J/A+A/355/398 Celestial Ephemeris Origin definition (Capitaine+, 2000)
Definition of the Celestial Ephemeris Origin and of UT1 in the
International Celestial Reference Frame.
Capitaine N., Guinot B., McCarthy D.D.
<Astron. Astrophys. 355, 398 (2000)>
=2000A&A...355..398C 2000A&A...355..398C
ADC_Keywords: Ephemerides ; Earth
Keywords: astrometry - ephemerides - reference systems - time
Abstract:
The adoption of the International Celestial Reference System ICRS, and
of the corresponding Frame, ICRF, by the 23rd General Assembly of the
International Astronomical Union, calls for a redefinition of the
departure point on the true equator. Several possibilities have been
suggested. This paper considers the use of the non-rotating origin
(Guinot, 1979, In: McCarthy D.D., Pilkington J.D. (eds.) Time and the
Earth's Rotation. D. Reidel Pub. Co, p. 7). The ``Celestial Ephemeris
Origin'' (CEO) is defined here as the non-rotating origin on the
equator of the Celestial Ephemeris Pole (CEP). Developments valid at
the microarcsecond, based on the best model for precession, nutation
and pole offset at J2000.0 with respect to the pole of ICRF, are
provided for computing the CEP coordinates and the position of the
CEO. It is shown that an operational definition of UT1 based on the
CEO leads to values which are insensitive at the microarcsecond level
to future improvements of this model.
Description:
The tables contain the parameters of the development as functions of
time t (expressed in centuries since J2000.0) of the Celestial Pole
Coordinates X and Y, expressed in arcseconds, has the following form:
X=-0.017130 + 2004.193319t - 0.4271605t2 - 0.1986210t3
-0.0000461t4 + 0.0000058t5
+{Sum on i}[(as,0)isin(ARGUMENT)+(ac,0)icos(ARGUMENT)]
+{Sum on i}[(as,1)i.t.sin(ARGUMENT)+(ac,1)i.t.cos(ARGUMENT)]
+{Sum on i}[(as,2)i.t2.sin(ARGUMENT)+(ac,2)i.t2.cos(ARGUMENT)]
Y=-0.005202 - 0.0219421t - 22.4072863t2 + 0.0018416t3
-0.0000037t4 + 0.0000019t5
+{Sum on i}[(bc,0)icos(ARGUMENT)+(bs,0)isin(ARGUMENT)]
+{Sum on i}[(bc,1)i.t.cos(ARGUMENT)+(bs,1)i_.t.sin(ARGUMENT)]
+{Sum on i}[(bc,2)i.t2.cos(ARGUMENT)+(bs,2)i_.t2.sin(ARGUMENT)]
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1a.dat 97 269 Numerical Development of the coordinates X(t),
Y(t) of the Celestial Ephemeris Pole in the ICRS
consistent with the IERS 1996 Conventions and
the IERS Annual report for 1997 (unit µas)
table1b.dat 82 112 Numerical Development of the planetary nutations
in the coordinates X(t), Y(t) of the CEP in the
ICRS consistent with the IERS 1996 Conventions
and the IERS Annual report for 1997 (unit µas)
tables.tex 319 469 LaTeX version of the tables
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Byte-by-byte Description of file: table1a.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- i [1/269]+ Number i
5- 6 I2 --- l Mean anomaly of the Moon coefficient
8- 9 I2 --- l' Mean anomaly of the Sun coefficient
11- 12 I2 --- F L - Omega (L: Mean longitude of the Moon)
coefficient
14- 15 I2 --- D Mean elongation from the Moon to the Sun
coefficient
17 I1 --- Omega Mean longitude of the ascending node of the Moon
coefficient
19- 27 F9.2 d Per Period of the nutation
29- 36 I8 uas as0i (as,0)i coefficient (1)
38- 42 I5 uas/hyr as1i (as,1)i coefficient (2)
44- 47 I4 uas/hyr2 as2i (as,2)i coefficient (2)
49- 52 I4 uas ac0i (ac,0)i coefficient
54- 59 I6 uas/hyr ac1i (ac,1)i coefficient
61- 62 I2 uas/hyr2 ac2i (ac,2)i coefficient
64- 70 I7 uas bc0i (bc,0)i coefficient (1)
72- 75 I4 uas/hyr bc1i (bc,1)i coefficient (2)
77- 81 I5 uas/hyr2 bc2i (bc,2)i coefficient (2)
83- 86 I4 uas bs0i (bs,0)i coefficient
88- 93 I6 uas/hyr bs1i (bs,1)i coefficient
95- 97 I3 uas/hyr2 bs2i (bs,2)i coefficient
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Note (1): The amplitudes (as,0)i, (bc,0)i are equal to the amplitudes
Ai.sinε0 and Bi of the IERS 1996 series for nutation
in longitude x sinε0 and obliquity, except for 20 terms in
each coordinate X and Y in which appears a contribution from
crossed-nutation effect.
Note (2): The amplitudes (as,j)i, (bc,j)i, for j=1,2, are due to crossed
terms between precession and nutation i, of the form t.sin or
t.cos for j=1 and of the form t2.sin or t2.cos for j=2.
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Byte-by-byte Description of file: table1b.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- i [1/112]+ Number i
5- 7 I3 --- lVe Mean longitude of Venus coefficient
9- 11 I3 --- lE Mean longitude of the Earth coefficient
13- 15 I3 --- lMa Mean longitude of Mars coefficient
17- 18 I2 --- lJ Mean longitude of Jupiter coefficient
20- 21 I2 --- lSa Mean longitude of Saturn coefficient
23- 24 I2 --- pa General precession in longitude coefficient
26- 27 I2 --- D Mean elongation from the Moon to the Sun
coefficient
29- 30 I2 --- F L - Omega (L: Mean longitude of the Moon)
coefficient
32- 33 I2 --- l Mean anomaly of the Moon coefficient
35- 36 I2 --- Omega Mean longitude of the ascending node of the Moon
coefficient
38- 46 F9.2 d Per Period of the nutation
48- 50 I3 uas as0i (as,0)i coefficient
52- 53 I2 uas/hyr as1i (as,1)i coefficient
55 I1 uas/hyr2 as2i (as,2)i coefficient
57- 59 I3 uas ac0i (ac,0)i coefficient
61- 62 I2 uas/hyr ac1i (ac,1)i coefficient
64 I1 uas/hyr2 ac2i (ac,2)i coefficient
66- 68 I3 uas bc0i (bc,0)i coefficient
70- 71 I2 uas/hyr bc1i (bc,1)i coefficient
73 I1 uas/hyr2 bc2i (bc,2)i coefficient
75- 77 I3 uas bs0i (bs,0)i coefficient
79- 80 I2 uas/hyr bs1i (bs,1)i coefficient
82 I1 uas/hyr2 bs2i (bs,2)i coefficient
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Acknowledgements: Nicole Capitaine
(End) Patricia Bauer [CDS] 20-Mar-2000