Latest update: 2005-Oct-26 (by Nelva Perón)

In response to an invitation received from the International Square Kilometre Array Steering Committee (ISSC) on September 2003, the radioastronomers of Argentina prepared an Initial Site Analysis document. The goal of this document was to pindown sites within Argentina that could be suitable to host the Square Kilometre Array (SKA). The document was submitted to the ISSC on March 30, 2004.

A complete version of such document (pdf format) can be downloaded by clicking here

A Power Point version of the oral contribution made by Dr. G. Dubner at the SKA meeting held in Pencticton (Canadá) last July can be found here

Visit of Dr. Schilizzi to Argentina here

"SKA, el mayor radiotelescopio jamás concebido ¿lo tendremos en Argentina?"
Charla Magistral de la Dra. Gloria Dubner en el Planetario Galileo Galilei, el 21 de octubre de 2005.Download

A proposal for siting SKA in territories of Argentina - Brazil - Final document. Click here

General Introduction

The Square Kilometre Array (SKA) will constitute a milestone in astronomical research and instrumental development. To achieve its ambitious goals, regardless of what its final technical design implementation will be, it is essential that the area hosting this instrument has a very low level of electromagnetic pollution. Furthermore, in the foreseeable future this condition should not deteriorate. More information about this international project can be found at the official SKA site.

The SKA in Argentina

In order to seek potential sites to locate the central core of the SKA within the frontiers of Argentina, the following criteria were set out:

a) The sites should be radiofrequency quiet in order to achieve high sensitivity levels.

b) The geographical location of the sites should allow easy access to the entire Southern Celestial hemisphere (e.g: Galactic Center, Magellanic Clouds) and most of the Northern sky objects.

c) High as well as low altitude areas should be considered. The former have usually small atmospheric water vapor content, thereby favouring observations at the high frequency extreme of the tuning range of the SKA.

d) Highly skilled human resources and institutions with medium to high level of technological complexity should be available at a reasonable distance from the sites.

e) There must be a good chance of leasing or purchasing land at a reasonable cost.

f) Possible existence of a legal regulatory framework (for example, a provincial or a Federal law) to help enforce the radio quietness of the site. In those places were such regulations do not exist at present, there should be a strong commitment from the local government, the federal communication authority (Comisión Nacional de Comunicaciones) and the astronomical community to work together to establish a radio quite zone in the selected area.

Some of the material presented here, specially the one concerning the RFI measurements, should be regarded as preliminary. Further activities to gather much more sensitive RFI measurements and to look for other candidate sites are planned for the near future. Progress reports of these studies will be submitted to the SKA International Committee in due time.
It is worth mentioning that national and provincial authorities strongly endorse the candidacy of Argentina to host the SKA telescope (see letters of support).

Initial radio frequency interference (RFI) measurements were conducted in two intermediate and high altitude areas located in the western provinces of San Juan and La Rioja. A third region, located in the province of La Pampa will be surveyed during the current year. We face the limitations that the sites selected in this first step had to be close enough to commercial power lines in order to use our equipment, thus implying that the RFI measurements may have not been carried out at the best possible spots.

Argentina is located in southern South America, bordering the South Atlantic Ocean, Uruguay, Brazil, Paraguay, Bolivia and Chile.

With a total surface of 2.8 millions square kilometres, it is the second largest country in Latin America and the eighth largest country in the world.

It stretches 3800 kilometres from north to south and 1400 km east-west.

Because of its large extension, Argentina has a great diversity of climates and topographies.

Click here

Click here

A map of Argentina depicting its political division in provinces as well as the location of the tree SKA candidate sites (CASLEO, CRILAR and Chacharramendi) is shown.

The northernmost big green dots marks the position of CRILAR (La Rioja) and CASLEO (San Juan).
Originally a third region close to Victorica (La Pampa - red dot in left figure) was selected to carry out a RFI campaign. Later on, based upon logistics grounds, it was decided to conduct this RFI survey in the proximity of Chacharramendi (La Pampa - Southernmost green dot).

