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