986 research outputs found
Optical turbulence forecast in the Adaptive Optics realm
(35-words maximum) In this talk I present the scientific drivers related to
the optical turbulence forecast applied to the ground-based astronomy supported
by Adaptive Optics, the state of the art of the achieved results and the most
relevant challenges for future progresses.Comment: 1 figure, Orlando, Florida United States, 25 - 28 June 2018, ISBN:
978-1-943580-44-6,Turbulence & Propagation, JW5I.1 Adaptive Optics: Analysis,
Methods and System
Forecast of surface layer meteorological parameters at Cerro Paranal with a mesoscale atmospherical model
This article aims at proving the feasibility of the forecast of all the most
relevant classical atmospherical parameters for astronomical applications (wind
speed and direction, temperature) above the ESO ground-base site of Cerro
Paranal with a mesoscale atmospherical model called Meso-Nh. In a precedent
paper we have preliminarily treated the model performances obtained in
reconstructing some key atmospherical parameters in the surface layer 0-30~m
studying the bias and the RMSE on a statistical sample of 20 nights. Results
were very encouraging and it appeared therefore mandatory to confirm such a
good result on a much richer statistical sample. In this paper, the study was
extended to a total sample of 129 nights between 2007 and 2011 distributed in
different parts of the solar year. This large sample made our analysis more
robust and definitive in terms of the model performances and permitted us to
confirm the excellent performances of the model. Besides, we present an
independent analysis of the model performances using the method of the
contingency tables. Such a method permitted us to provide complementary key
informations with respect to the bias and the RMSE particularly useful for an
operational implementation of a forecast system.Comment: 20 pages, 8 figures, 18 tables, published in MNRA
International Conference on Adaptive Optics for Extremely Large Telescopes III
The third edition of the International Conference on Adaptive Optics systems for extremely large telescopes took place in Florence on May 2013. These systems make it possible to obtain astronomical images with ground-based telescopes of similar, or in some cases even higher, spatial resolution than that achieved by space-borne telescopes in orbit beyond the Earth’s atmosphere. Among the highlights of the Conference: discussion on the status of the systems to be mounted on next-generation telescopes with diameters greater than 30-40 meters
Forecasts of the atmospherical parameters close to the ground at the LBT site in the context of the ALTA project
In this paper we study the abilities of an atmospherical mesoscale model in forecasting the classical atmospherical parameters relevant for astronomical applications at the surface layer (wind speed, wind direction, temperature, relative humidity) on the Large Binocular Telescope (LBT) site - Mount Graham, Arizona. The study is carried out in the framework of the ALTA project aiming at implementing an automated system for the forecasts of atmospherical parameters (Meso-Nh code) and the optical turbulence (Astro-Meso-Nh code) for the service-mode operation of the LBT. The final goal of such an operational tool is to provide predictions with high time frequency of atmospheric and optical parameters for an optimized planning of the telescope operation (dome thermalization, wind-dependent dome orientation, observation planning based on predicted seeing, adaptive optics optimization, etc...). Numerical simulations are carried out with the Meso-Nh and Astro-Meso-Nh codes, which were proven to give excellent results in previous studies focused on the two ESO sites of Cerro Paranal and Cerro Armazones (MOSE Project). In this paper we will focus our attention on the comparison of atmospherical parameters forescasted by the model close to the ground with measurements taken by the observatory instrumentations and stored in the LBT telemetry in order to validate the numerical predictions. As previously done for Cerro Paranal (Lascaux et al., 2015), we will also present an analysis of the model performances based on the method of the contingency tables, that allows us to provide complementary key information with the respect to the bias and RMSE (systematic and statistical errors), such as the percentage of correct detection and the probability to obtain a correct detection inside a defined interval of values
Forecasting surface-layer atmospheric parameters at the Large Binocular Telescope site
In this paper, we quantify the performance of an automated weather forecast system implemented on the Large Binocular Telescope (LBT) site at Mt Graham (Arizona) in forecasting the main atmospheric parameters close to the ground. The system employs a mesoscale non-hydrostatic numerical model (Meso-Nh). To validate the model, we compare the forecasts of wind speed, wind direction, temperature and relative humidity close to the ground with the respective values measured by instrumentation installed on the telescope dome. The study is performed over a large sample of nights uniformly distributed over 2 yr. The quantitative analysis is done using classical statistical operators [bias, root-mean-square error (RMSE) and σ] and contingency tables, which allows us to extract complementary key information, such as the percentage of correct detections (PC) and the probability of obtaining a correct detection within a defined interval of values (POD). The results of our study indicate that the model performance in forecasting the atmospheric parameters we have just cited are very good, in some cases excellent: RMSE for temperature is below 1°C, for relative humidity it is 14 per cent and for the wind speed it is around 2.5 m s-1. The relative error of the RMSE for wind direction varies from 9 to 17 per cent depending on the wind speed conditions. This work is performed in the context of the ALTA (Advanced LBT Turbulence and Atmosphere) Center project, whose final goal is to provide forecasts of all the atmospheric parameters and the optical turbulence to support LBT observations, adaptive optics facilities and interferometric facilities
Dealing with the forecast of the optical turbulence as a tool to support astronomy assisted by AO facilities
