Thirty Meter Telescope Observatory Corporation

San Jose, CA, United States

Thirty Meter Telescope Observatory Corporation

San Jose, CA, United States
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Uchimoto Y.K.,Tohoku University | Uchimoto Y.K.,University of Tokyo | Uchimoto Y.K.,Japan National Astronomical Observatory | Yamada T.,Tohoku University | And 14 more authors.
Astrophysical Journal | Year: 2012

We present the results of wide-field deep JHK imaging of the SSA22 field using the MOIRCS instrument equipped with the Subaru telescope. The observed field is 112 arcmin2 in area, which covers the z = 3.1 protocluster characterized by the overdensities of Lyα emitters (LAEs) and Lyα blobs (LABs). The 5σ limiting magnitude is K AB = 24.3. We extract the potential protocluster members from the K-selected sample by using the multi-band photometric-redshift selection as well as the simple color cut for distant red galaxies (DRGs; J - K AB > 1.4). The surface number density of DRGs in our observed fields shows clear excess compared with those in the blank fields, and the location of the densest area whose projected overdensity is twice the average coincides with the large-scale density peak of LAEs. We also found that K-band counterparts with z phot ≃ 3.1 are detected for 75% (15/20) of the LABs within their Lyα halo, and the 40% (8/20) of LABs have multiple components, which gives a direct evidence of the hierarchical multiple merging in galaxy formation. The stellar mass of LABs correlates with their luminosity, isophotal area, and the Lyα velocity widths, implying that the physical scale and the dynamical motion of Lyα emission are closely related to their previous star formation activities. Highly dust-obscured galaxies such as hyper extremely red objects (J - K AB > 2.1) and plausible K-band counterparts of submillimeter sources are also populated in the high-density region. © 2012. The American Astronomical Society. All rights reserved.


Gilles L.,Thirty Meter Telescope Observatory Corporation | Massioni P.,CNRS Ampere Laboratory | Kulcsar C.,University Paris - Sud | Raynaud H.-F.,University Paris - Sud | Ellerbroek B.,Thirty Meter Telescope Observatory Corporation
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2013

This paper discusses the performance and cost of two computationally efficient Fourier-based tomographic wavefront reconstruction algorithms for wide-field laser guide star (LGS) adaptive optics (AO). The first algorithm is the iterative Fourier domain preconditioned conjugate gradient (FDPCG) algorithm developed by Yang et al. [Appl. Opt. 45, 5281 (2006)], combined with pseudo-open-loop control (POLC). FDPCG's computational cost is proportional to N log(N), where N denotes the dimensionality of the tomography problem. The second algorithm is the distributed Kalman filter (DKF) developed by Massioni et al. [J. Opt. Soc. Am. A 28, 2298 (2011)], which is a noniterative spatially invariant controller. When implemented in the Fourier domain, DKF's cost is also proportional to N log(N). Both algorithms are capable of estimating spatial frequency components of the residual phase beyond the wavefront sensor (WFS) cutoff frequency thanks to regularization, thereby reducing WFS spatial aliasing at the expense of more computations. We present performance and cost analyses for the LGS multiconjugate AO system under design for the Thirty Meter Telescope, as well as DKF's sensitivity to uncertainties in wind profile prior information. We found that, provided the wind profile is known to better than 10% wind speed accuracy and 20 deg wind direction accuracy, DKF, despite its spatial invariance assumptions, delivers a significantly reduced wavefront error compared to the static FDPCG minimum variance estimator combined with POLC. Due to its nonsequential nature and high degree of parallelism, DKF is particularly well suited for real-time implementation on inexpensive off-the-shelf graphics processing units. © 2013 Optical Society of America.


