Technical Description of Solutions BoehmS_etal2022_INTvie.eopi and BoehmS_etal2022_SI.eopi
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1. Purpose of solution:	estimation of UT1-UTC from VLBI intensive sessions (SI, INT1, INT3)

2. Analysis Center:	VIE (TU Wien)

3. Analysis Software: Vienna VLBI and Satellite Software (VieVS) 

4. Estimated parameters:

    a. Celestial reference frame: no 
       
    b. Terrestrial reference frame: no 

    c. Earth orientation: UT1-UTC is set-up as piece-wise linear
	   offsets (360 min) with 1e-4 mas constraints, reference epoch is mid of session.

    d. Zenith troposphere: piece-wise linear offset (360 min), relative
	   constraints 0.1 cm.

    e. Troposphere gradients: no

    f. Station clocks (per station): piece-wise linear offset (360 min).

	g. Baseline-dependent clock offset: no
 
 
5. A priori CRF, TRF and EOP

     a. CRF source positions: ICRF3 (including Galactic Aberration)

     b. TRF station positions/velocities: vievsTrf - https://www.vlbi.at/data/analysis/ggrf/trf_vie2020_211030_withVGOS.TXT

     c. Precession/nutation model: IAU2006A

     d. x and y pole coordinates, UT1-UTC and celestial pole offsets dX, dY: 
        EOP finals: https://datacenter.iers.org/data/9/finals2000A.all, lagrange interpolation, zonal
		tidal variations are removed from UT1-UTC before interpolation

     e. A priori short period (~diurnal and semidiurnal) tidal variations in 
        x, y, dUT1: Desai & Sibois (2016) (ocean tides) and libration according to IERS Conventions 2010.

6. A priori station models
	 
	 a. Axis offsets:
        https://github.com/anothnagel/antenna-info.git/trunk/antenna-info.txt

     b. Eccentricities: 'ECCDAT_v2019Dec19.ecc'
	 
	 c. Thermal deformation: according to IVS conventions 
        https://github.com/anothnagel/antenna-info.git/trunk/antenna-info.txt
	 
	 d. Gravitational deformation:    
	    https://ivscc.gsfc.nasa.gov/IVS_AC/apriori/gravity_deform_model_v2019Nov21.txt
		 
	 e. Solid Earth tides: IERS Conventions 2010

     f. Tidal ocean loading: TPXO.7.2 

     g. Solid Earth pole tide: secular pole function as described in IERS Conventions ch.7 	   
	    update from 2018-02-01
	 
	 h. Ocean pole tide: according to IERS Conventions 2010

     e. Tidal atmospheric loading:    
	    https://vmf.geo.tuwien.ac.at/APL_products/TIDAL/s1_s2_s3_cm_noib_vlbi.dat

     f. Non-tidal atmospheric loading: VIENNA_APL from    
	    https://vmf.geo.tuwien.ac.at/APL_products/VLBI/
 
 
7.  A priori troposphere:

     a. zenith delay:
        - hydrostatic part is calculated from surface pressure + Saastamoinen.
        - wet part is estimated, no a priori model
     
	 b. mapping functions:
        - hydrostatic: VMF3	 
		- wet: VMF1
	 
	             
 8.  Data type: Group delays from vgosDB

 9.  Data editing: none (no elevation cut-off)

 10. Data weighting: 
     - Only observations with a zero quality flag in vgosDB are used.
     - A constant noise of 0.5 cm is added to all observations.
     - All observations are subject to an outlier test.
	 
References:

1. Altamimi, Z., P. Rebischung, L. Métivier, and X. Collilieux,
   "ITRF2014: A new release of the International Terrestrial Reference 
   Frame modeling nonlinear station motions, J. Geophys. Res. Solid Earth,
   vol. 121, Issue #8, pp. 6109-6131, 2016. doi:10.1002/2016JB013098. 

2. Charlot, P., et al, 'The Third Realization of the International
   Celestial Reference Frame by Very Long Baseline Interferometry';
   Astronomy and Astrophysics, 2020, DOI: https://doi.org/10.1051/0004-6361/202038368.
   
3. MacMillan, D.S. and C. Ma, "Atmospheric gradients from very long baseline
   interferometry observations", Geophys. Res. Lett., 22, 1041-1044, 1995.
 
4. MacMillan, D.S. and C. Ma, "Atmospheric gradients and the VLBI terrestrial
   and celestial reference frames", Geophys. Res. Lett., 24, 453-456, 1997.

5. Petit, Gerard and Luzum, Brian, 'IERS Conventions (2010), IERS Technical 
   Note 36, 2010.

6. Nothnagel, A., "Short Note: Conventions on Thermal Expansion Modelling of
   Radio Telescopes for Geodetic and Astrometric VLBI," Journal of Geodesy, 
   DOI: 10.1007/s00190-008-0284-z, 2008.