*************************************************************************** Gazette IERS Gazette IERS Gazette IERS Gazette IERS Gazette No 08, 29 October 1996 *************************************************************************** > > > > > > CAUTION (4 April 1997): There was a sign error in the periodic correction to UT1. Please see erratum in IERS Gazette No 16. Thanks. > > > > > > > > ------------------- IERS ANNOUNCEMENT ------------------- REVISION OF IERS EOP SERIES ON 1 JANUARY 1997 As announced in IERS Gazette No 3, the IERS Earth Orientation Parameters (EOP) with epochs on or after 1 January 1997 at 0h UTC (MJD=50449.0) will be expressed in a new system that matches the International Celestial and Terres- trial Reference Frames, ITRF and ICRF. After that date, users will no longer need to apply corrections (Table II-2 in the 1995 IERS Annual Report) to make the Earth orientation data consistent with the ITRF and ICRF. IERS EOP series recomputed in the new system will be available under the following names. ____________________________________________________________________________ | Old name | Time New name start Comment | | |resol. year | |_________________|__________________________________________________________| | Bulletin A | 1d Bulletin A 1976 New, homogeneous series | | Bulletin B | 1d Bulletin B 1988 Past values NOT revised | | EOP(IERS) C 01 | 0.05yr EOP(IERS) 97 C 01 1846 New, homogeneous series | | EOP(IERS) C 02 | 5d EOP(IERS) 97 C 02 1962 New, homogeneous series | | EOP(IERS) C 03 | 1d EOP(IERS) 97 C 03 1984 New, homogeneous series | | EOP(IERS) C 04 | 1d EOP(IERS) 97 C 04 1962 New, homogeneous series | |_________________|__________________________________________________________| The applied corrections are derived from analyses published in the 1995 IERS Annual Report (pp. II-17 and II-79+). In addition, the change in UT1 includes the effect of adopting a more complete and accurate definition of GST [addition of the sin(Omega) and sin(2.*Omega) terms (see the IERS Conventions (1996), IERS T. N. No 21, p. 21)]. The corrections are listed in the following table. ____________________________________________________________________________ | | | Correction to IERS EOP series on 1 Jan 1997 (MJD=50449.0) Units | |____________________________________________________________________________| | x_new - x_old = + 0.4 + 0.10*(T-50449.0)/365.2422 0.001" (mas) | | y_new - y_old = + 1.2 + 0.10*(T-50449.0)/365.2422 0.001" (mas) | | | | UT1_new - UT1_old = - 0.2 + 0.03 (T-50449.0)/365.2422 0.0001s | | + 1.76 sin(Omega) + 0.04 sin(2.*Omega) 0.0001s | | | | dPsi_new - dPsi_old = - 0.2 0.001" (mas) | | dEps_new - dEps_old = 0.0 0.001" (mas) | |----------------------------------------------------------------------------| | Where | | - T is the date in Modified Julian Days (MJD) | | - Omega = mean longitude of the ascending node of the Moon | | = 125.04 deg - 0.052954 deg*(T-51544.5) | |____________________________________________________________________________| Users will see discontinuities in the Bulletin A and Bulletin B values of 0.4 mas in x, 1.2 mas in y, -0.02 ms in UT1-UTC, and -0.2 mas in dPsi on 1 January 1997. Contributors to the IERS should continue not to apply any corrections to the reported Earth orientation data for inconsistencies in the reference frames. Analysis Centres submitting UT1 results to IERS should make clear what GST definition they are using. Contacts: Bulletin A: dmc@maia.usno.navy.mil Bulletin B, EOP 97 C 01,02,03,04: gambis@obspm.fr