C2IXYS Subroutine

  1. astro_module.f90
  2. astro_module
  3. C2IXYS

public subroutine C2IXYS(x, y, s, rc2i)

Form the celestial to intermediate-frame-of-date matrix given the CIP X,Y and the CIO locator s.

Status: support routine.

Notes

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

  2. The CIO locator s (in radians) positions the Celestial Intermediate Origin on the equator of the CIP.

  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.

Reference

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

History

  • IAU SOFA revision: 2014 November 7

Arguments

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

Celestial Intermediate Pole (Note 1)
real(kind=wp), intent(in) :: y

Celestial Intermediate Pole (Note 1)
real(kind=wp), intent(in) :: s

the CIO locator s (Note 2)
real(kind=wp), intent(out), dimension(3,3):: rc2i

celestial-to-intermediate matrix (Note 3)

Calls

proc~~c2ixys~~CallsGraph proc~c2ixys C2IXYS proc~ir IR proc~c2ixys->proc~ir proc~rz RZ proc~c2ixys->proc~rz proc~ry RY proc~c2ixys->proc~ry

Called by

proc~~c2ixys~~CalledByGraph proc~c2ixys C2IXYS proc~apci APCI proc~apci->proc~c2ixys proc~apco APCO proc~apco->proc~c2ixys proc~c2i06a C2I06A proc~c2i06a->proc~c2ixys proc~c2ixy C2IXY proc~c2ixy->proc~c2ixys proc~c2ibpn C2IBPN proc~c2ibpn->proc~c2ixy proc~c2txy C2TXY proc~c2txy->proc~c2ixy proc~apco13 APCO13 proc~apco13->proc~apco proc~apci13 APCI13 proc~apci13->proc~apci proc~c2t06a C2T06A proc~c2t06a->proc~c2i06a proc~atco13 ATCO13 proc~atco13->proc~apco13 proc~atci13 ATCI13 proc~atci13->proc~apci13 proc~atic13 ATIC13 proc~atic13->proc~apci13 proc~c2i00a C2I00A proc~c2i00a->proc~c2ibpn proc~c2i00b C2I00B proc~c2i00b->proc~c2ibpn proc~atoc13 ATOC13 proc~atoc13->proc~apco13 proc~c2t00a C2T00A proc~c2t00a->proc~c2i00a proc~c2t00b C2T00B proc~c2t00b->proc~c2i00b

Contents

Source Code

C2IXYS

Source Code

    subroutine C2IXYS ( x, y, s, rc2i )

    implicit none

    real(wp),intent(in) :: x !! Celestial Intermediate Pole (Note 1)
    real(wp),intent(in) :: y !! Celestial Intermediate Pole (Note 1)
    real(wp),intent(in) :: s !! the CIO locator s (Note 2)
    real(wp),dimension(3,3),intent(out) :: rc2i !! celestial-to-intermediate matrix (Note 3)

    real(wp) :: r2, e, d

    !  Obtain the spherical angles E and d.
    r2 = x*x+y*y
    if ( r2>0.0_wp ) then
       e = atan2 ( y, x )
    else
       e = 0.0_wp
    end if
    d = atan ( sqrt ( r2 / (1.0_wp-r2) ) )

    !  Form the matrix.
    call IR ( rc2i )
    call RZ ( e, rc2i )
    call RY ( d, rc2i )
    call RZ ( -(e+s), rc2i )

    end subroutine C2IXYS