J/A+A/450/855Methods for CIP and CIO localisation (Capitaine+, 2006)

High precision methods for locating the celestial intermediate pole and origin. Capitaine N., Wallace P.T. <Astron. Astrophys. 450, 855 (2006)> =2006A&A...450..855CADC_Keywords: Positional data ; Ephemerides ; EarthKeywords: astrometry - reference systems - ephemerides - celestial mechanics - timeAbstract: The precession-nutation transformation describes the changing directions on the celestial sphere of the Earth's pole and an adopted origin of right ascension. The coordinate system for the celestial sphere is the geocentric celestial reference system, and the two directions are the celestial intermediate pole (CIP) and the celestial intermediate origin (CIO), the latter having supplanted the equinox for this purpose following IAU resolutions in 2000. The celestial coordinate triad based on the CIP and CIO is called the celestial intermediate reference system; the prediction of topocentric directions additionally requires the Earth rotation angle (ERA), the counterpart of Greenwich sidereal time (GST) in the former equinox based system. The purpose of this paper is to review the different ways of calculating the CIP and CIO directions to precisions of a few microarcseconds over a time span of several centuries, meeting the requirements of high-accuracy applications.Description: Various implementations are described, their theoretical bases compared and the relationships between the expressions for the relevant parameters are provided. Semi-analytical and numerical comparisons have been made, based on the P03 precession and the IAU 2000A nutation, with slight modifications to the latter to make it consistent with P03. Methods based on the recent P03 precession model can be found in Capitaine et al. (2003A&A...412..567C, 2005A&A...432..355C). Tables 5-11 contain the coefficients in microarcseconds (uas) of the series developments (i.e. Fourier and Poisson terms) as functions of (terrestrial) time t (expressed in centuries since J2000.0) for the quantities s (Eq. (53)), s+XY/2 (Eq. (58)), s+XY/2+D (Eq. (60)), EO+Dpsi*cos(epsilon_A) (where EO is given by Eq. (69)), x_{CIO}, y_{CIO}, z_{CIO} (Eq. (70)), respectively, retaining all terms larger than 0.1 uas. The general formula is: S=Sum{on i}[Sum{j=0,5}[(Sj_{i})*t^{j}*sin(ARG)+(Cj_{i}*cos(ARG)]*t^{j}]] where: ARG = nl*l + nl'*l' + nF*F + nD*D + nOm*Om +nLMe*LMe + nLV*LV + nLE*LE + nLMa*LMa + nLJ*LJ + nLS*LS + nLU*LU + nLN*LN +npa*pa l, l', F, D, Om, LMe, LV, LE, LMa, LJ, LS, LU, LN, pa being the fundamental lunisolar and planetary arguments of the nutation theory.File Summary:

FileName Lrecl Records Explanations

ReadMe 80 . This file sp03.dat 95 177 Terms in the series development for the quantity s based on P03 precession and IAU 2000A nutation (table 5 of the paper) sxy2p03.dat 95 72 Terms in the series development for the quantity s+XY/2 based on P03 precession and IAU 2000A nutation (table 6 of the paper)(06-Nov-2006 version) sxy2dp03.dat 95 42 Terms in the series development for the quantity s+XY/2+D based on P03 precession and IAU 2000A nutation (table 7 of the paper) eep03.dat 95 39 Terms in the series development for the quantity EO+Dpsi*cos(epsilon_A) based on P03 precession and IAU 2000A nutation (table 8 of the paper) xciop03.dat 95 263 Terms in the series development for the quantity x_CI0 based on P03 precession and IAU 2000A nutation (table 9 of the paper) yciop03.dat 95 72 Terms in the series development for the quantity y_CI0 based on P03 precession and IAU 2000A nutation (table 10 of the paper) zciop03.dat 95 1607 Terms in the series development for the quantity z_CI0 based on P03 precession and IAU 2000A nutation (table 11 of the paper)

See also: J/A+A/400/1145 : IAU 2000A precession-nutation (Capitaine+, 2003) J/A+A/406/1135 : UT1 definitions in IAU 2000 (Capitaine+, 2003) J/A+A/355/398 : Celestial Ephemeris Origin definition (Capitaine+, 2000)Byte-by-byte Description of file: *.dat

Bytes Format Units Label Explanations

1- 4 I4 --- N Number of records of order j 5- 6 I2 --- j Order of the Poisson term (power of t) 7- 11 I5 --- i Term number i 12- 23 F12.2 uas Sji (Sj)_{i}coefficient, in µas 24- 39 F16.2 uas Cji (Cj)_{i}coefficient, in µas 40- 43 I4 --- nl Mean anomaly of the Moon coefficient 44- 47 I4 --- nl' Mean anomaly of the Sun coefficient 48- 51 I4 --- nF L-Omega (L: Mean longitude of the Moon) coefficient 52- 55 I4 --- nD Mean elongation from the Moon to the Sun coefficient 56- 59 I4 --- nOm Mean longitude of the ascending node of the Moon (Omega) coefficient 60- 63 I4 --- nLMe Mean longitude of Mercury coefficient 64- 67 I4 --- nLV Mean longitude of Venus coefficient 68- 71 I4 --- nLE Mean longitude of the Earth coefficient 72- 75 I4 --- nLMa Mean longitude of Mars coefficient 76- 79 I4 --- nLJ Mean longitude of Jupiter coefficient 80- 83 I4 --- nLS Mean longitude of Saturn coefficient 84- 87 I4 --- nLU Mean longitude of Uranus coefficient 88- 91 I4 --- nLN Mean longitude of Neptune coefficient 92- 95 I4 --- npa Accumulated general precession in longitude coefficient

Acknowledgements: Nicole Capitaine, n.capitaine(at)obspm.frHistory: File sxy2p03.dat corrected on 06-Nov-2006 (from author)(End)Patricia Vannier [CDS] 13-Apr-2006

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