TTTCG Subroutine

  1. astro_module.f90
  2. astro_module
  3. TTTCG

public subroutine TTTCG(tt1, tt2, tcg1, tcg2, j)

Time scale transformation: Terrestrial Time, TT, to Geocentric Coordinate Time, TCG.

Status: canonical.

Note

TT1+TT2 is Julian Date, apportioned in any convenient way between the two arguments, for example where TT1 is the Julian Day Number and TT2 is the fraction of a day. The returned TCG1,TCG2 follow suit.

References

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

  • IAU 2000 Resolution B1.9

History

  • IAU SOFA revision: 2019 June 20

Arguments

TypeIntentOptionalAttributesName
real(kind=wp), intent(in) :: tt1

TT as a 2-part Julian Date
real(kind=wp), intent(in) :: tt2

TT as a 2-part Julian Date
real(kind=wp), intent(out) :: tcg1

TCG as a 2-part Julian Date
real(kind=wp), intent(out) :: tcg2

TCG as a 2-part Julian Date
integer, intent(out) :: j

Contents

Source Code

TTTCG

Source Code

    subroutine TTTCG ( tt1, tt2, tcg1, tcg2, j )

    implicit none

    real(wp),intent(in) :: tt1 !! TT as a 2-part Julian Date
    real(wp),intent(in) :: tt2 !! TT as a 2-part Julian Date
    real(wp),intent(out) :: tcg1 !! TCG as a 2-part Julian Date
    real(wp),intent(out) :: tcg2 !! TCG as a 2-part Julian Date
    integer,intent(out) :: j !! status:  0 = OK

    !  JD for MJD 0
    real(wp),parameter :: djm0 = 2400000.5_wp

    !  1977 Jan 1 00:00:32.184 TT, as MJD
    real(wp),parameter :: t77t = 43144.0003725_wp

    !  L_G = 1 - dTT/dTCG
    real(wp),parameter :: elg = 6.969290134e-10_wp

    !  TT to TCG rate
    real(wp),parameter :: elgg = elg/(1.0_wp-elg)

    !  Result, safeguarding precision.
    if ( abs(tt1)>abs(tt2) ) then
       tcg1 = tt1
       tcg2 = tt2 + ( ( tt1-djm0 ) + ( tt2-t77t ) ) * elgg
    else
       tcg1 = tt1 + ( ( tt2-djm0 ) + ( tt1-t77t ) ) * elgg
       tcg2 = tt2
    end if

    !  Status (always OK).
    j = 0

    end subroutine TTTCG