A phase-coherent link via synchronous satellite developed for very long baseline radio interferometry


  • S. H. Knowles,

  • W. B. Waltman,

  • J. L. Yen,

  • J. Galt,

  • D. N. Fort,

  • W. H. Cannon,

  • D. Davidson,

  • W. Petrachenko,

  • J. Popelar


A high-precision, phase coherent link between remote interferometer stations has been developed and has been utilized in a transcontinental radio interferometer to assess the feasibility of improved astrometric and geodetic measurements. A dual-tone transmission method effectively cancels most phase-degrading effects. An experimental Allen variance curve indicates that stability of 1 × 10−13 was achieved over a 1-hour period; the slope of the Allen variance curve was close to − 1 for all time intervals up to 24 hours, indicating that the link is truly phase stable at frequencies of less than 1 GHz. Changes in the link path were measured with an accuracy of 300 ps, corresponding to 10 cm, over periods of several hours.