Bandwidth Synthesis Algorithms for Post-Processing RT-32 VLBI Observations using RASFX Correlator

V. A. Shantyr, A. S. Kumeyko, I. F. Surkis

Transactions of IAA RAS, issue 63, 17–27 (2022)

DOI: 10.32876/ApplAstron.63.17-27

Keywords: cross-correlation function, group delay, interference frequency, phase calibration signal, bandwidth synthesis

Abstract

Since 2019 the software RASFX correlator has been using to process VLBI observations of RT-32 radio telescopes with a bandwidth of frequency channels 8 MHz, separated by a distance of up to 720 MHz. The group delay is defined with synthesized band during correlation processing. The phase calibration before bandwidth synthesis is performed by two methods. The first is based on using of initial and corrected phase calibration signals of the station picosecond pulse generators. The second method uses reference observations for phase calibration. Algorithms for both methods are presented. To estimate the quality of synthesis by two methods, post-processing of several RT-32 VLBI one-hour observations on RASFX correlator was performed. The results of secondary processing of these sessions are given in comparison with results of correlator ARC with its own post-processing software and correlator DiFX with the PIMA package. The secondary processing was performed with help of QUASAR package. For most observations the UT estimates from RASFX correlator are close to the results of ARC and DiFX correlators, and in some observations the accuracy of calculations is higher. Development of both methods to improve results will be continued.

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