For reference, on the Chilean side of the Andes the location of the ESO VLT at Paranal, of the international observatories near La Serena (CTIO, ESO, LCO) and the future ALMA site are marked by big blue dots.

Some of the geographical characteristics of the SKA candidate sites are given in Table 1.

Table 1- Candidate sites

Site Geographical Location Altitude

Site Id

CASLEO ( San Juan)

69° 18' W , -31° 29' 2550 m Green Dot

CRILAR (La Rioja)

66° 34' W , -28° 29' 1400 m Green Dot

Chacharramendi (La Pampa)

65° 38' W , -37° 20' 317 m Green Dot

 

 

 

Their global characteristics are given in Table 2

Table 2 - Site characteristics and climate

Characteristic CASLEO CRILAR Chacharramendi
Average Temp. (C) 17 (Summer)
5 (Winter)
16.5 (year round) 24 (Summer)
7 (Winter)
Aver. Maximum Temp.(C) 30.5 37.2 31.0
Aver. Minimum Temp. (C) -15.5 -5.9 +2.1
Mean Rainfall (mm/yr) 30 360 730
Max. Rainfall (mm/yr) 60 400 960
Aver. Wind Speed (km/h) 10 5 12
Aver. Rel. Humidity (%) 20 45 68
Max. Wind Speed (km/h) 100 93 87
Hail (days per yr) 1 to 2 6 to 10 0
Icing (days per yr) None 12 to 15 20 to 25
Lightening (days per yr) 6 to 8 20 to 25 10 to 15
Max. Snowfall (cm) 20 to 30 10 to 20 0
Fire Danger No fire last 20yr Negligible Negligible
Seismic Activity Yes Yes No

 

 

 

 

 

 

 

 

 

 

The meteorological data listed above are provided by local weather stations.

RFI measurements at CASLEO and CRILAR were conducted early this year during the period February 9 to February 23 (CASLEO) and February 26 to March 1 (CRILAR). The area at Chacharramendi was surveyed between June 26 and July 2. The same equipment and set up was used throughout the entire RFI campaign. The RFI data acquisition system is briefly described the following table:

Equipment used for RFI measurements

 Total Measurement Period   9th February - 1st March 2004 ; 26th Jun - 2nd July
 Test Antennas  Biconic 25-200 MHz
 Log Periodic 200 - 1100 MHz
 Circular Horn 1100- 3000 MHz 
 Low Noise Amplifier (LNA)   Miteq AFS3, 100 - 3000 MHz
 32 dB gain, 1.2 DB Noise Figure 
 Spectrum Analyzer  Hewlett Packard 8593E 
 Control and Acquisiton system   Special Purpose software 
 Total data collecting time (hours)  400

 

 

 

 

 

 

Particular emphasis was put on obtaining RFI measurements along the low frequency range (50 to 1100 MHz) of the spectrum. At each site a quick-look survey with lower sensitivity was carried out in the high frequency band (1100 to 3000 MHz). From de RFI data, CASLEO turns out to be the place with the least amount of RFI activity. Further testing at CASLEO using more sensitive equipment is planned along the forthcoming Winter-Spring season (Southern Hemisphere).

Ionospheric Conditions

Two possible ways of characterizing the ionospheric conditions are through the cut-off frequency foF2 and through the scintillation index S4. The former (foF2) measures the maximum reflection frequency for normal incidence and ordinary mode, i.e. it is a measure of ionospheric transparency, while the second parameter (S4) measures the standard deviation of the signal intensity normalized by the average intensity, estimated from ground to a geostationary satellite.

 

The left panel displays results from systematic monitoring of foF2 obtained for a year of medium solar activity (1971, R12 = 70), and, for comparison purposes, the right panel shows the same parameter for a year of high solar activity (1981, R12 = 140).

