Found 7 talks width keyword atmospheric effects
The precipitable water vapour (PWV) is the main absorber in the Earth's atmosphere at infrared (IR) and microwave wavelengths. In the last years, the IAC Sky team has been providing real-time PWV data from a monitor based on the GNSS (GPS) technique (GNSS PWV Monitors; GPM). Among other things, the PWV values help in the scheduling of the telescopes with IR instrumentation. The GPM have undergone a continuous process of upgrading. More recently, we have undertaken the PWV forecasting. We will present in the talk a brief summary of the monitors and details of ForO ("Forecasting the Observatories"), the forecasting system for PWV at the Observatories. ForO is based on a mesoscale Numerical Weather Prediction (NWP) model. The ForO system has been validated and calibrated with PWV data from the GPM and will deliver accurate PWV daily predictions for ORM and OT on a 24, 48 and 72 hours windows. This is a definitive improvement to optimize the flexible scheduling for IR observations, in particular for CanaryCAM and EMIR at the GTC.
In the past years, intensive Site Characterization campaigns have been performed to chose the sites for the future giant ELTs. Various atmospheric turbulence profilers with different resolution and sensed altitude ranges have been used, as well as climatological tools and satellite data analysis. Mixing long term statistics at low altitude resolution with high resolution data collected during short term campaigns allows to produce the reference profiles as input to the Adaptive Optics (AO) instrument performance estimators. In this talk I will perform a brief review of the principal and most used instruments and tools in order to give to the audience a panorama of the work and the efforts to monitor the atmospheric turbulence for astronomical purposes.
AbstractA new method of imaging in the visible has given the highest resolution images ever taken anywhere. It needs a natural guide star of only 18.5 mag (I band). This talk will show how it can be done on the WHT, the VLT and even on the GTC.
AbstractMeasuring the Aerosol Optical Depth (AOD) is of particular importance in monitoring aerosol contributions to global radiative forcing and air quality. Most measuring methods are based on direct or indirect observation of sunlight and thus are only available for use during daylight hours. Attempts have been made to measure AOD behavior at night from star photometry, and more recently moon photometry. Star photometry method uses spectrally calibrated stars as reference targets this provides somewhat more flexibility than a sun photometer but there are low-signal and calibration issues which can make these measurements problematic. Moon photometry is only possible when the moon is present in the sky. We suggest a complementary method, based on the observation of artificial sky glow generated by light pollution. The methodology requires (1) the implementation of an heterogeneous 3D light pollution model and (2) the design of an automated light pollution spectrometer which will be presented here. The instrument designated as the Spectrometer for Aerosol Night Detection (SAND) is now in its third version. Basically, SAND-3 is an automated CCD based, long-slit spectrometer protected from inclement weather by an acrylic dome. SAND have been used successfully in many astronomical sites along with some urban sites. Our first day/night (continuity) AOD measurements comparisons with AERONET/AEROCAN sunphotometer data will be shown for Sherbrooke university (Quebec, Canada) atmospheric optical observatory.
An analysis of the impact of seismic and volcanic activity was carried out at selected astronomical sites, namely the observatories of El Teide (Tenerife, Canary Islands), Roque de los Muchachos (La Palma, Canary Islands), Mauna Kea (Hawaii) and Paranal (Chile) and the candidate site of Cerro Ventarrones/Armazones (Chile). In this sense, we studied the impact of seismicity, volcanic ash clouds, lava flows and ground deformation. Hazard associated with volcanic activity is low or negligible at all sites, whereas seismic hazard is very high in Chile and Hawaii. The lowest geological hazard in both seismic and volcanic activity was found at Roque de los Muchachos observatory, in the island of La Palma.
Instituto de Astrofísíca de Canarias, Spain
There are many parameters accounting for the quality of an astronomical site, namely seeing, cloud cover, ground winds, high-altitude winds, etc. The water vapor content is the main parameter affecting the IR quality of astronomical sites. The fraction of nights with good IR conditions (small column of water vapor) as a function of the epoch of the year will allow an optimal scheduling of telescope observing time. Global Positioning System (GPS) is an increasingly operational tool for measuring the precipitable water vapor (PWV). In this seminar, we briefly describe the procedure to estimate the PWV through GPS and we present the statistical results derived from a 7.5-year long time series of PWV estimations derived from GPS at the Roque de los Muchachos Observatory.
AbstractThe ambitious astrophysical objectives of the Extremely Large Telescopes (ELTs) will be achievable only with innovative Adaptive Optics (AO) systems to correct for the wavefront distortions induced by the turbulence in the atmosphere. One of the key components of an AO system is the wavefront reconstruction, which is a real-time estimate of the wavefront distortions above the telescope aperture from data. This reconstruction can be described by an inverse problem approach (IPA),taking advantage of the modeling of second-order statistics of both turbulence and data noise.
First, the benefits of the IPA to wavefront reconstruction is enhanced for two particularities of the ELTs: very high number of estimated parameters (~104) and elongated spots on the sensor for AO using Laser Guide Stars. Moreover, this IPA can be implemented with a fast algorithm for high number of degrees of freedom, which makes it a candidate for the implementation on a future AO system of the E-ELT. The correction performance in closed-loop AO has also been assessed thanks to end-to-end simulations of single-conjugate AO and Ground-Layer AO with Laser Guide Stars on the E-ELT.
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