spu0003i.eops.txt Technical description of solution spu0003i 1. Purpose of solution: Session EOP 2. Analysis Center: Saint-Petersburg University (SPU) 3. Short narrative description of solution: Observational VLBI time delays (IRIS-A and NEOS-A since 2-Jan-1989 and R1, R4 since 1-Jan-2002) have been analyzed for this solution. Reductional model is realised in accordance with IERS Conventions (2003). Relativistic corrections are calculated in accordance with IERS consensus model. Celestial reference frame was fixed to ICRF Extension catalogue. A priori terrestrial reference frame was VTRF2003 catalog, but daily station coordinates have been estimated under NNR and NNT constraints. All stations for 24-hour session are used for the constraints exception the TIGOCONC VLBI site. Associated velocity field is used for station coordinates calculation. All parameters under estimation have been adjusted using Kalman filter technique. Station Wettzell is used as clock reference station when available on default. Tropospheric wet delay is modeled as a stochastic process like random walk with a priori spectral density equal to 0.1 picosec**2/sec. Clock offsets are considered as a random walk stochastic processes with a priori spectral densities equal to 1.0 picosec**2/sec. Clock rates usually are considered as a constant parameters exception to cases when behavior of hydrogen masers at the any VLBI site is obviously unusual and can not be appoximated by straight line. Tropospheric gradients are modeled as a constant parameters. 4. Estimated parameters: a. celestial frame: No b. terrestrial frame: Yes c. Earth orientation: X, Y, UT1-UTC, dpsi, deps d. zenith troposphere: Random walk process e. troposphere gradient: constant parameters f. station clocks: Offset as a random walk process, rate as a constant g. baseline clocks: No h. other: No 5. Celestial reference frame: a. a priori source positions: ICRF Ext.1 b. source positions adjusted in solution: No e. solution identification or reference: ICRF Ext.1 6 - Terrestrial reference frame: a. a priori station positions: VTRF2003 b. a priori station velocities: VTRF2003 velocity field c. reference epoch: 1997.0 d. station positions/velocities adjusted in solution: station positions adjusted on daily basis l. solution identification or reference: VTRF2003 7. Earth orientation: a. a priori precession model: IAU(1976) b. a priori nutation model: IAU(1980) c. a priori short-period tidal variations in x, y, UT1: Model (IERS Conventions 2003) d. EOP estimation: X, Y, UT1-UTC, dpsi, deps every session 8. A priori geophysical models: a. troposphere: Niell mapping function for dry and wet delays b. solid Earth tide: IERS Conventions 2003. c. ocean loading: IERS Conventions 2003. d. atmosphere loading: information about local pressure for separate VLBI sites has been used from server of Onsala Space Observatory 9. Data type: delays 10. Data editing: Only data with zero quality flag in NGS format are used 11. Data weighting: Observations with elevation less than 5 degrees to be divided by sin(elevation). Observations with elevation more than 5 degrees are not weighted as a rule, but Kalman filter approach checks a quality of every observation and downweights it in case of bad result. 12. Standard errors reported: Formal errors are derived from Kalman filter adjustment 13 Software: OCCAM v. 5.1 14. Other information: ------------------------------------------------------------------------------ Maria Kudryashova Post-graduate student of Astronomy department Tel: +7-(812)-428-41-99 Fax: +7-(812)-428-71-29 Sobolev Astronomical Institute of Saint-Peterburg University Universitetskii pr., 28, Petrodvorets, Saint-Petersburg, Russia, 198504 kudryashova@mercury.astro.spbu.ru