C2IXY Subroutine

  1. astro_module.f90
  2. astro_module
  3. C2IXY

public subroutine C2IXY(date1, date2, x, y, rc2i)

Form the celestial to intermediate-frame-of-date matrix for a given date when the CIP X,Y coordinates are known. IAU 2000.

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 Celestial Intermediate Pole coordinates are the x,y components of the unit vector in the Geocentric Celestial Reference System.

  3. 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.

  4. Although its name does not include "00", this routine is in fact specific to the IAU 2000 models.

Reference

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

History

  • IAU SOFA revision: 2007 June 1

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(in) :: x

Celestial Intermediate Pole (Note 2)
real(kind=wp), intent(in) :: y

Celestial Intermediate Pole (Note 2)
real(kind=wp), intent(out), dimension(3,3):: rc2i

celestial-to-intermediate matrix (Note 3)

Calls

proc~~c2ixy~~CallsGraph proc~c2ixy C2IXY proc~s00 S00 proc~c2ixy->proc~s00 proc~c2ixys C2IXYS proc~c2ixy->proc~c2ixys proc~faom03 FAOM03 proc~s00->proc~faom03 proc~falp03 FALP03 proc~s00->proc~falp03 proc~fae03 FAE03 proc~s00->proc~fae03 proc~fal03 FAL03 proc~s00->proc~fal03 proc~faf03 FAF03 proc~s00->proc~faf03 proc~fad03 FAD03 proc~s00->proc~fad03 proc~fave03 FAVE03 proc~s00->proc~fave03 proc~fapa03 FAPA03 proc~s00->proc~fapa03 proc~ry RY proc~c2ixys->proc~ry proc~ir IR proc~c2ixys->proc~ir proc~rz RZ proc~c2ixys->proc~rz

Called by

proc~~c2ixy~~CalledByGraph proc~c2ixy C2IXY proc~c2ibpn C2IBPN proc~c2ibpn->proc~c2ixy proc~c2txy C2TXY proc~c2txy->proc~c2ixy proc~c2i00a C2I00A proc~c2i00a->proc~c2ibpn proc~c2i00b C2I00B proc~c2i00b->proc~c2ibpn proc~c2t00a C2T00A proc~c2t00a->proc~c2i00a proc~c2t00b C2T00B proc~c2t00b->proc~c2i00b

Contents

Source Code

C2IXY

Source Code

    subroutine C2IXY ( date1, date2, x, y, 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),intent(in) :: x !! Celestial Intermediate Pole (Note 2)
    real(wp),intent(in) :: y !! Celestial Intermediate Pole (Note 2)
    real(wp),dimension(3,3),intent(out) :: rc2i !! celestial-to-intermediate matrix (Note 3)

    !  Compute s and then the matrix.
    call C2IXYS ( x, y, S00 ( date1, date2, x, y ), rc2i )

    end subroutine C2IXY