|GK Radio Telescope Interferometry|
This article attempts to explain why and how a radio telescope uses interferometry to achieve high sensitivity of performance in revealing the sky. SKA Telescope is such a radio interferometry telescope.
Why- The Britanica Encyclopedia defines Radio Interferometer as an apparatus consisting of two or more separate antennas that receive radio waves from the same astronomical object and are joined to the same receiver. The antennas may be placed close together or thousands of kilometers apart.
o The principle of a radio interferometer’s operation is the same as for an optical interferometer, but, because radio waves are much longer than light waves, the scale of the instrument is generally correspondingly greater. Parts of a radio wave reach the spaced antennas at different times. This time difference is compensated for by a variable-delay mechanism and the waves can be made to interfere.
o The simplest radio interferometer consists of two aerials connected together via lengths of coaxial cable to a multiplier and integrator. The voltages A and B from the aerials (proportional to the electric field at each aerial) are multiplied giving AB* at the output. The AB* term when averaged over several radio frequency cycles in the integrator is proportional to the cross - correlation R12 of the electric field received by the two aerials. The multiplier and integrator (and other electronics) are collectively called the correlator for this reason.