Baseline design of the LSST hexapods and rotator

Neill, Douglas R.; Sneed, Ryan C.; Dawson, Jake; Sebag, Jacques; Gressler, Willaim

doi:10.1117/12.2056799

Cited by 9 publications

(4 citation statements)

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“…However, for ground-based telescopes with wide fields of view, the effect of cryogenic temperatures on the active optical focusing system has not been investigated and verified in detail. For example, the performance tests for the hexapod platform in Large Synoptic Survey Telescope are conducted only in a room-temperature environment (Neill et al 2012(Neill et al , 2014Sneed et al 2016Sneed et al , 2018. Thus, the relevant research is incomplete.…”

Section: Introductionmentioning

confidence: 99%

Design and Cryogenic Performance of a Hexapod Platform for a Large Ground-based Wide Field Survey Telescope

Yu,

Wang,

Zhang

et al. 2023

Res. Astron. Astrophys.

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Thermal gradient is an important factor causing degradation in the image quality of telescopes. In order to ensure the accurate alignment of the primary focus unit and the primary mirror, the hexapod platform (as a corrector) is investigated in this paper. First, a ground-based telescope with 2.5 m aperture and 3.5 deg field of view is described. The telescope is under construction, and it is expected to be finished in 2023. Secondly, the hexapod platform with flexure hinges utilized to adjust the primary focus unit is proposed, which is applied as a corrector. Then, the inverse kinematics of the platform is established and an open-loop control system is built based on it. Finally, the cryogenic performance test for the hexapod platform is performed. The experimental results show that the resolution and repeatability of the translation for the hexapod platform can be achieved at the micro-meter level. The resolution and repeatability of the rotation can be achieved at the arc-second level. Therefore, the cryogenic performance of the hexapod platform can meet the optical imaging requirements of the wide-field ground-based telescope. The kinematic analysis and cryogenic performance tests in the paper provide a technical reference for the precise alignment of the primary focus unit and the primary mirror, which can improve the imaging quality of the telescope.

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Section: Introductionmentioning

confidence: 99%

Design and Cryogenic Performance of a Hexapod Platform for a Large Ground-based Wide Field Survey Telescope

Yu,

Wang,

Zhang

et al. 2023

Res. Astron. Astrophys.

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“…The William Herschel Telescope uses four Focus Translation Units to correct the primary focus for the three DOFs of the piston tip/tilt [5,6]. The Stewart stage is employed in the secondary mirror adjustment mechanism (SMAM) of large aperture telescopes, such as VST telescopes [7][8][9] and LSST telescopes [10,11]. It offers many advantages, such as high stiffness, six degrees of freedom of adjustment, and non-accumulation of position errors [12].…”

Section: Introductionmentioning

confidence: 99%

Design of a Dynamic Secondary Mirror Truss Adjustment Mechanism for Large Aperture Telescopes

Wang

Zhang

2023

Applied Sciences

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This study focuses on the dynamic secondary mirror truss adjustment mechanism for large aperture telescopes. The relative positions between the primary and secondary mirrors have stringent requirements for large aperture optical telescopes, with an aperture of more than 2 m. Due to the large mass of the primary mirror, the secondary mirror system is designed as an adjustable mechanism with multiple degrees of freedom, dramatically impacting telescope imaging. The kinematic modeling is followed by a detailed description of the designed adjustment mechanism, and then a static and modal analysis of the designed mechanism is performed. Subsequently, a kinematic performance test of the experimental prototype is conducted. The developed mechanism can travel up to ±5 mm in the z-direction with an accuracy of 16 µm and deflection of ±0.574° in the xy-direction. It provides accuracy better than 6.4 arcseconds.

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“…The absolute accuracy and repeatability requirements for TMT's secondary mirror hexapod and LSST's camera hexapod are listed in Table 1. [8][9] 0.5arcsec about axis in XY plane (repeatability) 3arcsec about axis in XY plane (absolute accuracy)…”

Section: Introductionmentioning

confidence: 99%

Error reduction and modeling for hexapod positioners of secondary mirrors for large ground-based telescopes

Sneed

Keas

2014

SPIE Proceedings

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The positioning requirements for secondary mirrors and instruments for large ground-based telescopes are becoming increasingly challenging. Modern telescope designs, such as LSST and TMT, are specifying repeatability and/or absolute accuracy limits below 10 µm and 10 µrad for the hexapod positioning systems generally used for these applications. Hexapod error sources, including lead screw pitch variations, windup, backlash, friction, thermal expansion, compliance, sensing, and joint node location uncertainties, are examined along with methods for reducing or eliminating these errors by mechanical means or through calibration. Alternative sensing approaches are discussed and their relative benefits are evaluated. Finally, a model-based design approach is presented for conducting initial design trade studies, assessing technical risk, predicting achievable performance, establishing subsystem and component requirements, and tracking positioning error budgets through the entire development process. A parametric actuator model and its initial results are described, and testing approaches are outlined to identify key model parameters and verify subsystem and component performance.

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Baseline design of the LSST hexapods and rotator

Cited by 9 publications

References 0 publications

Design and Cryogenic Performance of a Hexapod Platform for a Large Ground-based Wide Field Survey Telescope

Design and Cryogenic Performance of a Hexapod Platform for a Large Ground-based Wide Field Survey Telescope

Design of a Dynamic Secondary Mirror Truss Adjustment Mechanism for Large Aperture Telescopes

Error reduction and modeling for hexapod positioners of secondary mirrors for large ground-based telescopes

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