iaao9907.eops.txt
Last updated:  02.11.2000


Technical description of solution iaao9907.eops

1.  Purpose of solution:  Session EOP

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

3.  Short narrative description of solution:

IRIS-A, NEOS-A, CORE and other 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 (1996)
except relativistic correction which is computed according to the IERS
Standards (1992).  Celestial reference frame is fixed to RSC(IAA)99R02.
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 ITRF97 with the associated
velocity field is used for station coordinates.

4.  Estimated parameters:

    a. celestial frame:  No

    b. terrestrial frame:  No

    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:  RSC(IAA)99R02

    b. source positions adjusted in solution:  No

    e. solution identification or reference:  RSC(IAA)99R02

6 - Terrestrial reference frame:

    a. a priori station positions:  ITRF97

    b. a priori station velocities:  ITRF97 velocity field

    c. reference epoch:  1997.0

    d. station positions/velocities adjusted in solution:  No

    l. solution identification or reference:  ITRF97

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:
               IERS Conventions (1996);
               tidal variations are included in UT;
               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: NMF mapping function

    b. solid Earth tide:  IERS Conventions (1996)

    c. ocean loading:  IERS Conventions (1996)

    d. atmosphere loading:  IERS Conventions (1996)

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 v. 3.5

14. Other information:

    1. Fields 17-23 in file iaao9907.eops contain:

     - number of stations
     - number of delays
     - experiment name
     - chi-square
     - reference station for clock estimation
     - degree of polynomial for deterministic part of clock variations
     - radio source catalogue

    2. More data can be found on quasar.ipa.nw.ru anonymous ftp
       in directory /pub/EOS/IAA.