Australia Telescope National Facility

Introduction to Radio Astronomy and Interferometry

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Radio astronomy uses radio waves to study regions of space.

Single-dish radio telescopes produce blurry images.

Interferometry is a technique used to overcome the blurring and produce sharper radio images.

The spacing between the radio telescope dishes in an interferometer determines the size of the objects that can be resolved by the interferometer.

Using many dishes together in an interferometer array allows astronomers to form more complete images of objects.

This is how an aperture synthesis telescope such as the Australia Telescope Compact Array works.

VLBI (Very Long Baseline Interferometry) enables very small objects to be clearly resolved.

To clearly resolve very fine detail and small objects the radio telescope dishes have to be very far apart. For VLBI the elements of the interferometer may be separated by thousands of kilometres, over several continents, and even on spacecraft. For such large separations it is impractical to physically connect the dishes together. In VLBI, the signals from each element are separately recorded along with the timing pulses from an atomic clock. The recordings are then physically brought together at a later date and processed by a computer which uses the time signals to ensure the correct registration of one radio signal with respect to another.

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Last update by Michelle Storey. 14/2/99

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