-------------------------------- Project of a Universal EOP format -------------------------------- Having in mind the large variety of EOP format and well aware of the confusion it leads to, IERS EOP Product Center and IERS CB are endeavoring to unify these formats in the most flexible way. The unified format will account for two basic constraints: 1. Any EOP file not only encompass EOP but also their associated parameters (rates, correlations,...). 2. EOP file are time series, consisting of Date, EOP and other numerical or string parameters ordered in columns separated by blank Also acknoledging that modern code do not require any fixed format, the significant figure are let free, depending on the formal uncertainty of the parameters and time sampling for the dates. The content of each column as well the corresponding unit is specified by in a one line header by a symbolic label. This symbolic label is built according the principle of multiple declension obeying the rules and symbol specified her-after. This format is intermediate between Virtual Observatory format, requiring the anchoring of each data according to their label and current IERS practice where non present parameters are flagged by 0 or 999! Anyway it requires a strict labelling. Note that nor the labelling nor the full set of parameter is fixed yet. ------------------------- A. Symbols for the dating DA_JD : date in JD DA_MJD : date in MJD DA_BY : date in besselian year YR : civil year MM : civil month DD : civil day HH : UT hour MN : UT minut SS : UT sec Noting that the time of resolution of EOP is above 15 minutes, difference between time scale UTC, TAI, TT, TE and TDB is not relevant for contemporaneous observations. ---------------------------------------------------- B. Symbols for EOP parameters and derived parameters ----------------------- 1. Basic EOP parameters XP : x pole coordinate YP : x pole coordinate UT1 : Universal Time 1 DX : celestial pole offset dX wrs IERS Conventional model of precession-nutation DY : celestial pole offset dX wrs IERS Conventional model of precession-nutation DP : celestial pole offset dPsi wrs IERS Conventional model of precession-nutation DE : celestial pole offset dEps wrs IERS Conventional model of precession-nutation ------------ 2. EOP rates EOP_RT Mot current cases are the pole coordinates rates: XP_RT : dx/dt YP_RT : dy/dt Instead of UT1 rate, we favor the excess of the length of day LOD = - 86400 s SI * dUT1/dt , symbolized by LOD --------------------------------------------------- 3. Specifying a possible a-priori reference for EOP Most current case are: UT1_UTC : UTC - UTC UT1_TAI : UT1 - TAI DP_IAU80 : celestial pole offset dPsi wrs IAU 1980 precession-nutation model DE_IAU80 : celestial pole offset dEps wrs IAU 1980 precession-nutation model ---------------------------------------------------------------------------------- 4. Specifying a correction associated with a model recommended by IERS Conventions UT1_TAI_R : UT1 - TAI corrected from the zonal tide effect modeled according to the current IERS convention LOD_R : LOD corrected from the zonal tide effect modeled according to the current IERS convention If model is no the one of the current convention but of past one, it is flagged as follow: LOD_R.2003 : LOD corrected from the zonal tide effect modeled according to the current IERS convention 2003 LOD_R.2010 : LOD corrected from the zonal tide effect modeled according to the current IERS convention 2010 -------------------------------------------- 5. Symbols for uncertainty of EOP parameters EOP_ER Example: X_RT_ER : Uncertainty on x pole coordinate rate ----------------------------------- 6. Specifying the unit if necessary The basic unit are arc-second (") and day of 86400 SI second (d). The EOP and their rates are free to be expressed in any negative or positive power p of 10 of 1", 1 s, 1 "/s If the EOP is given in the basic unit, then there is no mention of the unit. The specification of the unit is done through the coefficient p placed after the flag *. Example: X_RT_ER*-6 : Uncertainty on x pole coordinate rate in micro-arc-second/d (10^-6"/d) ----------------- 7. Generalization Total description of any EOP parameter or derived EOP parameter is done according to PARAM_REF_COR.NUM*p PARAM : basic parameter REF : a-priori / reference for this parameters COR : modeled correction applied NUM : version number of the model according to the IERS Conventions p : power of ten defining the unit -------------------- C. Others parameters 1. Correlation between EOP parameters COR_XP_YP : correlation between XP and YP COR_XP_UT1 : correlation between XP and UT1 COR_YP_UT1 : correlation between YP and UT1 COR_DX_DY : correlation between DX and DY 2. rms residual of the least squares solution providing the EOP RMS 3. Indicators for VLBI / SLR NO number of observation SO span of the observation 4. Indicators for GNSS NR nb of receivers in the solution NRF nb of receivers with "fixed" solution NS nb of satellites (transmitters) in the solution ------------------------------------------- D. Most current parameters met in EOP files: 1. Earth Orientation Parameters / rates XP YP UT1_UTC, UT1_TAI, UT1_UTC_R, UT1_TAI_R DX, DY, DP, DE, DP_IAU1980, DE_IAU1980 XP_RT YP_RT LOD, LOD_R, LOD_R.1992 2. Uncertainties do not depend on a-priori reference or correction models are thus restricted to XP_ER YP_ER UT1_ER DX_ER, DY_ER, DP_ER, DE_ER XP_RT_ER YP_RT_ER LOD_ER 3. EOP CORRELATION COR_X_Y COR_X_UT1 COR_Y_UT1 COR_DX_DY / COR_DP_DE ----------------------------------------- E. Example a new format for C04 at 12hUTC Current format # C04 sampled at 12 h UTC # # FORMAT(4(I4),F9.2,2(F12.6),2(F12.7),2(F12.6),2(F12.6),2(F12.7),2(F12.6)) #YR MM DD HH MJD x y UT1-UTC LOD dX dY x Err y Err UT1-UTC Err LOD Err dX Err dY Err # " " s s " " " " s s " " # 1984 1 1 12 45700.50 -0.132809 0.092060 0.3949652 0.0016989 0.001789 -0.001846 0.001368 0.001536 0.0001446 0.0002034 0.000968 0.000599 1984 1 2 12 45701.50 -0.136163 0.094666 0.3933000 0.0016343 0.001479 -0.000837 0.001368 0.001514 0.0001403 0.0001989 0.000948 0.000580 In unified format #DATE_MJD XP XP UT1_UTC LOD DX DY XP_ER YP_ER UT1_UTC_ER LOD_ER DX_ER DY_ER 45700.50 -0.132809 0.092060 0.3949652 0.0016989 0.001789 -0.001846 0.001368 0.001536 0.0001446 0.0002034 0.000968 0.000599 45701.50 -0.136163 0.094666 0.3933000 0.0016343 0.001479 -0.000837 0.001368 0.001514 0.0001403 0.0001989 0.000948 0.000580