PR00 Subroutine

  1. astro_module.f90
  2. astro_module
  3. PR00

public subroutine PR00(date1, date2, dpsipr, depspr)

Precession-rate part of the IAU 2000 precession-nutation models (part of MHB2000).

Status: canonical model.

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 precession adjustments are expressed as "nutation components", corrections in longitude and obliquity with respect to the J2000.0 equinox and ecliptic.

  3. Although the precession adjustments are stated to be with respect to Lieske et al. (1977), the MHB2000 model does not specify which set of Euler angles are to be used and how the adjustments are to be applied. The most literal and straightforward procedure is to adopt the 4-rotation epsilon_0, psi_A, omega_A, xi_A option, and to add DPSIPR to psi_A and DEPSPR to both omega_A and eps_A.

  4. This is an implementation of one aspect of the IAU 2000A nutation model, formally adopted by the IAU General Assembly in 2000, namely MHB2000 (Mathews et al. 2002).

References

  • Lieske, J.H., Lederle, T., Fricke, W. & Morando, B., "Expressions for the precession quantities based upon the IAU (1976) System of Astronomical Constants", Astron.Astrophys., 58, 1-16 (1977)

  • Mathews, P.M., Herring, T.A., Buffet, B.A., "Modeling of nutation and precession New nutation series for nonrigid Earth and insights into the Earth's interior", J.Geophys.Res., 107, B4,

    1. The MHB2000 code itself was obtained on 9th September 2002 from ftp://maia.usno.navy.mil/conv2000/chapter5/IAU2000A.

  • Wallace, P.T., "Software for Implementing the IAU 2000 Resolutions", in IERS Workshop 5.1 (2002).

History

  • IAU SOFA revision: 2009 December 15

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)
real(kind=wp), intent(out) :: dpsipr

precession corrections (Notes 2,3)
real(kind=wp), intent(out) :: depspr

precession corrections (Notes 2,3)

Called by

proc~~pr00~~CalledByGraph proc~pr00 PR00 proc~ee00a EE00A proc~ee00a->proc~pr00 proc~ee00b EE00B proc~ee00b->proc~pr00 proc~pn00 PN00 proc~pn00->proc~pr00 proc~bp00 BP00 proc~pn00->proc~bp00 proc~bp00->proc~pr00 proc~pn00a PN00A proc~pn00a->proc~pn00 proc~gst00a GST00A proc~gst00a->proc~ee00a proc~pn00b PN00B proc~pn00b->proc~pn00 proc~gst00b GST00B proc~gst00b->proc~ee00b proc~c2tpe C2TPE proc~c2tpe->proc~pn00 proc~pmat00 PMAT00 proc~pmat00->proc~bp00 proc~pnm00a PNM00A proc~pnm00a->proc~pn00a proc~num00a NUM00A proc~num00a->proc~pn00a proc~num00b NUM00B proc~num00b->proc~pn00b proc~pnm00b PNM00B proc~pnm00b->proc~pn00b proc~xys00a XYS00A proc~xys00a->proc~pnm00a proc~s00a S00A proc~s00a->proc~pnm00a proc~c2i00b C2I00B proc~c2i00b->proc~pnm00b proc~c2i00a C2I00A proc~c2i00a->proc~pnm00a proc~s00b S00B proc~s00b->proc~pnm00b proc~xys00b XYS00B proc~xys00b->proc~pnm00b proc~c2t00b C2T00B proc~c2t00b->proc~c2i00b proc~c2t00a C2T00A proc~c2t00a->proc~c2i00a

Contents

Source Code

PR00

Source Code

    subroutine PR00 ( date1, date2, dpsipr, depspr )

    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),intent(out) :: dpsipr !! precession corrections (Notes 2,3)
    real(wp),intent(out) :: depspr !! precession corrections (Notes 2,3)

    real(wp) :: t

    !  ------------------------------------
    !  Precession and obliquity corrections (radians per century)
    !  ------------------------------------

    real(wp),parameter :: precor = -0.29965_wp * das2r
    real(wp),parameter :: oblcor = -0.02524_wp * das2r

    !  Interval between fundamental epoch J2000.0 and given date (JC).
    t = ( ( date1-dj00 ) + date2 ) / djc

    !  Precession rate contributions with respect to IAU 1976/80.
    dpsipr = precor * t
    depspr = oblcor * t

    end subroutine PR00