Global Reference Frame VLBI solution VIE2025 (SX+VG+K)

Context and methodology

Global reference frame solution (TRF + EOP + CRF) from Very Long Baseline Interferometry based on  S/X-band, VGOS and K-band sessions until 2026.0. Analyzed with VieVS software package.

• TRF: station position (epoch 2020.0) and linear velocity
• EOP: pole coordinates and UT1-UTC reported for 0 UT, CPO reported for the middle of the session
• CRF: radio source coordinates (J2000 frame at 2015.0 Galactic aberration epoch with 5.8 uas/y GA amplitude). Formal errors are directly from the adjustment (without any noise floor or inflation)

Technical details

• DATA_START       1979-08-03T00:00:00
• DATA_END          2025-12-30T00:00:00
• DESCRIPTION      VLBI global solution S/X + VGOS + K with TRF+EOP+CRF estimated
• FREQUENCY BANDS  S/X, VG, K
• ANALYSIS_CENTER  VIE (TU Wien, Austria) within Astro2Geo project
• CONTACT            Hana Krasna (hana.krasna@tuwien.ac.at) 
• SOFTWARE          VieVS v4.0 
• TECHNIQUE         VLBI 

Data origin

S/X and VGOS: IVS data centers https://cddis.nasa.gov/archive

K band

• projects BR079, BL115, 128 and BL122: Lanyi et al. (2010), Petrov et al. (2011)
• since 2014 Astro2Geo project: de Witt et al. (2023), Krásná et al. (2023), Gordon et al. (2026)
• VLBA: bj083, ud001, ud009, ud015, ud017, ud019, and ud020 
• HARTRAO-HOBART26: ks14, ks16-ks21 (+TIDBIN64, TIANMA65)
• HARTRAO-YEBES40M: km22-km23 
• HARTRAO, HOBART26, MOPRA, ATCA-TIE, CEDUNA, PARKES, SEJONG: vt29a
• KVN, YEBES40M, MOPRA, SEJONG: n23aw, n23jh, n24jh

Data format

Plain ASCII files.

Files

• vie2025_sxvgk_TRF.txt: Terrestrial Reference Frame, globally adjusted station positions at reference epoch 2020.0 with linear velocity
• vie2025_sxvgk_TRFred.txt: simplified format of the TRF (without formal errors, external TRF VieVS input format) which in addition includes mean position of the session-wise reduced telescopes
• vie2025_sxvgk_EOP.eoxy.txt: Earth Orientation Parameters, reported is one offset per EOP per session. Earth rotation parameters are reported for 0 UT, celestial pole offsets for the middle of the session
• vie2025_sxvgk_CRF.txt: Celestial Reference Frame, source positions are in the J2000 frame, but at the 2015.0 galactic aberration epoch with 5.8 uas/y GA amplitude

Acknowledgements

The International VLBI Service for Geodesy and Astrometry and all its components are acknowledged for providing the S/X and VGOS data.

The use of the Very Long Baseline Array under the US Naval Observatory's time allocation is acknowledged, which supports USNO's ongoing research into the celestial reference frame and geodesy. The VLBA is operated by the National Radio Astronomy Observatory, which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

This study also made use of data collected from radio telescopes at HartRAO, Hobart, Yebes Observatory, the Korean VLBI network (KVN), the Australian Telescope Compact Array, Mopra, Parkes, Ceduna, Tidbinbilla, Sejong, and Tianma. Radio telescopes observing K-band sessions within the Astro2Geo project are acknowledged https://sites.google.com/sarao.ac.za/k-bandastrogeovlbi/network

Other

Work done within the Astro2Geo K-band collaboration.

Related journal article is under review.