The data were taken at the position Long., Lat. = 68o.5W,-31o.6S, close to the CASLEO site using a conventional ionosonde.
The middle curves (black filled diamonds) depict average foF2 values for the period January-December versus local time, while the upper and lower ones (pink squares and yellow triangles, respectively) show extreme values of the parameter during those years.
The lowest foF2 curves in each panel corresponds to June-July (Southern Winter time), while the highest ones to November- March (Southern Summer time). Upper foF2 limits are below 18 MHz even in the worst conditions.

Systematic monitoring is also carried out near Buenos Aires and Tucumán, giving similar results (data from Servicio Naval de Investigación y Desarrollo of the Argentinean Navy and University of Tucumán, respectively).


Global map of the Maximum Usable Frequency (MUF) corresponding to 8am and 8pm (local time) (as obtained from Solar Terrestrial Dispatch ) to illustrate the best and worst ionospheric conditions (left and right panels, respectively). The approximate position of the proposed Argentinean sites is indicated by a green dot in the left panel.

At thre different frequencies (100MHz left panel, 250MHz middle panel and 1000MHz rigth panel) the blue stars mark the position of the selected sites.

Map depicting the modelled ionospheric scintillation index S4 for solar maximum conditions (kindly provided by Dr. J. Secan from the NWRA Scintillation Prediction Services).

The three selected places are relatively far from the equatorial anomaly and have acceptable ionospheric conditions.

Acknowledgements

It would have been impossible to prepare the initial SKA submission without the help of many individuals and institutions. We would also like to thank the Secretary of Science and Technology, Dr. J. Tulio del Bono, the President of the CONICET, Dr. Eduardo H. Charreau and the Board of Directors of the same institution, and Eng. J.J. Valorio, Head of the Enginneering Division of CNC, and his staff for their contribution. Special thanks are also due to Geof. Jerónimo Ainchil, Economist Andrés Asiain, Eng. Alfredo De Antueno, Dr. Eduardo Kruse, Lic. Guillermo Lemarchand, Lic. Patricio Marcó, Lic. Marta Mosert, Prof. Michelle Pacht, Geof. Silvio Peralta, Geof. Nora Sabione and Eng. Juan Sanz. We deeply thank Mr. J. M. Semegone, who was in charged of performing the field RFI measurements.

Finally, we would like to thank the Director of CASLEO, Dr. O.H. Levato, and CRILAR, Dr. D. E. Gorla, and their staff for having taken care of every possible detail in order to make the RFI measurements campaign feasible. We acknowledge the financial support of the IAR to carry out such campaigns, and the tireless collaboration of the IAR staff. We would also like to thank Dra. M. Rovira, Director of IAFE.

SKA-Argentina Committee members

Dr. E. Marcelo ARNAL
Prof. Titular Dedicación Exclusiva - UNLP
Investigador Principal CONICET
Instituto Argentino de Radioastronomía (IAR)
arnal@iar.unlp.edu.ar
arnal@fcaglp.fcaglp.unlp.edu.ar
Dr. Gloria M. DUBNER
Investigador Principal CONICET
Instituto de Astronomía y Física del Espacio (IAFE)
gdubner@iafe.uba.ar
Dr. Elsa B. GIACANI
Prof. Adjunto Semi-Dedicación - UBA
Investigador Independiente CONICET
Instituto de Astronomía y Física del Espacio (IAFE)
egiacani@iafe.uba.ar
Dr. O. Hugo LEVATO
Prof. - UNSJ
Investigador Principal CONICET
Complejo Astronómico El Leoncito (CASLEO)
hlevato@casleo.gov.ar
Dr. Ricardo MORRAS
Prof. Adjunto Semi-Dedicación - UNLP
Investigador Independiente CONICET
Instituto Argentino de Radioastronomía (IAR)
rimorras@isis.unlp.edu.ar
rmorras@iar.unlp.edu.ar
Dr. Estela M. REYNOSO
Investigador Adjunto CONICET
Instituto de Astronomía y Física del Espacio (IAFE)
ereynoso@iafe.uba.ar

 


2005 - SKA Argentine Committee