INTERNATIONAL EARTH ROTATION SERVICE EARTH ROTATION PARAMETERS EOP(IERS) C 04 ---------- WARNING EOP(IERS) C 01, C02, C03 and C04 which were the current solutions before the adoption of the "1997 system" (see gazettes 8 and 16) have been removed from the web/ftp site on 1 September, 1998. These series will still be available on request (iers@obspm.fr). Taking advantage of various long series which have been recently re-analysed by analysis centers of the various techniques, EOP(IERS) C 04 has been recom- puted since 1983. It is regularly recomputed to take advantage on one hand of the improvement of the various individual contributions and in the other hand of the refinement of the analyses procedures. To date, it is twice-weekly updated. In the course of the analyses the determination of the systematic corrections of individual series entering the combination and the weighting procedure has been re-examined.In addition,smoothing characteristics have been changed to carefully take into account the relative improvement of the individual series. This series EOP(IERS) C 04 is given in the 1997 system. The following tables show the adopted smoothing characteristics over the successive intervals. To be consistent with this new solution, EOP(IERS) C01, C02, C03 have also been recomputed. For more explanation, contact "gambis@obspm.fr" or "eisop@hpvlbi.obspm.fr" This series is given at one-day intervals and can be interpolated linearly. The oscillations in UT and duration of the days due to zonal tides for periods under 35 days, as well as the 14d terms in dPsi, dEpsi are present in full size in the series. Due to insufficient data over 1962-1984 dPsi and dEpsi are based on a conventional model. Oceanic diurnal/sub-diurnal effects are not present and should be added back for users who require high accuracy information. EOP(IERS)97 C04 was computed over six intervals, 1962-1967, 1968-1971, 1972-1979, 1980-1982, 1983-1987 and 1988-present. After being homogeneized and merged, the contributing series of each of the EOP are slightly smoothed by Vondrak algorithm . The two tables below give : 1 - The caracteristics of the smoothing adopted for each period (the variations with periods shorter than the value in the table are smoothed out, except the short term variations in UT1 due to zonal tides and the 14d terms in celestial pole offsets, see above) 2 - The uncertainty of one daily value of EOP for each period . Table 1a. Frequency filtering characteristic of smoothing for EOP(IERS) C 04 Pole Components. ------------------------------------------------------------ PERIOD FOR Epsilon REMAINING AMPLITUDE Year 5% 50% 95% ----------------------------------------------------------- 1E -0.6 3.2d 10.0d 17.0d 1983-1985 1E +0.6 2.0d 6.3d 10.7d 1986-1989 1E +1.0 1.7d 5.4d 9.2d 1990-1991 1E +1.4 1.5d 4.5d 7.9d 1992 1E +1.6 1.4d 4.2d 7.3d 1993 1E +2.0 1.2d 3.7d 6.3d 1994-1997 ----------------------------------------------------------- Table 1b. Frequency filtering characteristic of smoothing for EOP(IERS) C 04 Universal Time. ----------------------------------------------------------- PERIOD FOR Epsilon REMAINING AMPLITUDE Year 5% 50% 95% ----------------------------------------------------------- 1E -0.5 3.0d 9.6d 16.3d 1983-1987 1E +0.2 2.3d 7.4d 12.5d 1988-1989 1E +1.0 1.7d 5.4d 9.2d 1990-1991 1E +1.5 1.5d 4.5d 7.6d 1992-1993 1E +2.0 1.2d 3.7d 6.3d 1994-1997 ----------------------------------------------------------- Table 2 - Uncertainty of one daily value for the EOP(IERS) C 04 ------------------------------------------------------------------------------ Period 1962-1967 1968-1971 1972-1979 1980-1983 1984-1995 1996-1997 ------------------------------------------------------------------------------ X (mas) 30 20 15 2 0.7 0.3 Y (mas) 30 20 15 2 0.7 0.3 UT (0.1ms) 20 15 10 4 0.4 0.2 LOD (0.1ms) 14 10 7 1.5 0.3 0.2 dPsi*sin(eps)(mas) 12 9 5 3 0.6 0.3 dEpsi (mas) 2 2 2 2 0.6 0.3 ------------------------------------------------------------------------------