http://www.skyandtelescope.com.au 15IT’S A SPECTACULAR SUNSET, with hues ranging from
subtle pink and pearl to flaming orange and gold. Venus
shines high in the west; Earth’s shadow creeps up in the east.
Low, thorny vegetation makes it hard to wander around. And
dangerous, too — there are scorpions here. I’m in the Great
Karoo, a vast semi-arid region, some five hundred kilometres
northeast of Cape Town. It’s incredibly quiet. Hardly anyone
lives here; the nearest small town, Carnarvon, is roughly one
hundred kilometres away.
Still, there’s ample sign of human activity. Silhouetted
against the colourful clouds are the dishes of the South
African MeerKAT radio telescope array, which is still very
much under construction during my visit in late November- “By the end of 2017, all 64 MeerKAT antennae will
hopefully be in place,” says my host Angus Flowers, the
project’s media liaison, as he drives us back to the Losberg
Lodge, a former farmstead close to the observatory’s central
area now operated by radio astronomers.
A few kilometres away from the budding MeerKAT is a
broken ring of low mountains that help to keep out unwanted
radio interference from distant farms and towns. Later that
night, when we are outside under the stars, enjoying our braai
dinner (the popular South African version of barbecue), I
imagine what the site may look like some 15 years from now.
If you could fly up, high above the flat-topped mesas, you’d
be looking down at the largest collection of radio dishes ever
built — the South African part of the Square Kilometre Array
(SKA). Comprising 2,000 antennae, it will spread out over
much of the Karoo, way beyond the horizon, and even into
other African countries.
And that’s only part of the story. While the African array
(called SKA-mid) will focus on mid-frequency radio waves, its
Australian counterpart (SKA-low), made up of more than a
million simpler antennae, will study the low-frequency radio
universe. So far, only the first phase of the ambitious, two-
continent project (SKA1) has been funded. SKA1, cost-capped
at 650 million euros (nearly $920 million), will comprise
200 dishes in South Africa and many tens of thousands of
antennae in Australia. The hope is to complete the second
phase (SKA2) in 2030, with a whopping tenfold increase in
observing power.
The SKA is an unprecedented multi-phase, multi-
wavelength, multi-continent endeavour. “It never ceases to
impress me,” says Flowers.
Aperture synthesis
Radio astronomy is a young discipline. After Karl Jansky’s
1933 discovery of radio waves from the Milky Way, it took
until the late 1950s before giant dishes were erected, such as
the venerable 76-metre Lovell Telescope at the Jodrell Bank
Observatory in northern England. But only with the advent
of the techniques called radio interferometry and aperture
synthesis in the 1960s did astronomers succeed in obtainingSUNSET OVER THE KAROO MeerKAT dishes stand
sentinel at dusk at South Africa’s remote SKA site.
GOVERT SCHILLING