Massioni P.,University Claude Bernard Lyon 1 | Gilles L.,Thirty Meter Telescope Observatory Corporation | Ellerbroek B.,Thirty Meter Telescope Observatory Corporation
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2015

In the framework of adaptive optics (AO) for astronomy, it is a common assumption to consider the atmospheric turbulent layers as "frozen flows" sliding according to the wind velocity profile. For this reason, having knowledge of such a velocity profile is beneficial in terms of AO control system performance. In this paper we show that it is possible to exploit the phase estimate from a Kalman filter running on an AO system in order to estimate wind velocity. This allows the update of the Kalman filter itself with such knowledge, making it adaptive. We have implemented such an adaptive controller based on the distributed version of the Kalman filter, for a realistic simulation of a multi-conjugate AO system with laser guide stars on a 30 m telescope. Simulation results show that this approach is effective and promising and the additional computational cost with respect to the distributed filter is negligible. Comparisons with a previously published slope detection and ranging wind profiler are made and the impact of turbulence profile quantization is assessed. One of the main findings of the paper is that all flavors of the adaptive distributed Kalman filter are impacted more significantly by turbulence profile quantization than the static minimum mean square estimator which does not incorporate wind profile information. © 2015 Optical Society of America.


Gilles L.,Thirty Meter Telescope Observatory Corporation | Correia C.,National Research Council Canada | Veran J.-P.,National Research Council Canada | Wang L.,Thirty Meter Telescope Observatory Corporation | Ellerbroek B.,Thirty Meter Telescope Observatory Corporation
Applied Optics | Year: 2012

This paper discusses an innovative simulation model based approach for long exposure atmospheric point spread function (PSF) reconstruction in the context of laser guide star (LGS) multiconjugate adaptive optics (MCAO). The approach is inspired from the classical scheme developed by Véran et al. [J. Opt. Soc. Am. A 14, 3057 (1997)] and Flicker et al. [Astron. Astrophys. 400, 1199 (2003)] and reconstructs the long exposure optical transfer function (OTF), i.e., the Fourier transformed PSF, as a product of separate long-exposure tip/tilt removed and tip/tilt OTFs, each estimated by postprocessing system and simulation telemetry data. Sample enclosed energy results assessing reconstruction accuracy are presented for the Thirty Meter Telescope LGS MCAO system currently under design and show that percent level absolute and differential photometry over a 30 arcsec diameter field of view are achievable provided the simulation model faithfully represents the real system. © 2012 Optical Society of America.


Gilles L.,Thirty Meter Telescope Observatory Corporation | Massioni P.,CNRS Ampere Laboratory | Ellerbroek B.,Thirty Meter Telescope Observatory Corporation
Adaptive Optics: Analysis, Methods and Systems, AO 2015 | Year: 2015

We report on an Adaptive Distributed Kalman Filter (ADKF) for laser guide star tomography on extremely large telescopes capable of achieving the same performance level as the static minimum variance reconstructor (MVR) at a fraction of the computational cost. © 2015 OSA.


Gilles L.,Thirty Meter Telescope Observatory Corporation | Correia C.,Herzberg Institute for Astrophysics | Veran J.P.,Herzberg Institute for Astrophysics | Wang L.,Thirty Meter Telescope Observatory Corporation | Ellerbroek B.L.,Thirty Meter Telescope Observatory Corporation
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

In adaptive optics systems employing laser guide stars, the tip/tilt contribution to the long exposure point spread function must be estimated separately from the high-order tip/tilt removed point spread function because this component is estimated separately from a single or multiple low-order natural guide star wavefront sensors. This paper investigates this problem for laser guide star multi conjugate adaptive optics. The approach is based on the scheme developed by Flicker in 2003 [1], and consists in post-processing the measurement covariance matrix of multiple low-order natural guide star wavefront sensors controlling tip/tilt and tilt anisoplanatism. An innovative simulation model based "balanced" algorithm is introduced to capture error terms not accounted for in Flicker's algorithm. Sample enclosed energy results for the Thirty Meter Telescope multi conjugate adaptive optics system demonstrate the superiority of the balanced method and call for further analytical work and experimental validation. © 2012 SPIE.


