The Square Kilometre ArrayThe Square kilometer Array (SKA) will be the major radio telescope for the 21st century. It will consist of a large number of antennas with a total collecting area of ONE SQUARE KM, i.e. about 50 times the collecting area of any existing facility. Vigorous technological developments in computing and antenna design, arising from an international collaboration, make such a radio telescope possible. The signals will be digitally combined to simulate a telescope having a diameter of several 1000 km with an enormous resolving power and sensitivity.

SKA Designs

50% of the stations will be concentrated in a core of about 10 km diameter, the remaining stations will be located on spiral arms with several 1000 km extent.

The low-frequency part of the SKA will be an updated version of LOFAR. A design study (SKADS) for the frequency range 0.4–1.6 GHz is currently undertaken by 29 European institutes. The Istituto diRadioastronomia INAF participates to this project using the Northern Cross Radio Telescope at Medicina as a test-bed for SKA. Low-cost high-frequency parabola antennas are developed in Australia, India, South Africa, and USA. Canada and China plan to construct large spherical mirrors as SKA prototypes.

The major technological challenge is to reduce the cost per unit area to about 1000 USD/m2, which is about a factor of ten lower than costs of current and past radio telescopes.

A station of low-frequency antennas

High-frequency antennas with focal plane arrays at their foci

High-frequency antennas with offset foci

SKA Science Projects

The SKA will be a revolutionary radio telescope. As the SKA will open new windows to the Universe, discoveries of many new phenomena can be expected. Based on what today´s scientists can imagine as transformational science in astrophysics and fundamental physics the following Key Science Projects were defined:

- Tests of general relativity with pulsars and black holes, and detection of gravitational waves;

- Measurement of the large-scale Hubble flow and of dark energy from HI emission of distant galaxies;

- Detection of HI signals from the Epoch of Reionization in the early Universe;

- Detection of the first magnetic fields in the Universe, through polarization, and study of their evolution to the fields that are observed today;

- Observation of the formation of protoplanets.

Studies of AGN will include:- evolutionary history of AGN populations from redshifts 0 to 6;- disks, tori, cocoons: emission, absorption, polarization and diagnostics of AGN environments;- surveys of compact radio sources.

SKA specifications

The SKA will simultaneouslyobserve in several directions ofthe sky. It will consist of low frequency antennas (100 MHz to 1 GHz) and antennas for high frequencies (1 - 25 GHz).

Frequency : 100 MHz ÷ 25 GHz Bandwidth : 25% of frequency

(4 GHZ above 16 GHz)Minimum baseline : 20 mMaximun baseline : > 3000 kmField of view: > 1 deg2 at 1.4 GHzAngular resolution : 0.1”

at 1.4 GHzRms Sensitivity : 0.13 μJy in 1 h

at 1.4 GHz

SKA SiteProposals for radio-quiet sites have been submitted by:

- Argentina- Australia - China- South Africa

TimelineAug 2006 : Ranking of sites2007-8 : Final decision on site2009 : Design concept definition2014 : 10% SKA2020 : Full SKA

www.skatelescope.org

Cylindric reflector