Technical description of solution iaa2017a_dsnx

1.  Purpose of solution:  24 hour session solution for combination techniques

2 - Analysis Center:  Institute of Applied Astronomy Russian Academy of Science

3.  Short narrative description of solution:

All available dual-band Mark III/IV/V observations from 1984 on were analysed for this
solution. The CRF is defined by ICRF2 catalogue. The TRF is defined by no-net-translation
and rotation constraints for the coordinates of all sites in a VLBI session related to
VTRF2005. The values of the official list of VLBI antenna axis offsets issued by the
IVS Analysis Coordinator were used.

We perform next analysis steps:

1. Retrieve the NGS card file and it transforms into QUASAR internal binary format with the empty correction file.
2. Calculate the O-C vector, using ITRF2014, ICRF2 and other necessary models.
3. Calculate preliminary session solution without stochastic signals, stations coordinates, EOP rates.
4. Visualisation of obtained preliminary solution, manual removing of clock breaks and 4-sigma outliers, save results in correction file.
5. Calculate new O-C vector
6. Form and invert LSC covariation matrix for stochastic signal estimation
7. Calculate solution with fixed station coordinates, estimate VTPV, chi squared.
8. Calculate SINEX matrices and vectors, calculate interpolated EOP values for SINEX a priory field, save results.

We use meteo data from NGS cards for Saastamoinen's formula and thermal deformations (if NGS data was wrong or not presented then we use VMF1 meteo data).
We also use VMF1 mapping function.
We take into account the cable cal data (if presented).


4.  Estimated parameters:

    a. celestial frame:  No

    b. terrestrial frame:  X, Y, Z

    c. Earth orientation: CIP-X, CIP-Y, Xp, Yp, UT1-UTC, Xpdot, Ypdot, LOD

    d. zenith troposphere:  linear trend+stochastic

    e. troposphere gradient:  east and north offset

    f. station clocks:  quadratic trend+stochastic

    g. other:  No

5.  Celestial reference frame:

    a. a priori source positions:  ICRF2
       For sources that not in the ICRF2 lists we use our own estimations.

    b. definition of orientation: fixed source coordinates of the ICRF-ext.2

6 - Terrestrial reference frame:

    a. a priori station positions:  ITRF2014

    b. a priori station velocities:  ITRF2014

    c. reference epoch:  2000.0

    d. station positions adjusted in solution: Yes

    e. definition of origin, orientation, and their time evolution:

       no-net-translation and no-net-rotation of position with respect to
       VTRF2008 for all stations of the VLBI session


7.  Earth orientation:

    a. a priori precession-nutation model:  IAU2000A

    b. Short-period tidal variations in x, y, UT1:

       PMUT1_OCEANS by Ch. Bizouard (2002) ( ftp://hpiers.obspm.fr/eop-pc/models/interp.f )

    d. EOP estimation: CIP-X, CIP-Y, Xp, Yp, UT1-UTC, Xpdot, Ypdot, LOD each session
       for the middle epoch of it

8.  A priori geophysical models:

    a. troposphere: hydrostatic component with VMF1 mapping function

    b. solid Earth tide:  IERS Conventions(2010)

    c. ocean loading:  IERS Conventions(2010)

    d. atmosphere loading:  numerical
    
    e. antenna thermal deformations 
    2h time lag for antenna
    6h time lag for foundation
    For first 6h temperature modeled by 
    T1+T2*dt+T3*sin(twopi*dt)+T4*cos(twopi*dt)- Temp0 
	gs=1.2d-5   ! expansion coefficient for steel
	ga=2.31d-5  ! expansion coefficient for aluminium
	gc=1.0d-5   ! expansion coefficient for concrete

9.  Data type:  Group delays

10. Data editing: editing of outliers during adjustment when necessary.

11. Data weighting:  Observations are weighted using std reported
    in observational files

12. Standard errors reported:  Reported formal errors are derived from
    least-squares estimation propagated from data uncertainties and
    re-weighted to achieve the chi-square unity.

13  Software:  QUASAR