Correia C.,Herzberg Institute for Astrophysics | Veran J.-P.,Herzberg Institute for Astrophysics | Herriot G.,Herzberg Institute for Astrophysics | Ellerbroek B.,Thirty Meter Telescope Observatory Corporation | And 2 more authors.
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2013

Laser-guide-star multiconjugate adaptive optics (MCAO) systems require natural guide stars (NGS) to measure tilt and tilt-anisoplanatism modes. Making optimal use of the limited number of photons coming from such, generally dim, sources is mandatory to obtain reasonable sky coverage, i.e., the probability of finding asterisms amenable to NGS wavefront (WF) sensing for a predefined WF error budget. This paper presents a Strehl-optimal (minimum residual variance) spatiotemporal reconstructor merging principles of modal atmospheric tomography and optimal stochastic control theory. Simulations of NFIRAOS, the first light MCAO system for the thirty-meter telescope, using ~500 typical NGS asterisms, show that the minimum-variance (MV) controller delivers outstanding results, in particular for cases with relatively dim stars (down to magnitude 22 in the H-band), for which lowtemporal frame rates (as low as 16 Hz) are required to integrate enough flux. Over all the cases tested ~21 nm rms median improvement in WF error can be achieved with the MV compared to the current baseline, a type-II controller based on a double integrator. This means that for a given level of tolerable residual WF error, the sky coverage is increased by roughly 10%, a quite significant figure. The improvement goes up to more than 20% when compared with a traditional single-integrator controller. © 2013 Optical Society of America.


Gilles L.,Thirty Meter Telescope Observatory Corporation | Ellerbroek B.L.,Thirty Meter Telescope Observatory Corporation
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2010

Real-time turbulence profiling is necessary to tune tomographic wavefront reconstruction algorithms for widefield adaptive optics (AO) systems on large to extremely large telescopes, and to perform a variety of image post-processing tasks involving point-spread function reconstruction. This paper describes a computationally efficient and accurate numerical technique inspired by the slope detection and ranging (SLODAR) method to perform this task in real time from properly selected Shack-Hartmann wavefront sensor measurements accumulated over a few hundred frames from a pair of laser guide stars, thus eliminating the need for an additional instrument. The algorithm is introduced, followed by a theoretical influence function analysis illustrating its impulse response to high-resolution turbulence profiles. Finally, its performance is assessed in the context of the Thirty Meter Telescope multi-conjugate adaptive optics system via end-to-end wave optics Monte Carlo simulations. © 2010 Optical Society of America.


Gilles L.,Thirty Meter Telescope Observatory Corporation | Ellerbroek B.,Thirty Meter Telescope Observatory Corporation
3rd AO4ELT Conference - Adaptive Optics for Extremely Large Telescopes | Year: 2013

This paper discusses a wind profile estimation algorithm for laser guide star tomography adaptive optics systems, which generalizes a previously published slope detection and ranging turbulence profiler [Gilles and Ellerbroek, J. Opt. Soc. Am. A27, A76 (2010)] to the case of spatio-temporal cross-correlations between a single or multiple pairs of wavefront sensors. The estimated wind profile is fed to a computationally efficient Distributed Kalman Filter to perform atmospheric tomography. Residual wavefront error is assessed for the Thirty Meter Telescope and compared to that of a static, single-frame, minimum mean square error estimator. We found that the superior turbulence rejection of the Kalman filter is a delicate feature requiring wind profile estimation to better than ~20% accuracy.


Kornilov V.,Moscow State University | Sarazin M.,European Southern Observatory | Tokovinin A.,Cerro Tololo Inter American Observatory | Travouillon T.,Thirty Meter Telescope Observatory Corporation | Voziakova O.,Moscow State University
Astronomy and Astrophysics | Year: 2012

Aims. Scintillation noise is a major limitation of ground-based photometric precision. Methods. An extensive dataset of stellar scintillation collected at 11 astronomical sites world-wide with MASS instruments was used to estimate the scintillation noise of large telescopes in the fast photometry and traditional long-exposure regime. Results. Statistical distributions of the corresponding parameters are given. The scintillation noise is mostly determined by turbulence and wind in the upper atmosphere and is comparable at all sites, with slightly lower values at Mauna Kea and the highest noise at Tolonchar in Chile. We show that the classical Young's formula underestimates the scintillation noise. The temporal variations of the scintillation noise are also similar at all sites, showing short-term variability at time scales of 1-2 h and slower variations, including marked seasonal trends (stronger scintillation and less clear sky during local winter). Some correlation was found between nearby observatories. © ESO, 2012.

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