EXPERIMENTAL INVESTIGATION OF THE COHERENCE DISTANCE OF THE ATMOSPHERE FOR MICROWAVES.
Abstract
An attempt has been made to measure the phase fluctuations of radio waves induced by the earth's atmosphere. The strong radio source Cygnus A was observed at a frequency of 3075 Mc/s using a two-element interferometer consisting of a two 30-foot diameter parabaloid antennas on equatorial mounts. The fringe pattern was recorded for periods of several hours, and the phase of each fringe, relative to a theoretical fringe pattern, was obtained. The fluctuation in the phase values shows an rms variation of one to three times the value expected from the system noise. It is not clear whether this excess fluctuation is attributable to the atmosphere, or whether it is a measure of the limiting phase stability of the instrument. The measurements do, however, provide an upper limit to the fluctuation in the effective angle of arrival of the radio waves, which is less than one second of arc for elevation angles greater than 30 deg. A description is also given of the antennas, the equatorial mounts, and the control units developed for the traveling-wave preamplifiers. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1965
- Accession Number
- AD0624991
Entities
People
- R. N. Bracewell
Organizations
- Stanford University