BP00 Subroutine

  1. astro_module.f90
  2. astro_module
  3. BP00

public subroutine BP00(date1, date2, rb, rp, rbp)

Frame bias and precession, IAU 2000.

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 matrix RB transforms vectors from GCRS to mean J2000.0 by applying frame bias.

  3. The matrix RP transforms vectors from J2000.0 mean equator and equinox to mean equator and equinox of date by applying precession.

  4. The matrix RBP transforms vectors from GCRS to mean equator and equinox of date by applying frame bias then precession. It is the product RP x RB.

Reference

  • Capitaine, N., Chapront, J., Lambert, S. and Wallace, P., "Expressions for the Celestial Intermediate Pole and Celestial Ephemeris Origin consistent with the IAU 2000A precession-nutation model", Astron.Astrophys. 400, 1145-1154 (2003)

  • n.b. The celestial ephemeris origin (CEO) was renamed "celestial intermediate origin" (CIO) by IAU 2006 Resolution 2.

History

  • IAU SOFA revision: 2013 August 21

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), dimension(3,3):: rb

frame bias matrix (Note 2)
real(kind=wp), intent(out), dimension(3,3):: rp

precession matrix (Note 3)
real(kind=wp), intent(out), dimension(3,3):: rbp

bias-precession matrix (Note 4)

Calls

proc~~bp00~~CallsGraph proc~bp00 BP00 proc~ry RY proc~bp00->proc~ry proc~rx RX proc~bp00->proc~rx proc~ir IR proc~bp00->proc~ir proc~pr00 PR00 proc~bp00->proc~pr00 proc~bi00 BI00 proc~bp00->proc~bi00 proc~rz RZ proc~bp00->proc~rz proc~rxr RXR proc~bp00->proc~rxr

Called by

proc~~bp00~~CalledByGraph proc~bp00 BP00 proc~pn00 PN00 proc~pn00->proc~bp00 proc~pmat00 PMAT00 proc~pmat00->proc~bp00 proc~pn00a PN00A proc~pn00a->proc~pn00 proc~pn00b PN00B proc~pn00b->proc~pn00 proc~c2tpe C2TPE proc~c2tpe->proc~pn00 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

BP00

Source Code

    subroutine BP00 ( date1, date2, rb, rp, rbp )

    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),dimension(3,3),intent(out) :: rb !! frame bias matrix (Note 2)
    real(wp),dimension(3,3),intent(out) :: rp !! precession matrix (Note 3)
    real(wp),dimension(3,3),intent(out) :: rbp !! bias-precession matrix (Note 4)

    !  J2000.0 obliquity (Lieske et al. 1977)
    real(wp),parameter :: eps0 = 84381.448_wp * das2r

    real(wp) :: t, dpsibi, depsbi, dra0, psia77, oma77, chia, &
                dpsipr, depspr, psia, oma, rbw(3,3)

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

    !  Frame bias.
    call BI00 ( dpsibi, depsbi, dra0 )

    !  Precession angles (Lieske et al. 1977)
    psia77 =        ( 5038.7784_wp + &
                    (   -1.07259_wp + &
                    (   -0.001147_wp ) * t ) * t ) * t * das2r
    oma77  = eps0 + ( &
                    (    0.05127_wp + &
                    (   -0.007726_wp ) * t ) * t ) * t * das2r
    chia   =        (   10.5526_wp + &
                    (   -2.38064_wp + &
                    (   -0.001125_wp ) * t ) * t ) * t * das2r

    !  Apply IAU 2000 precession corrections.
    call PR00 ( date1, date2, dpsipr, depspr )
    psia = psia77 + dpsipr
    oma  = oma77  + depspr

    !  Frame bias matrix: GCRS to J2000.0.
    call IR ( rbw )
    call RZ ( dra0, rbw )
    call RY ( dpsibi*sin(eps0), rbw )
    call RX ( -depsbi, rbw )
    call CR ( rbw, rb )

    !  Precession matrix: J2000.0 to mean of date.
    call IR ( rp )
    call RX ( eps0, rp )
    call RZ ( -psia, rp )
    call RX ( -oma, rp )
    call RZ ( chia, rp )

    !  Bias-precession matrix: GCRS to mean of date.
    call RXR ( rp, rbw, rbp )

    end subroutine BP00