We present preliminary results of the commissioning and testing of SALT-CRISP (SALT-Calibration Ruler for Increased Spectrograph Precision), a Laser Frequency Comb (LFC) built by Heriot-Watt University and temporarily installed at the Southern African Large Telescope (SALT). The comb feeds the High Stability mode of SALT's High Resolution Spectrograph (HRS) and fully covers the wavelength range of the red channel of the HRS: 555-890 nm. The LFC provides significantly improved wavelength calibration compared to a standard Thorium-Argon (ThAr) lamp and hence offers unprecedented opportunities to characterise the resolution, stability and radial velocity precision of the HRS. Results from this field trial will be incorporated into subsequent LFC designs.
The project for the proposed Large Synoptic Survey Telescope (LSST) performed more than two years of data
collection, site evaluation, and analysis to support the selection of its prime site. LSST assessment was based on
using an existing site with existing infrastructure and historical performance information. A large and diverse set of
comparative information was compiled for potential sites using results from other site campaigns, measurements
from existing large telescopes, new astro-climate measurements, logistical and feasibility information, and from
existing satellite and climate databases. Several analyses were performed on these data including the assessment of
survey performance using the LSST operation simulator. An independent site selection committee of experts
provided recommendations to the Project leading to three finalist sites, one in Mexico, and two in northern Chile.
The finalist sites were assessed thoroughly with additional data collection from all-sky cameras and site proposals.
Cerro Pachon in Chile was selected to be the site for LSST after a difficult decision between the high quality final
candidates. This paper describes the data, analysis and approach used to support the site evaluation.
A survey of northwest Africa and southern Spain (including the Canary Islands) has been carried out using satellite data from the Meteosat Operational Service (in geostationary orbit at 0o longitude). The study was funded by European Southern Observatory (ESO) as part of the site survey effort for the Overwhelmingly Large Telescope (OWL), recently re-baselined as the European Extremely Large Telescope (E-ELT). Cloud cover and water vapor were surveyed over the area 20oN to 40oN and 20oW to 10oE using satellite data for the 7-year period January 1996 to December 2002. The study included a calibration of the Upper Tropospheric Humidity (UTH) for Meteosat-5, an aerial analysis of cloud cover and precipitable water vapor (PWV) and a verification of the satellite cloud cover using ground-based observations of sky conditions derived from extinction measurements made at the Observatorio del Roque de los Muchachos (ORM) on La Palma. In view of the importance of establishing the accuracy of the satellite method, a summary of results from earlier verification studies has been included in the relevant section.
The California Extremely Large Telescope, CELT, is a proposed 30-m telescope. Choosing the best possible site for CELT is essential in order to extract the best science from the observations and to reduce the complexity of the telescope. Site selection is therefore currently one of the most critical pacing items of the CELT project. In this paper, we first present selected results from a survey of the atmospheric transparency at optical and infrared wavelengths over the southwestern USA and northern Mexico using satellite data. Results of a similar study of South America have been reported elsewhere. These studies will serve as the pre-selection criterion of the sites at which we will perform on-site testing. We then describe the current status of on-site turbulence evaluation efforts and the future plans of the CELT site testing program.
Astronomical observatories are extremely dependent on sky transparency. As the expensive new very large telescopes enter into operation, flexible observing modes are being introduced, which allow each 'observing block' to be scheduled at the most appropriate time. In such modes, it makes sense to develop tools for forecasting ambient conditions. We present here the operational water vapor and cirrus cloud forecast model developed for ESO observatories in Northern Chile.
The Japanese National Large Telescope (JNLT) will use a thin meniscus mirror of 7.5 m diameter and 0.2 m thickness as a primary mirror. One of the biggest concerns is mirror deflection due to dome-inside wind loading, which varies with time not only in its pressure amplitude but also in its pressure profile on the mirror surface. To analyze such mirror deflection, a method combining modal analysis and random vibration analysis was introduced. From the rms mirror deflection obtained by this method, the image quality degradation is considered to be better than that budgeted as wind loading degradation. Information about the method and typical result of the analysis are presented.