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

A dedicated tool for a full 3D Cn2 investigation

We present in this study a mapping of the optical turbulence (OT) above different astronomical sites. The mesoscale model Meso-NH was used together with the Astro-Meso-Nh package and a set of diagnostic tools allowing for a full 3D investigation of the Cn2. The diagnostics implemented in the Astro-Meso-Nh, allowing for a full 3D investigation of the OT structure in a volumetric space above different sites, are presented. To illustrate the different diagnostics and their potentialities, we investigated one night and looked at instantaneous fields of meteorologic and astroclimatic parameters. To show the potentialities of this tool for applications in an Observatory we ran the model above sites with very different OT distributions: the antarctic plateau (Dome C, Dome A, South Pole) and a mid-latitude site (Mt. Graham, Arizona). We put particular emphasis on the 2D maps of integrated astroclimatic parameters (seeing, isoplanatic angles) calculated in different slices at different heights in the troposhere. This is an useful tool of prediction and investigation of the turbulence structure. It can support the optimization of the AO, GLAO and MCAO systems running at the focus of the ground-based telescopes.From this studies it emerges that the astronomical sites clearly present different OT behaviors. Besides, our tool allowed us for discriminating these sites.Comment: 7 pages, 5 figures, SPIE 2010 conferenc

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

Forecasting water vapour above the sites of ESO's Very Large Telescope (VLT) and the Large Binocular Telescope (LBT)

Water vapour in the atmosphere is the main source of the atmospheric opacity in the infrared and sub-millimetric regimes and its value plays a critical role in observations done with instruments working at these wavelengths on ground-based telescopes. The scheduling of scientific observational programs with instruments such as the VLT Imager and Spectrometer for mid Infrared (VISIR) at Cerro Paranal and the Large Binocular Telescope Interferometer (LBTI) at Mount Graham would definitely benefit from the ability to forecast the atmospheric water vapour content. In this contribution we present a study aiming at validating the performance of the non-hydrostatic mesoscale Meso-NH model in reliably predicting precipitable water vapour (PWV) above the two sites. For the VLT case we use, as a reference, measurements done with a Low Humidity and Temperature PROfiling radiometer (LHATPRO) that, since a few years, is operating routinely at the VLT. LHATPRO has been extensively validated on previous studies. We obtain excellent performances on forecasts performed with this model, including for the extremely low values of the PWV (<= 1 mm). For the LBTI case we compare one solar year predictions obtained with the Meso-NH model with satellite estimates again obtaining an excellent agreement. This study represents a further step in validating outputs of atmospheric parameters forecasts from the ALTA Center, an operational and automatic forecast system conceived to support observations at LBT and LBTI.Comment: 15 pages, 8 figures, 11 tables, MNRAS accepted on 28 November 201

Meso-Nh simulations of the atmospheric flow above the Internal Antarctic Plateau

Mesoscale model such as Meso-Nh have proven to be highly reliable in reproducing 3D maps of optical turbulence (see Refs. 1, 2, 3, 4) above mid-latitude astronomical sites. These last years ground-based astronomy has been looking towards Antarctica. Especially its summits and the Internal Continental Plateau where the optical turbulence appears to be confined in a shallow layer close to the icy surface. Preliminary measurements have so far indicated pretty good value for the seeing above 30-35 m: 0.36" (see Ref. 5) and 0.27" (see Refs. 6, 7) at Dome C. Site testing campaigns are however extremely expensive, instruments provide only local measurements and atmospheric modelling might represent a step ahead towards the search and selection of astronomical sites thanks to the possibility to reconstruct 3D Cn2 maps over a surface of several kilometers. The Antarctic Plateau represents therefore an important benchmark test to evaluate the possibility to discriminate sites on the same plateau. Our group8 has proven that the analyses from the ECMWF global model do not describe with the required accuracy the antarctic boundary and surface layer in the plateau. A better description could be obtained with a mesoscale meteorological model. In this contribution we present the progress status report of numerical simulations (including the optical turbulence - Cn2) obtained with Meso-Nh above the internal Antarctic Plateau. Among the topic attacked: the influence of different configurations of the model (low and high horizontal resolution), use of the grid-nesting interactive technique, forecasting of the optical turbulence during some winter nights.Comment: 12 pages, 4 figures, SPIE 2008 conferenc

Meteorologic parameters analysis above Dome C made with ECMWF data

In this paper we present the characterization of all the principal meteorological parameters (wind speed and direction, pressure, absolute and potential temperature) extended over 25 km from the ground and over two years (2003 and 2004) above the Antarctic site of Dome C. The data set is composed by 'analyses' provided by the General Circulation Model (GCM) of the European Center for Medium Weather Forecasts (ECMWF) and they are part of the catalog MARS. A monthly and seasonal (summer and winter time) statistical analysis of the results is presented. The Richardson number is calculated for each month of the year over 25 km to study the stability/instability of the atmosphere. This permits us to trace a map indicating where and when the optical turbulence has the highest probability to be triggered on the whole troposphere, tropopause and stratosphere. We finally try to predict the best expected isoplanatic angle and wavefront coherence time employing the Richardson number maps, the wind speed profiles and simple analytical models of CN2 vertical profiles.Comment: 28 pages, 14 figures, pdf file, to be published on July 2006 - PASP, see also http://www.arcetri.astro.it/~masciad

ALTA Center: Advanced LBT Turbulence and Atmosphere Center Report 12/2019

ALTA Center is a project funded by the Large Binocular Telescope Observatory conceived to support science operations of LBT and LBTI. The main goal is to set-up a completely automatic system to forecast the most important atmospheric and astroclimatic parameters (seeing, isoplanatic angle, wavefront coherence time) relevant for the ground-based astronomical observations, particularly those supported by Adaptive Optics. The project started on 2015 and it has been conceived as a long term project and it is organised on a sequence of contracts of typically five years. The plan has been defined and agreed with the LBTO Director so to be able to supply the required informations on the atmospheric conditions necessary for the LBTO facilities operations, particularly those supported by the Adaptive Optics and the Interferometry. The project has been warmly solicited by the LBTO Director, Christian Veil- let as a piece of a more extended plan aiming to equip LBTO with a set of tools/instrumentations necessary to provide a complete monitoring and character- isation of the atmosphere of Mt.Graham, site of the LBT. The outputs of ALTA Center are supposed to be injected in the LBT Science Operation system designed to optimise the management of the LBT observations [1]. The first contract of ALTA has been conceived to cover a five years activity in the period 2015-2019. At present time ALTA Center is one of the very few centers existent in the astronomical context at a worldwide scale that is able to predict all the key atmo- spherical and astroclimatic parameters relevant for the ground-based astronomy. It is at our knowledge the first and unique center that is able to provide forecasts at short time scales (i.e. a few hours) with such accuracies (see Section 7). It is important to mention that ALTA Center is in continuous evolution. A few functionalities of ALTA could not yet been validated because of a lack of presence of dedicated monitors in situ that are however supposed to be implemented in the next future (for example a MASS - Multi Aperture Scintillation Sensor). This will be included in a forthcoming contract