Influence of Signal Delay Instability in Radio Telescope Equipment on Optimal Accumulation Time of Radio Interferometer Signal

Y. V. Vekshin, V. O. Ken, S. M. Mironova, S. L. Kurdubov

Transactions of IAA RAS, issue 60, 21–26 (2022)

DOI: 10.32876/ApplAstron.60.21-26

Keywords: radio interferometer, very long baseline interferometry, tri-band receiver, FX-correlator, signal-to-noise ratio, fringe delay, group delay, delay stability, Universal Time

Abstract

Accuracy of the Universal Time determination is to a great extent dependent on measurement accuracy of a signal propagation delay difference from a cosmic source to radio telescopes, that are part of the radio interferometer. Measurement error of a group delay depends on the signal delay instability in the radio telescope equipment. Evaluations of delay instability should be used when planning source observation time in radio VLBI sessions. The aim of the work is to create a technique for determining an optimal accumulation time of a radio interferometer a signal and to apply this technique while processing the Universal Time determination sessions. The correlation response delay stability is analyzed from a record of continuous 1-hour source tracking. The optimal signal accumulation time (which helps to achieve the minimum error of delay measuring) is determined by calculating Allan deviation. An optimal accumulation time of the source signal is determined in such a way that the RMS delay calculated is not less than the equipment instability deviation. The article presents the results of the delay stability measurement of the radio interferometer correlation response based on RT-13 radio telescopes in the S-, X-, Ka-bands. The comparison of the Universal Time determination and its errors with the current and proposed optimal accumulation time of the source signal are also presented.

Citation