Radio-Interferometric Array

The objective of a radio-interferometric array is to sample the coherence function over as much of the u-v plane as 

The Earth s atmosphere can be a major source of error in the final coherence samples. At centimeter wavelengths the effect of the troposphere can be ignored for resolutions 

Once a correlator has produced the coherence samples, a Fourier inversion is required to produce an image. For this process modem computers have proven to be 

Name Location Number of antennas Maximum baseline (km) Observing wavelength (cm) 

Australia Telescope Compact Array Narrabri, Australia 6 6 20,13, 6, 3 

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LOFAR, recently built in Holland, is a new radio interferometric array consisting of many low-cost antennae, organised in stations arranged in an area of 100 km diameter as well as several international stations and operating between 10 and 250 MHz. 

Independent arrays of telescopes have been discussed for decades but have generally not been successful, except for radio telescopes, where interferometry is a key virtue, aided by the fact that the individual telescope signals can be amplihed and combined while preserving phase information. This is not practical in the optical, thus there are significant inefficiencies in sensitivity by coherently combining the light from an array of optical telescopes. Instrumentation for an array of telescopes has also been a cause of difficulty. Perhaps the best known successful array has been the VLT with four 8-m telescopes, each with its own suite of science instruments, and the capacity to combine all telescopes together for Interferometric measurements. 

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