Technical description of solution opa2008d 1. Purpose of the solution: daily SINEX files 2. Analysis center: OPA ( Paris Observatory ) 3. Short narrative description of solution: The solution estimates position of all stations, all EOP and rates and positions of some radio sources for each session. NNR/NNT constraint is applied to station position. 4. Estimated parameters: a. celestial frame: right ascension, declination of the sources that were already estimated as locals in the opa2008d global solution (see list in the batch solve control listed in the comment part of the SINEX file) for each session independently. b. terrestrial frame: X, Y, Z (local) c. Earth orientation: x, y, UT1-UTC, xdot, ydot, UT1dot, dpsi, deps (local) d. zenith troposphere: continuous piece-wise linear; 20-min interval; rate constraint generally 50 ps/hr; 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; offset constraint 0.5 mm, rate constraint 2.0 mm/day (segmented) f. station clocks: quadratic + continuous piece-wise linear with 60-min interval; rate constraint generally 5.0E-14 (segmented) g. baseline clocks: set in initial analysis - usually used (local) 5. Celestial reference frame: a. a priori source positions: opa2008d catalogue b. source positions adjusted in solution: yes (some) If yes, c. definition of orientation: no-net-rotation with respect to the opa2008d catalogue tied to the 212 ICRF defining sources. d. source position estimation: when estimated, as local parameters 6. Terrestrial reference frame: a. a priori station positions: opa2008d catalogue b. a priori station velocities: opa2008d catalogue c. reference epoch: 1997.0 d. station positions/velocities adjusted in solution: positions only e. definition of origin, orientation, and their time evolution: no-net -translation and no-net-rotation of position with respect to the opa2008d catalogue. All stations except GILCREEK participate in equations of constraints. Equations of constraints are equally weighted. f. station parameter estimation: X, Y, Z, locally for all stations g. stations with constraints: none h. stations with discontinuous positions and date of discontinuity: none i. stations with nonlinear velocities: none 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: IERS 2003 b. a priori nutation model: IAU 2000A c. a priori short-period tidal variations in x, y, UT1: hf1102 d. EOP estimation: X, Y, UT1, Xdot, Ydot, UT1dot, deps, dpsi each day with a priori error of 45 mas for pole and 3 ms for UT1, 45 mas/day and 3 ms/day for pole rate and UT1 rate; The output deps and dpsi are relative to IAU 1976 precession and IAU 1980 nutation models. Time tag of EOP series is the middle epoch of the observing session. The model of high frequency variations in polar motion and UT1 hf1102 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: 3D ocean loading displacements computed by SPOTL software are used. The model of displacements caused by ocean loading contains 28 constituents. 3D displacements computed by convolving global surface pressure field on a 2.5x2.5 degrees grid with 6 hour temporal resolution using the NCEP Reanalysis model (APLO service, Petrov & Boy 2004). 9. Data type: group delays 10. Data editing: 6 deg 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 2008.07.31 14. Other information: solution is reported at http://ivsopar.obspm.fr/