Prototype development of the integral-field unit for VIRUS

Kelz, Andreas; Bauer, Svend M.; Grupp, F.; Hill, Gary J.; Popow, Emil; Palunas, Povilas; Roth, Martin; MacQueen, Phillip J.; Tripphahn, Ute

doi:10.1117/12.672878

Cited by 16 publications

(14 citation statements)

References 15 publications

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“…Development of the prototype IFUs at AIP 15 and UT 11 has explored several ways of setting up the required matrix of fibers at the input end. Setting up a matrix fused silica capillary tubes to set the spacing proved very successful.…”

Section: Integral Field Unitmentioning

confidence: 99%

“…Fiber IFUs can utilize microlens arrays, providing close to 100% fill-factor 13 , or be of the simpler "densepak" type 14 . For VIRUS we have elected to use the densepak type of bare fiber bundle to maximize iiIri throughput and minimize cost 15 . The primary advantage of lenslets is in coupling the slower f/ratios of typical foci to the fast ratio required to minimize focal ratio degradation 16 , and such IFUs are ideal for retro-fitting existing spectrographs.…”

Section: Integral Field Unitmentioning

confidence: 99%

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Design, construction, and performance of VIRUS-P: the prototype of a highly replicated integral-field spectrograph for HET

et al. 2008

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We describe the design, construction, and performance of VIRUS-P (Visible Integral-field Replicable Unit Spectrograph -Prototype), the prototype for 150+ identical fiber-fed integral field spectrographs for the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX ‡ ). VIRUS-P was commissioned in 2007, is in regular service on the McDonald Observatory 2.7 m Smith telescope, and offers the largest field of any integral field spectrograph. The 246-fiber IFU uses a densepak-type fiber bundle with a 1/3 fill factor. It is fed at f/3.65 through a telecentric, two-group dioptric focal reducer. The spectrograph's double-Schmidt optical design uses a volume phase holographic grating at the pupil between the articulating f/3.32 folded collimator and the f/1.33 cryogenic prime focus camera. High on-sky throughput is achieved with this catadioptric system by the use of high reflectivity dielectric coatings, which set the 340-670 nm bandwidth. VIRUS-P is gimbal-mounted on the telescope to allow short fibers for high UV throughput, while maintaining high mechanical stability. The instrument software and the 18 square arcmin field, fixed-offset guider provide rapid acquisition, guiding, and precision dithering to fill in the IFU field. Custom software yields Poisson noise limited, sky subtracted spectra. The design characteristics are described that achieved uniformly high image quality with low scattered light and fiber-to-fiber cross talk. System throughput exceeds requirements and peaks at 40%. The observing procedures are described, and example observations are given.

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Section: Integral Field Unitmentioning

confidence: 99%

Section: Integral Field Unitmentioning

confidence: 99%

Design, construction, and performance of VIRUS-P: the prototype of a highly replicated integral-field spectrograph for HET

et al. 2008

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“…It is similar to a design developed by the Southern African Large Telescope (SALT) 45 compensator. The PFIP also supports the integral field unit (IFU) 6 for the VIRUS instrument. The IFU is an array of 145 fiber bundle inputs in the focal plane.…”

Section: Wide Field Upgradementioning

confidence: 99%

The wide field upgrade for the Hobby-Eberly Telescope

Booth¹,

MacQueen²,

Good³

et al. 2006

SPIE Proceedings

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A major performance upgrade for the Hobby-Eberly Telescope (HET) is in the conceptual design phase. The extensive upgrade will include a wide field optical corrector, a new HET tracker with increased payload capacity, and improved telescope pointing and tracking accuracy. The improvements will support the HET Dark Energy Experiment (HETDEX), which seeks to characterize the evolution of dark energy by mapping the imprint of baryonic oscillations on the large scale structure of the Universe. HETDEX will use the increased field-of-view and payload to feed an array of approximately 145 fiber-fed spectrometers, called VIRUS for "Visible Integral field Replicable Unit Spectrograph".The new corrector will have a science field-of-view diameter of 18 arcminutes, in contrast to the original corrector's 4 arcminute field, a twenty-fold increase in area. A new HET tracker with increased payload capacity will be designed to support the wide field corrector. Improved pointing and tracking will be accomplished using new autocollimation and distance measuring metrology combined with real-time wavefront sensing and correction. The upgrade will maintain operation of the current suite of facility instruments, consisting of low, medium, and high resolution spectrometers.

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“…The fibers can be anti-reflection (AR) coated or immersed against an ARcoated cover plate to improve coupling efficiency. As an example, VIRUS uses 75 large fixed IFUs, each with 448 fibers in a 1/3 fill-factor hexagonal close pack to achieve very large areal grasp with 33 600 fibers in total, each 1.5 arcsec diameter on sky [31]. A 'dither' pattern of three offset exposures fills in the 50 × 50 sq.…”

Section: Multiplexing Modesmentioning

confidence: 99%

Replicated spectrographs in astronomy

Hill

2014

Advanced Optical Technologies

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Abstract:As telescope apertures increase, the challenge of scaling spectrographic astronomical instruments becomes acute. The next generation of extremely large telescopes (ELTs) strain the availability of glass blanks for optics and engineering to provide sufficient mechanical stability. While breaking the relationship between telescope diameter and instrument pupil size by adaptive optics is a clear path for small fields of view, survey instruments exploiting multiplex advantages will be pressed to find costeffective solutions. In this review we argue that exploiting the full potential of ELTs will require the barrier of the cost and engineering difficulty of monolithic instruments to be broken by the use of large-scale replication of spectrographs. The first steps in this direction have already been taken with the soon to be commissioned MUSE and VIRUS instruments for the Very Large Telescope and the Hobby-Eberly Telescope, respectively. MUSE employs 24 spectrograph channels, while VIRUS has 150 channels. We compare the information gathering power of these replicated instruments with the present state of the art in more traditional spectrographs, and with instruments under development for ELTs. Design principles for replication are explored along with lessons learned, and we look forward to future technologies that could make massivelyreplicated instruments even more compelling.

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Prototype development of the integral-field unit for VIRUS

Cited by 16 publications

References 15 publications

Design, construction, and performance of VIRUS-P: the prototype of a highly replicated integral-field spectrograph for HET

Design, construction, and performance of VIRUS-P: the prototype of a highly replicated integral-field spectrograph for HET

The wide field upgrade for the Hobby-Eberly Telescope

Replicated spectrographs in astronomy

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