EOP(IERS) C 01
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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.
SOLUTIONS AVAILABLE: Two available format
1) eopc01.1846-1899
eopc01.1900-now
Format:
col1: date : Besselian year
col2, col3 : x pole, uncertainty (")
col4, col5 : y pole, uncertainty (")
col6, col7 : UT1-UTC, uncertainty (s)
col8, col9 : nutation offset dX wrt IAU1980, uncertainty (")
col10,col11: nutation offset dX wrt IAU1980, uncertainty (")
2) Common IERS format
eopc01.1846-now : nutation respectively relative to IAU1980
eopc01.iau2000.1846-now : nutation respectively relative to IAU2000
Contents: the same as in the case 1)
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