EOP(IERS) C 01
                         ----------------------------
 
 EOP(IERS) C 01 is a series of the earth Orientation Parameters given  at 0.1 
 year interval (1846 - 1889) and 0.05 year over the interval 1890 to now. 
This series is the basis of the IERS system for long-term studies.
 
 
 EOP(IERS) C 01 is based on the following data:
 
 
 1993 - now  : IERS solution of x, y, UT1-UTC, LOD, dPsi, dEpsilon (normal points),
               based on VLBI, LLR, GPS  and SLR.
               
 1980 - 1992 : IERS solution of x, y, UT1-UTC, dPsi, dEpsilon (normal points),
               based on VLBI, LLR, GPS (from 1992), and SLR.

 1962 - 1979 : IERS and BIH solutions, giving x, y, UT1-UTC (normal points). 
               Space techniques are introduced starting with 1969 (LLR: UT)
               and 1972 (Doppler: polar motion).

 1900 - 1961 : Vondrak(1995), Solution derived from optical astrometry 
               analyses the series give polar motion, celestial pole offsets 
               and Universal Time (since 1956).
     
		
 
 1846 - 1899 :

               The solution derived by L.V. Rikhlova (Fedorov et al., 1976) 
               from three series of absolute declination programs (Pulkovo, 
               Greenwhich, Washington). The frequency band of the variations 
               kept encompasses only the annual and Chandler terms. The y
               coordinate of the pole is missing from 1858.9 through 1860.9.
 
 
 PRECISION AND ACCURACY

 The individual values are accompanied by uncertainties which attempt to 
 reflect their quality. For the IERS/BIH solutions, they are  derived from the
 scattering of the independant measurements contributing to each normal point,
 with added variance taking into account possible systematic errors. For the 
 earlier period, they are based on the estimations given by Fedorov et al. 
 (1976), scaled to match the agreement woth the IERS/BIH solution over
 1962-1968. In addition some isolated outliers are deweighted (uncertainty
 multiplied by 3). 

 The following remarks can be made concerning the drift and the annual term
 before 1962:

 Trend: as a result of the Fedorov et al. treatment, any drift in polar
        motion existing before 1900 is ignored in the series. For the period
        starting with 1900, although no external evidence is available for 
        the pre-1972 polar motion, it should be mentionned that the low 
        frequency spectrum of polar motion both before and after the advent 
        of space techniques (giving the possibility of cross-checks) is that
        pf random walk at a similar level.
 
 Annual term: it is influenced by errors in nutation and local seasonal errors.
        Comparisons of the Fedorov et al. solution with the IERS/BIH one over 
        1962 - 1968 suggest that the amplitude of the annual term is accurate
        to +/- 0.03" over 1900 - 1962.
 
 REFERENCES
 
 - Fedorov,E.P., Korsun,A.A, Mayor,S.P., Pantschenko,N.I., Tarady,V.K., and
    Yatskiv,Y.S., 1972: Dvizhenie polyusa Zemli s 1890.0 po 1969.0. Naukova 
    Dumka, Kiev. [English translation of the text available].
 - Vondrak J., Ron C., Pesek I., Cepek A., 1995, Astron. and Astrophys. 
    297,899-906.
 - IERS Annual reports