How does aperture synthesis create the effect of a much larger radio telescope?

Aperture synthesis is a technique in radio astronomy that allows astronomers to simulate a single, massive radio telescope by using an array of smaller, movable antennas.12

The process works through the following principles:

• Interferometry: By using multiple antennas, the system measures the interference patterns—or "Fourier components"—of incoming radio signals. As the Earth rotates, the changing positions and spacings of these antennas relative to the radio source allow the array to sample a wide range of these components.2
• Synthesis: Each pair of antennas acts as an interferometer, measuring specific data points that represent the brightness distribution of the source. By combining these measurements, scientists can synthesize an effective aperture with a diameter approximately equal to the largest spacing between the individual antennas.12
• Computational Reconstruction: Because the array uses discrete spacings rather than a continuous surface, high-speed computers use the fast Fourier transform to reconstruct high-resolution images from the collected data.2

This method enables the achievement of extraordinary angular resolution that would be physically and economically impossible to attain with a single, solid-dish antenna.2