Technical description of solution USNO9903 1. Purpose of solution: Session EOP 2. Analysis center: USNO 3. Short narrative description of solution: The Navy 1999-3 reference system is intended for operational reduction of VLBI EOP data from the USNO VLBI program. The particular solution submitted to the IVS Annual Report for 1998 provides positions for a total of 115 observing stations, including 14 "episodic" position estimates, and rate estimates for 89 stations (including 6 pairs of stations "tied" together). The solution also provides static position estimates for 652 sources; another 11 sources have "arc" position estimates. This frame is tied directly, in a minimum no-net rotation and translation sense, to the ICRF and the ITRF-97. 4. Estimated parameters: a. Celestial frame: Right ascension and declination for all sources. b. Terrestrial frame: CIO X0, Y0, Z0, Xdot, Ydot, Zdot for all stations, except as noted below for stations with insufficient data to estimate station rates. c. Earth orientation: PM-X, PM-Y, UT1-TAI, PM-Xdot, PM-Ydot, UT1dot, dpsi, deps d. Zenith troposphere: Continuous piecewise linear with 60 min interval. Rate constraint is 75 psec / hour. e. Troposphere gradient: Continuous piecewise linear with 3 hour interval for East and North gradients. Constraint on session offset is 1.25 mm, constraint on rates is 15 mm / day. f. Station clocks: Continuous piecewise linear with 90 min interval. Rate constraint is 5 E-14. g. Baseline clocks: Set in database; default is turned on. h. Other: Global antenna axis offsets are estimated for all stations. 5. Celestial reference frame: a. A priori source positions: ICRF b. Source positions adjusted in solution: yes If yes, c. definition of orientation: No-Net rotation tie to the ICRF using only the ICRF Defining Sources. The following ICRF Defining Sources were judged to have problems as indicated and were NOT used in this constraint : Current success ratio < 40% : IIIZW2 0834-201 1038+52B 1148-671 1718-649 1727+502 1604-333 CL4 2312-319 Normalized Residual Delay > 1.5 : 0821+394 Wrms delay > 100 psec : 3C138 1416+067 Rss position sigma > 1 mas : 0629-418 2329-384 d. Source position estimation: All sources estimated globally except for the following 11 ``arc'' sources : 3C273B 3C345 3C454.3 3C84 LSI61303 0710+439 1031+567 1117+146 1947+079 HD32918 3C48 6 - Terrestrial reference frame: a. A priori station positions: ITRF-97 b. A priori station velocities: ITRF-97 c. Reference epoch: 1997.0 d. Station positions/velocities adjusted in solution: yes If yes, e. definition of origin, orientation and their time evolution : The evolution of the TRF is set by a no-net-translation, no-net-rotation, no-net-translation-rate and no-net-rotation-rate conditions on the horizontal position and velocity adjustments of the following 27 stations : ALGOPARK BR-VLBA DSS45 FD-VLBA FORTLEZA GILCREEK HARTRAO HN-VLBA HOBART26 KASHIMA KAUAI KOKEE KP-VLBA LA-VLBA MATERA MK-VLBA NL-VLBA NOTO NRAO_140 NRAO20 NYALES20 ONSALA60 OV-VLBA PIETOWN SC-VLBA WESTFORD WETTZELL f. station parameter estimation: Position is estimated globally for all stations. g. stations with constraints: The following stations with insufficient data or time interval do not have velocities estimated and thus will move with the ITRF-97 velocity. HOHNBERG BERMUDA SEATTLE1 CHLBOLTN VICTORIA HALEAKAL HOHENFRG CARNUSTY BREST GRASSE SEST TOULOUSE AZORES METSHOVI KARLBURG HOFN FTD_7900 MCD_7850 OVR_7853 MOJ_7288 OCOTILLO MILESMON AUSTINTX CARROLGA LEONRDOK TSUKUB32 The velocities of the following groups of sites are constrained to be identical: DSS65 ROBLED32 YELLOWKN YLOW7296 NRAO85_1 NRAO85_3 WETTZELL TIGOWTZL FORT_ORD FORTORDS DSS65 ROBLED32 h. stations with discontinuous positions, and date of discontinuity : YAKATAGA 871201 SOURDOGH 871201 KODIAK 871201 WHTHORSE 871201 FORTORDS 891001 PRESIDIO 891001 NRAO85 3 901201 DSS15 920627 GOLDVENU 920627 GOLDMARS 920627 MOJAVE12 920627 EFLSBERG 960701 MEDICINA 960701 DSS65 970415 i. Stations with nonlinear velocities: NONE. j. Relativity scale: LE : local Earth in agreement with TCG (IUGG Resolution) k. Permanent tide correction: YES "Yes" means that both the permanent and the periodic tides have been modeled, so that the output station position is for after the removal of both the permanent and the periodic tidal effect. 