Development of a wide-field spherical aberration corrector for the Hobby Eberly Telescope

Burge, James H.; Benjamin, Scott D; Dubin, Matthew; Manuel, Anastacia M.; Novak, Matt; Oh, Chang Wan; Valente, M.; Zhao, Chunyu; Booth, John A.; Good, John M.; Hill, Gary J.; Lee, Hanshin; MacQueen, Phillip J.; Rafal, Marc D.; Savage, Richard; Smith, Michael P.; Vattiat, Brian L.

doi:10.1117/12.857835

Cited by 30 publications

(21 citation statements)

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“…The new Wide-Field Corrector (WFC) replaces the old SAC, thereby widening the telescope instantaneous field of view (FOV) from 4 arcmin to 22 arcmin in diameter, increasing the telescope aperture from 9.2m to 10m, and finely tuning the focal ratio to f/3.65 ideal for coupling optical fibers at its focal surface [1]. Much improved all-kinematic and passively athermalized opto-mechanical structures [2] ensures the structural stability of the system over the range of motions and temperatures to which the WFC is subject and the state-of-the-art protected silver reflective coatings ensures the highest telescope photon efficiency possible across the wavelength range from 360nm to 1800nm.…”

Section: Introductionmentioning

confidence: 99%

Delivery, installation, on-sky verification of the Hobby Eberly Telescope wide field corrector

et al. 2016

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The Hobby-Eberly Telescope (HET) † , located in West Texas at the McDonald Observatory, operates with a fixed segmented primary (M1) and has a tracker, which moves the prime-focus corrector and instrument package to track the sidereal and non-sidereal motions of objects. We have completed a major multi-year upgrade of the HET that has substantially increased the pupil size to 10 meters and the field of view to 22 arcminutes by deploying the new Wide Field Corrector (WFC), new tracker system, and new Prime Focus Instrument Package (PFIP). The focus of this paper is on the delivery, installation, and on-sky verification of the WFC. We summarize the technical challenges encountered and resolutions to overcome such challenges during the construction of the system. We then detail the transportation from Tucson to the HET, on-site ground verification test results, post-installation static alignment among the WFC, PFIP, and M1, and on-sky verification of alignment and image quality via deploying multiple wavefront sensors across 22 arcminutes field of view. The new wide field HET will feed the revolutionary new integral field spectrograph called VIRUS, in support of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), a new low resolution spectrograph (LRS2), an upgraded high resolution spectrograph (HRS2), and later the Habitable Zone Planet Finder (HPF).

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Section: Introductionmentioning

confidence: 99%

Delivery, installation, on-sky verification of the Hobby Eberly Telescope wide field corrector

et al. 2016

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“…The catalyst for the replacement of this hardware is the wide field upgrade to the corrector optics. Replacing the current spherical aberration corrector (SAC) with the wide field corrector 5 (WFC) will increase the HET field of view from 4' to 22'. In addition, the current science instruments 6 are not in general being replaced.…”

Section: Introductionmentioning

confidence: 99%

Tracker controls development and control architecture for the Hobby-Eberly Telescope Wide Field Upgrade

et al. 2010

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To enable the Hobby-Eberly Telescope Wide Field Upgrade, the University of Texas Center for Electromechanics and McDonald Observatory are developing a precision tracker system -a 15,000 kg robot to position a 3,100 kg payload within 10 microns of a desired dynamic track. Performance requirements to meet science needs and safety requirements that emerged from detailed Failure Modes and Effects Analysis resulted in a system of 14 precision controlled actuators and 100 additional analog and digital devices (primarily sensors and safety limit switches). This level of system complexity and emphasis on fail-safe operation is typical of large modern telescopes and numerous industrial applications. Due to this complexity, demanding accuracy requirements, and stringent safety requirements, a highly versatile and easily configurable centralized control system that easily links with modeling and simulation tools during the hardware and software design process was deemed essential. The Matlab/Simulink simulation environment, coupled with dSPACE controller hardware, was selected for controls development and realization. The dSPACE real-time operating system collects sensor information; motor commands are transmitted over a PROFIBUS network to servo amplifiers and drive motor status is received over the same network. Custom designed position feedback loops, supplemented by feed forward force commands for enhanced performance, and algorithms to accommodate self-locking gearboxes (for safety), reside in dSPACE. To interface the dSPACE controller directly to absolute Heidenhain sensors with EnDat 2.2 protocol, a custom communication board was developed. This paper covers details of software and hardware, design choices and analysis, and supporting simulations (primarily Simulink).

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“…The catalyst for the replacement of this hardware is the wide field upgrade to the corrector optics. Replacing the current spherical aberration corrector (SAC) with the wide field corrector 6 will increase the HET field of view from 4' to 22'. In addition, the current science instruments 7 will be supplemented with the Visible Integral-field Replicable Unit Spectrograph 8,9,10 (VIRUS).…”

Section: Introductionmentioning

confidence: 99%

The development of high-precision hexapod actuators for the Hobby-Eberly Telescope wide field upgrade

et al. 2010

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Hexapods are finding increased use in telescope applications for positioning large payloads. Engineers from The University of Texas at Austin have been working with engineers from ADS International to develop large, high force, highly precise and controllable hexapod actuators for use on the Wide Field Upgrade (WFU) as part of the Hobby Eberly Telescope Dark Energy Experiment (HETDEX) ‡ . These actuators are installed in a hexapod arrangement, supporting the 3000+ kg instrument payload which includes the Wide Field Corrector (WFC), support structure, and other optical/electronic components. In addition to force capability, the actuators need to meet the tracking speed (pointing) requirements for accuracy and the slewing speed (rewind) requirements, allowing as many observations in one night as possible. The hexapod actuator stroke (retraction and extension) was very closely monitored during the design phase to make sure all of the science requirements could be met, while minimizing the risk of damaging the WFC optical hardware in the unlikely event of a hexapod actuator or controller failure. This paper discusses the design trade-offs between stiffness, safety, back-drivability, accuracy, and leading to selection of the motor, high ratio worm gear, roller screw, coupling, end mounts, and other key components.

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Development of a wide-field spherical aberration corrector for the Hobby Eberly Telescope

Cited by 30 publications

References 0 publications

Delivery, installation, on-sky verification of the Hobby Eberly Telescope wide field corrector

Delivery, installation, on-sky verification of the Hobby Eberly Telescope wide field corrector

Tracker controls development and control architecture for the Hobby-Eberly Telescope Wide Field Upgrade

The development of high-precision hexapod actuators for the Hobby-Eberly Telescope wide field upgrade

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