Why one square kilometre?
Increasing a telescope's collecting area increases its sensitivity. Thanks
to higher sensitivity, weaker signals emitted by more distant or fainter
celestial objects, can be received. One of the aims of the SKA is to receive
signals from the early Universe (the most distant objects that can be
observed). These signals are very faint and hence require a very sensitive
telescope so that they can be detected. This means the SKA needs to be
very large.
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Technology
To provide a million square metres of aperture at an acceptable cost the
Square Kilometre Array must make a revolutionary break with current radio
telescopes. Institutions
participating in the SKA are now designing and building prototype
systems, and the key technologies will be determined from these. Many
different technological solutions will be selected and integrated into
the final instrument.
Both planar phased arrays and reflectors are being considered for the
antennas. The technology must allow for multibeaming (viewing the sky
in more than one direction at once over large areas of sky, preferably
with fields of view that can be targeted independently).
Reference Design
The SKA’s collecting area of order one million square metres will
be distributed over a number of “stations” – perhaps
as many as a few hundred. Each station will have a diameter of 100-200
m. For comparison, Arecibo is the world’s largest radio telescope
with a diameter of 305 m (although not steerable), followed by the GBT
(100 x 110 m), and the Effelsberg telescope (100 m).
The Reference Design is composed of planar Aperture Arrays for the low
frequency band and small steerable dishes with “smart feeds”
for the intermediate and high frequency bands. The “smart feeds”
comprise Focal Plane Arrays for the intermediate frequencies and wide-band
feeds at higher frequencies.
Ongoing technology development work includes:
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