Technical description of the intensive solution opa2025a

1. Origin of input data: databases from IVS data center, version 4 or more.

2. Authentic processing steps after data retrieval: use VGOSDB format.
   Pre-2018 data were originally stored in MK3 format in Paris Observatory
   disks. These data were transformed to VGOSDB. Some of them (oldest ones)
   were preliminary re-calced with Calc 11.0. Post-2018 data were directly
   retrieved in VGOSDB format and processed with no modification.

3. Origin of meteorological data: use database content.

4. Use numerical weather model: ECMWF for computing VMF1.

5. Setting of mapping functions: VMF1.

6. Origin of cable cal data: use database content.

7. Application of cable cal flags: use database settings.

8. Selection/settings of geophysical models: replace database settings.

   8.1. Nutation/precession: IAU 2000A nutation and IAU 2006 precession.
   
   8.2. Short-period tidal variations in x, y, UT1: IERS 2010.
   
   8.3. Troposphere mapping functions: VMF1.
   
   8.4. A priori mean gradients: from VLBI data or DAO weather model.
 
   8.5. Solid Earth tide: IERS 2010.

   8.6. Ocean loading displacements: FES 2004.

   8.7. Atmospheric loading displacements: APLO.
   
   8.8. Permanent tide correction: applied.

   8.9. Thermal expansion: Nothnagel (2008).
   
   8.10. A priori station positions and velocities: ITRF 2020 or database
         content for new stations.
   
   8.11. A priori source coordinates: opa2025a catalog.

   8.12. Galactic aberration: applied with amplitude of 5.8 micros/yr and
         epoch 2015.01.01.

9. Parameterization

   9.1. Clock: max degree auto 2 intervals no.

   9.2. Atmosphere: force.

   9.3. Gradients: no.
     
   9.4. Earth orientation: UT1 only.
        
   9.5. Station positions:
        
        9.5.1. None estimated.

        9.5.2. The data relevant to the stations used for polarization tests
        or backend tests were removed:

     NOTOX    WIDE85_3 VLBA85_3 MOJAVLBA LEFT85_1 HARTDBBC YEBESDBC YEBDBBC  \
     ONSALAAN YEBEDBBC OHIGGADS WETTDBBC LEFTKOK  LEFT85_3 NYALDBBC HOBADBBC \
     SVERT13V

   9.6. Station velocities: no.
   
   9.7. Source coordinates:
        
        9.7.1. None estimated.
             
        9.7.2. The data relevant to the following sources were removed:
        
        The radio stars:
   
     0236+610 0459-753 1612+339 0334+004 0323+285 1458-083 \
     
        The known gravitational lenses:

     0218+35A 0218+35B 0218+357 1422+231 1830-21A 1830-21B 1830-211 0132-097

   9.8. Antenna axis offsets: no.

10. Outlier elimination: use database settings.

11. Constraints: none.

12. Generation of pre-reduced datum-free normal equations: no.

13. Further details

   13.1. Data type: group delays.

   13.2. Data editing: 5 degree elevation cutoff.

   13.3. Data weighting: weights are defined as follows: 1/sqrt(f**2+a**2) 
         where "f" is the formal uncertainty of the ionosphere free linear
         combination of group delays at X- and S-band obtained by fringe fitting
         on the base of achieved signal to noise ratio. Station-dependent 
         parameter "a" was computed for each session by an iterative procedure 
         such that the ratio of the sum of squares of the weighted residuals to 
         the estimate of their mathematical expectation is about unity.
 
   13.4. Standard errors reported: all errors are derived from least-squares 
         estimation propagated from the data weights and the constraints applied 
         to the troposphere, clock and EOP parameters.
         
   13.5. Software: Calc 11.0, Solve revision date 2025.xx.xx.

   13.6. Other informations about the solution are reported at
         http://ivsopar.obspm.fr.