Roger Clifton Jennison

Roger Clifton Jennison (18 December 1922 – 29 December 2006) worked as a radio astronomer at Jodrell Bank under the guidance of Robert Hanbury Brown. 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.

Jennison was born in Grimsby, England, in 1922. His education was at Clee Grammar School for Boys. He was commissioned from RAF aircrew to the Technical Branch-Signals, where he developed radar and microwave systems using the Magnetron.

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 performed 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.

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