To improve the modeling of seeing and its forecast over Armazones and Paranal, we applied two different C<sup>2</sup><sub>n</sub> methods to estimate the vertical refractive index structure. One method, using temperature, pressure and turbulent kinetic energy (TKE), simulates the planetary boundary layer (PBL) C<sup>2</sup><sub>n</sub> . The second method simulates in the free atmosphere, using temperature, pressure and vertical wind shear. The combination of both methods delivers the whole vertical structure of the C<sup>2</sup><sub>n </sub>from ground level up to the stratosphere, and consequently we can derive the astronomical seeing. These atmospheric variables were calculated using WRF, configured in high temporal and spatial resolution. Our results show that the combination of these two methods gives improved results than when are used separately. We compared our simulations with measured data from MASS and DIMM instruments located at both sites.
In 2015 the Institute of Physics and Astronomy of the Universidad de Valparaiso in Chile received as a donation the Bochum 0.61-meter telescope. Here we preset the ongoing project to convert this senior member of La Silla Observatory to modern standards aiming at performing state-of-art science, as well as teaching and outreach. Firstly, the site characterization was performed in order to verify the observing conditions. The preliminary results were auspicious in relation to the nights available for observation. In early 2016 began the transfer work form La Silla Observatory to the new site of operations. The actual status of the telescope was analyzed and an upgrade plan was proposed to make it usable remotely using a web-based telescope control system developed in Chile by ObsTech SpA. Future upgrade and scientific collaboration will be discussed based on the site characterization and technical studies regarding the potential for new instrumentation.
We present the performance characteristics of a water vapour monitor that has been permanently deployed at ESO’s
Paranal observatory as a part of the VISIR upgrade project. After a careful analysis of the requirements and an open call for tender, the Low Humidity and Temperature Profiling microwave radiometer (LHATPRO), manufactured by
Radiometer Physics GmbH (RPG), has been selected. The unit measures several channels across the strong water vapour emission line at 183 GHz, necessary for resolving the low levels of precipitable water vapour (PWV) that are prevalent on Paranal (median ~2.5 mm). The unit comprises the above humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared radiometer (~10 μm) for cloud detection. The instrument has been commissioned during a 2.5 week period in Oct/Nov 2011, by comparing its measurements of PWV and atmospheric profiles with the ones obtained by 22 radiosonde balloons. In parallel an IR radiometer (Univ. Lethbridge) has been operated, and various observations with ESO facility spectrographs have been taken. The RPG radiometer has been validated across the range 0.5 – 9 mm demonstrating an accuracy of better than 0.1 mm. The saturation limit of the radiometer is about 20 mm. Currently, the radiometer is being integrated into the Paranal infrastructure to serve as a high time-resolution monitor in support of VLT science operations. The water vapour radiometer’s ability to provide high precision, high time resolution information on this important aspect of the atmosphere will be most useful for conducting IR observations with the VLT under optimal conditions.
The content of precipitable water vapor (PWV) in the atmosphere is very important for astronomy in the infrared and
radio (sub-millimeter) spectral regions. Therefore, the astrometeorology group has developed different methods to derive
this value from measurements and making forecasts using a meteorological model. The goal is use that model to predict
the atmospheric conditions and support the scheduling of astronomical observations. At ESO, several means to
determine PWV over the observatories have been used, such as IR-radiometers (IRMA), optical and infrared
spectrographs as well as estimates using data from GOES-12 satellite. Using all of these remote sensing methods a study
undertaken to compare the accuracy of these PWV measurements to the simultaneous in-situ measurements provided by
radiosondes. Four dedicated campaigns were conducted during the months of May, July, August and November of 2009
at the La Silla, APEX and Paranal observatory sites. In addition, the astrometeorological group employs the WRF
meteorological model with the goal of simulating the state of the atmosphere (every 6 hours) and forecasting the PWV.
With these simulations, plus satellite images, radiosonde campaign data can be classified synoptically and at the same
time the model can be validated with respect to PWV.
The European Southern Observatory (ESO), the Institute for Space Imaging Science (ISIS) and the AstroMeteorology
group at the Universidad de Valparaiso collaborated on a project to understand the precipitable water
vapour (PWV) over the La Silla Paranal Observatory. Both La Silla and Paranal were studied with the goal of
using them as reference sites to evaluate potential E-ELT sites. As ground-based infrared astronomy matures,
our understanding of the atmospheric conditions over the observatories becomes paramount, specifically water
vapour since it is the principle source of atmospheric opacity at infrared wavelengths. Several years of archival
optical spectra (FEROS) have been analysed to reconstruct the PWV history above La Silla using an atmospheric
radiative transfer model (BTRAM) developed by ISIS. In order to better understand the systematics involved, a
dedicated atmospheric water vapour measurement campaign was conducted in May 2009 in close collaboration
with Las Campanas observatory and the GMT site testing team. Several methods of determining the water column
were employed, including radiosonde launches, continuous measurements by infrared radiometers (IRMA),
a compact echelle spectrograph (BACHES) and several high-resolution optical echelle spectrographs (FEROS,
HARPS and MIKE). All available observations were compared to concurrent satellite estimates of water vapour
in an attempt to ground-truth the satellite data. We present a comparison of the methods used, and results
from the archival study and measurement campaign. A mean PWV of 3.4 ± 2.4 mm is found for La Silla using
FEROS data covering the period 2005-2009. Important lessons on the strengths and limitations of satellite data
are presented. The value of a stand-alone high time resolution PWV monitor has been demonstrated in the
context of parallel observations from Las Campanas and La Silla.
The Macón's zone (24°S, 66°W) is preselected for possible construction of the astronomical observatory ELT (Extremely Large Telescope) by ESO. Preliminary analysis shows that this area is optimal for astronomical activity, therefore data of turbulence has been collected, important factor in seeing and for adaptive optics (AO). In this area, campaigns of measurements of meteorological variables were made, with an automatic station. Simulations with the weather system modeling MM5 were performed on the collected data and were correlated with the corresponding satellite images. In the analysis of the atmospheric conditions it was found that the greatest contribution of atmospheric instability in this area, is produced by high trough and jet stream. The trajectory analysis identified that the air that reaches the summit Macón comes from about 4500 meters above sea level, in average. This confirm that the turbulence that forms on the salt of Arizaro (3500 m.a.s.l.) does not rise to the top of Macón (4500 m.a.s.l.).