Spectral Line Interferometry with Independent Time Standards at Stations Separated by 845 Kilometers

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Science  11 Aug 1967:
Vol. 157, Issue 3789, pp. 676-677
DOI: 10.1126/science.157.3789.676


An upper limit of 0.02 second of arc has been determined for a hydroxyl radical (OH) emission region associated with the radio source W3, with the use of a Michelson interferometer consisting of two radio telescopes 845 kilometers apart. Timing was provided at the stations by independent atomic frequency standards. The 1665-megahertz radiation was translated to video frequency and recorded digitally on magnetic tapes which were later processed by computer, yielding fringe phase and amplitude as a function of frequency over the received bandwidth.