Argentina and Brazil A possible site to host

the SKA

M. Arnal, G. Dubner, E. Giacani, J. Lepine, H. Levato, R. Morras, E. Reynoso

AAA, 2005, La Plata

The SKA will have 1 million square meters of physical collecting area distributed in

Configuration of the SKA

a) Large number of small size receptors (LNSD)

b) Small number of large size receptors (SNLD)

Schematic distribution of the SKA collecting area

SKA Core0.5 km nominal radius20% collecting areaClose pack

SKA far remote stationsInner radius 150 kmOuter radius (at least) 3000 km24% collecting areaOur log spiral

SKA near remote stationsInner radius 2.5 kmOuter radius 150 km24% collecting areaOur log spiral

SKA central areaInner radius 0.5 kmOuter radius 2.5 km32% collecting area5-arm symmetric logspiral

• Radioquietness of potencial sites

• Technical and scientific resources of the country

• Physical characteristic of the site

• Tropospheric and ionospheric conditions

• Capital and operating costs

• Political and economic situation of the region

Initial Site Analysis Document

Geographical location of the core site

98 km

CENTRAL SITE

CASLEO Pampa del Medio

Pampa del Peñasco

Province of San Juan, Argentina Altitude ~ 2550m above sea level λ= 69o 16‘ 18“ W; φ= -31o 42‘ 21"

Satellite View

Pampa del Medio

Pampa del Peñasco

~12 km

RFI Measurements

RFI measurement equipment

Twin diesel generator group

Antennae towerData transfer systemLigthning rod

Control room

SKA Site CASLEO IAR

~ 1260 km

~ 12 km•Log Periodic 0.1 – 3.3 GHz•Circular Horn 3.3 – 18.0 GHz•Circular Horn 15.0 – 25 GHz

Some RFI Measurements

S

W

N

Frequency (MHz)

Pow

er (

dB

m)

Core and Central region

CASLEO (2550m)

Cordón de los Naranjos (3225 m)

Sierra del Tontal

(4368 m)

Pampa del Peñasco(2650 m)5 km

Cor

dón

del

Med

io (

2800

m)

Five arm asymmetric configuration

Paraguay

BoliviaC

hile

Uruguay

10% locationtolerance

Atlantic Ocean

Pac

ific

Oce

an

To measure the performance of the proposed configurations Figures of Merit (FOM) will be evaluated

Sky VisibilityThe SKA visible sky is defined as the sky that is above the 30o elevation

limit simultaneously at all stations in the proposed array, for at least

4 hours a day

UV coverageThe FOM will be:

a) The weight as a function of radius in the uv plane

b) The ¨circularity¨of the uv-coverage

c) The percentage of empty uv-cells as a function of radius

Beam shape

Five Key Science Projects (KSPs)

• At least two of the three nearest dark clouds (Taurus, Ophiucus, Chamaeleon) (KSP 1 )

• Coverage of at least 70% (including Galactic Centre) between 235o ≤ l ≤ 125o ( KSP 1, 2, 3)

• ~20.000 sq.d. of the sky out of the galactic plane, including the coldest regions of the sky and HI fluctuations (KSP 4, 5)

(or a list of key astronomical sources that NEED to be considered)

Source Visibility

Declination

Vis

ibil

ity

(hou

rs)

h =30o

h= 25oElevation limit (h)=20o

Tau

rus

Op

hiu

cus

Ch

amae

leon

Gal

acti

c C

entr

e

(210, 50)(230,-55) (225, -50)

Source Visibility

Declination

Vis

ibil

ity

(hou

rs)

h =30o

h= 25oElevation limit (h)=20o

SMC

LMCGalactic Plane(305o, 0o) (195o , 0o)(~72%)

(54o, 0o)

Opportunities for co-observation with existing (or future) ground-based facilities

Vis

ibil

ity

(hou

rs)

Declination

CTIOESOLCOSOARVLTGEMINI-S

ALMAAPEXCBIASTE

SKA

Altitude limit of 30o

Conclusions• The SKA will have unique scientific capabilities and it will open up a new era in scientific

research.

• The chosen core site, CASLEO, has low amount of RFI, low atmospheric opacity at high frequencies, and is located within a region with very low population density. It is not expected a significant change in the future.

• Easy access by road. Relatively close to major urban centers. Overall weather conditions are unlikely to impact on the operation of the central SKA region.

• The longest baselines will be provided by stations located in Brazil.

• The proposed SKA layout fullfills the requirements of the KSPs and will be able to carry out simultaneus observations with existing (or future) major ground-based observing facilities

• Strong commitment of the Federal and local governments, academic institutions and science related Federal agencies.

• The SKA is a multi-millon dollar project. Our bid to host it, represents a low risk-high return investment. Involvement of our scientific and technical communities.

• The location of the SKA in our countries will give a tremendous boost to the scientific activity and will bring many economic (participation in major infrastructure and enginering contracts for the construction of the SKA and resultant spins-offs into other applications) and other benefits.

Water vapor content

Peak opacity at 210 GHz

Pampa del Peñasco

Viewing CASLEO from the SKA site

CASLEO

Some RFI Measurements

S

W

N

Frequency (MHz)

Pow

er (

dB

m)

North

EastSouth

West

uv coverage

National Army Geographical Service(cartography, geo-referenced satellite images)

Researchers of different fields of the CONICET, UNLP and UNSJ(geographers, geologists, meteorologists)(population geography. spatial analysis, spatial planning)

National Commision of Communications (CNC)

J. Benedetti S. Sassonne D. Sanchez R. Plastina

Collaborators

•The National House of Representatives

• The National Secretary of Science and Technology

• The Board of Directors of the National Research Council of Science and Technology

• The Government of the Province of San Juan

• “Consejo Académico” of the Faculty of Astronomy of the UNLP

• “Consejo Superior” of the National University of La Plata

The Argentinean candidacy has the endorsement of:

Common sky among VLBA, VLA and SKA V

isib

ilit

y (h

ours

)

Declination

SKA

VLA

VLBA

Altitude limit= 30o

S4 scintillation index

S4 measures the standard deviation of the signal intensity normalized by the average intensity (ground to geo-stattionary satellite)