Deriving Ionospheric Total Electron Content by VLBI Global Observing System Data Analysis During the CONT17 Campaign

Abstract

This article focuses on the new generation of geodetic very long baseline interferometry (VLBI), the VLBI global observing system (VGOS), and measurements carried out during the CONT17 campaign. It uses broadband technology that increases both the number and precision of observations. These characteristics make VGOS a suitable tool for studying the atmosphere. This study focuses on the effects of the ionosphere on VGOS signals using a model that incorporates and extends ideas originally published in Hobiger et al. (2006, https://doi.org/10.1029/2005RS003297). Our investigation revealed that the differential total electron content (dTEC) data product calculated with the VGOS post‐processing software had a sign error that fortunately, does not change the final values of the phase and group delay. Therefore, this study was a way to identify this problem within the dTEC product. After diagnosing and solving this problem, the underlying model was modified such that instead of considering a single unknown for the latitude gradient of the ionosphere, a time series of latitude gradients were considered that enhanced the resulting vertical total electron content (VTEC) estimates. For evaluation purposes, time series of VTEC at each station during the CONT17 campaign were compared with VTEC obtained from the global navigation satellite system (GNSS). The final agreement between VGOS and GNSS was between 1.1 and 5.9 TEC units (TECU).

Single band VLBI absolute astrometry

“…;Hobiger et al (2006);Dettmering et al (2011);Motlaghzadeh et al (2022) claimed a good agreement between TEC derived from VLBI and GNSS. And indeed, the plot of ionospheric contributions in zenith direction from VLBI after removal clock biases against the ionospheric contributions from GNSS shows no peculiarities and fits the straight line τ vi = −3.9 ps + 1.06 • τ gi .…”

“…A number of authors compared the ionospheric contribution from GNSS, VLBI, DORIS, radio occultation observation, and dual-band satellite altimeters (Sekido et al 2003;Hobiger et al 2006;Dettmering et al 2011;Hernández-Pajares et al 2017;Cokrlic et al 2018;Li et al 2018Li et al , 2019Xiang & Gao 2019;Wielgosz et al 2021;Zhao et al 2021;Motlaghzadeh et al 2022). A message these publications convey is there is a reasonable agreement between GNSS TEC maps and other techniques and there are no majors problems.…”

“…Comparison in the past was often performed using very short continuous dataset of VLBI observations, from 5 to 15 days (Hobiger et al 2005;Dettmering et al 2011;Etemadfard et al 2021;Motlaghzadeh et al 2022). The level of the agreement was characterized in terms of additive errors of GNSS TEC model.…”

Single-band VLBI Absolute Astrometry

“…Sekido et al (2003),Hobiger et al (2006),Dettmering et al (2011), andMotlaghzadeh et al (2022) claimed a good agreement between the TEC derived from VLBI and GNSS. And indeed, the plot of the ionospheric contributions in the zenith direction from the VLBI after removal of the clock biases against the ionospheric contributions from GNSS (Figure8) shows no peculiarities.…”

“…A number of authors compared the ionospheric contribution from GNSS, VLBI, DORIS, radio occultation observations, and dual-band satellite altimeters (Sekido et al 2003;Hobiger et al 2006;Dettmering et al 2011;Hernández-Pajares et al 2017;Cokrlic et al 2018;Li et al 2018Li et al , 2019Xiang & Gao 2019;Wielgosz et al 2021;Zhao et al 2021;Motlaghzadeh et al 2022). A message these publications convey is there is a reasonable agreement between GNSS TEC maps and other techniques and there are no majors problems.…”