Active optics and control architecture for a giant segmented mirror telescope

Angeli, George Z.; Cho, Myung K.; Whorton, Mark

doi:10.1117/12.459850

Cited by 15 publications

(8 citation statements)

References 6 publications

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“…Both decomposition show the same characteristic, namely most of the wind energy is concentrated in the lowest order, smoothest modes. This result is consistent with earlier simulation results obtained with different wind models [6,13].…”

Section: Figure 9 a Snapshot Of The Pressure Field In And Around The supporting

confidence: 93%

Modeling tools to estimate the performance of the Thirty Meter Telescope: an integrated approach

et al. 2004

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A sound system engineering approach and the appropriate tools to support it are essential in achieving the scientific and financial objectives of the Thirty Meter Telescope project. Major elements of the required tool set are those providing estimates for the performance of the telescope. During the last couple of years, the partners in the consortium developed a wide range of modeling and simulation tools with various levels of fidelity and flexibility. There are models available for time domain and frequency domain simulations and analysis, as well as for lower fidelity, parametric investigations of design trade-offs and for high fidelity, integrated modeling of structure, optics and control. Presented are characteristic simulation results using the existing preliminary point designs of the TMT, with emphasis on the telescope performance degradation due to wind buffeting. Under the conditions modeled, the wind induced image jitter and image quality degradation was found comparable to good atmospheric seeing.

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Section: Figure 9 a Snapshot Of The Pressure Field In And Around The supporting

confidence: 93%

Modeling tools to estimate the performance of the Thirty Meter Telescope: an integrated approach

et al. 2004

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“…Estimates of the impact of wind buffeting on the telescope structure have been made both using the data directly 8,9,14 and using models motivated by the results discussed above. 10,11 For ELT's, based on simple structural models, the most significant impact is the excitation of the primary due to the wind loads on the secondary support structure coupling into the primary mirror support structure.…”

Section: Wind-buffeting and Control Bandwidthmentioning

confidence: 99%

“…Furthermore, the loads on the secondary structure can couple into the primary mirror causing further optical distortions. 11,14 Broadly speaking, there are three main control challenges faced in developing active optics systems for the next generation of extremely large, 30 m or larger optical telescopes:…”

Section: Introductionmentioning

confidence: 99%

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Control challenges for extremely large telescopes

MacMartin

2003

SPIE Proceedings

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The next generation of large ground-based optical telescopes are likely to involve a highly segmented primary mirror that must be controlled in the presence of wind and other disturbances, resulting in a new set of challenges for control. The current design concept for the California Extremely Large Telescope (CELT) includes 1080 segments in the primary mirror, with the out-of-plane degrees of freedom actively controlled. In addition to the 3240 primary mirror actuators, the secondary mirror of the telescope will also require at least 5 degree of freedom control. The bandwidth of both control systems will be limited by coupling to structural modes. I discuss three control issues for extremely large telescopes in the context of the CELT design, describing both the status and remaining challenges. First, with many actuators and sensors, the cost and reliability of the control hardware is critical; the hardware requirements and current actuator design are discussed. Second, wind buffeting due to turbulence inside the telescope enclosure is likely to drive the control bandwidth higher, and hence limitations resulting from control-structure-interaction must be understood. Finally, the impact on the control architecture is briefly discussed.

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“…Previous papers describe the preliminary design concepts for the active control hardware for CELT, 15 and preliminary analysis of the control problem for CELT 14,[16][17][18] and the Giant Segmented Mirror Telescope (GSMT). 19,20 The control challenges for active optics result primarily from compensating for wind buffeting. Previous work 9 relied on parametric structural models that were validated against finite element models.…”

Section: Introduction and Overviewmentioning

confidence: 99%

Initial Control Results for the Thirty Meter Telescope

MacMynowski

Blaurock

Angeli³

et al. 2005

AIAA Guidance, Navigation, and Control Conference and Exhibit

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The next generation of large ground-based optical telescopes are likely to involve a highly segmented primary mirror that must be controlled in the presence of wind and other disturbances, resulting in a new set of challenges for control. The current design concept for the Thirty Meter Telescope (TMT) has 738 segments in the primary mirror, with the out-of-plane degrees of freedom actively controlled. The secondary mirror also requires at least 5 degree of freedom control. We discuss control issues for extremely large segmented-mirror telescopes and present preliminary simulation results for the current TMT design. The most significant departure from existing telescope control systems is that wind buffeting due to turbulence inside the telescope enclosure drives the desired control bandwidth higher, and hence limitations resulting from control-structure-interaction must be understood. The bandwidth of the main telescope elevation drive is limited by interaction with structural modes. In order to achieve a significant reduction in image motion, a fast tip/tilt control of the secondary requires momentum compensation to mitigate interaction with structural dynamics. Control of the primary mirror segments is limited only by interaction with the segment support resonant frequencies, and not with the "global" modes of the telescope structure.

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Active optics and control architecture for a giant segmented mirror telescope

Cited by 15 publications

References 6 publications

Modeling tools to estimate the performance of the Thirty Meter Telescope: an integrated approach

Modeling tools to estimate the performance of the Thirty Meter Telescope: an integrated approach

Control challenges for extremely large telescopes

Initial Control Results for the Thirty Meter Telescope

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