Design and production of the DESI fibre cables

The Dark Energy Spectroscopic Instrument (DESI) embarked on an ambitious 5 yr survey in 2021 May to explore the nature of dark energy with spectroscopic measurements of 40 million galaxies and quasars. DESI will determine precise redshifts and employ the baryon acoustic oscillation method to measure distances from the nearby universe to beyond redshift z > 3.5, and employ redshift space distortions to measure the growth of structure and probe potential modifications to general relativity. We describe the significant instrumentation we developed to conduct the DESI survey. This includes: a wide-field, 3.°2 diameter prime-focus corrector; a focal plane system with 5020 fiber positioners on the 0.812 m diameter, aspheric focal surface; 10 continuous, high-efficiency fiber cable bundles that connect the focal plane to the spectrographs; and 10 identical spectrographs. Each spectrograph employs a pair of dichroics to split the light into three channels that together record the light from 360–980 nm with a spectral resolution that ranges from 2000–5000. We describe the science requirements, their connection to the technical requirements, the management of the project, and interfaces between subsystems. DESI was installed at the 4 m Mayall Telescope at Kitt Peak National Observatory and has achieved all of its performance goals. Some performance highlights include an rms positioner accuracy of better than 0.″1 and a median signal-to-noise ratio of 7 of the [O ii] doublet at 8 × 10−17 erg s−1 cm−2 in 1000 s for galaxies at z = 1.4–1.6. We conclude with additional highlights from the on-sky validation and commissioning, key successes, and lessons learned.

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“…The middle panel of Figure 9 shows one of these fiber cable bundles. See Schmoll et al (2018) for more details about the fiber cable production.…”

Section: Fiber Cables and Slit Headsmentioning

confidence: 99%

Overview of the Instrumentation for the Dark Energy Spectroscopic Instrument

Abareshi

Aguilar

Ahlen

et al. 2022

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130

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“…The petal/fiber/spectrograph system is modular: a fiber cable from each petal carries the 500 optical fibers to a slithead, which is installed in one spectrograph. The fiber cables 15 and slitheads 16 were designed and built by Durham University (United Kingdom). The petals are mounted to the corrector via a cone-shaped adapter (the FPD, from Fermilab), which bolts to the end flange of the corrector and presents a circular mounting ring (FPR) to which the petals are attached.…”

Section: Mock Petal Installationmentioning

confidence: 99%

Installation of the Dark Energy Spectroscopic Instrument at the Mayall 4-meter telescope

Besuner¹,

Allen²,

Baltay³

et al. 2020

Ground-Based and Airborne Instrumentation for Astronomy VIII

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The Dark Energy Spectroscopic Instrument (DESI) is a Stage IV ground-based dark energy experiment that will measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 35 million galaxies and quasars over 14000 square degrees will be measured during the life of the experiment. We describe the installation of the major elements of the instrument at the Mayall 4m telescope, completed in late 2019. The previous prime focus corrector, spider vanes, and upper rings were removed from the Mayall's Serrurier truss and replaced with the newlyconstructed DESI ring, vanes, cage, hexapod, and optical corrector. The new corrector was optically aligned with the primary mirror using a laser tracker system. The DESI focal plane system was integrated to the corrector, with each of its ten 500-fiber-positioner petal segments installed using custom installation hardware and the laser tracker. Ten DESI spectrographs with 30 cryostats were installed in a newly assembled clean room in the Large Coude Room. The ten cables carrying 5000 optical fibers from the positioners in the focal plane were routed down the telescope through cable wraps at the declination and hour angle axes, and their integral slitheads were integrated with the ten spectrographs. The fiber view camera assembly was installed to the Mayall's primary mirror cell. Servers for the instrument control system replaced existing computer equipment. The fully integrated instrument has been commissioned and is ready to start its operations phase.

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The Robotic Multiobject Focal Plane System of the Dark Energy Spectroscopic Instrument (DESI)

Silber

Fagrelius

Fanning

et al. 2022

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A system of 5020 robotic fiber positioners was installed in 2019 on the Mayall Telescope, at Kitt Peak National Observatory. The robots automatically retarget their optical fibers every 10–20 minutes, each to a precision of several microns, with a reconfiguration time of fewer than 2 minutes. Over the next 5 yr, they will enable the newly constructed Dark Energy Spectroscopic Instrument (DESI) to measure the spectra of 35 million galaxies and quasars. DESI will produce the largest 3D map of the universe to date and measure the expansion history of the cosmos. In addition to the 5020 robotic positioners and optical fibers, DESI’s Focal Plane System includes six guide cameras, four wave front cameras, 123 fiducial point sources, and a metrology camera mounted at the primary mirror. The system also includes associated structural, thermal, and electrical systems. In all, it contains over 675,000 individual parts. We discuss the design, construction, quality control, and integration of all these components. We include a summary of the key requirements, the review and acceptance process, on-sky validations of requirements, and lessons learned for future multiobject, fiber-fed spectrographs.

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Design and production of the DESI fibre cables

Cited by 3 publications

References 5 publications

Overview of the Instrumentation for the Dark Energy Spectroscopic Instrument

Overview of the Instrumentation for the Dark Energy Spectroscopic Instrument

Installation of the Dark Energy Spectroscopic Instrument at the Mayall 4-meter telescope

The Robotic Multiobject Focal Plane System of the Dark Energy Spectroscopic Instrument (DESI)

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