For deeper understanding of the physical processes occurring in many astronomical objects,
scientists combine observations made at different wavelengths in what is known as `multi-
wavelength astronomy'. Beginning with space missions, and now expanding to include most
major ground-based observatories, such data have been and continue to be archived into large,
central computer databases which (at least in the case of nationally funded observatories and
missions) are made publicly available to astronomers over the Internet. Working with such huge
databases, however, and combining the data effectively can be difficult and time-consuming. It is
now feasible to consider accessing an atlas of the entire sky taken at a resolution of 0.1 seconds of
arc56 - but such an atlas would correspond to 100 terabytes (TB)56 - that's 100 000 gigabytes
(GB)! Distributing such a giant database is obviously impossible (just think, your home or school
PC most likely contains everything on a ~100-GB hard disk, so you'd need 1 000 of them to store
this atlas). Enter the International Virtual Observatory Alliance (IVOA), which aimed to simplify
the process through the power of the World Wide Web.
The IVOA has created standards for formatting such data and provided suitable software by
which to access these huge datasets remotely. So there is only one copy of the atlas(it could be
located anywhere in the world) and you simply query it, work with it, and get results, which are
then sent over the Internet to your own computer. Such is the power of the IVOA. But to work
effectively it needs high-speed Internet links.
The Digital divide and South Africa's SKA bid:
The date Karoo skies and `dark' (or `quiet') at radio frequencies too, giving South Africa a
further geographic advantage this time for radio astronomy. As a result, with the support of other
countries in the region, South Africa is on the short-list (together with Australia) as one of the two
potential sites to host the Square Kilometer Array (SKA).
With an effective collecting area of a million square meters, the SKA will be the most powerful
radio telescope on Earth, achieving sensitivity a hundred times greater than current instruments,
and costing ~US$2 billion. If the SKA is located in southern Africa, an array of antennas will be
distributed over the entire southern African region, with its central core area concentrated near
Carnarvon in the Northern Cape. This remote, radio-quiet area is ideal because of the very small
number of people living and working there -no people means no cell-phones, television, or radio
transmission, all of which cause the high levels of radio `interference' over so much of our world.
In preparation for the SKA, South Africa and Australia are both constructing `SKA pathfinder'
radio telescope arrays. In South Africa, the KAT (Karoo Array Telescope) Project Team has
commenced design and construction of the MeerKAT, a world-class radio telescope, composed
initially of 80 12-m dishes and extending over a distance of up to 10 km in the Karoo.
The current limitation in data transmission from the Northern Cape is a very large factor in the
MeerKAT construction. To complete it at this stage would be impossible, because the bandwidth,
computer processing power, and data storage required simply do not yet exist anywhere. The
problem will partly be solved through Moore's Law, the remarkably well-established relation by
which raw cpu (central processing unit) power and hard disk storage capacity essentially double
every two years. Extrapolating this into the future indicates that the necessary technology should
be available by about 2014 (even if we don't yet know what form that technology might take).For
South Africa, the main problem lies in the data transmission. We are way behind in terms of
56
A second Arc is a very small unit of angular measure, equivalent to one-sixtieth of an arc minute. The
prefix tera-(T) is used in the metric system to denote one million times, so 1 terabyte (TB) = 1 000
gigabytes (GB)
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