iaao0106.eops.txt
Contact: Elena Skurikhina (sea@quasar.ipa.nw.ru)
Last updated:  21.12.2001


Technical description of solution iaao0106.eops

1.  Purpose of solution:  Session EOP

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

3.  Short narrative description of solution:

24h VLBI sessions (delays only) are analyzed for this solution.  Files in
the NGS format are used as source of observables.  Model of reduction
follows IERS Conventions (2000) 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.  Station Wettzell is used as
reference station for clocks estimation when available.  Terrestrial
reference frame ITRF2000 with the associated velocity field is used for
station coordinates.  Antenna thermal deformations are modelled using
IAG/ETC MG 6 model (DGFI Report, No.71) with modification providing
accounting for horizontal deformations.  Antenna dimensions file supported
by the IVS AC is taken for this computation.

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:  No

    f. station clocks:  Polynomial + random walk process

    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:  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:  IAU(1976)

    b. a priori nutation model:  MHB2000

    c. a priori short-period tidal variations in x, y, UT1:
               IERS Conventions (2000);
               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 every session

8.  A priori geophysical models:

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

    b. solid Earth tide:  IERS Conventions (2000)

    c. ocean loading:  IERS Conventions (2000)

    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:  First, observations are weighted using std reported
    in observational files and a priori additive variance;
    further re-weighting is applied for each session to achieve chi-square
    of unity in a session solution

12. Standard errors reported:  Reported formal errors are derived from
    least-square and 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
format 1:
     - reference station for clock estimation
     - degree of polynomial for deterministic part of clock variations
     - TRF/CRF catalog used
format 2:
     - degree of polynomial for deterministic part of clock variations
     - TRF/CRF catalog used
     - list of stations used for computation of reported EOP, reference
       station for clock estimation is listed first