In the context of the research activities related to the forecast of the optical turbulence and the atmospherical parameters being relevant for ground-based astronomy we focus here our attention on two specific topics: 1. pros and cons of different solutions to supply wind speed and direction stratification on the whole atmosphere all along a night to support AO facilities; 2. the necessity of instrumentation for optical turbulence monitoring (vertical profiles on the whole atmosphere) to be used operationally. In the last two decades the development and the use of different vertical profilers covering the whole atmosphere or part of it in application to the astronomy took place. Several instruments based on different principles (with associated pros and cons) have been applied in different contexts in astronomy with a main use in the site characterization and site selection. Time changed and the necessity of the astronomy supported by AO facilities is much more demanding with a diversification of applications. Recently, motivated by a precise necessity related to the identification of an absolute reference to carry out studies on optical turbulence forecasts (MOSE project), we carried out a verification of the reliability of a few instruments that lead us to put in evidence some limitations for a few of them. At the same time such a detailed analysis permitted us to clarify the nature of some astroclimatic parameters. The main conclusion at which we arrived is two-fold. From one side we could trace a list of warnings related to different uses of such instruments. On the other side we could identify open problems that indicate that there is still space for research in the field of turbulence monitoring in application to the astronomy. Some suggestions are proposed
Numerical control matrix rotation for the LINC-NIRVANA Multi-Conjugate Adaptive Optics system
LINC-NIRVANA will realize the interferometric imaging focal station of the
Large Binocular Telescope. A double Layer Oriented multi-conjugate adaptive
optics system assists the two arms of the interferometer, supplying high order
wave-front correction. In order to counterbalance the field rotation,
mechanical derotation for the two ground wave-front sensors, and optical
derotators for the mid-high layers sensors fix the positions of the focal
planes with respect to the pyramids aboard the wave-front sensors. The
derotation introduces pupil images rotation on the wavefront sensors: the
projection of the deformable mirrors on the sensor consequently change. The
proper adjustment of the control matrix will be applied in real-time through
numerical computation of the new matrix. In this paper we investigate the
temporal and computational aspects related to the pupils rotation, explicitly
computing the wave-front errors that may be generated.Comment: 6 pages, 2 figures, presented at SPIE Symposium "Astronomical
Telescopes and Instrumentation'' conference "Adaptive Optics Systems
II'',Sunday 27 June 2010, San Diego, California, US
SCExAO as a precursor to an ELT exoplanet direct imaging instrument
The Subaru Coronagraphic Extreme AO (SCExAO) instrument consists of a high
performance Phase Induced Amplitude Apodisation (PIAA) coronagraph combined
with an extreme Adaptive Optics (AO) system operating in the near-infrared (H
band). The extreme AO system driven by the 2000 element deformable mirror will
allow for Strehl ratios >90% to be achieved in the H-band when it goes closed
loop. This makes the SCExAO instrument a powerful platform for high contrast
imaging down to angular separations of the order of 1lambda/D and an ideal
testbed for exploring coronagraphic techniques for ELTs. In this paper we
report on the recent progress in regards to the development of the instrument,
which includes the addition of a visible bench that makes use of the light at
shorter wavelengths not currently utilized by SCExAO and closing the loop on
the tip/tilt wavefront sensor. We will also discuss several exciting guest
instruments which will expand the capabilities of SCExAO over the next few
years; namely CHARIS which is a integral field spectrograph as well as
VAMPIRES, a visible aperture masking experiment based on polarimetric analysis
of circumstellar disks. In addition we will elucidate the unique role extreme
AO systems will play in enabling high precision radial velocity spectroscopy
for the detection of small companions.Comment: 7 pages, 2 figures Proceedings of AO4ELTs3 conference, paper 13396,
Florence, Italy, May 201
Operational optical turbulence forecast for the service mode of top-class ground based telescopes
In this contribution we present the most relevant results obtained in the context of a feasibility study (MOSE) undertaken for ESO. The principal aim of the project was to quantify the performances of an atmospherical non-hydrostatical mesoscale model (Astro-Meso-NH code) in forecasting all the main atmospherical parameters relevant for the ground-based astronomical observations and the optical turbulence (CN2 and associated integrated astroclimatic parameters) above Cerro Paranal (site of the VLT) and Cerro Armazones (site of the E-ELT). A detailed analysis on the score of success of the predictive capacities of the system have been carried out for all the astroclimatic as well as for the atmospherical parameters. Considering the excellent results that we obtained, this study proved the opportunity to implement on these two sites an automatic system to be run nightly in an operational configuration to support the scheduling of scientific programs as well as of astronomical facilities (particularly those supported by AO systems) of the VLT and the E-ELT. At the end of 2016 a new project for the implementation of a demonstrator of an operational system to be run on the two ESO's sites will start. The fact that the system can be run simultaneously on the two sites is an ancillary appealing feature of the system. Our team is also responsible for the implementation of a similar automatic system at Mt.Graham, site of the LBT (ALTA Project). Our system/method will permit therefore to make a step ahead in the framework of the Service Mode for new generation telescopes. Among the most exciting achieved results we cite the fact that we proved to be able to forecast CN2 profiles with a vertical resolution as high as 150 m. Such a feature is particularly crucial for all WFAO systems that require such detailed information on the OT vertical stratification on the whole 20 km above the ground. This important achievement tells us that all the WFAO systems can rely on automatic systems that are able to support their optimized use. <P /
- …