WORKSHOP ON ASTRONOMICAL SITE EVALUATION

Organized by
Instituto de Astronomía
Universidad Nacional Autónoma de México
San Pedro Mártir, Baja California, México

Date: March 13-15, 2007

Scientific Program

Tuesday March 13 Morning

09:15

Opening remarks by Director Dr. Franco

09:30

Invited Talk Mauricio Tapia & David Hiriart: Site Evaluation at San Pedro Martir

10:30

Contributed talk John Storey, Jon Lawrence & Michael Ashley: Site testing in Antarctica

11:00

Contributed talk Joanna Thomas-Osip: GMT Site Evaluation at LCO

11:30

Coffee break

12:00

Discussion

13:00

Lunch

Tuesday March 13 Afternoon

15:00

Invited talk Marc Sarazin, Jean Vernin & Casiana Muñoz-Tuñón: Site Selection for the European ELT

16:00

Contributed talk Matthias Schoeck: Status of the TMT Astronomical Site Evaluation Process

16:30

Contributed talk Casiana Muñoz-Tuñón: Recent results on site characterization at the Canarian Observatories

17:00

Coffee break

17:30

Discussion

18:00

Dinner

19:30

Visit to SPM sky

Wednesday March 14 Morning

09:30

Invited talk Marc Sarazin, Tim Butterley, Julio Navarrete & Richard Wilson: Assembling Composite Vertical Atmospheric Turbulence Profiles from DIMM, SLODAR and MASS Contemporaneous Records at Paranal

10:30

Contributed talk Konstantinos Vogiatzis: Numerical Wind Modeling for Site Evaluation

11:00

Contributed talk Jesús Fuensalida: Sampling and Characterization of the Turbulence Vertical Distribution. Statistics of SCIDAR Profiling

11:30

Coffee break

12:00

Discussion

13:00

Lunch

Wednesday March 14 Afternoon

15:00

Invited talk Remy Avila: Turbulence Profiling at San Pedro Mártir Observatory: Lessons Learnt about the Site and the Techniques

16:00

Contributed talk Richard Wilson: SLODAR Turbulence Profiling for Astronomical Site Characterization

16:30

Discussion

17:00

Coffee break

17:30

Discussion

19:00

Dinner

Thursday March 15 Morning

08:30

Contributed talk Erika Sohn: Reconnaissance Field Report for the Search of Large Telescope Sites in the Sierra San Pedro Mártir, BC, Mexico

09:00

Excursion to the TIM, Altar and Antenas Sites

12:00

Discussion

13:00

Lunch

Thursday March 15 Afternoon

15:00

Invited talk Andrei Tokovinin: Turbulence Profiles from Scintillation of Stars, Planets, and Moon

16:00

Contributed talk Antonia Varela, C. Bertolin, C. Muñoz-Tuñon, J. J. Fuensalida & S. Ortolani: In Situ Calibration Using Satellite Data Results

16:30

Contributed talk Jacques Sebag, J. Barr, A. Sakha. C. Claver, V. Krabbendam: LSST Cloud Cover Measurement for Observation Scheduling

17:00

Coffee break

17:30

Final discussion and conclusions

19:00

Dinner

ABSTRACTS

1.

Site Evaluation at San Pedro Martir

 

Mauricio Tapia & David Hiriart
Instituto de Astronomía y Observatorio Astronómico Nacional, UNAM

 

The Observatorio Astronómico Nacional at San Pedro Mártir is located $31^\circ 02' 40''$N and $115^\circ 28' 00''$W on the summit of the Sierra San Pedro Mártir in the Baja California peninsula, Mexico, at approximately 2800 m above sea level. We will present the results of nearly three decades, up to about the year 2006, of site characterization work. These cover the following aspects: weather, cloud coverage, local meteorology, atmospheric optical extinction, millimetric opacity and seeing. We will also present the results of site testing at places nearby to the Observatory that may be considered as a potential sites for new telescope developments Overall, Sierra San Pedro Mártir seems to be one the most favorable sites in the world for astronomical observations.

2.

Site testing in Antarctica

 

John Storey, Jon Lawrence & Michael Ashley
University of New South Wales, Australia

 

For astronomers, the high Antarctic plateau offers several advantages over temperate sites. The most obvious of these advantages are the dramatically reduced sky background in the infrared, the thinness of the turbulent surface layer, the reduced free-atmosphere turbulence, and absence of high altitude turbulence. In this talk I will review the measurements that have been made over the past decade at South Pole and Dome C, highlight the remaining gaps in our knowledge of these sites, and look forward at the future plans to fully characterize the Antarctic plateau.

3.

GMT Site Evaluation at LCO

 

Joanna Thomas-Osip
Las Campanas Observatory, Chile

 

We report preliminary results obtained during the first two years of the GMT site testing campaign at Las Campanas Observatory. Meteorological (cloud cover, temperature, wind, and humidity) and DIMM seeing data are being obtained at three potential sites, and are compared with identical data being taken at the Magellan telescopes site. In addition, measurements of the turbulence profile of the free-atmosphere above LCO are being collected with a MASS/DIMM. We examine the contribution to the seeing arising in the ground layer (defined here as below an altitude of 500 m) through the difference between the turbulence integrals in the full atmosphere (as measured by DIMM) and in the free atmosphere (as measured by MASS). Furthermore, we report on our efforts to calibrate the relationship at LCO between the precipitable water vapor as measured via optical echelle spectroscopy and opacity at 225 GHz from a tipping radiometer.

