ATCIQZ Subroutine

  1. astro_module.f90
  2. astro_module
  3. ATCIQZ

public subroutine ATCIQZ(rc, dc, astrom, ri, di)

Quick ICRS to CIRS transformation, given precomputed star-independent astrometry parameters, and assuming zero parallax and proper motion.

Use of this routine is appropriate when efficiency is important and where many star positions are to be transformed for one date. The star-independent parameters can be obtained by calling one of the routines APCI[13], APCG[13], APCO[13] or APCS[13].

The corresponding routine for the case of non-zero parallax and proper motion is ATCIQ.

Status: support routine.

Note

All the vectors are with respect to BCRS axes.

References

  • Urban, S. & Seidelmann, P. K. (eds), Explanatory Supplement to the Astronomical Almanac, 3rd ed., University Science Books (2013).

  • Klioner, Sergei A., "A practical relativistic model for micro- arcsecond astrometry in space", Astr. J. 125, 1580-1597 (2003).

History

  • IAU SOFA revision: 2013 August 31

Arguments

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

ICRS astrometric RA (radians)
real(kind=wp), intent(in) :: dc

ICRS astrometric Dec (radians)
real(kind=wp), intent(in), dimension(30):: astrom

star-independent astrometry parameters: (1) PM time interval (SSB, Julian years) (2-4) SSB to observer (vector, au) (5-7) Sun to observer (unit vector) (8) distance from Sun to observer (au) (9-11) v: barycentric observer velocity (vector, c) (12) sqrt(1-|v|^2): reciprocal of Lorenz factor (13-21) bias-precession-nutation matrix (22) longitude + s' (radians) (23) polar motion xp wrt local meridian (radians) (24) polar motion yp wrt local meridian (radians) (25) sine of geodetic latitude (26) cosine of geodetic latitude (27) magnitude of diurnal aberration vector (28) "local" Earth rotation angle (radians) (29) refraction constant A (radians) (30) refraction constant B (radians)
real(kind=wp), intent(out) :: ri

CIRS RA (radians)
real(kind=wp), intent(out) :: di

CIRS Dec (radians)

Calls

proc~~atciqz~~CallsGraph proc~atciqz ATCIQZ proc~c2s C2S proc~atciqz->proc~c2s proc~rxp RXP proc~atciqz->proc~rxp proc~ab AB proc~atciqz->proc~ab proc~ldsun LDSUN proc~atciqz->proc~ldsun proc~s2c S2C proc~atciqz->proc~s2c proc~anp ANP proc~atciqz->proc~anp proc~pdp PDP proc~ab->proc~pdp proc~ld LD proc~ldsun->proc~ld proc~ld->proc~pdp proc~pxp PXP proc~ld->proc~pxp

Contents

Source Code

ATCIQZ

Source Code

    subroutine ATCIQZ ( rc, dc, astrom, ri, di )

    implicit none

    real(wp),intent(in) :: rc !! ICRS astrometric RA (radians)
    real(wp),intent(in) :: dc !! ICRS astrometric Dec (radians)
    real(wp),dimension(30),intent(in) :: astrom !! star-independent astrometry parameters:
                                                !! (1)      PM time interval (SSB, Julian years)
                                                !! (2-4)    SSB to observer (vector, au)
                                                !! (5-7)    Sun to observer (unit vector)
                                                !! (8)      distance from Sun to observer (au)
                                                !! (9-11)   v: barycentric observer velocity (vector, c)
                                                !! (12)     sqrt(1-|v|^2): reciprocal of Lorenz factor
                                                !! (13-21)  bias-precession-nutation matrix
                                                !! (22)     longitude + s' (radians)
                                                !! (23)     polar motion xp wrt local meridian (radians)
                                                !! (24)     polar motion yp wrt local meridian (radians)
                                                !! (25)     sine of geodetic latitude
                                                !! (26)     cosine of geodetic latitude
                                                !! (27)     magnitude of diurnal aberration vector
                                                !! (28)     "local" Earth rotation angle (radians)
                                                !! (29)     refraction constant A (radians)
                                                !! (30)     refraction constant B (radians)
    real(wp),intent(out) :: ri !! CIRS RA (radians)
    real(wp),intent(out) :: di !! CIRS Dec (radians)

    real(wp) :: pco(3), pnat(3), ppr(3), pi(3), w

    !  BCRS coordinate direction (unit vector).
    call S2C ( rc, dc, pco )

    !  Light deflection by the Sun, giving BCRS natural direction.
    call LDSUN ( pco, astrom(5), astrom(8), pnat )

    !  Aberration, giving GCRS proper direction.
    call AB ( pnat, astrom(9), astrom(8), astrom(12), ppr )

    !  Bias-precession-nutation, giving CIRS proper direction.
    call RXP ( astrom(13), ppr, pi )

    !  CIRS RA,Dec.
    call C2S ( pi, w, di )
    ri = ANP ( w )

    end subroutine ATCIQZ