iaao0301.eops.txt
Contact: Elena Skurikhina (sea@quasar.ipa.nw.ru)
Last updated:  18.02.2003


Technical description of solution iaao0301.eops

1.  Purpose of solution:  Session EOP

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

3.  Short narrative description of solution:

Sessions with duration more than 16h are analyzed for this solution.
Files in the NGS format are used as source of observables.  Model of
reduction follows IERS Conventions (2003) except relativistic correction
which is computed according to the IERS Standards (1992).  Wet tropospheric
delays and clock offsets are modeled as random walk stochastic process and
estimated using Kalman filter technique.  Terrestrial reference frame
ITRF2000 with the associated velocity field is used for station coordinates.
Antenna thermal deformations are modelled using the IERS Conventions (2003)
model with modification providing accounting for horizontal deformations and
suitable for all mount types.

The differences with the previous solutions iaao0201.eops/iaao0201.eopi are:

- tropospheric gradients are estimated as single constant value during the
  session;
- updated reference pressure and regression coefficients for stations;
- updated coordinates for TIGOCONC and GILCREEK (post-EQ);
- other changes with no significant systematic effect:
  - updated model of tropospheric refraction;
  - new a priori STD of estimated parameters (100 mas for EOP, 100 m for
    station coordinates);
  - GOT00 model for ocean loading;
  - new algorithm for selection of clock reference station;
- XY(CIO) are reported instead of dPsi/dEps (it is not a result of real
  estimation of dX/dY, but mere transformation of estimated dPsi/dEps);
- postfit RMS is reported, though we are not sure that it's correctly
  computed/extracted from the OCCAM Kalman filtering procedure; so, please
  use it with caution.


4.  Estimated parameters:

    a. celestial frame:  No

    b. terrestrial frame:  Station positions for every session

    c. Earth orientation:  X, Y, UT1-UTC, dPsi, dEps

    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:  (Station positions + dPsi, dEps (optionally)) and
       (X, Y, UT1-UTC, dPsi, dEps) are estimated in separate runs.

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:  ITRF2000

    b. a priori station velocities:  ITRF2000 velocity field

    c. reference epoch:  1997.0

    d. station positions/velocities adjusted in solution:  No

    l. solution identification or reference:  ITRF2000

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,
                    NMF mapping function

    b. solid Earth tide:  IERS Conventions (2003)

    c. ocean loading:  IERS Conventions (2003)

    d. atmosphere loading:  dH = C*(P-P0)

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.  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