Combining VGOS, legacy S/X and GNSS for the determination of UT1

Diamantidis, Periklis-Konstantinos; Haas, Rüdiger; Schartner, Matthias; Matsumoto, Saho

doi:10.1007/s00190-022-01648-3

Cited by 3 publications

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

Assessment of the Tropospheric Delay Coefficients at Co-located Sites with VGOS and GNSS

Walenta,

Flohrer,

Thaller

et al. 2024

International Association of Geodesy Symposia

View full text Add to dashboard Cite

An assessment of the tropospheric parameters independently derived from the analysis of Very Long Baseline Interferometry (VLBI) and Global Navigation Satellite Systems (GNSS) data serves as a cross-validation of the two space geodetic techniques on the parameter level. Time series of the tropospheric parameters are studied for the most frequently observed VLBI stations at 7 co-located sites covering a time span between 2019 and middle of 2023. These sites are equipped in total with 10 small and fast-slewing antennas that have been specifically built to satisfy the concept of the VLBI Global Observing System (VGOS). Next to the VGOS antennas, 5 legacy VLBI antennas are located providing an additional source of the VLBI observations for comparison. VLBI conducts observations on a session-wise basis of 24 hours at least twice a week, whereas GNSS observes continuously. As a consequence, the paired tropospheric parameters are restricted to epochs where VLBI data are available. The closest GNSS receivers are chosen next the VGOS or VLBI antennas to ensure the same path propagation delays. For the sake of a meaningful comparison, the parameterization of the troposphere is homogenized between the two techniques in favor of the VLBI analysis: the VLBI observations are scheduled to provide even sky-coverage within every hour. After omitting modelled offsets between the reference points of the VLBI and GNSS antennas expected due to the height differences, the obtained tropospheric estimates of two independent techniques show a good agreement level, which lays within their scatter. The remaining tropospheric variations are averaged at the level of 4-6 mm in terms of root mean square differences. A larger scatter of these tropospheric variations is obtained for a few stations at the level between 8–10 mm. These extreme cases can be explained by specific issues at each individual station, i.e. the short paired time series.

show abstract

Assessment of the Tropospheric Delay Coefficients at Co-located Sites with VGOS and GNSS

Walenta,

Flohrer,

Thaller

et al. 2024

International Association of Geodesy Symposia

View full text Add to dashboard Cite

show abstract

On the importance of accurate pole and station coordinates for VLBI Intensive baselines

Kern,

Schartner,

Böhm

et al. 2023

J Geod

View full text Add to dashboard Cite

Very long baseline interferometry (VLBI) is a geodetic technique capable of deriving the complete set of Earth orientation parameters, including the highly variable Earth’s phase of rotation. This observable can be expressed through UT1–UTC, the difference between the Universal Time and the Coordinated Universal Time. The so-called Intensive sessions, or Intensives, are typically 1-h sessions between two to three stations that are observed daily with the primary goal of determining UT1–UTC with a short latency. In this publication, we examine the impact of erroneous a priori information on the UT1–UTC estimation with VLBI Intensive sessions in a systematic way and on a global scale. Our findings are based on a simulation study which is carried out on a regular $$10 \times 10$$ 10 × 10 degree grid of artificial telescopes. In the simulations, realistic errors are introduced in the station coordinates, polar motion and nutation to get a global picture of the impact of these errors on the estimation of UT1–UTC. Our results reveal that in contrast to errors in the horizontal components of the station coordinates, an error in the station height only slightly affects the UT1–UTC estimate. North–south-oriented baselines are in general strongly affected by errors in the a priori information. In all cases, very short and very long baselines as well as baselines with a midpoint close to the equatorial plane are less robust. On the other hand, east–west-oriented baselines, except equatorial baselines, seem to be rather resistant against errors of these a priori values.

show abstract

Evaluation of the first three years of Vgos 24 h sessions using a Kalman filter with C5++

Diamantidis

Haas

2023

Earth Planets Space

View full text Add to dashboard Cite

We analyzed the first three years of VGOS 24 h sessions, and evaluated the performance in terms of Earth orientation parameters (EOP) and station positions. We estimated radio source coordinates which might be of particular importance in VGOS due to the different observing frequencies compared to legacy S/X VLBI. We investigated the impact of this procedure in the determination of the celestial reference, and detected possible increased crosstalk between radio source positions and nutation. We, thus, created an updated source coordinate catalogue that contains information from the VGOS observations and utilized that as our a priori for further analysis. We found that this procedure significantly attenuates mean biases in the estimated EOP time series. We then utilized a kalman filter with an empirically tuned stochastic modelling for nutation and polar motion and estimated repeatabilities on the 60–80 $$\mu$$ μ as level for nutation, and 100–130 $$\mu$$ μ as level for polar motion. The station position repeatabilities were evaluated to be 1.80 and 2.12 mm for the east and north components and 3.98 mm for the vertical, while the baseline length repeatabilities were estimated to be 4.22 mm at 6000 km. These results are promising with respect to the expected future VGOS performance, while increased attention should be paid to the celestial frame determination in the VGOS observing bands. Graphical Abstract

show abstract

Combining VGOS, legacy S/X and GNSS for the determination of UT1

Cited by 3 publications

References 29 publications

Assessment of the Tropospheric Delay Coefficients at Co-located Sites with VGOS and GNSS

Assessment of the Tropospheric Delay Coefficients at Co-located Sites with VGOS and GNSS

On the importance of accurate pole and station coordinates for VLBI Intensive baselines

Evaluation of the first three years of Vgos 24 h sessions using a Kalman filter with C5++

Contact Info

Product

Resources

About