Design of an atmospheric dispersion corrector and double scrambler for improved fiber coupling and illumination uniformity for the HET HRS
Abstract
The Hobby--Eberly Telescope High Resolution Spectrograph (HET--HRS) is undergoing a major instrument upgrade to improve its performance over the 360--1000 nm wavelength range. As part of this effort, a new fiber-feed system has been developed to increase throughput and enhance illumination stability. This paper presents the optical and opto-mechanical designs of the upgraded HRS Input Head Module Package and lens-based Double Scramblers. The Input Head incorporates a static Atmospheric Dispersion Corrector (ADC) and relay optics optimized for the HET operational zenith-angle range, reducing the residual atmospheric dispersion to less than 0.42 arcsec while improving wavelength-dependent fiber coupling. Separate Double Scrambler designs were developed for the 260 \textmu m and 320 \textmu m science fibers to exchange the near-field and far-field illumination distributions. Geometrical image analyses demonstrate stable near-field and far-field illumination, reduced coupling losses, and acceptable angular acceptance across both fiber geometries. The opto-mechanical designs supporting the Input Head and Double Scrambler are also presented to provide the alignment accuracy and mechanical stability required for the upgraded fiber-feed system. These results establish the proposed architecture as a practical solution for improving the optical performance and illumination stability of HET--HRS.
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BibTeX
@misc{divakar2026design,
title = {{Design of an atmospheric dispersion corrector and double scrambler for improved fiber coupling and illumination uniformity for the HET HRS}},
author = {Devika K Divakar and Joseph Strubhar and Andrew Pinckney and Phillip MacQueen},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.16505},
eprint = {2609.16505},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.16505},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Design of an atmospheric dispersion corrector and double scrambler for improved fiber coupling and illumination uniformity for the HET HRS
AU - Devika K Divakar
AU - Joseph Strubhar
AU - Andrew Pinckney
AU - Phillip MacQueen
PY - 2026
DA - 2026/09/15
PB - arXiv
DO - 10.48550/arxiv.2609.16505
UR - https://arxiv.org/abs/2609.16505
AB - The Hobby--Eberly Telescope High Resolution Spectrograph (HET--HRS) is undergoing a major instrument upgrade to improve its performance over the 360--1000 nm wavelength range. As part of this effort, a new fiber-feed system has been developed to increase throughput and enhance illumination stability. This paper presents the optical and opto-mechanical designs of the upgraded HRS Input Head Module Package and lens-based Double Scramblers. The Input Head incorporates a static Atmospheric Dispersion Corrector (ADC) and relay optics optimized for the HET operational zenith-angle range, reducing the residual atmospheric dispersion to less than 0.42 arcsec while improving wavelength-dependent fiber coupling. Separate Double Scrambler designs were developed for the 260 \textmu m and 320 \textmu m science fibers to exchange the near-field and far-field illumination distributions. Geometrical image analyses demonstrate stable near-field and far-field illumination, reduced coupling losses, and acceptable angular acceptance across both fiber geometries. The opto-mechanical designs supporting the Input Head and Double Scrambler are also presented to provide the alignment accuracy and mechanical stability required for the upgraded fiber-feed system. These results establish the proposed architecture as a practical solution for improving the optical performance and illumination stability of HET--HRS.
ER -