Kick-off meeting

 09 Jul 2025 during the IVS AC & CC Working Meeting #9

Presentation slides: https://bscw.bund.de/sec/bscw.cgi/343740399 and mirrored below:

• Soja_IVSACCCWM9_reprocessing.pdf
• IVS_AC-CC_WM_2025-07-09.pdf
• Nothnagel_AnalysisMeeting20250709_Ionosphere.pdf
• Addressing vgosDBs with no master file entries - v2 - 2025-07-10.pdf

Main outcome: decision to go ahead with a full IVS reprocessing to be included in the ITRF2020-u2025 update!

Sessions

Time range: full history of VLBI sessions until 2026.0

Detailed session lists

S/X (7598): SX_sessionlist_itrf2020-u2025.dat

VGOS (234): VGOS_sessionlist_itrf2020-u2025.dat

K-band VLBI (229): K_sessionlist_ITRF2020-u2025.dat

Note the two important initiatives to correct vgosDB files:

• Inconsistencies in vgosDB files, station naming conventions, etc. (complete)

• Inconsistent ionosphere calibrations in vgosDB files (complete)

The issue with ionosphere calibrations affects only S/X vgosDB files. It has been corrected for sessions from 2022 onward on 19 December 2025. List of corrected sessions: sessions_with_corrected_iono-updated.txt

Analysis setup

General: ACs should use a similar strategy and models as for the previous update, but the most up-to-date vgosDB files and the following important changes: 

• It should be a dedicated reprocessing effort, not the operational solutions 
• ITRF2020-u2024 should be used as a priori station positions: https://itrf.ign.fr/en/solutions/ITRF2020-u2024
• In terms of station-specific models, use the "antenna-info.txt" files published in October 2025: https://doi.org/10.48436/b00xg-3vg05
  • This contains a new antenna offset at SEJONG: Survey-Based the Axis-Offset for the Sejong VLBI_final.pdf
  • The Calc/Solve file gsfc_itrf2020_v2025Oct03.axo has also been updated for this change. 
• Use the most recent grav. deformation file published in September 2025: gravity_deform_model_v2025-09-28.txt
  • This contains a new gravitational deformation model for HOBART26: https://doi.org/10.1186/s40623-024-02110-8
• Like for ITRF2020, radio source coordinates should be estimated, and the corresponding datum-free NEQs should be written into SINEX files. ICRF3 should be used as a priori source coordinates and galactic aberration corrected. 

Submission

• Please submit the SINEX files (datum-free normal equations, as in previous ITRF contributions) under a new solution code to one of the IVS Data Centres. Please contact Dirk Behrend first to register the new solution code.
• The naming convention for the SINEX files is to only use the new vgosDB session names this time, also for past sessions.
• Please inform the IVS ACo (Benedikt Soja) and the IVS CC (Alexander Kehm) under which solution code the contribution has been uploaded.

Timeline

• until September 2025: finalization of model updates & session lists, resolving vgosDB issues
• 1 Oct 2025-15 Feb 2026: reprocessing of VLBI sessions by ACs, resolving remaining vgosDB issues
• 15 Feb - 15 Mar 2026: combination by CC & if needed iterations of AC solutions

Status

as of 2026-02-06

Data publication

I (Benedikt) would like to collect the names of everyone who made a significant contribution to this major effort. You would then be listed as authors when we register a DOI for this dataset (session-wise combined normal equations). 

General guideline: up to 4 names each for the following IVS components: analysis coordinator, combination center, and all 15 analysis centers that submitted a solution. If more than 4 people should be listed for a certain component, please contact me. If somebody else would like to be included and is not part of such an IVS component, please contact me as well. 

Please add your component, name, and details to this spreadsheet by June 14: 
https://docs.google.com/spreadsheets/d/15tgVP0mgHtUfIul5Huut-9hDZucOZsdRNZuXKXuqxJM/edit?usp=sharing

For reference, the DOI for ITRF2014 was published like this: https://dataservices.gfz-potsdam.de/panmetaworks/showshort.php?id=escidoc%3A682020. We have not yet decided which platform to use this time. The licence will again be CC BY 4.0. 

History

• 2025-07-09: kick-off meeting, page created
• 2025-09-20: antenna-info file updated
• 2025-09-29: K-band VLBI session list added
• 2025-10-01: session lists for S/X and VGOS added 
• 2025-10-03: information finalized for the official call 
• 2025-12-03: updated ionospheric corrections
• 2026-02-08: moved 15 VGOS sessions from S/X list to VGOS list
• 2026-02-17: submission instructions added
• 2026-04-28: preliminary combined solution submitted to ITRS CCs for testing
• 2026-05-25: collection of authors for DOI