Processing and Analysis of VLBI Observations of GLONASS Spacecraft by Quazar VLBI Network

V. V. Pasynkov, I. F. Surkis, E. V. Titov, D. A. Gulidov, S. M. Shirokiy

Transactions of IAA RAS, issue 61, 3–27 (2022)

DOI: 10.32876/ApplAstron.61.3-27

Keywords: Quazar VLBI Network, Earth Rotation Parameters, Universal Time, VLBI, colocation, GLONASS

Abstract

The paper describes an approach to solving the problem of improving the accuracy of GLONASS ephemerides to a level that ensures the competitiveness of this system in the global market of relevant services. The approach is based on a combination of GNSS, satellite laser ranging (SLR) and VLBI observations of GLONASS satellites with joint data analysis. It shows that a necessary condition for the implementation of the approach is the procedure of alignment of coordinate systems used by the listed techniques. The possibility of such alignment is demonstrated by the example of the joint use of GNSS technology (a posteriori ephemerides), as well as the SLR and VLBI techniques. In May 2017, an experiment was conducted to observe GLONASS satellites with RT-32 radio telescopes of the Badary, Svetloe, Zelenchukskaya observatories of the Quasar VLBI network. Due to the limited frequency range of radio telescopes the observations were carried out only in the L1 band (18 cm). Correlation processing was performed on the RASFX software correlator with specially modified software. The group and phase VLBI delays of the signal were determined. During the analysis of the observational data, the ionospheric delay was taken into account using ionospheric maps of the total electronic content (TEC) obtained from GNSS receivers. Several methods were used to calculate tropospheric delays: SINEX information from different data sources, VLBI and water vapor radiometers (WVR) data; the most accurate data in this experiment turned out to be SINEX file data. The time scales parameters of the stations were determined both from GNSS receivers with the involvement of information from the SLR system about the range to the spacecraft, and from VLBI observations. The analysis results show that a millimeter precision level (6–18 mm) of interpretation of the new VLBI delay navigation function is achieved. The delay is obtained during VLBI observations of the single-frequency (L1 band) GLONASS satellites navigation signals. Besides, there is attained a centimeter accuracy level of coordinates mismatch estimation, determined by using various techniques (VLBI – GNSS – SLR). Proposals have been developed to improve VLBI technology when working on GLONASS spacecraft navigation signals.

Citation