iaao0411.eops.txt
Contact: Elena Skurikhina (sea@quasar.ipa.nw.ru)
Last updated:  03.03.2005


Technical description of solution iaao0411.eops

1.  Purpose of solution:  Session EOP

2 - Analysis Center:  Institute of Applied Astronomy (IAA)

3.  Short narrative description of solution:

Sessions with the duration 16h and longer are analyzed for this solution.
Files in the NGS format are used as source of observables.  Model of reduction
mainly follows IERS Conventions (2003).  Wet tropospheric delays and
clock offsets are modeled as random walk stochastic process and estimated
using Kalman filter technique.  Terrestrial reference frame VTRF2003 with the
associated velocity field is used for station coordinates, except SVETLOE,
GILCREEK after 2003.11.03, GGAO7108 after 2003.01.01, TOMAKO11, KAINAN,
METSHAOV, KANOZAN, KOGANEI3, CTVASTJ.
New axis offsets were applied as recommended IVS.
Antenna thermal deformations are computed using the IERS Conventions
(2003) model with modification providing modelling the
effect for all mount types, corrected.
Bad meteo data replaced to average daily data corresponding this period
of year time.

The main differences with the previous solutions are:

- ICRF-Ext.2 is used for sourse positions;
- Vienna Mapping Function implemented;
- Antenna thermal deformation model has been corrected;
- Axis offset values recommended by the IVS Analysis Coordinator are used;
- Relativistic model of IERS Conventions (2003) is used.
- Meteo data correction - seasonal model (for themperature).

4.  Estimated parameters:

    a. celestial frame:  No

    b. terrestrial frame:  Session station coordinates (see note below)

    c. Earth orientation:  Xp, Yp, UT1-UTC, Xc, Yc (see note below)

    d. zenith troposphere:  Random walk process

    e. troposphere gradient:  Yes

    f. station clocks:  Polynomial + random walk process

    g. baseline clocks:  No

    h. other:  No

Note:  (Session station positions + dXc, dYc (optionally)) and
       (Xp, Yp, UT1-UTC, Xc, Yc) are estimated in separate runs.

5.  Celestial reference frame:

    a. a priori source positions:  ICRF-Ext.2

    b. source positions adjusted in solution:  No

    e. solution identification or reference:  ICRF-Ext.2

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:  No

    l. solution identification or reference:  VTRF2003

7.  Earth orientation:

    a. a priori precession model:  IAU2000A

    b. a priori nutation model:  IAU2000A + FCN contribution from MHB model

    c. a priori short-period tidal variations in x, y, UT1:
               IERS Conventions (2003);
               zonal tidal variations are included in UT1;
               daily and subdaily variations are not included in EOP

    d. EOP estimation:  X, Y, UT1-UTC, dPsi, dEps for every session

8.  A priori geophysical models:

    a. troposphere: Saastamoinen model for zenith delay,
                    VMF mapping function

    b. solid Earth tide:  IERS Conventions (2003)

    c. ocean loading:  IERS Conventions (2003)

    d. atmosphere loading:  numerical (convolution) model, GSFC time series

9.  Data type:  delays

10. Data editing:  Only data with zero quality flag in NGS file are used;
    supplemental editing of outliers is applied during adjustment when
    necessary

11. Data weighting:  Observations are weighted using std reported in NGS
    file and a priori additive variance depending on session and/or station.
    Elevation depending weighting is applied to the observations made below
    10 deg.

12. Standard errors reported:  Reported formal errors are derived from
    Kalman filter adjustment without supplemental correction

13  Software:  OCCAM/GROSS

14. Other information:

    1. Supplement fields after standard IERS/IVS ones contain:

     - experiment name
     - number of stations
     - chi-square
     - number of rejected observations
     - three columns containing internal information
     - list of stations used for computation of reported EOP, clock reference
       station is listed first