4.

Site Selection for the European ELT

 

Casiana Muñoz-Tuñón$^1$, Jean Vernin$^2$ & Marc Sarazin$^3$
$^1$ Instituto Astrofíisico de Canarias, Spain
$^2$ LUAN, France
$^3$ European Southern Observatory, Germany

 

The site selection for the future European Extremely Large Telescope is a key issue which is being addressed within the ``ELT Design Study'' jointly funded by several European astronomical institutes and the European Union Sixth Framework Program. The organization of the site selection worpackage, working scheme and instruments are summarized here. Important use has been made of all efforts been carried out during the past decade in the definition of techniques and tools reliable for the study of the atmosphere over astronomical sites. Also important is the relevance that the studies of the atmosphere has acquired, becoming key projects for most important observatories. Therefore we have also taken advantage of the large database already available as a baseline for pre-selecting the candidate sites.

5.

Status of the TMT Astronomical Site Evaluation Process

 

Matthias Schoeck and the TMT Site Selection Team
Thirty Meter Telescope Project, USA

 

The Thirty Meter Telescope (TMT) is currently acquiring site characterization data at five candidate sites. The site testing equipment includes instruments for measuring the seeing and seeing profiles, meteorological conditions, cloudiness, precipitable water vapor, etc. All site testing equipment and data have gone through extensive calibrations and verifications in order to assure that a reliable and quantitative comparison between the candidate sites will be possible. Here, we present an update on the status of the site selection work, the equipment characterizations and the resulting accuracies of our site selection data.

6.

Recent Results on Site Characterization at the Canarian Observatories

 

Casiana Muñoz-Tuñón
Instituto Astrofíisico de Canarias, Spain

 

During the last years a mayor effort has been carried out both, for defining key parameters to quantify the quality of a site for astronomical observations, and to design reliable techniques and tools to compare different sites. In the talk I will revise some of the parameters relevant for astronomical site evaluation, and I will also brief on the instruments currently available for their measurements. The Observatories at the Canaries, Observatorio del Roque del los Muchachos (ORM) and Observatorio del Teide (OT) have been test benches for the development of new techniques and tools for more than three decades. A revision of statistical measurements and techniques, emphasizing the most recent results in the framework of the FP6 site selection program at the Canarian Observatories will be presented.

7.

Assembling Composite Vertical Atmospheric Turbulence Profiles from DIMM, SLODAR and MASS Contemporaneous Records at Paranal

 

Marc Sarazin$^1$, Tim Butterley$^2$, Julio Navarrete$^1$, Richard Wilson$^2$
$^1$ European Southern Observatory, Garching bei Munchen, Germany
$^2$ University of Durham, England

 

Combining DIMM and MASS data provides access to the full profile of the atmospheric turbulence with a 500m resolution at ground level. This has become a standard feature of most site monitoring programs worldwide. A version of SLODAR which probes the first kilometer above ground with 150m resolution has been used in campaign mode at Paranal during the past years. The database accumulated when all three instruments were operated together is used to build a statistical estimate of standard turbulence profiles at Paranal.

8.

Numerical Wind Modeling for Site Evaluation

 

Konstantinos Vogiatzis
Thirty Meter Telescope Project, USA

 

Numerical simulations of airflow over various potential sites for telescopes have been performed. Information such as wind speed and temperature profiles, turbulence levels (fluctuating velocity RMS), wake lengths and boundary (ground) layer thickness are retrieved. This information is then use to model local “ seeing, thus providing an essential evaluation tool in the site selection process. The seeing modeling methodology is presented along with the domain configuration strategy. A compilation of simulations follows, carried out over possible site locations for telescope projects. In the past, results included evaluation of ground layer as a function of wind speed and direction for a given site or even comparison between neighboring sites when applicable. Since the local seeing (combined mirror, dome and ground layer seeing) is strongly affected by site development and enclosure geometry, the focus has now shifted to airflow-topography-structure interactions. Examples demonstrate the value of this type of modeling as a design and operations strategy tool.

9.

Sampling and Characterization of the Turbulence Vertical Distribution. Statistics of SCIDAR Profiling

 

Jesús J. Fuensalida
Instituto de Astrofísica de Canarias, Spain

 

Unlike the trial procedures, a reliable characterization of the vertical turbulence distribution on a site should be based in unbiased statistical sample criteria. The sample size is as important as the criteria under which it becomes. We will present the statistical results of the optical turbulence profiles at the Roque de los Muchachos Observatory (La Palma, Canary Islands) over annual periods, as well as the developed instrumentation to fulfill the established criteria. The data were obtained using the generalized SCIDAR technique at the Jacobus Kapteyn Telescope and the campaigns were done monthly. In order to extend the statistics of the profiles to other important parameters for Adaptive Optics Systems, we will show the expected heights of virtual conjugated mirrors so that they provided the optimal isoplanatic patch. Different number of mirrors will be considered.

