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J/A+A/406/1135      UT1 definitions in IAU 2000               (Capitaine+, 2003)

Expressions to implement the IAU 2000 definition of UT1. Capitaine N., Wallace P.T., McCarthy D.D. <Astron. Astrophys. 406, 1135 (2003)> =2003A&A...406.1135C
ADC_Keywords: Earth ; Ephemerides Keywords: astrometry - reference systems - ephemerides - time Abstract: This paper provides expressions to be used to implement the new definition of UT1 corresponding to the IAU 2000 resolutions either in the new (CEO-based) or classical (equinox-based) transformations between the International Terrestrial Reference System (ITRS) and the Geocentric Celestial Reference System (GCRS). The new expression for Greenwich Sidereal Time (GST) has to be in agreement at the micro-arcsecond level, for one century, with the IAU 2000 expressions for the Earth Rotation Angle (ERA) and for the quantity s positioning the Celestial Ephemeris Origin (CEO) on the equator of the CIP. The computations of the new expressions using the IAU 2000 precession-nutation model are performed in such a manner as to ensure that there is no discontinuity in UT1 on 1 January 2003 and that there is equivalence of the classical and new transformations between the ITRS and GCRS relative to the rotation about the axis of the CIP when these expressions are used. The equinox offset that is considered in the computations refers to the dynamical mean equinox of J2000.0. The resulting expressions have been included in the IERS Conventions 2000. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file tablea.dat 112 1600 Expression (IAU 2000A) of the X coordinate of the CIP in the GCRS provided by N. Capitaine tableb.dat 112 1275 Expression (IAU 2000A) of the Y coordinate of the CIP in the GCRS provided by N. Capitaine tablec.dat 112 66 Expression (IAU 2000A) of the s(t)+XY/2 quantity provided provided by N. Capitaine tablef.dat 112 34 Expression for Greenwich Sidereal Time based on the IAU2000A precession-nutation model
Description of file: table[abcf].dat The expressions for the X and Y coordinates of the CIP in the GCRS and the quantity s(t)+XY/2 are based on the IAU2000A precession-nutation model. They are in the form : polynomial part + non-polynomial part In the non-polynomial part, ARG being for various combination of the fundamental arguments of the nutation theory) The expressions for the fundamental arguments appearing in columns 6 to 10 (luni-solar part) and in columns 11 to 19 (planetary part) are those of the IERS Conventions 2000 X expression (tablea.dat): Polynomial part (unit microarcsecond) -16616.99 + 2004191742.88t - 427219.05t2 - 198620.54t3 - 46.05t4 + 5.98t5 Non-polynomial part (unit microarcsecond) Sumi[a{s,0})_i*sin(ARG) + a{c,0})i*cos(ARG)] + Sum_i)j=1,4 [a{s,j})i*tj*sin(ARG) + a{c,j})i*cos(ARG)]*tj] Y expression (tableb.dat): Polynomial part (unit microarcsecond) -6950.78 - 25381.99t - 22407250.99t2 + 1842.28t3 + 1113.06t4 + 0.99t5 Non-polynomial part (unit microarcsecond) Sumi[b{c,0})_i*cos(ARG) + b{s,0})i*sin(ARG)] + Sum_i)j=1,4 [b{c,j})i*tj*cos(ARG) + b{s,j})i*sin(ARG)]*tj] s + XY/2 expression (tablec.dat): Polynomial part (unit microarcsecond) 94.0 + 3808.35t - 119.94t2 - 72574.09t3 + 27.70t4 + 15.61t5 Non-polynomial part (unit microarcsecond) Sumi[C{s,0})_i*sin(ARG) + C{c,0})i*cos(ARG)] + Sum_i)j=1,4 [C{s,j})i*tj*sin(ARG) + C{c,j})i*cos(ARG)]*tj] Updated Table (12/11/2003) for ensuring continuity of UT1 on 1st January 2003 Cutoff (0.1 microarcsecond and periods less than 500 years) GST expression (tablef.dat): Expression ensuring continuity of UT1 on 1st January 2003 GST = Theta(UT1) + polynomial part + DeltaPsi*cos(epsilon_A) + non-polynomial part Theta(UT1) = 2*Pi*(0.7790572732640 + 1.00273781191135448.Tu) where Tu = Julian UT1 date - 2451545.0, and UT1 = UTC + (UT1 - UTC) Polynomial part (unit arcsecond) 0.014506 + 4612.15739966t + 1.39667721t2 - 0.00009344t3 + 0.00001882t4 DeltaPsi*cos(epsilon_A) = classical expression for the equation of the Non-polynomial part (unit microarcsecond) Sumi[C{s,0})_i*sin(ARG) + C{c,0})i*cos(ARG)] + Sumi[C{s,1})_i*t*sin(ARG) + C{c,1})i*cos(ARG)]*t] Cutoff (0.1 microarcsecond and periods less than 500 years) See also: J/A+A/355/398 : Celestial Ephemeris Origin definition (Capitaine+, 2000) J/A+A/400/1145 : Celestial Intermediate Pole + Ephemeris Origin (Capitaine+, 2003) Byte-by-byte Description of file: table?.dat
Bytes Format Units Label Explanations
1 I1 --- j [0/4] Number j 3- 6 I4 --- nj Number of terms (i) for j 9- 12 I4 --- i Number i (range [0 .. nj]) 17- 27 F11.2 --- i(s,j) a{s,j})i (X), b{s,j})i (Y) or c{s,j})i (S(t)+XY/2) coefficient 33- 42 F10.2 --- i(c,j) a{c,j})i (X), b{c,j})i (Y) or c{c,j})i (S(t)+XY/2) coefficient 47 I1 --- l Mean anomaly of the Moon coefficient 51- 52 I2 --- l' Mean anomaly of the Sun coefficient 56- 57 I2 --- F L - Omega (L: Mean longitude of the Moon) coefficient 61- 62 I2 --- D Mean elongation from the Moon to the Sun coefficient 66- 67 I2 --- Omega Mean longitude of the ascending node of the Moon coefficient 71- 72 I2 --- LMe Mean longitude of Mercure coefficient 75- 77 I3 --- LVe Mean longitude of Venus coefficient 80- 82 I3 --- LE Mean longitude of the Earth coefficient 85- 87 I3 --- LMa Mean longitude of Mars coefficient 91- 92 I2 --- LJ Mean longitude of Jupiter coefficient 96- 97 I2 --- LSa Mean longitude of Saturn coefficient 101-102 I2 --- LU Mean longitude of Uranus coefficient 106-107 I2 --- LNe Mean longitude of Neptune coefficient 111-112 I2 --- pA General precession in longitude coefficient
History: Copied at
(End) Patricia Bauer [CDS] 30-Jul-2003
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