearby dwarf galaxies and the galactic halo.
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.
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