61 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
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
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