TCGTT Subroutine

  1. astro_module.f90
  2. astro_module
  3. TCGTT

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

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

Status: canonical.

Note

TCG1+TCG2 is Julian Date, apportioned in any convenient way between the two arguments, for example where TCG1 is the Julian Day Number and TCG2 is the fraction of a day. The returned TT1,TT2 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) :: tcg1

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

TCG as a 2-part Julian Date
real(kind=wp), intent(out) :: tt1

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

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

Contents

Source Code

TCGTT

Source Code

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

    implicit none

    real(wp),intent(in) :: tcg1 !! TCG as a 2-part Julian Date
    real(wp),intent(in) :: tcg2 !! TCG as a 2-part Julian Date
    real(wp),intent(out) :: tt1 !! TT as a 2-part Julian Date
    real(wp),intent(out) :: tt2 !! TT 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

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

    !  Status (always OK).
    j = 0

    end subroutine TCGTT