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: GSFC hf996b UT1 tidal terms (microseconds) l l' F D Om GST | Cos | Sin | +pi | | | ----------------------------------------- 0 0 0 0 0 -1 8.390541 15.603754 0 0 2 -2 2 -1 -2.270974 -4.520974 0 0 2 0 2 -1 -13.496891 -17.709334 1 0 2 0 2 -1 -2.863498 -4.787981 0 1 0 0 0 -1 -.891044 1.863314 1 0 0 0 0 -1 1.485515 .709235 0 0 0 0 0 -2 .247526 1.665623 0 0 2 -2 2 -2 -.981241 8.048208 0 0 2 0 2 -2 -10.109943 14.766708 1 0 2 0 2 -2 -2.418065 3.362383 2 0 2 0 2 -2 -.423254 .898874 0 0 2 2 2 -2 -1.017729 .588472 -1 0 2 2 2 -2 .105177 .494085 0 0 2 0 1 -2 -.351840 -1.137950 -1 0 2 0 2 -2 .383683 -.160874 0 1 2 -2 2 -2 -.472836 .097590 0 0 0 0 1 -2 2.173278 .735157 0 0 2 2 2 -1 -.289042 -.403689 1 0 2 0 1 -1 -.539830 -.902636 -1 0 2 2 2 -1 -1.082247 -1.486773 0 0 2 0 1 -1 -2.545049 -3.339370 -1 0 2 0 2 -1 .800661 .621148 0 1 2 -2 2 -1 .171219 -.180862 0 0 0 0 1 -1 1.137897 2.116129 -1 0 0 0 0 -1 -.714221 1.017338 0 0 -2 0 -2 -1 1.498264 -.334916 0 0 -2 0 -1 -1 1.120941 .793015 ----------------------------------------- Polar motion tidal terms (microarcseconds) l l' F D Om GST | Cos | Sin | +pi | | | ----------------------------------------- 0 0 0 0 0 1 144.320341 -78.879960 0 0 -2 2 -2 1 -47.081071 21.289918 0 0 -2 0 -2 1 -142.621076 50.739409 -1 0 -2 0 -2 1 -32.603034 12.082873 0 0 0 0 0 -2 -26.667130 2.956205 0 0 2 -2 2 -2 -69.723790 103.830117 0 0 2 0 2 -2 -4.469703 261.522044 1 0 2 0 2 -2 -3.537164 39.891304 0 0 0 0 0 2 1.935495 -30.107929 0 0 -2 2 -2 2 -.486089 -15.524156 0 0 -2 0 -2 2 12.664993 -66.365149 -1 0 -2 0 -2 2 .137290 -13.615587 -2 0 -2 0 -2 2 -.671647 5.131798 0 0 -2 -2 -2 2 -4.298936 -2.595443 1 0 -2 -2 -2 2 5.282140 -.843876 0 0 -2 0 -1 2 -13.053854 11.657971 1 0 -2 0 -2 2 8.292567 3.728337 0 -1 -2 2 -2 2 -.417373 -3.437100 0 0 0 0 -1 2 25.902757 .373514 0 0 -2 -2 -2 1 -.896038 -.249728 -1 0 -2 0 -1 1 -6.147779 2.277775 1 0 -2 -2 -2 1 -5.697683 3.578188 0 0 -2 0 -1 1 -26.893352 9.567638 1 0 -2 0 -2 1 -11.768551 4.050336 0 -1 -2 2 -2 1 -1.052071 -3.590543 0 0 0 0 -1 1 19.572080 -10.697407 1 0 0 0 0 1 .828564 -5.020211 0 0 2 0 2 1 11.042002 -11.297487 0 0 2 0 1 1 3.918362 -1.787878 2 0 2 0 2 -2 1.194979 10.942462 0 0 2 2 2 -2 -3.686578 5.621777 -1 0 2 2 2 -2 -8.400973 14.598007 0 0 2 0 1 -2 -3.252330 .560673 -1 0 2 0 2 -2 3.524189 -10.972068 0 1 2 -2 2 -2 -8.310187 -5.687969 0 0 0 0 1 -2 -1.871795 16.865984 2 0 2 0 2 -1 -.13 -1.24 ----------------------------------------- d. EOP estimation: PM-X, PM-Y, UT1-TAI, PM-Xdot, PM-Ydot, UT1dot, dpsi, deps for each session. 8. A priori geophysical models: a. Troposphere: NMF ``dry'' mapping function with surface pressure. NMF ``wet'' mapping function for zenith troposphere partials. b. Solid Earth tide: IERS Conventions c. Ocean loading: IERS Conventions d. Atmosphere loading: NONE 9. Data type: Group delays and phase delay rates 10. Data editing: 7 deg elevation cutoff 11. Data weighting: Additive variance for data from each site for each session from database. 12. Standard Errors Reported : All of the standard errors are derived from Solve formal errors, based on the propagation of the delay and rate errors (including an additive variance to make the residual CHI square consistent with the number of degrees of freedom, as discussed in # 11) into the parameter covariance matrix. 13. Software: CALC 8.2, SOLVE 5.0115, dated 97.07.23 14. Other information: See ftp://casa.usno.navy.mil/navnet/README.n9903 for further information. Solution statistics : a. Data span: 19790803 - 19990504. b. Number of observations / sessions : 2,295,502 delay and rate observation pairs from 2695 observing sessions. c. Number of source positions estimated : 652 sources d. Number of positions estimated : 115 stations. e. Residual Statistics : Weighted Root Sum Square (wrms) delay residual scatter of 29.97 picoseconds, and a wrms phase delay rate scatter of 89.67 femto seconds / second.