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Papadopoulos, G. D.

Publications and source records attributed to Papadopoulos, G. D..

A statistical technique for processing radio interferometer data

The output of a radio interferometer is the Fourier transform of the object under investigation. Due to the limited coverage of the Fourier plane, the reconstruction of the image of the source is blurred by the beam of the synthesized array. A maximum-likelihood processing technique is described which uses the statistical properties of the received noise-like signals. This technique has been used extensively in the processing of large-aperture seismic arrays. This inversion method results in a synthesized beam that is more uniform, has lower sidelobes, and higher resolution than the normal Fourier transform methods. The maximum-likelihood method algorithm was applied successfully to very long baseline and short baseline interferometric data.

Papadopoulos, G. D.

The M.I.T. Ku-band radio interferometer.

The construction of a Ku-band radio interferometer and some preliminary observations are reported. The interferometer was built for the purpose of mapping discrete radio sources like the Crab Nebula, Cassiopeia A, and Cygnus A. It has two 8-ft parabolic antennas operating at 17.128 GHz. The maximum baseline of 100 m corresponds to a resolution of 35 sec of arc. A PDP-8 computer is incorporated in the system and is used for pointing, tracking, delay compensation, and real-time data analysis. The phase stability of the system was better than 10 deg over a period of 2 hours. Consistent fringe components were obtained from the Crab Nebula with a baseline set at 8 m.

Papadopoulos, G. D.