Metrology systems of Hobby-Eberly Telescope wide field upgrade

Lee, Hanshin; Hill, Gary J.; Cornell, Mark E.; Vattiat, Brian L.; Perry, Dewayne E.; Rafferty, Tom; Taylor, Trey; Hart, Michael; Rafal, Marc D.; Savage, Richard

doi:10.1117/12.926732

Cited by 10 publications

(9 citation statements)

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“…The WFU will employ wavefront sensing in conjunction with other metrology systems [3] to close the control loop on all axes of the telescope. The wavefront sensor (WFS) will have low-order (i.e.…”

Section: Introductionmentioning

confidence: 99%

Phase retrieval analysis of the Hobby-Eberly Telescope primary mirror segment figure error and its implication for wavefront sensing for the new wide-field upgrade

2010

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Primary mirror segment figure error is potentially deleterious to the wavefront sensing in the new Hobby-Eberly Telescope (HET) Wide-Field Upgrade (WFU). Previous measurements indicated the presence of figure errors including prominent surface astigmatism on the segments, but need a systematic analysis to quantify the amounts. We developed a Phase Retrieval procedure that estimates the surface figure map by applying the iterative transform method to a set of focus-diversed images of a point source formed by the 91 segments of the 11m HET primary mirror. In this paper, we discuss this analysis and the implication of the analysis results for wavefront sensing on the upgraded HET.

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Section: Introductionmentioning

confidence: 99%

Phase retrieval analysis of the Hobby-Eberly Telescope primary mirror segment figure error and its implication for wavefront sensing for the new wide-field upgrade

2010

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“…To track astronomical objects, a robotic x-y tracker sweeps the pupil across the over-sized primary mirror rather than moving the whole telescope structure. The Prime Focus Instrument Package (PFIP) that rides on the tracker contains the spherical aberration correcting optics, metrology instrumentation, 3 and fiber feeds for the science instruments. Currently, the HET is undergoing a major wide-field upgrade (WFU; Ref.…”

Section: Introductionmentioning

confidence: 99%

LRS2: the new facility low resolution integral field spectrograph for the Hobby-Eberly telescope

et al. 2014

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The second generation Low Resolution Spectrograph (LRS2) is a new facility instrument for the Hobby-Eberly Telescope (HET). Based on the design of the Visible Integral-field Replicable Unit Spectrograph (VIRUS), which is the new flagship instrument for carrying out the HET Dark Energy Experiment (HETDEX), LRS2 provides integral field spectroscopy for a seeing-limited field of 12 ×6 . For LRS2, the replicable design of VIRUS has been leveraged to gain broad wavelength coverage from 370 nm to 1.0 µm, spread between two fiber-fed dualchannel spectrographs, each of which can operate as an independent instrument. The blue spectrograph, LRS2-B, covers 370 ≤ λ (nm) ≤ 470 and 460 ≤ λ (nm) ≤ 700 at fixed resolving powers of R = λ/δλ ≈ 1900 and 1100, respectively, while the red spectrograph, LRS2-R, covers 650 ≤ λ (nm) ≤ 842 and 818 ≤ λ (nm) ≤ 1050 with both of its channels having R ≈ 1800. In this paper, we present a detailed description of the instrument's design in which we focus on the departures from the basic VIRUS framework. The primary modifications include the fore-optics that are used to feed the fiber integral field units at unity fill-factor, the cameras' correcting optics and detectors, and the volume phase holographic grisms. We also present a model of the instrument's sensitivity and a description of specific science cases that have driven the design of LRS2, including systematically studying the spatially resolved properties of extended Lyα blobs at 2 < z < 3. LRS2 will provide a powerful spectroscopic follow-up platform for large surveys such as HETDEX.

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“…The upgrade adds wavefront sensing 6,[28][29][30][31] to HET in order to close the control loop on all axes of the system, in conjunction with the DMI and TTS adapted from the current tracker metrology system. There is redundancy built into the new metrology system in order to obtain the highest reliability.…”

Section: Introduction: Het Wide Field Upgrade and Industrial Replicatmentioning

confidence: 99%

“…Their function is to provide feedback on the low-order errors in the wavefront (focus, coma, spherical, and astigmatism) [28][29][30] . These errors are caused by misalignment of the corrector with the primary mirror focal surface and by global radius of curvature and astigmatism errors in the primary mirror shape.…”

Section: Introduction: Het Wide Field Upgrade and Industrial Replicatmentioning

confidence: 99%

VIRUS: a massively replicated 33k fiber integral field spectrograph for the upgraded Hobby-Eberly Telescope

et al. 2010

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The Visible Integral-field Replicable Unit Spectrograph (VIRUS) consists of a baseline build of 150 identical spectrographs (arrayed as 75 units, each with a pair of spectrographs) fed by 33,600 fibers, each 1.5 arcsec diameter, deployed over the 22 arcminute field of the upgraded 10 m Hobby-Eberly Telescope (HET). The goal is to deploy 96 units. VIRUS has a fixed bandpass of 350-550 nm and resolving power R~700. VIRUS is the first example of industrial-scale replication applied to optical astronomy and is capable of spectral surveys of large areas of sky. The method of industrial replication, in which a relatively simple, inexpensive, unit spectrograph is copied in large numbers, offers significant savings of engineering effort, cost, and schedule when compared to traditional instruments.The main motivator for VIRUS is to map the evolution of dark energy for the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX ‡ ) using 0.8M Lyman-α emitting galaxies as tracers. The full VIRUS array is due to be deployed in late 2011 and will provide a powerful new facility instrument for the HET, well suited to the survey niche of the telescope. VIRUS and HET will open up wide field surveys of the emission-line universe for the first time. We present the design, cost, and current status of VIRUS as it enters production, and review performance results from the VIRUS prototype. We also present lessons learned from our experience designing for volume production and look forward to the application of the VIRUS concept on future extremely large telescopes (ELTs). * The Hobby -Eberly Telescope is operated by McDonald Observatory on behalf

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Metrology systems of Hobby-Eberly Telescope wide field upgrade

Cited by 10 publications

References 0 publications

Phase retrieval analysis of the Hobby-Eberly Telescope primary mirror segment figure error and its implication for wavefront sensing for the new wide-field upgrade

Phase retrieval analysis of the Hobby-Eberly Telescope primary mirror segment figure error and its implication for wavefront sensing for the new wide-field upgrade

LRS2: the new facility low resolution integral field spectrograph for the Hobby-Eberly telescope

VIRUS: a massively replicated 33k fiber integral field spectrograph for the upgraded Hobby-Eberly Telescope

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