Sky coverage and tip/tilt error analysis for TMT

Clare, Richard; Ellerbroek, Brent L.; Véran, Jean-Pierre; Herriot, Glen; Andersen, David R.

doi:10.1117/12.669680

Cited by 4 publications

(6 citation statements)

References 17 publications

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“…9 This code evaluates the overall tip/tilt error associated with each randomly generated NGS asterism, accounting for the combined effects of anisoplanatism, servo lag, WFS noise, telescope windshake, and any partial "sharpening" of the NGS images provided by the LGS AO system. Low-order (but tip-tilt removed)…”

Section: Performance Modelingmentioning

confidence: 99%

NFIRAOS: TMT narrow field near-infrared facility adaptive optics

et al. 2006

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Although many of the instruments planned for the TMT (Thirty Meter Telescope) have their own closely-coupled adaptive optics systems, TMT will also have a facility Adaptive Optics (AO) system, NFIRAOS, feeding three instruments on the Nasmyth platform. This Narrow-Field Infrared Adaptive Optics System, employs conventional deformable mirrors with large diameters of about 300 mm. The requirements for NFIRAOS include 1.0-2.5 microns wavelength range, 30 arcsecond diameter science field of view (FOV), excellent sky coverage, and diffraction-limited atmospheric turbulence compensation (specified at 133 nm RMS including residual telescope and science instrument errors.) The reference design for NFIRAOS includes six sodium laser guide stars over a 70 arcsecond FOV, and multiple infrared tip/tilt sensors and a natural guide star focus sensor within instruments. Larger telescopes require greater deformable mirror (DM) stroke. Although initially NFIRAOS will correct a 10 arcsecond science field, it uses two deformable mirrors in series, partly to provide sufficient stroke for atmospheric correction over the 30 m telescope aperture, but mainly to improve sky coverage by sharpening near-IR natural guide stars over a 2 arcminute diameter "technical" field. The planned upgrade to full performance includes replacing the ground-conjugated DM with a higher actuator density, and using a deformable telescope secondary mirror as a "woofer." NFIRAOS feeds three live instruments: a near-Infrared integral field Imaging spectrograph, a near-infrared echelle spectrograph, and after upgrading NFIRAOS to full multi-conjugation, a wide field (30 arcsecond) infrared camera.

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Section: Performance Modelingmentioning

confidence: 99%

NFIRAOS: TMT narrow field near-infrared facility adaptive optics

et al. 2006

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“…The model assumes perfect TTF correction in the field using a sufficient number of natural guide star WFSs (see [9] for sky coverage).…”

Section: Beacon Typementioning

confidence: 99%

Constraining the GLAO parameter space with turbulence profile models

Stoesz

2006

SPIE Proceedings

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Nature provides reduced turbulence at intermediate altitudes and as a result the mean image quality of a ground layer adaptive optics (GLAO) corrected field degrades slowly with increasing diameter. If this function has a shallow slope all the way out to the maximum seeing limited field of view of the telescope then surveys at that telescope may significantly benefit from GLAO. Using published optical turbulence profile models for Cerro Pachon we show that the GLAO gains require that the full seeing limited field of view be corrected for two example telescopes, each attempting two example science cases. We also show that using only four sodium laser guide stars the very wide GLAO system with optimal actuator and subaperture pitch will not be affected by servo lag and wavefront sensor noise.

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“…The tip/tilt error for 50 per cent sky coverage at the galactic pole is estimated to be about 65 nm RMS wavefront error (including both turbulenceinduced tip/tilt jitter and telescope wind shake effects), under the assumption that IR detectors arrays with 5-10 electrons of read out noise at frame rates of approximately 500 Hz will be available. 21 Unlike most existing AO systems, NFIRAOS does not include a separate steering mirror for tip/tilt compensation. The ground-layer DM is instead mounted on a tip/tilt stage to avoid the additional optical surfaces which would be necessary using the conventional approach.…”

Section: Narrow Field Ir Ao System (Nfiraos)mentioning

confidence: 99%

“…Additional LGS AO modeling capabilities include a Monte Carlo sky coverage simulator for systems which employ multiple tip/tilt natural guide stars such as MCAO and MOAO. 21 This code evaluates the overall tip/tilt error associated with each randomly generated NGS asterism, accounting for the combined effects of anisoplanatism, servo lag, WFS noise, telescope windshake, and any partial "sharpening" of the NGS images provided by the LGS AO system. Loworder (but tip-tilt removed)…”

Section: Simulation and Analysismentioning

confidence: 99%

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A conceptual design for the Thirty Meter Telescope adaptive optics systems

et al. 2006

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In this paper, we provide an overview of the adaptive optics (AO) program for the Thirty Meter Telescope (TMT) project, including an update on requirements; the philosophical approach to developing an overall AO system architecture; the recently completed conceptual designs for facility and instrument AO systems; anticipated first light capabilities and upgrade options; and the hardware, software, and controls interfaces with the remainder of the observatory. Supporting work in AO component development, lab and field tests, and simulation and analysis is also discussed. Further detail on all of these subjects may be found in additional papers in this conference.

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Sky coverage and tip/tilt error analysis for TMT

Cited by 4 publications

References 17 publications

NFIRAOS: TMT narrow field near-infrared facility adaptive optics

NFIRAOS: TMT narrow field near-infrared facility adaptive optics

Constraining the GLAO parameter space with turbulence profile models

A conceptual design for the Thirty Meter Telescope adaptive optics systems

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