Roger Clifton Jennison (18 December 1922 ? 29 December 2006) worked as a radio astronomer at Jodrell Bank under the guidance of Robert Hanbury Brown. In the 1950s he developed a new observable for obtaining information about visibility phases in an interferometer when delay errors are present called the closure phase. He utilised the undergraduate teaching laboratories to perform the first measurements of closure phase at optical wavelengths. Jennison saw greater potential for his technique in radio interferometry, and proposed that it should be tested on a three-element radio interferometer at Jodrell Bank. In 1958 he successfully demonstrated its effectiveness at radio wavelengths, but it only became widely used for long baseline radio interferometry in 1974. A minimum of three antennas are required. This method was used for the first VLBI measurements, and a modified form of this approach ("Self-Calibration") is still used today at radio, optical and infrared wavelengths.

Jennison made a number of discoveries in the field of radio astronomy, including the discovery of the double nature of radio source Cygnus A (3C 405.0) with M K Das Gupta and the mapping of Cassiopeia A with V Latham.

References

Roger Jennison, A phase sensitive interferometer technique for the measurement of the Fourier transforms of spatial brightness distributions of small angular extent, Monthly Notices of the Royal Astronomical Society vol 118 pp 276 1958

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