Advancement of the segment support system for the Thirty Meter Telescope primary mirror

Williams, Eric; Baffes, Curtis; Mast, Terry S.; Nelson, Jerry; Platt, Benjamin C.; Ponchione, R. J.; Ponslet, Eric; Setoodeh, Shahriar; Sirota, Mark J.; Stephens, Vince; Stepp, Larry M.; Tubb, Alan

doi:10.1117/12.790176

Cited by 16 publications

(10 citation statements)

References 6 publications

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“…[2] A finite element model has been developed in NASTRAN, and model parameters have been adjusted to provide a better match with static load tests. The prototype PSA has an aluminum blank in place of the mirror segment and a customized mirror cell triangle for support.…”

Section: Structuresmentioning

confidence: 99%

“…The same load spread evenly around the mirror cell produces a response that is dominated by the support structure, which in absolute terms is very stiff, but relative to the single point response, is much more compliant. 2 The finite element models used here are 608 model of the PSA, so-called because it was delivered to the controls team on June 8, 2009, and the 2008 DSL model of the telescope. …”

Section: Structuresmentioning

confidence: 99%

“…This image is from the NASTRAN finite element model developed at HYTEC, Inc. [2] Example frequency responses for the mirror cell and PSA are also included in Figure 1. The frequency responses are discussed later in the text.…”

Section: Introductionmentioning

confidence: 99%

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Servo design and analysis for the Thirty Meter Telescope primary mirror actuators

et al. 2010

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The Thirty Meter Telescope has 492 primary mirror segments, each incorporated into a Primary Segment Assembly (PSA), each of which in turn has three actuators that control piston, tip, and tilt, for a total of 1476 actuators. Each actuator has a servo loop that controls small motions (nanometers) and large motions (millimeters). Candidate actuators were designed and tested that fall into the categories of "hard" and "soft," depending on the offload spring stiffness relative to the PSA structural stiffness. Dynamics models for each type of actuator are presented, which respectively use piezo-electric transducers and voice coils. Servo design and analysis are presented that include assessments of stability, performance, robustness, and control structure interaction. The analysis is presented for a single PSA on a rigid base, and then using Zernike approximations the analysis is repeated for 492 mirror segments on a flexible mirror cell. Servo requirements include low-frequency stiffness, needed for wind rejection; reduced control structure interaction, specified by a bound on the sensitivity function; and mid-frequency damping, needed to reduce vibration transmission. The last of these requirements, vibration reduction, was found to be an important distinguishing characteristic for actuator selection. Hard actuators have little inherent damping, which is improved using PZT shunt circuits and force feedback, but still these improvements were found to result in less damping than is provided by the soft actuator. Results of the servo analysis were used for an actuator down-select study.

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Section: Structuresmentioning

confidence: 99%

Section: Structuresmentioning

confidence: 99%

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Servo design and analysis for the Thirty Meter Telescope primary mirror actuators

et al. 2010

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“…4 Three unique moment limits exist depending upon the location of the actuator. The moment limits are shown in Fig.…”

Section: Influence Functionsmentioning

confidence: 99%

“…Discussion of the measurement and estimation errors is followed in Sec. 4, which details additional inputs for the Wavefront Correction block. The PSSN values are presented in Sec.…”

Section: Introductionmentioning

confidence: 99%

Investigation of primary mirror segment's residual errors for the Thirty Meter Telescope

Seo

Nissly

Angeli

et al. 2009

Optical Modeling and Performance Predictions IV

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The primary mirror segment aberrations after shape corrections with warping harness have been identified as the single largest error term in the Thirty Meter Telescope (TMT) image quality error budget. In order to better understand the likely errors and how they will impact the telescope performance we have performed detailed simulations. We first generated unwarped primary mirror segment surface shapes that met TMT specifications. Then we used the predicted warping harness influence functions and a Shack-Hartmann wavefront sensor model to determine estimates for the 492 corrected segment surfaces that make up the TMT primary mirror. Surface and control parameters, as well as the number of subapertures were varied to explore the parameter space. The corrected segment shapes were then passed to an optical TMT model built using the Jet Propulsion Laboratory (JPL) developed Modeling and Analysis for Controlled Optical Systems (MACOS) ray-trace simulator. The generated exit pupil wavefront error maps provided RMS wavefront error and image-plane characteristics like the Normalized Point Source Sensitivity (PSSN). The results have been used to optimize the segment shape correction and wavefront sensor designs as well as provide input to the TMT systems engineering error budgets.

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Creating a large aspheric primary mirror using spherical segments

Jacob

Parihar

James³

2020

Exp Astron

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Advancement of the segment support system for the Thirty Meter Telescope primary mirror

Cited by 16 publications

References 6 publications

Servo design and analysis for the Thirty Meter Telescope primary mirror actuators

Servo design and analysis for the Thirty Meter Telescope primary mirror actuators

Investigation of primary mirror segment's residual errors for the Thirty Meter Telescope

Creating a large aspheric primary mirror using spherical segments

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