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Optimal Signal Averaging Time in VLBI Sessions

Yuriy Vekshin, Voytsekh Ken, Sergei Kurdubov

IVS 2022 General Meeting Proceedings, Kyla L. Armstrong, Dirk Behrend, and Karen D. Baver (eds), 144–147 (2023)

Ключевые слова: radio interferometer, VLBI, tri-band receiver, correlator, signal-to-noise ratio, group delay, delay stability, Universal Time

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We propose a technique for determining an optimal averaging time of source signal in VLBI taking into account signal delay instability in radio telescope’s equipment. Delay instability is determined by calculating fringe parameters over a continuous 1-hour source tracking session. Optimal signal averaging time (which provides minimum error of delay measuring) is determined by calculating Allan deviation. Delay measurement error increases at longer averaging time due to delay instability. Source signal averaging time is determined in such a way that the delay’s calculated standard deviation is not less than the radio telescope equipment’s delay instability Allan deviation. The results of measuring delay instability of RT-13 radio telescopes of Quasar VLBI Network in the S-, X- and Ka-bands were applied to R-X session postprocessing. Some of previous sessions were recalculated by changing the scheduled source signal averaging time to an optimal one for a few most intensive sources. The comparison of UT1-UTC determination and its formal errors obtained with scheduled averaging time and optimal averaging time is presented.