Chapter 5 (Updated): Transformation between the International Terrestrial Reference System and Geocentric Celestial Reference System

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All content in the updated pages should be considered under development and are not definitive nor officially approved as a registered edition. For the official IERS Conventions (2010), please download the packaged v 1.0.0.

Updates

  • 21 December 2013:
    • Report the yearly update fcnnut130701 to the Free Core Nutation model
  • 10 August 2012: Changes with respect to previous version of the chapter:
    • Report the yearly update fcnnut120701 to the Free Core Nutation model and correct a typo in the value of the FCN period.
  • 14 October 2011:
    • The header of the subroutine PMSDNUT2.F has been corrected to point to the correct section of Chapter 5 and to provide a new test case.
  • 13 July 2011: Main changes with respect to previous version of the chapter:
    • Correct Tables 5.3a and 5.3b: Column headers misplaced in the "paper" version; One typo in the electronic version.
    • Report an error in the version of Table 5.3b that was published with the Conventions (2003).
    • Correct in Table 5.2f the formula for the polynomial part of Y_IAU 2006 - Y_IAU 2000A.
    • Clarify the text describing the implementation of the IAU 2000A nutation model by the SOFA (Software of Fundamental Astronomy) service.
    • Report the yearly update fcnnut110701 to the Free Core Nutation model.
    • Correct several typos or improper wordings.

Software

  • Routines that support the transformations described in Chapter 5 (see Section 5.9) are included in the SOFA collection.
  • PMSDNUT2.F - Subroutine to compute the diurnal lunisolar effect on polar motion. Based on the subroutine PMsdnut.for. [1]
    • Differences between the two subroutines are typically smaller than 0.1 μas.
  • UTLIBR.F - Subroutine to compute the subdiurnal librations in UT1. [1]
  • FUNDARG.F - Subroutine to compute the lunisolar fundamental arguments. [2]
  • FCNNUT.F - Computes corrections to the coordinates of the CIP to account for Free Core Nutation. Contains data table to be updated each year. [3] (Updated 10 August 2012)

Additional Information

  • Table 5.2a - IAU 2006/2000A expression of the X coordinate of the CIP in the GCRS. [4]
  • Table 5.2b - IAU 2006/2000A expression of the Y coordinate of the CIP in the GCRS. [4]
  • Table 5.2d - IAU 2006/2000A expression of the quantity s(t) + XY/2.[4]
  • Table 5.2e - IAU 2006/2000A expression for Greenwich Sidereal Time GST. [4]
  • Table 5.2f - Expression for the difference between the IAU 2006 (or IAU 2000A_R06) and IAU 2000 expression for various quantities (X, Y, Dpsi, Deps, s+XY/2). [4]
  • Table 5.3a - Nutation in longitude (IAU 2000_R06 expression) derived from the IAU 2000A lunisolar and planetary components with slight IAU 2006 adjustments. [4]
  • Table 5.3b - Nutation in obliquity (IAU 2000_R06 expression) derived from the IAU 2000A lunisolar and planetary components with slight IAU 2006 adjustments. [4]

[1] Provided by A. Brzezinski.

[2] From the model by Simon et al. (1994).

[3] Provided by S. Lambert

[4] Provided by N. Capitaine