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)