Quarterly VLBI EOP Solution opa2010b

1. Purpose of solution: TRF/CRF and EOP series.

2. Analysis center: OPA (Paris Observatory).

3. Short narrative description of solution: The OPA quarterly solution estimates
all EOP and rates and station positions/velocities and radio source coordinates.

4. Estimated parameters:
 
a. celestial frame: right ascension, declination (some global, some local).
 
b. terrestrial frame: X, Y, Z, Xdot, Ydot, Zdot (global).

c. Earth orientation: x, y, UT1-UTC, xdot, ydot, UT1dot, dX, dY (all local).

d. zenith troposphere: continuous piece-wise linear 20-min interval; NMF 
wet partial derivative (segmented).
 
e. troposphere gradients: 8-hour East and North piece-wise continuous at all 
stations except a set of 110 stations (segmented).
 
f. station clocks: quadratic + continuous piece-wise linear with 60-min 
interval (segmented).
 
g. baseline clocks: set in initial analysis - usually used (local).
 
h. other: global antenna axis offsets for 61 stations (global).

5. Celestial reference frame:
 
a. a priori source positions: ICRF2.
 
b. source positions adjusted in solution: yes.
 
If yes,
 
c. definition of orientation: NNR tie to the 295 ICRF2 defining sources.
 
d. source position estimation: mostly global and some local (see control file).

6. Terrestrial reference frame:
 
a. a priori station positions: VTRF 2008a.
 
b. a priori station velocities: VTRF 2008a.
 
c. reference epoch for site positions: 1997.01.01.
 
d. station positions/velocities adjusted in solution: yes.
 
If yes,
 
e. definition of origin, orientation, and their time evolution: no-net-
translation and no-net-rotation of position and velocity with respect to 
ITRF 2000 for 26 stations:
  ALGOPARK BR-VLBA  CRIMEA   DSS45    FD-VLBA  FORTLEZA HARTRAO  HN-VLBA  \
  HOBART26 KASHIM34 KOKEE    KP-VLBA  LA-VLBA  MATERA   MK-VLBA  NL-VLBA  \
  NOTO     NYALES20 ONSALA60 OV-VLBA  SC-VLBA  SESHAN25 SVETLOE  TSUKUB32 \
  WESTFORD WETTZELL
  
f. station parameter estimation: X, Y, Z, Xdot, Ydot, Zdot globally for all 
stations.

g. stations with constraints: a priori velocity of U, E, and N components 
were constrained to the ITRF 2000 velocities with reciprocal weights 0.1, 
3.0, and 3.0 mm/yr respectively for stations having too short history of 
observations, in many cases only one occupation.
 
h. stations with discontinuous positions and date of discontinuity:

YAKATAGA 1987.12.01: Earthquake
SOURDOGH 1987.12.01: Earthquake
WHTHORSE 1987.12.01: Earthquake
FORTORDS 1989.10.01: Earthquake
PRESIDIO 1989.10.01: Earthquake
MOJAVE12 1992.06.27: Earthquake
DSS15    1992.06.27: Earthquake
MEDICINA 1996.06.01: Rail repair
EFLSBERG 1996.10.01: Rail repair
DSS65    1997.04.15: Rail repair
MIURA    2000.06.01: Earthquake
TATEYAMA 2000.06.01: Earthquake
GGAO7108 2003.01.01: Station relocation
SINTOTU3 2003.09.15: h/z
TIGOCONC 2010.02.27: Earthquake

For TIGOGONC, no significant nonlinearity in the velocity is visible yet.

i. stations with nonlinear velocities: GILCREEK, HRAS_085, PIETOWN.

j. relativity scale:
G_oo = -1 + (2W/c^2 + W^2/c^4) - 2L_g
G_oa = -4W^a/c^3
G_ab = \delta_ab (1 + 2W/c^2 - 2L_g)

k. permanent tide correction: yes.

7. Earth orientation:

a. a priori precession model: IAU 2000.
 
b. a priori nutation model: IAU 2000.
 
c. a priori short-period tidal variations in x, y, UT1: IERS 2003.
 
d. EOP estimation: X, Y, UT1, Xdot, Ydot, UT1dot, dX, dY each day. 
In this solution, the option NUTATION XY_OFFSET is turned on, so that 
estimated nutation quantities are the celestial pole offsets dX, dY wrt
the IAU 2000 precession-nutation (consisting of the IAU 2000A nutation 
and the IAU 1976 precession corrected by Herring et al. 2002) using the
non-rotating origin-based coordinate transformation between the TRF and the
CRF (Capitaine et al. 2003). The .eob file produced by a homemade getpar 
program contains dX and dY (and NOT dpsi and deps) wrt IAU 2006 consisting
of the IAU 2000 nutation supplemented by the P03 precession of
Capitaine et al. (2003). Time tag of EOP series is the middle epoch 
of the observing session. The IERS 2003 model of high frequency variations 
in polar motion and UT1 was added to the apriori EOP during data 
reduction. The reported values of polar motion and UT1 are the sum 
of the adjustments and the apriori EOP without contribution due to 
the high frequency variations. Thus, the final series of polar motion 
and UT1 DO NOT contain contributions due to the high frequency variations.

8. A priori geophysical models:
 
a. troposphere: NMF dry mapping function; Saastamoinen zenith delay calculated 
using logged pressure, temperature; a priori mean gradients from VLBI data or 
DAO weather model.
 
b. solid Earth tide: IERS Conventions 1996, p.56-65, step 1 and step 2, 
anelasticity variant, including tides of the 3-rd order.
 
c. pressure loading: ocean loading displacements computed from FES 2004.
Atmospheric loading displacements obtained from the APLO service 
(Petrov & Boy 2004).

9. Data type: group delays.
 
10. Data editing: 5 degree elevation cutoff.
 
11. Data weighting: weights are defined as follows: 1/sqrt ( f**2 + a**2 ) 
where "f" is the formal uncertainty of the ionosphere free linear combination 
of group delays at X- and S-band obtained by fringe fitting on the base of 
achieved signal to noise ratio. Station-dependent parameter "a" was computed 
for each session by an iterative procedure such that the ratio of the sum of 
squares of the weighted residuals to the estimate of their mathematical 
expectation is about unity.
 
12. Standard errors reported: all errors are derived from least-squares 
estimation propagated from the data weights and the constraints applied 
to the troposphere, clock and EOP parameters.
 
13. Software: CALC 10.0, SOLVE revision date 2008.12.05.

14. Other information: solution is reported at http://ivsopar.obspm.fr.