The Hector Instrument: optical design of the new higher-resolution spectrograph

Ross Zhelem; Robert Content; Will Saunders; Jon Lawrence; Jessica Zheng; Julia Bryant; Joss Bland-Hawthorn; David Robertson; Mahesh Mohanan; Sudharshan Venkatesan

doi:10.1117/12.2562634

The Hector Instrument: optical design of the new higher-resolution spectrograph

Ross Zhelem, Robert Content, Will Saunders, Jon Lawrence, Jessica Zheng, Julia Bryant, Joss Bland-Hawthorn, David Robertson, Mahesh Mohanan, Sudharshan Venkatesan

Australian Astronomical Optics

Research output: Chapter in Book/Report/Conference proceeding › Conference proceeding contribution › peer-review

Abstract

The Hector instrument is the new multi-object facility at the Anglo-Australian Telescope. It consists of new-format hexabundle IFU’s, complex robotic positioner with magnetic system, unique sky-fibre system, guiding system, optical cable and two spectrographs. Light is captured at the telescope prime focus by optical fiber imaging bundles (hexabundles) at f/3.25 and delivered to the spectrograph slit via ~50 m long fiber cable. At the spectrograph end, the fibers are reformatted into a curved slit relaying unconverted telescope input. The spectrograph optics includes fast collimators and cameras reimaging the slit onto 4k x 4k E2V detectors at f/1.3 with magnification 1/2.5. The challenge of good image quality with the large pupil size (180 mm) and the field of view (±12° at detector) was met by introduction of several aspheric surfaces in the all-refractive design. The blue and red arms, 372-591 nm and 571-778 nm, respectively, are implemented with the help of a dichroic beam splitter in the diverging beam followed by a collimating doublet lens for each arm. An upgrade is possible to the infra-red arm with the help of an additional dichroic beam splitter. The dispersers are asymmetric VPH gratings with slanted fringes optimised for the passband of each arm. Optical performance of the dichroic beamsplitter and gratings has been confirmed and complemented by in-house metrology. The spectrograph throughput is predicted based on transmittance of materials and coatings.

Original language	English
Title of host publication	Ground-based and Airborne Instrumentation for Astronomy VIII
Editors	Christopher J. Evans, Julia J. Bryant, Kentaro Motohara
Place of Publication	Bellingham, Washington
Publisher	SPIE
Pages	114478U-1-114478U-12
Number of pages	12
ISBN (Electronic)	9781510636828
ISBN (Print)	9781510636811
DOIs	https://doi.org/10.1117/12.2562634
Publication status	Published - 13 Dec 2020
Event	Ground-based and Airborne Instrumentation for Astronomy VIII - Virtual, United States Duration: 14 Dec 2020 → 22 Dec 2020

Publication series

Name	Proceedings of SPIE
Publisher	SPIE
Volume	11447
ISSN (Print)	0277-786X
ISSN (Electronic)	1996-756X

Conference

Conference	Ground-based and Airborne Instrumentation for Astronomy VIII
Country/Territory	United States
Period	14/12/20 → 22/12/20

Keywords

spectrograph
IFU
multi-object
fiber slit
dichroic beamsplitter
VPH grating

Access to Document

10.1117/12.2562634

Cite this

Zhelem, R., Content, R., Saunders, W., Lawrence, J., Zheng, J., Bryant, J., Bland-Hawthorn, J., Robertson, D., Mohanan, M., & Venkatesan, S. (2020). The Hector Instrument: optical design of the new higher-resolution spectrograph. In C. J. Evans, J. J. Bryant, & K. Motohara (Eds.), Ground-based and Airborne Instrumentation for Astronomy VIII (pp. 114478U-1-114478U-12). [114478U] (Proceedings of SPIE; Vol. 11447). SPIE. https://doi.org/10.1117/12.2562634

Zhelem, Ross ; Content, Robert ; Saunders, Will ; Lawrence, Jon ; Zheng, Jessica ; Bryant, Julia ; Bland-Hawthorn, Joss ; Robertson, David ; Mohanan, Mahesh ; Venkatesan, Sudharshan. / The Hector Instrument : optical design of the new higher-resolution spectrograph. Ground-based and Airborne Instrumentation for Astronomy VIII. editor / Christopher J. Evans ; Julia J. Bryant ; Kentaro Motohara. Bellingham, Washington : SPIE, 2020. pp. 114478U-1-114478U-12 (Proceedings of SPIE).

