C2TPE Subroutine

  1. astro_module.f90
  2. astro_module
  3. C2TPE

public subroutine C2TPE(tta, ttb, uta, utb, dpsi, deps, xp, yp, rc2t)

Form the celestial to terrestrial matrix given the date, the UT1, the nutation and the polar motion. IAU 2000.

Status: support routine.

Notes

  1. The TT and UT1 dates TTA+TTB and UTA+UTB are Julian Dates, apportioned in any convenient way between the arguments UTA and UTB. For example, JD(UT1)=2450123.7 could be expressed in any of these ways, among others:

         UTA            UTB

 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 and MJD methods are good compromises between resolution and convenience. In the case of UTA,UTB, the date & time method is best matched to the Earth rotation angle algorithm used: maximum accuracy (or, at least, minimum noise) is delivered when the UTA argument is for 0hrs UT1 on the day in question and the UTB argument lies in the range 0 to 1, or vice versa.

  2. The caller is responsible for providing the nutation components; they are in longitude and obliquity, in radians and are with respect to the equinox and ecliptic of date. For high-accuracy applications, free core nutation should be included as well as any other relevant corrections to the position of the CIP.

  3. XP and YP are the coordinates (in radians) of the Celestial Intermediate Pole with respect to the International Terrestrial Reference System (see IERS Conventions 2003), measured along the meridians to 0 and 90 deg west respectively.

  4. The matrix RC2T transforms from celestial to terrestrial coordinates:

    [TRS]  =  RPOM * R_3(GST) * RBPN * [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), RBPN is the bias-precession-nutation matrix, GST is the Greenwich (apparent) Sidereal Time and RPOM is the polar motion matrix.

  5. 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: 2009 April 1

Arguments

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

TT as a 2-part Julian Date (Note 1)
real(kind=wp), intent(in) :: ttb

TT as a 2-part Julian Date (Note 1)
real(kind=wp), intent(in) :: uta

UT1 as a 2-part Julian Date (Note 1)
real(kind=wp), intent(in) :: utb

UT1 as a 2-part Julian Date (Note 1)
real(kind=wp), intent(in) :: dpsi

nutation (Note 2)
real(kind=wp), intent(in) :: deps

nutation (Note 2)
real(kind=wp), intent(in) :: xp

coordinates of the pole (radians, Note 3)
real(kind=wp), intent(in) :: yp

coordinates of the pole (radians, Note 3)
real(kind=wp), intent(out), dimension(3,3):: rc2t

celestial-to-terrestrial matrix (Note 4)

Calls

proc~~c2tpe~~CallsGraph proc~c2tpe C2TPE proc~pn00 PN00 proc~c2tpe->proc~pn00 proc~c2teqx C2TEQX proc~c2tpe->proc~c2teqx proc~ee00 EE00 proc~c2tpe->proc~ee00 proc~gmst00 GMST00 proc~c2tpe->proc~gmst00 proc~sp00 SP00 proc~c2tpe->proc~sp00 proc~pom00 POM00 proc~c2tpe->proc~pom00 proc~obl80 OBL80 proc~pn00->proc~obl80 proc~numat NUMAT proc~pn00->proc~numat proc~bp00 BP00 proc~pn00->proc~bp00 proc~rxr RXR proc~pn00->proc~rxr proc~pr00 PR00 proc~pn00->proc~pr00 proc~c2teqx->proc~rxr proc~rz RZ proc~c2teqx->proc~rz proc~eect00 EECT00 proc~ee00->proc~eect00 proc~anp ANP proc~gmst00->proc~anp proc~era00 ERA00 proc~gmst00->proc~era00 proc~rx RX proc~pom00->proc~rx proc~ry RY proc~pom00->proc~ry proc~pom00->proc~rz proc~ir IR proc~pom00->proc~ir proc~numat->proc~rx proc~numat->proc~rz proc~numat->proc~ir proc~bp00->proc~rx proc~bp00->proc~ry proc~bp00->proc~rxr proc~bp00->proc~pr00 proc~bp00->proc~rz proc~bp00->proc~ir proc~bi00 BI00 proc~bp00->proc~bi00 proc~faom03 FAOM03 proc~eect00->proc~faom03 proc~falp03 FALP03 proc~eect00->proc~falp03 proc~fae03 FAE03 proc~eect00->proc~fae03 proc~fal03 FAL03 proc~eect00->proc~fal03 proc~faf03 FAF03 proc~eect00->proc~faf03 proc~fad03 FAD03 proc~eect00->proc~fad03 proc~fave03 FAVE03 proc~eect00->proc~fave03 proc~fapa03 FAPA03 proc~eect00->proc~fapa03 proc~era00->proc~anp

Contents

Source Code

C2TPE

Source Code

    subroutine C2TPE ( tta, ttb, uta, utb, dpsi, deps, xp, yp, &
                       rc2t )

    implicit none

    real(wp),intent(in) :: tta !! TT as a 2-part Julian Date (Note 1)
    real(wp),intent(in) :: ttb !! TT as a 2-part Julian Date (Note 1)
    real(wp),intent(in) :: uta !! UT1 as a 2-part Julian Date (Note 1)
    real(wp),intent(in) :: utb !! UT1 as a 2-part Julian Date (Note 1)
    real(wp),intent(in) :: dpsi !! nutation (Note 2)
    real(wp),intent(in) :: deps !! nutation (Note 2)
    real(wp),intent(in) :: xp !! coordinates of the pole (radians, Note 3)
    real(wp),intent(in) :: yp !! coordinates of the pole (radians, Note 3)
    real(wp),dimension(3,3),intent(out) :: rc2t !! celestial-to-terrestrial matrix (Note 4)

    real(wp) :: epsa, rb(3,3), rp(3,3), rbp(3,3), rn(3,3), &
                rbpn(3,3), gmst, ee, sp, rpom(3,3)

    !  Form the celestial-to-true matrix for this TT.
    call PN00 ( tta, ttb, dpsi, deps, &
                    epsa, rb, rp, rbp, rn, rbpn )

    !  Predict the Greenwich Mean Sidereal Time for this UT1 and TT.
    gmst = GMST00 ( uta, utb, tta, ttb )

    !  Predict the equation of the equinoxes given TT and nutation.
    ee = EE00 ( tta, ttb, epsa, dpsi)

    !  Estimate s'.
    sp = SP00 ( tta, ttb)

    !  Form the polar motion matrix.
    call POM00 ( xp, yp, sp, rpom )

    !  Combine to form the celestial-to-terrestrial matrix.
    call C2TEQX ( rbpn, gmst+ee, rpom, rc2t )

    end subroutine C2TPE