C2I00A Subroutine

  1. astro_module.f90
  2. astro_module
  3. C2I00A

public subroutine C2I00A(date1, date2, rc2i)

Form the celestial-to-intermediate matrix for a given date using the IAU 2000A precession-nutation model.

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 matrix RC2I is the first stage in the transformation from celestial to terrestrial coordinates:

    [TRS]  =  RPOM * R_3(ERA) * RC2I * [CRS]

       =  RC2T * [CRS]

    where [CRS] is a vector in the Geocentric Celestial Reference System and [TRS] is a vector in the International Terrestrial Reference System (see IERS Conventions 2003), ERA is the Earth Rotation Angle and RPOM is the polar motion matrix.

  3. A faster, but slightly less accurate result (about 1 mas), can be obtained by using instead the C2I00B routine.

References

  • 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.

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

History

  • IAU SOFA revision: 2010 January 18

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):: rc2i

celestial-to-intermediate matrix (Note 2)

Calls

proc~~c2i00a~~CallsGraph proc~c2i00a C2I00A proc~pnm00a PNM00A proc~c2i00a->proc~pnm00a proc~c2ibpn C2IBPN proc~c2i00a->proc~c2ibpn proc~pn00a PN00A proc~pnm00a->proc~pn00a proc~c2ixy C2IXY proc~c2ibpn->proc~c2ixy proc~bpn2xy BPN2XY proc~c2ibpn->proc~bpn2xy proc~nut00a NUT00A proc~pn00a->proc~nut00a proc~pn00 PN00 proc~pn00a->proc~pn00 proc~s00 S00 proc~c2ixy->proc~s00 proc~c2ixys C2IXYS proc~c2ixy->proc~c2ixys proc~faju03 FAJU03 proc~nut00a->proc~faju03 proc~fae03 FAE03 proc~nut00a->proc~fae03 proc~faf03 FAF03 proc~nut00a->proc~faf03 proc~faom03 FAOM03 proc~nut00a->proc~faom03 proc~fasa03 FASA03 proc~nut00a->proc~fasa03 proc~fame03 FAME03 proc~nut00a->proc~fame03 proc~fal03 FAL03 proc~nut00a->proc~fal03 proc~fave03 FAVE03 proc~nut00a->proc~fave03 proc~fama03 FAMA03 proc~nut00a->proc~fama03 proc~faur03 FAUR03 proc~nut00a->proc~faur03 proc~fapa03 FAPA03 proc~nut00a->proc~fapa03 proc~obl80 OBL80 proc~pn00->proc~obl80 proc~numat NUMAT proc~pn00->proc~numat proc~bp00 BP00 proc~pn00->proc~bp00 proc~pr00 PR00 proc~pn00->proc~pr00 proc~rxr RXR proc~pn00->proc~rxr proc~s00->proc~fae03 proc~s00->proc~faf03 proc~s00->proc~faom03 proc~s00->proc~fal03 proc~s00->proc~fave03 proc~falp03 FALP03 proc~s00->proc~falp03 proc~s00->proc~fapa03 proc~fad03 FAD03 proc~s00->proc~fad03 proc~ir IR proc~c2ixys->proc~ir proc~ry RY proc~c2ixys->proc~ry proc~rz RZ proc~c2ixys->proc~rz proc~numat->proc~ir proc~numat->proc~rz proc~rx RX proc~numat->proc~rx proc~bp00->proc~ir proc~bp00->proc~ry proc~bp00->proc~pr00 proc~bp00->proc~rz proc~bp00->proc~rxr proc~bp00->proc~rx proc~bi00 BI00 proc~bp00->proc~bi00

Called by

proc~~c2i00a~~CalledByGraph proc~c2i00a C2I00A proc~c2t00a C2T00A proc~c2t00a->proc~c2i00a

Contents

Source Code

C2I00A

Source Code

    subroutine C2I00A ( date1, date2, rc2i )

    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) :: rc2i !! celestial-to-intermediate matrix (Note 2)

    real(wp) :: rbpn(3,3)

    !  Obtain the celestial-to-true matrix (IAU 2000A).
    call PNM00A ( date1, date2, rbpn )

    !  Form the celestial-to-intermediate matrix.
    call C2IBPN ( date1, date2, rbpn, rc2i )

    end subroutine C2I00A