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Zhang X.-F.,Beijing Institute of Technology | Wang L.-Q.,Thirty Meter Telescope Project
Research in Astronomy and Astrophysics

Adaptive optics (AO), which provides diffraction limited imaging over a field-of-view (FOV), is a powerful technique for solar observation. In the tomographic approach, each wavefront sensor (WFS) is looking at a single reference that acts as a guide star. This allows a 3D reconstruction of the distorted wavefront to be made. The correction is applied by one or more deformable mirrors (DMs). This technique benefits from information about atmospheric turbulence at different layers, which can be used to reconstruct the wavefront extremely well. With the assistance of the MAOS software package, we consider the tomography errors and WFS aliasing errors, and focus on how the performance of a solar telescope (pointing toward zenith) is related to atmospheric anisoplanatism. We theoretically quantify the performance of the tomographic solar AO system. The results indicate that the tomographic AO system can improve the average Strehl ratio of a solar telescope in a 10″-80″ diameter FOV by only employing one DM conjugated to the telescope pupil. Furthermore, we discuss the effects of DM conjugate altitude on the correction achievable by the AO system by selecting two atmospheric models that differ mainly in terms of atmospheric properties at ground level, and present the optimum DM conjugate altitudes for different observation sites. © 2014 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd. Source

Wang L.,Thirty Meter Telescope Project | Ellerbroek B.,Thirty Meter Telescope Project
Proceedings of SPIE - The International Society for Optical Engineering

The adaptive optics (AO) simulations at the Thirty Meter Telescope (TMT) have been carried out using the efficient, C based multi-threaded adaptive optics simulator (MAOS, http://github.com/lianqiw/maos). By porting time-critical parts of MAOS to graphical processing units (GPU) using NVIDIA CUDA technology, we achieved a 10 fold speed up for each GTX 580 GPU used compared to a modern quad core CPU. Each time step of full scale end to end simulation for the TMT narrow field infrared AO system (NFIRAOS) takes only 0.11 second in a desktop with two GTX 580s. We also demonstrate that the TMT minimum variance reconstructor can be assembled in matrix vector multiply (MVM) format in 8 seconds with 8 GTX 580 GPUs, meeting the TMT requirement for updating the reconstructor. We also benchmarked applying MVM in GPUs and got 1.7 ms end-to-end latency with 7 GTX 580 GPUs. © 2012 SPIE. Source

MacMartin D.G.,Thirty Meter Telescope Project | Thompson H.,Thirty Meter Telescope Project
3rd AO4ELT Conference - Adaptive Optics for Extremely Large Telescopes

In order for TMT to deliver the required adaptive optics (AO) image quality, vibration sources throughout the observatory need to be understood and their resulting optical response characterized. The sensitivity to vibration has been determined using a finite element model of the telescope structure and mirror segments coupled to optical models. Frequency dependent models of the AO, active optics and mount control systems are included allowing end-to-end assessment of vibration sources on AO-corrected image quality; future work will improve estimates of the propagation of vibrations from equipment in the summit support building and enclosure to the telescope pier. Modeling separately predicts effects on image jitter caused by relative rigid body motion of main optical elements, and the dynamic motion of the 492 individual primary mirror segments. These results have been used to develop allocated requirements on source amplitudes at different locations and as a function of frequency, which will lead to subsystem design requirements (e.g. for isolation systems at various locations both in the support building and enclosure and on the telescope structure). In order to meet an aggressive target for this contribution to the AO error budget, vibration forces on the telescope itself must be limited to a few Newtons in the most sensitive frequency range of 5-20Hz; larger forces of order 100N can be tolerated for equipment mounted off the telescope in the summit facilities building. Source

Wang L.,Thirty Meter Telescope Project | Andersen D.,Herzberg Institute for Astrophysics | Ellerbroek B.,Thirty Meter Telescope Project
Applied Optics

The scientific productivity of laser guide star adaptive optics systems strongly depends on the sky coverage, which describes the probability of finding natural guide stars for the tip/tilt wavefront sensor(s) to achieve a certain performance. Knowledge of the sky coverage is also important for astronomers planning their observations. In this paper, we present an efficient method to compute the sky coverage for the laser guide star multiconjugate adaptive optics system, the Narrow Field Infrared Adaptive Optics System (NFIRAOS), being designed for the Thirty Meter Telescope project.We show that NFIRAOS can achieve more than 70% sky coverage over most of the accessible sky with the requirement of 191 nm total rms wavefront. © 2012 Optical Society of America. Source

Rogers J.,Thirty Meter Telescope Project | Thompson H.,Thirty Meter Telescope Project
Proceedings of SPIE - The International Society for Optical Engineering

The Thirty Meter Telescope is comprised of thirty five individual sub-systems which include optical systems, instruments, adaptive optics systems, controls, mechanical systems, supporting software and hardware and the infrastructure required to support their operation. These thirty five sub-systems must operate together as a system to enable the telescope to meet the science cases for which it is being developed. These science cases are formalized and expressed as science requirements by the project's Science Advisory Committee. From these, a top down requirements engineering approach is used within the project to derive consistent operational, architectural and ultimately detailed design requirements for the sub-systems. The various layers of requirements are stored within a DOORS requirements database that also records the links between requirements, requirement rationale and requirement history. This paper describes the development of the design requirements from science cases, the reasons for recording the links between requirements and the benefits that documenting this traceability will yield during the design and verification of the telescope. Examples are given of particular science cases, the resulting operational and engineering requirements on the telescope system and how individual sub-systems will contribute to these being met. © 2010 Copyright SPIE - The International Society for Optical Engineering. Source

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