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Creating The Basic Image

A radio synthesis telescope array does not actually produce images of the radio sky at which it points, but obtains information from which such images can be constructed. The data that radio telescope arrays collect are transformed into a usable format for producing images via a complicated mathematical operation called a Fourier Transformation. Taking advantage of powerful digital computers, a special form of this operation, called the Fast Fourier Transformation (FFT), is used to reduce the time spent on this otherwise very time-consuming computation.

Because FFT's require a great number of calculations, they require hours of computation time. Using a standard engineering workstation such as Sparc 10, it may take 14 hours to crunch the numbers. Running the same calculations on massively parallel computer like the Connection Machine 5 cuts the computation time to less than ten minutes. As part of a multicenter radiosynthesis imaging project, efforts are underway to harness the growing power of high performance computers in order to further reduce the delay between data collection and imaging.

FFT-generated image of the galaxy, Cygnus A : FFT

This image was produced from an FFT computation. While the intense radio source, Cygnus A, is visible, it is still not very clearly defined. An additional data processing step, namely deconvolution, would help clean up the image.
JPEG Image (47K); Credits and Copyrights

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NCSA. Last modified 11/13/95