Technical description of dgfd0001.snx ------------------------------------- 1. Purpose: Datum free VLBI session normal equation files in SINEX 2.0 format, including epoch coordinates and EOP. 2. Analysis Center: Deutsches Geodaetisches Forschungsinstitut (DGFI), Munich, Germany 3. Short description: More than 2500 VLBI session SINEX files starting on january 4th, 1984 are generated. All in all, this set of files contains VLBI data of 49 telescopes. These sessions were selected considering the following criteria (with a few exceptions): - 24 h or longer sessions only - at least three telescopes participating (each with more than 100 obs) - at least 250 observations per session - only non-mobile telescopes - only telescopes with sufficient data allowing to determine reliable velocities The following stations are be assumed to have discontinuities (jumps) in their position time series: NRAO85 3 901201 MOJAVE12 920627 DSS15 920627 (only data after 920627 included in this series) MEDICINA 960601 EFLSBERG 961001 DSS65 970415 TSUKUB32 990401 GILCREEK 021103 4. Estimated parameters: a. Celestial frame: No b. Terrestrial frame: Yes c. Earth orientation: Pole coordinates and their first derivatives, UT1-UTC and LOD, dpsi, deps, each valid for the duration of the session (normally 24 h), reference epoch is mid of session d. Zenith troposphere (per station): one offset for the whole session plus a piece-wise-linear function with rates valid for one hour, each of the rates constrained to 0 with 10 mm/sqrt(h) e. Troposphere gradient: one offset per station for the whole session, constrained to 0 with 0.5 mm f. Station clocks: Quadratic function plus a piece-wise-linear function with rates valid for one hour, each of the rates constrained to 0 with 30 mm/sqrt(h) (occasionally are clock jumps estimated additionally) g. Baseline clocks: None h. Other: None 5. Celestial reference frame: a. A priori source positions: solution DGFI04R02, which was computed with the 199 stable sources (according to Feissel-Vernier, A&A, 2003) constrained to have NNR w.r.t. ICRF-Ext1 b. Source positions adjusted in solution: No 6 Terrestrial reference frame: a. A priori station positions: solution DGFI04R02, which was computed with coordinates and velocities of 25 long term stable and globally distributed stations constrained to have NNR and NNT w.r.t. ITRF2000 b. A priori station velocities: solution DGFI04R02, which was computed with coordinates and velocities of 25 long term stable and globally distributed stations constrained to have NNR and NNT w.r.t. ITRF2000 c. Axis offsets: compiled according to Engelhard, G., D. MacMillan, A. Nothnagel, priv. com., 2004 (mainly weighted averages of values estimated in two VLBI solutions provided by: G. Engelhard, BKG, and D. MacMillan, GSFC. Exceptions: EFLSBERG, NYALES20 and ONSALA60, which are higly precise terrestrial measurements, provided by A. Nothnagel. Value for KWAJAL26 is from blokq and is supected to has its origin from the telecope's construction plans): name offset[m] --------------------- GILCREEK 7.29018 TSUKUB32 -.00003 DSS65 -.00234 EFLSBERG .01030 MEDICINA 1.82539 MOJAVE12 -.00331 NRAO85 3 6.71174 NYALES20 .52420 ONSALA60 -.00600 CRIMEA -.00794 NOTO 1.83030 MATERA -.00521 YEBES -.00201 WETTZELL .00039 SESHAN25 .00338 URUMQI -.00151 KASHIMA -.00480 KASHIM34 -.01188 HARTRAO 6.69298 ALGOPARK .00115 WESTFORD .31672 HRAS 085 6.70181 RICHMOND 5.18415 OVRO 130 .01203 HAYSTACK -.00204 HATCREEK -.01173 KAUAI 2.43638 KOKEE .52084 PIETOWN 2.13716 NRAO20 .50896 LA-VLBA 2.13273 FD-VLBA 2.13200 KP-VLBA 2.13195 NL-VLBA 2.12916 OV-VLBA 2.13186 HN-VLBA 2.12948 BR-VLBA 2.13140 MK-VLBA 2.13497 DSS15 -.00394 FORTLEZA .00637 SANTIA12 -.00003 SC-VLBA 2.13340 DSS45 -.00400 HOBART26 8.20117 KWAJAL26 .00000 OHIGGINS -.03185 SYOWA -.02447 TIGOCONC -.00599 SVETLOE -.01627 d. Reference epoch: session epoch e. Relativity scale: IERS Conventions 1992 ("consensus model") 7. Earth orientation: a. A priori precession model: IERS 1996 b. A priori nutation model: IERS 1996 (no FCN corrections applied) c. A priori x and y pole coordinates and rates, dUT1 and LOD: IERS EOP-C04, linearly interpolated (before the interpolation of dUT1, UT1R variations according to IERS Conventions 2003 are substracted from the daily UTC 0h C04 values. After the linear interpolation, the UT1R corrections are added again). d. A priori short period (~daily and subdaily) tidal variations in x, y, dUT1: IERS Conventions 2003 e. EOP estimation: Pole coordinates and rates, UT1-UTC and LOD, dpsi, deps, each valid for the duration of the session (normally 24 h), reference epoch is mid of session (see the SOLUTION/APRIORI block) 8. A priori geophysical models: a. Troposphere: hydrostatic component from surface pressure (in general as reported in the NGS files) mapped with the Niell 1996 dry mapping function, wet delay is estimated with the Niell 1996 wet mapping function b. Solid Earth tide: IERS Conventions 2003 (no non-correction of the permanent tide; comment: this is not conform with the IAG resolution but common practice) c. Ocean loading: IERS Conventions 2003, per station 11 partial tides provided by H.G. Scherneck d. Pole Tide: IERS Conventions 2003, using the linear approximation of the mean pole path e. Atmosphere loading: - f. Thermal deformation: - 9. Data type: Group delays 10. Data editing: 5-degree elevation cutoff 11. Data weighting: Only observations with a zero quality flag in NGS cards are used. The weights determined during the correlation process (read from the NGS files) are refined by station and elevation dependent fractions. All observations are subject to an outlier test (data snooping). 12. Software: DOGS_CS and OCCAM 6.1e, least squares method (LSM) 13. Further information: The SINEX 2.0 files include datum free normal equations only, no solution. None of the station postion parameters or EOP reported in this file are subject to any constraints.