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title = "The Hector Instrument: optical design of the new higher-resolution spectrograph",

abstract = "The Hector instrument is the new multi-object facility at the Anglo-Australian Telescope. It consists of new-format hexabundle IFU{\textquoteright}s, complex robotic positioner with magnetic system, unique sky-fibre system, guiding system, optical cable and two spectrographs. Light is captured at the telescope prime focus by optical fiber imaging bundles (hexabundles) at f/3.25 and delivered to the spectrograph slit via ~50 m long fiber cable. At the spectrograph end, the fibers are reformatted into a curved slit relaying unconverted telescope input. The spectrograph optics includes fast collimators and cameras reimaging the slit onto 4k x 4k E2V detectors at f/1.3 with magnification 1/2.5. The challenge of good image quality with the large pupil size (180 mm) and the field of view (±12° at detector) was met by introduction of several aspheric surfaces in the all-refractive design. The blue and red arms, 372-591 nm and 571-778 nm, respectively, are implemented with the help of a dichroic beam splitter in the diverging beam followed by a collimating doublet lens for each arm. An upgrade is possible to the infra-red arm with the help of an additional dichroic beam splitter. The dispersers are asymmetric VPH gratings with slanted fringes optimised for the passband of each arm. Optical performance of the dichroic beamsplitter and gratings has been confirmed and complemented by in-house metrology. The spectrograph throughput is predicted based on transmittance of materials and coatings.",

keywords = "spectrograph, IFU, multi-object, fiber slit, dichroic beamsplitter, VPH grating",

author = "Ross Zhelem and Robert Content and Will Saunders and Jon Lawrence and Jessica Zheng and Julia Bryant and Joss Bland-Hawthorn and David Robertson and Mahesh Mohanan and Sudharshan Venkatesan",

year = "2020",

month = dec,

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language = "English",

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booktitle = "Ground-based and Airborne Instrumentation for Astronomy VIII",

address = "United States",

note = "Ground-based and Airborne Instrumentation for Astronomy VIII ; Conference date: 14-12-2020 Through 22-12-2020",

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Zhelem, R, Content, R, Saunders, W, Lawrence, J, Zheng, J, Bryant, J, Bland-Hawthorn, J, Robertson, D, Mohanan, M & Venkatesan, S 2020, The Hector Instrument: optical design of the new higher-resolution spectrograph. in CJ Evans, JJ Bryant & K Motohara (eds), Ground-based and Airborne Instrumentation for Astronomy VIII., 114478U, Proceedings of SPIE, vol. 11447, SPIE, Bellingham, Washington, pp. 114478U-1-114478U-12, Ground-based and Airborne Instrumentation for Astronomy VIII, United States, 14/12/20. https://doi.org/10.1117/12.2562634

The Hector Instrument : optical design of the new higher-resolution spectrograph. / Zhelem, Ross; Content, Robert; Saunders, Will; Lawrence, Jon; Zheng, Jessica; Bryant, Julia; Bland-Hawthorn, Joss; Robertson, David; Mohanan, Mahesh; Venkatesan, Sudharshan.

Ground-based and Airborne Instrumentation for Astronomy VIII. ed. / Christopher J. Evans; Julia J. Bryant; Kentaro Motohara. Bellingham, Washington : SPIE, 2020. p. 114478U-1-114478U-12 114478U (Proceedings of SPIE; Vol. 11447).

Research output: Chapter in Book/Report/Conference proceeding › Conference proceeding contribution › peer-review

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AB - The Hector instrument is the new multi-object facility at the Anglo-Australian Telescope. It consists of new-format hexabundle IFU’s, complex robotic positioner with magnetic system, unique sky-fibre system, guiding system, optical cable and two spectrographs. Light is captured at the telescope prime focus by optical fiber imaging bundles (hexabundles) at f/3.25 and delivered to the spectrograph slit via ~50 m long fiber cable. At the spectrograph end, the fibers are reformatted into a curved slit relaying unconverted telescope input. The spectrograph optics includes fast collimators and cameras reimaging the slit onto 4k x 4k E2V detectors at f/1.3 with magnification 1/2.5. The challenge of good image quality with the large pupil size (180 mm) and the field of view (±12° at detector) was met by introduction of several aspheric surfaces in the all-refractive design. The blue and red arms, 372-591 nm and 571-778 nm, respectively, are implemented with the help of a dichroic beam splitter in the diverging beam followed by a collimating doublet lens for each arm. An upgrade is possible to the infra-red arm with the help of an additional dichroic beam splitter. The dispersers are asymmetric VPH gratings with slanted fringes optimised for the passband of each arm. Optical performance of the dichroic beamsplitter and gratings has been confirmed and complemented by in-house metrology. The spectrograph throughput is predicted based on transmittance of materials and coatings.

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Zhelem R, Content R, Saunders W, Lawrence J, Zheng J, Bryant J et al. The Hector Instrument: optical design of the new higher-resolution spectrograph. In Evans CJ, Bryant JJ, Motohara K, editors, Ground-based and Airborne Instrumentation for Astronomy VIII. Bellingham, Washington: SPIE. 2020. p. 114478U-1-114478U-12. 114478U. (Proceedings of SPIE). https://doi.org/10.1117/12.2562634

The Hector Instrument: optical design of the new higher-resolution spectrograph

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