C2T00B Subroutine

  1. astro_module.f90
  2. astro_module
  3. C2T00B

public subroutine C2T00B(tta, ttb, uta, utb, xp, yp, rc2t)

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

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. 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.

  3. The matrix RC2T transforms 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), RC2I is the celestial-to-intermediate matrix, ERA is the Earth rotation angle and RPOM is the polar motion matrix.

  4. The present routine is faster, but slightly less accurate (about 1 mas), than the C2T00A routine.

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) :: xp

coordinates of the pole (radians, Note 2)
real(kind=wp), intent(in) :: yp

coordinates of the pole (radians, Note 2)
real(kind=wp), intent(out), dimension(3,3):: rc2t

celestial-to-terrestrial matrix (Note 3)

Calls

proc~~c2t00b~~CallsGraph proc~c2t00b C2T00B proc~c2i00b C2I00B proc~c2t00b->proc~c2i00b proc~era00 ERA00 proc~c2t00b->proc~era00 proc~pom00 POM00 proc~c2t00b->proc~pom00 proc~c2tcio C2TCIO proc~c2t00b->proc~c2tcio proc~c2ibpn C2IBPN proc~c2i00b->proc~c2ibpn proc~pnm00b PNM00B proc~c2i00b->proc~pnm00b proc~anp ANP proc~era00->proc~anp proc~rx RX proc~pom00->proc~rx proc~ry RY proc~pom00->proc~ry proc~ir IR proc~pom00->proc~ir proc~rz RZ proc~pom00->proc~rz proc~c2tcio->proc~rz proc~rxr RXR proc~c2tcio->proc~rxr proc~bpn2xy BPN2XY proc~c2ibpn->proc~bpn2xy proc~c2ixy C2IXY proc~c2ibpn->proc~c2ixy proc~pn00b PN00B proc~pnm00b->proc~pn00b proc~nut00b NUT00B proc~pn00b->proc~nut00b proc~pn00 PN00 proc~pn00b->proc~pn00 proc~s00 S00 proc~c2ixy->proc~s00 proc~c2ixys C2IXYS proc~c2ixy->proc~c2ixys proc~pn00->proc~rxr 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~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~c2ixys->proc~ry proc~c2ixys->proc~ir proc~c2ixys->proc~rz proc~numat->proc~rx proc~numat->proc~ir proc~numat->proc~rz proc~bp00->proc~rx proc~bp00->proc~ry proc~bp00->proc~ir proc~bp00->proc~rz proc~bp00->proc~rxr proc~bp00->proc~pr00 proc~bi00 BI00 proc~bp00->proc~bi00

Contents

Source Code

C2T00B

Source Code

    subroutine C2T00B ( tta, ttb, uta, utb, 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) :: xp !! coordinates of the pole (radians, Note 2)
    real(wp),intent(in) :: yp !! coordinates of the pole (radians, Note 2)
    real(wp),dimension(3,3),intent(out) :: rc2t !! celestial-to-terrestrial matrix (Note 3)

    real(wp) :: rc2i(3,3), era, rpom(3,3)

    !  Form the celestial-to-intermediate matrix for this TT (IAU 2000B).
    call C2I00B ( tta, ttb, rc2i )

    !  Predict the Earth rotation angle for this UT1.
    era = ERA00 ( uta, utb )

    !  Form the polar motion matrix (neglecting s').
    call POM00 ( xp, yp, 0.0_wp, rpom )

    !  Combine to form the celestial-to-terrestrial matrix.
    call C2TCIO ( rc2i, era, rpom, rc2t )

    end subroutine C2T00B