ECM06 Subroutine

  1. astro_module.f90
  2. astro_module
  3. ECM06

public subroutine ECM06(date1, date2, rm)

ICRS equatorial to ecliptic rotation matrix, IAU 2006.

Status: support routine.

Notes

  1. The TT date DATE1+DATE2 is a Julian Date, apportioned in any convenient way between the two arguments. For example, JD(TT)=2450123.7 could be expressed in any of these ways, among others:

        DATE1          DATE2

 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 method is best matched to the way the argument is handled internally and will deliver the optimum resolution. The MJD method and the date & time methods are both good compromises between resolution and convenience.

  2. The matrix is in the sense

    E_ep = RM x P_ICRS,

    where P_ICRS is a vector with respect to ICRS right ascension and declination axes and E_ep is the same vector with respect to the (inertial) ecliptic and equinox of date.

  3. P_ICRS is a free vector, merely a direction, typically of unit magnitude, and not bound to any particular spatial origin, such as the Earth, Sun or SSB. No assumptions are made about whether it represents starlight and embodies astrometric effects such as parallax or aberration. The transformation is approximately that between mean J2000.0 right ascension and declination and ecliptic longitude and latitude, with only frame bias (always less than 25 mas) to disturb this classical picture.

History

  • IAU SOFA revision: 2015 December 11

Arguments

TypeIntentOptionalAttributesName
real(kind=wp), intent(in) :: date1

TT as a 2-part Julian Date (Note 1)
real(kind=wp), intent(in) :: date2

TT as a 2-part Julian Date (Note 1)
real(kind=wp), intent(out), dimension(3,3):: rm

ICRS to ecliptic rotation matrix

Calls

proc~~ecm06~~CallsGraph proc~ecm06 ECM06 proc~obl06 OBL06 proc~ecm06->proc~obl06 proc~rx RX proc~ecm06->proc~rx proc~pmat06 PMAT06 proc~ecm06->proc~pmat06 proc~rxr RXR proc~ecm06->proc~rxr proc~ir IR proc~ecm06->proc~ir proc~pfw06 PFW06 proc~pmat06->proc~pfw06 proc~fw2m FW2M proc~pmat06->proc~fw2m proc~pfw06->proc~obl06 proc~fw2m->proc~rx proc~fw2m->proc~ir proc~rz RZ proc~fw2m->proc~rz

Called by

proc~~ecm06~~CalledByGraph proc~ecm06 ECM06 proc~eceq06 ECEQ06 proc~eceq06->proc~ecm06 proc~eqec06 EQEC06 proc~eqec06->proc~ecm06

Contents

Source Code

ECM06

Source Code

    subroutine ECM06 ( date1, date2, rm )

    implicit none

    real(wp),intent(in) :: date1 !! TT as a 2-part Julian Date (Note 1)
    real(wp),intent(in) :: date2 !! TT as a 2-part Julian Date (Note 1)
    real(wp),dimension(3,3),intent(out) :: rm !! ICRS to ecliptic rotation matrix

    real(wp) :: ob, bp(3,3), e(3,3)

    !  Obliquity, IAU 2006.
    ob = OBL06 ( date1, date2 )

    !  Precession-bias matrix, IAU 2006.
    call PMAT06 ( date1, date2, bp )

    !  Equatorial of date to ecliptic matrix.
    call IR ( e )
    call RX ( ob, e )

    !  ICRS to ecliptic coordinates rotation matrix, IAU 2006.
    call RXR ( e, bp, rm )

    end subroutine ECM06