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Phasing the antennas of the Very Large Array (VLA) for reception of telemetry from Voyager 2 at Neptune encounterThe Very Large Array (VLA) radio telescope is being instrumented at 8.4 GHz to receive telemetry from Voyager 2 during its encounter with Neptune in 1989. The procedure in which the 27 antennas have their phases adjusted in near real time so that the signals from the individual elements of the array can be added coherently is examined. Calculations of the expected signal to noise ratio, tests of the autophasing process at the VLA, and off-line simulations of that process are all presented. Various possible procedures for adjusting the phases are considered. It is shown that the signal to noise ratio at the VLA is adequate for summing the signals from the individual antennas with less than 0.1 dB of loss caused by imperfect coherence among the antennas. Tropospheric variations during the summer of 1989 could cause enough loss of coherence to make the losses higher than 0.1 dB. Experiments show that the losses caused by the troposphere can probably be kept below 0.2 dB if the time delay inherent in the phase adjustment process is no longer than approx. 5 secs. This relatively small combining loss meets the goal estabished to minimize the bit error rate in the Voyager telemetry and implies adequate autophasing of the VLA.
Document ID
19890000836
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Ulvestad, J. S. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
September 5, 2013
Publication Date
August 15, 1988
Publication Information
Publication: The Telecommunications and Data Acquisition Report
Subject Category
Space Communications, Spacecraft Communications, Command And Tracking
Accession Number
89N10207
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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