In its first phase, the Square Kilometre Array will consist of two telescopes:
SKA-Low, in Western Australia, and SKA-Mid, in South Africa.
SKA-Low will consist of about 130,000 dipole antennas, covering
the frequency range 50--350 MHz, with the design
of these antennas under active consideration.
As part of this process,
the Aperture Array Verification System (AAVS) 1.0 is being
constructed at the Murchison Radio-astronomy Observatory
to test the in situ performance of the SKALA-2 design log-periodic antennas.
(This follows the earlier deployment, in November 2012, of
16 antennas of the AAVS 0.5.)
The SKALA-2 antenna
is a log-periodic dipole array made of four identical metallic arms
forming two polarizations with nine dipoles each. The grey ring is the base
of the antenna. The cabling that runs vertically down the centre of the
antenna carries the optical fibre and power cables. The
cap on the top of each antenna contains the low-noise amplifiers
and an RF-over-Fibre transmitter. The
antenna has a footprint of 1.2 × 1.2 m and a height of 1.8 m.
The elements are arranged pseudo-randomly to avoid grating lobe and
scan blindness problems that typically affect regularly spaced arrays of antennas.
Completion of the deployment is expected later this year.