EE00B Function

  1. astro_module.f90
  2. astro_module
  3. EE00B

public function EE00B(date1, date2) result(res)

Equation of the equinoxes, compatible with IAU 2000 resolutions but using the truncated nutation model IAU 2000B.

Status: support routine.

Notes

  1. The TT date DATE1+DATE2 is a Julian Date, apportioned in any convenient way between the two arguments. For example, JD(TT)=2450123.7 could be expressed in any of these ways, among others:

        DATE1          DATE2

 2450123.7D0        0D0        (JD method)
  2451545D0      -1421.3D0     (J2000 method)
 2400000.5D0     50123.2D0     (MJD method)
 2450123.5D0       0.2D0       (date & time method)

    The JD method is the most natural and convenient to use in cases where the loss of several decimal digits of resolution is acceptable. The J2000 method is best matched to the way the argument is handled internally and will deliver the optimum resolution. The MJD method and the date & time methods are both good compromises between resolution and convenience.

  2. The result, which is in radians, operates in the following sense:

    Greenwich apparent ST = GMST + equation of the equinoxes

  3. The result is compatible with the IAU 2000 resolutions except that accuracy has been compromised for the sake of speed. For further details, see McCarthy & Luzum (2001), IERS Conventions 2003 and Capitaine et al. (2003).

References

  • Capitaine, N., Wallace, P.T. and McCarthy, D.D., "Expressions to implement the IAU 2000 definition of UT1", Astronomy & Astrophysics, 406, 1135-1149 (2003)

  • McCarthy, D.D. & Luzum, B.J., "An abridged model of the precession-nutation of the celestial pole", Celestial Mechanics & Dynamical Astronomy, 85, 37-49 (2003)

  • McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003), IERS Technical Note No. 32, BKG (2004)

History

  • IAU SOFA revision: 2006 November 13

Arguments

TypeIntentOptionalAttributesName
real(kind=wp), intent(in) :: date1

TT as a 2-part Julian Date (Note 1)
real(kind=wp), intent(in) :: date2

TT as a 2-part Julian Date (Note 1)

Return Value real(kind=wp)

equation of the equinoxes (Note 2)


Calls

proc~~ee00b~~CallsGraph proc~ee00b EE00B proc~pr00 PR00 proc~ee00b->proc~pr00 proc~nut00b NUT00B proc~ee00b->proc~nut00b proc~obl80 OBL80 proc~ee00b->proc~obl80 proc~ee00 EE00 proc~ee00b->proc~ee00 proc~eect00 EECT00 proc~ee00->proc~eect00 proc~faom03 FAOM03 proc~eect00->proc~faom03 proc~falp03 FALP03 proc~eect00->proc~falp03 proc~fae03 FAE03 proc~eect00->proc~fae03 proc~fal03 FAL03 proc~eect00->proc~fal03 proc~faf03 FAF03 proc~eect00->proc~faf03 proc~fad03 FAD03 proc~eect00->proc~fad03 proc~fave03 FAVE03 proc~eect00->proc~fave03 proc~fapa03 FAPA03 proc~eect00->proc~fapa03

Called by

proc~~ee00b~~CalledByGraph proc~ee00b EE00B proc~gst00b GST00B proc~gst00b->proc~ee00b

Contents

Source Code

EE00B

Source Code

    function EE00B ( date1, date2 ) result(res)

    implicit none

    real(wp),intent(in) :: date1 !!  TT as a 2-part Julian Date (Note 1)
    real(wp),intent(in) :: date2 !!  TT as a 2-part Julian Date (Note 1)
    real(wp) :: res !! equation of the equinoxes (Note 2)

    real(wp) :: dpsipr, depspr, epsa, dpsi, deps

    !  IAU 2000 precession-rate adjustments.
    call PR00 ( date1, date2, dpsipr, depspr )

    !  Mean obliquity, consistent with IAU 2000 precession-nutation.
    epsa = OBL80 ( date1, date2 ) + depspr

    !  Nutation in longitude.
    call NUT00B ( date1, date2, dpsi, deps )

    !  Equation of the equinoxes.
    res = EE00 ( date1, date2, epsa, dpsi )

    end function EE00B