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Publicações

Publicações por CTM

2015

AO for MOSAIC, the E-ELT multiple object spectrograph

Autores
Morris T.; Basden A.; Buey T.; Chemla F.; Conan J.M.; Correia C.; Dohlen K.; Fusco T.; Gendron E.; Gratadour D.; Jagourel P.; Myers R.; Neichel B.; Petit C.; Rees P.; Rousset G.;

Publicação
Adaptive Optics for Extremely Large Telescopes 4 - Conference Proceedings

Abstract
MOSAIC is the proposed multiple object spectrograph for the E-ELT that will eventually combine two AO observing modes within a single instrument. MOSAIC will contain up to 20 open-loop multiple object AO channels feeding NIR IFUs in addition to up to 200 seeing-limited (or GLAO corrected) VIS - NIR fibre pickoffs. Wavefront tomography will be implemented using a combination of LGS and a few high-order NGS distributed across the field with the wavefront correction applied in a split open/closed loop configuration. MOSAIC will be the only E-ELT instrument planned that can utilize the full 10 arcminute diameter field of view, enabling highly efficient observing modes for this workhorse instrument. Use of the full E-ELT field inevitably requires a closer integration between the telescope control system and the instrument AO systems, however this can bring several potential benefits to overall system performance. Here we present the initial design concept and baseline performance of the MOSAIC instrument and AO system(s) taking advantage of the CANARY on-sky results and inheriting from the previous Phase A study of EAGLE. Finally, we will highlight areas of system performance and calibration that will require further analysis and trade-off during the course of the upcoming Phase A study.

2015

Calibrating the Non-Common Path Aberrations on the MOAO system RAVEN and first science results using RAVEN

Autores
Lamb, M; Andersen, DR; Véran, JP; Correia, C; Lardière, O;

Publicação
Adaptive Optics for Extremely Large Telescopes 4 - Conference Proceedings

Abstract
Contemporary AO systems, such as the Multi-Object Adaptive Optics system (MOAO) RAVEN currently associated with the Subaru Telescope, can suffer from significant Non-Common Path Aberrations (NCPA). These errors ultimately affect image quality and arise from optical path differences between the wavefront sensor (WFS) path and the science path. A typical correction of NCPA involves estimating the aberration phase and correcting the system with an offset on the deformable mirror (DM). We summarize two methods used to correct for NCPA on an experimental bench. We also successfully calibrate the NCPA on RAVEN using one of these methods. Finally, we report on some first science results with RAVEN, obtained after NCPA correction.

2015

On-sky results of Raven, a MOAO science demonstrator at Subaru Telescope

Autores
Lardière, O; Ono, Y; Andersen, D; Bradley, C; Blain, C; Davidge, T; Gamroth, D; Gerard, B; Jackson, K; Lamb, M; Nash, R; Rosensteiner, M; Venn, K; Van Kooten, M; Véran, JP; Correia, C; Oya, S; Hayano, Y; Terada, H; Akiyama, M; Suzuki, G; Schramm, M;

Publicação
Adaptive Optics for Extremely Large Telescopes 4 - Conference Proceedings

Abstract
Raven is a Multi-Object Adaptive Optics science demonstrator which has been used on-sky at Subaru telescope from May 2014 to July 2015. Raven has been developed at the University of Victoria AO Lab, in partnership with NRC, NAOJ and Tohoku University. Raven includes three open loop WFSs, a central laser guide star WFS, and two science pick-off arms feeding light to the Subaru IRCS spectrograph. Raven supports different AO modes: SCAO, open-loop GLAO and MOAO. This paper gives an overview of the instrument design, compares the on-sky performance of the different AO modes and presents some of the science results achieved with MOAO.

2015

Spatio-angular minimum-variance tomographic controller for multi-object adaptive-optics systems

Autores
Correia, CM; Jackson, K; Véran, JP; Andersen, D; Lardière, O; Bradley, C;

Publicação
Applied Optics

Abstract
Multi-object astronomical adaptive optics (MOAO) is now a mature wide-field observation mode to enlarge the adaptive-optics-corrected field in a few specific locations over tens of arcminutes. The work-scope provided by open-loop tomography and pupil conjugation is amenable to a spatio-angular linear-quadratic-Gaussian (SA-LQG) formulation aiming to provide enhanced correction across the field with improved performance over static reconstruction methods and less stringent computational complexity scaling laws. Starting from our previous work [J. Opt. Soc. Am. A 31, 101 (2014)], we use stochastic time-progression models coupled to approximate sparse measurement operators to outline a suitable SA-LQG formulation capable of delivering near optimal correction. Under the spatio-angular framework the wavefronts are never explicitly estimated in the volume, providing considerable computational savings on 10-m-class telescopes and beyond. We find that for Raven, a 10-m-class MOAO system with two science channels, the SA-LQG improves the limiting magnitude by two stellar magnitudes when both the Strehl ratio and the ensquared energy are used as figures of merit. The sky coverage is therefore improved by a factor of ~5. © 2015 Optical Society of America.

2015

Spatio-angular minimum-variance tomographic controller for multi-object adaptive-optics systems

Autores
Correia, CM; Jackson, K; Veran, JP; Andersen, D; Lardiere, O; Bradley, C;

Publicação
APPLIED OPTICS

Abstract
Multi-object astronomical adaptive optics (MOAO) is now a mature wide-field observation mode to enlarge the adaptive-optics-corrected field in a few specific locations over tens of arcminutes. The work-scope provided by open-loop tomography and pupil conjugation is amenable to a spatio-angular linear-quadratic-Gaussian (SA-LQG) formulation aiming to provide enhanced correction across the field with improved performance over static reconstruction methods and less stringent computational complexity scaling laws. Starting from our previous work [J. Opt. Soc. Am. A 31, 101 (2014)], we use stochastic time-progression models coupled to approximate sparse measurement operators to outline a suitable SA-LQG formulation capable of delivering near optimal correction. Under the spatio-angular framework the wavefronts are never explicitly estimated in the volume, providing considerable computational savings on 10-m-class telescopes and beyond. We find that for Raven, a 10-m-class MOAO system with two science channels, the SA-LQG improves the limiting magnitude by two stellar magnitudes when both the Strehl ratio and the ensquared energy are used as figures of merit. The sky coverage is therefore improved by a factor of similar to 5. (C) 2015 Optical Society of America

2015

A microscope for the data centre

Autores
Pereira, N; Tennina, S; Loureiro, J; Severino, R; Saraiva, B; Santos, M; Pacheco, F; Tovar, E;

Publicação
INTERNATIONAL JOURNAL OF SENSOR NETWORKS

Abstract
Data centres are large energy consumers. A large portion of this power consumption is due to the control of physical parameters of the data centre (such as temperature and humidity). However, these physical parameters are tightly coupled with computations, and even more so in upcoming data centres, where the location of workloads can vary substantially due, for example, to workloads being moved in the cloud infrastructure hosted in the data centre. Therefore, managing the physical and compute infrastructure of a large data centre is an embodiment of a cyber-physical system (CPS). In this paper, we describe a data collection and distribution architecture that enables gathering physical parameters of a large data centre at a very high temporal and spatial resolution of the sensor measurements. We detail this architecture and define the structure of the underlying messaging system that is used to collect and distribute the data.

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