10.

Turbulence Profiling at San Pedro Mártir Observatory: Lessons learnt about the site and the techniques

 

Remy Avila Foucat
Centro de Radioastronomía y Astrofísica, UNAM

 

Two intensive campaigns aimed at the characterization of the optical turbulence profiles at San Pedro Mártir took place in 1998 and 2000. The first one involved Generalized Scidar and DIMM measurements, while in the latter the launch of instrumented balloons and an instrumented mast were also included. A number of important results were obtained in three fields: turbulence profile characterization, optical turbulence modeling, and technique developments. In this talk, a brief summary of the campaigns and the results is exposed. Also, a new method, the Low Layer Scidar (LOLAS) is briefly presented. the LOLAS is aimed at the monitoring the turbulence profiles in the first kilometer, with an altitude resolution that can reach 17 m. Its concept is based on the Generalized Scidar technique, but is implemented on a 40-cm dedicated telescope, which makes it an autonomous instrument, ideal for long term site studies.

11.

SLODAR turbulence profiling for astronomical site characterization

 

Richard Wilson
University of Durham, England

 

The application of the SLODAR (SLOpe Detection And Ranging) method to site characterization for astronomy will be reviewed. SLODAR is an optical technique for profiling of the altitude and velocity of atmospheric turbulence, via measurements of double stars with a wavefront sensor. SLODAR systems based on small telescopes have been deployed at the Cerro Paranal and Mauna Kea observatories, specifically to characterize the ground-layer turbulence at those sites. The capabilities and status of these systems will be reviewed, as well as early results, and possible future enhancements will be discussed.

12.

Reconnaissance Field Report for the Search of Large Telescope Sites in the Sierra San Pedro Mártir, BC, México

 

Erika Sohn Lopez-Forment
Instituto de Astronomía, UNAM, Mexico

 

In order to search for suitable sites for the installation of large telescopes and site evaluation access routes, a series of potential sites were visited either by foot or using a 4WD vehicle. Their GPS coordinates were marked and some access routes were devised. Photographs, a brief description of the sites, observed rocks as well as general comments are presented.

13.

Turbulence Profiles from Scintillation of Stars, Planets, and Moon

 

Andrei Tokovinin
Cerro Tololo Inter-american Observatory, Chile

 

The MASS turbulence profiler has been used extensively for measuring free-atmosphere turbulence over several sites. Its principle will be recalled and a short review of the results will be given, together with an update on the accuracy of this technique. By replacing a single star with a planet, we can evaluate turbulence at few hundred meters above the site, and such experiments have been made. However, of greater importance is to measure the turbulence in the immediate vicinity of a telescope or site monitor. Here, lunar scintillation is the method of choice. A simple lunar scintillometer, LuSci, is under development at CTIO. A new method to interpret its data and the results of first tests will be presented.

14.

In Situ Calibration Using Satellite Data Results

 

Antonia M. Varela$^1$, C. Bertolin$^2$, C. Muñoz-Tuñón$^1$, J. J. Fuensalida$^1$ & S. Ortolani$^3$
$^1$ Instituto de Astrofísica de Canarias (IAC), Tenerife, Canary Islands, Spain
$^2$Institute of Atmospheric and Climate Sciences (ISAC), Bologna, Italy
$^3$University of Padova, Italy.

 

The main goal of this work is the analysis of new approaches in order to study the properties of astronomical sites. The objective is to calibrate the atmospheric extinction provided by in situ techniques through remote sensing data retrieved from satellite-platforms. We have explored the usefulness of data provided by different spectrographs aboard NASA and ESA satellites with better spatial and temporal resolutions than TOMS and centered on channels of astronomical interest as a possible tool for site characterization. In addition, from these satellite data is possible to go back at the cloud coverage, the climatic trend or the atmospheric turbulence from troposphere winds. The main problem to use these values is their interpretation and their quantitative calibration. Data analysis need to be complemented with those provided by in situ instruments (telescopes, airborne particles counters, ground meteorological stations).

15.

LSST Cloud Cover Measurement for Observation Scheduling

 

Jacques Sebag, J. Barr, A. Saha. C. Claver & V. Krabbendam
National Optical Astronomical Observatory

 

The Large Synoptic Survey Telescope (LSST) science specifications require operating the telescope for a 10-year survey of the visible sky with frequent revisits in multiple filters. During regular night operation, an observatory scheduler will be used to select fields to be observed on a cadence of one every 30 seconds. To maximize the survey efficiency real time adjustments to the observation schedule will be assessed using input parameters like cloud cover. LSST is evaluating the use of infrared and optical all-sky cameras and satellite images to inform the scheduling process. Visible all-sky cameras are in operation at several observatory sites and routines have been developed to automatically quantify photometry in the images. A preliminary comparison between these all-sky images and contemporaneous satellite data has been made. The evaluation of techniques for cloud detection also includes an IR all sky camera that is expected to be deployed in mid 2007.