By: Keith Campbell
KAT-7 was originally conceived of as an engineering and technology test bed for the 64 dish MeerKAT radio telescope array which will be built in the Karoo and should enter operation in 2016, but will now also serve as an operational instrument until MeerKAT is ready.
MeerKAT itself is intended as a precursor to the €1.5-billion international Square Kilometre Array (SKA) radio telescope.
Radio telescope feeds are cryogenically cooled to very low temperatures in order to both reduce internally generated interference (known as “noise”) and to achieve the greatest possible sensitivity, as radio sources in the cosmos are very weak. In the case of KAT-7, the feeds are cooled to a temperature of 70 degrees Kelvin, or – 203 degrees C.
Previously, most of the dishes were fitted with uncooled feeds, which were perfectly adequate for engineering tests but were not suitable for doing science.
For example, last year four of the KAT-7 dishes, fitted with uncooled feeds, imaged the Centaurus A radio galaxy. The new image of the galaxy taken by KAT-7 has a far higher resolution, because of the cooled feeds and because all seven dishes were employed.
KAT-7 is now ready to do early science in preparation for the MeerKAT and SKA. This science will be focused on programmes applicable to the planned large survey projects planned for MeerKAT.
These will include the imaging of pulsars, radio transients and nearby galaxies. Such taskings are ideal for KAT-7.
A pulsar is a rapidly spinning neutron star which emits beams of radiation, which sweep across the line of sight of Earthly observers in a very regular period (a neutron star is itself the incredibly dense collapsed core of a massive star which has been destroyed in a supernova explosion. On earth, one teaspoonful of neutron star material would weight about a billion tons).
Radio transients are a wide range of celestial objects which emit bursts of radio waves. These include pulsars, stars and planets – a nearby example is the planet Jupiter.
(Engineering news,South Africa)