Technical description of intensive UT1 solution gsiint2c 

Last update: 22 January, 2018


 1.  Purpose of solution: 
     Ultra-rapid determination of UT1-UTC from the IVS INT2 sessions.

 2.  Analysis Center:  Geospatial Information Authority of Japan (GSI)

 3.  Short narrative description of solution:
     The intensive solution gsiint2c is for the ultra-rapid estimation of 
     UT1 from the IVS INT2 sessions. Most sessions consist of about 40 
     observations on one baseline (mainly Tsukuba-Wettzell until 2016 and 
     Ishioka-Wettzell from 2017). The solution includes all usable INT2 
     sessions since 2003.04.12. The rapid solution of INT2 can be submitted 
     within a few minutes after the observing session is completed. The 
     processing is automatically implemented by the K5 correlation software 
     and analysis software c5++[1]. The geophysical model follows IERS 
     Convention 2010. The terrestrial reference frame ITRF2014 is used for 
     station coordinates. Source positions are fixed to ICRF2. 
	

 3a. Differences with respect to previous (gsiint2b) solution:
     The baseline was switched from Tsukuba-Wettzell to Ishioka-
     Wettzell in 2017 after an overlap period of three months.
     Terrestrial reference frame was updated from VTRF2008 to ITRF2014.
     The analysis software c5++ was upgraded from beta version to 
     ver.0.0.1 series. Ver.0.0.1 is compliant to the IERS Convention 2010, 
     and the L1-norm patch is added for ambiguity resolution[2].


 4.  Estimated parameters:

     a. celestial frame:  No
     b. terrestrial frame:  No
     c. earth orientation:  UT1-UTC
     d. zenith troposphere:  A zenith wet delay offset per station
     e. troposphere gradient:  No
     f. station clocks:  
         Coefficients of the second order polynomial of clock functions.
     g. baseline clocks:  No

 5.  Celestial reference frame:

     a. a priori source positions:  ICRF2
     b. source positions adjusted in solution:  No
     c. solution identification or reference:  ICRF2

 6.  Terrestrial reference frame:

     a. a priori station positions:  ITRF2014
         The Ishioka 13-m position is derived from a global solution analyzed by GSI.
     b. a priori station velocities:  ITRF2014 velocity field
     c. reference epoch:  2010.0
     d. station positions/velocities adjusted in solution:  No
     e. solution identification or reference:  ITRF2014

 7.  Earth orientation:

     a. a priori precession model:  IERS Conventions 2010
     b. a priori nutation model:  IERS Conventions 2010
     c. a priori short-period tidal variations in x, y, UT1:  
         IERS Conventions 2010
     d. a priori UT1 and polar motion: finals2000A.daily provided by the 
         IERS Rapid Service/Predection Center
         (http://maia.usno.navy.mil/ser7/finals2000A.daily)

 8.  A priori geophysical models:

     a. troposphere: VMF1 for dry and wet delays
     b. solid Earth tide:  IERS Conventions 2010
     c. ocean loading:  FES2004 model
     d. pole tides: IERS Conventions 2010
     e. atmosphere loading: Created by S1 and S2 Atmospheric Tide Loading Calculator[4]
         
     f. antenna thermal deformation: 
         IVS antenna thermal deformation model [5]
     g. axis offsets:  
         Values of the official list of VLBI antenna axis offsets issued 
         by the IVS Analysis Coordinator based on gsfc-itrf2013.axo
         

 9.  Data type:  Group delays

 10. Data editing : Automatic ambiguity resolution using X/S band data
      only when both quality flags show no errors. Meteo data and cable
      cal are automatically extracted from the log files. 

 11. Data weighting: 
      Observations are weighted by their wet mapping function values. 

 12. Standard errors reported: 
      Formal errors at the one sigma level are derived from a 
      least-squares adjustment. 

 13. Software:  c5++ ver.0.0.1 rev.904

 
 References
 [1] Hobiger, T., T. Otsubo, M. Sekido, T. Gotoh, T. Kubooka, and 
     H. Takiguchi, Fully automated VLBI analysis with c5++ for ultra-rapid
     determination of UT1, Earth Planets Space, 45(2), 75-79, 2010.

 [2] Niko Kareinen, Thomas Hobiger, and Rudiger Haas, Automated 
     ambiguity estimation for VLBI Intensive sessions using L1-norm,
     Journal of Geodynamics, 102, 39-46, 2016.

 [3] Boehm, J., B. Werl, H. Schuh, Troposphere mapping functions
     for GPS and very long baseline interferometry from European Centre
     for Medium-Range Weather Forecasts operational analysis data,
     Journal of Geophysical Research, 111, B02406, 2006.

 [4] T. M. van Dam and R. Ray, 2010, Updated October 2010. S1 and S2 Atmospheric 
     Tide Loading Effects for Geodetic Applications 
     (http://geophy.uni.lu/ggfc-atmosphere/tide-loading-calculator.html)

 [5] Nothnagel, A., Modelling of Radio Telescopes for Geodetic and 
     Astrometric VLBI, Journal of Geodesy, 83, 787-792, 2009.



----
Tsukuba VLBI Analysis Center 
Contact: Takahiro Wakasugi (gsi-vlbi-oper@ml.mlit.go.jp)