APCI13 Subroutine

  1. astro_module.f90
  2. astro_module
  3. APCI13

public subroutine APCI13(date1, date2, astrom, eo)

For a terrestrial observer, prepare star-independent astrometry parameters for transformations between ICRS and geocentric CIRS coordinates. The caller supplies the date, and SOFA models are used to predict the Earth ephemeris and CIP/CIO.

The parameters produced by this routine are required in the parallax, light deflection, aberration, and bias-precession-nutation parts of the astrometric transformation chain.

Status: support routine.

Notes

  1. The TDB date DATE1+DATE2 is a Julian Date, apportioned in any convenient way between the two arguments. For example, JD(TDB)=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. For most applications of this routine the choice will not be at all critical.

    TT can be used instead of TDB without any significant impact on accuracy.

  2. All the vectors are with respect to BCRS axes.

  3. In cases where the caller wishes to supply his own Earth ephemeris and CIP/CIO, the routine APCI can be used instead of the present routine.

  4. This is one of several routines that inserts into the ASTROM array star-independent parameters needed for the chain of astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed.

    The various routines support different classes of observer and portions of the transformation chain:

        routines           observer        transformation

APCG APCG13    geocentric      ICRS <-> GCRS
APCI APCI13    terrestrial     ICRS <-> CIRS
APCO APCO13    terrestrial     ICRS <-> observed
APCS APCS13    space           ICRS <-> GCRS
APER APER13    terrestrial     update Earth rotation
APIO APIO13    terrestrial     CIRS <-> observed

    Those with names ending in "13" use contemporary SOFA models to compute the various ephemerides. The others accept ephemerides supplied by the caller.

    The transformation from ICRS to GCRS covers space motion, parallax, light deflection, and aberration. From GCRS to CIRS comprises frame bias and precession-nutation. From CIRS to observed takes account of Earth rotation, polar motion, diurnal aberration and parallax (unless subsumed into the ICRS <-> GCRS transformation), and atmospheric refraction.

  5. The context array ASTROM produced by this routine is used by ATCIQ and ATICQ.

History

  • IAU SOFA revision: 2017 March 12

Arguments

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

TDB as a 2-part...
real(kind=wp), intent(in) :: date2
real(kind=wp), intent(inout), 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) unchanged (23) unchanged (24) unchanged (25) unchanged (26) unchanged (27) unchanged (28) unchanged (29) unchanged (30) unchanged
real(kind=wp), intent(out) :: eo

equation of the origins (ERA-GST)

Calls

proc~~apci13~~CallsGraph proc~apci13 APCI13 proc~s06 S06 proc~apci13->proc~s06 proc~pnm06a PNM06A proc~apci13->proc~pnm06a proc~eors EORS proc~apci13->proc~eors proc~apci APCI proc~apci13->proc~apci proc~epv00 EPV00 proc~apci13->proc~epv00 proc~bpn2xy BPN2XY proc~apci13->proc~bpn2xy proc~faom03 FAOM03 proc~s06->proc~faom03 proc~falp03 FALP03 proc~s06->proc~falp03 proc~fae03 FAE03 proc~s06->proc~fae03 proc~fal03 FAL03 proc~s06->proc~fal03 proc~faf03 FAF03 proc~s06->proc~faf03 proc~fad03 FAD03 proc~s06->proc~fad03 proc~fave03 FAVE03 proc~s06->proc~fave03 proc~fapa03 FAPA03 proc~s06->proc~fapa03 proc~pfw06 PFW06 proc~pnm06a->proc~pfw06 proc~nut06a NUT06A proc~pnm06a->proc~nut06a proc~fw2m FW2M proc~pnm06a->proc~fw2m proc~c2ixys C2IXYS proc~apci->proc~c2ixys proc~apcg APCG proc~apci->proc~apcg proc~obl06 OBL06 proc~pfw06->proc~obl06 proc~ry RY proc~c2ixys->proc~ry proc~ir IR proc~c2ixys->proc~ir proc~rz RZ proc~c2ixys->proc~rz proc~nut00a NUT00A proc~nut06a->proc~nut00a proc~rx RX proc~fw2m->proc~rx proc~fw2m->proc~ir proc~fw2m->proc~rz proc~zpv ZPV proc~apcg->proc~zpv proc~apcs APCS proc~apcg->proc~apcs proc~nut00a->proc~faom03 proc~nut00a->proc~fae03 proc~nut00a->proc~fal03 proc~nut00a->proc~faf03 proc~nut00a->proc~fave03 proc~nut00a->proc~fapa03 proc~fame03 FAME03 proc~nut00a->proc~fame03 proc~fasa03 FASA03 proc~nut00a->proc~fasa03 proc~faju03 FAJU03 proc~nut00a->proc~faju03 proc~fama03 FAMA03 proc~nut00a->proc~fama03 proc~faur03 FAUR03 proc~nut00a->proc~faur03 proc~zp ZP proc~zpv->proc~zp proc~apcs->proc~ir proc~pn PN proc~apcs->proc~pn proc~pn->proc~zp proc~sxp SXP proc~pn->proc~sxp

Called by

proc~~apci13~~CalledByGraph proc~apci13 APCI13 proc~atci13 ATCI13 proc~atci13->proc~apci13 proc~atic13 ATIC13 proc~atic13->proc~apci13

Contents

Source Code

APCI13

Source Code

    subroutine APCI13 ( date1, date2, astrom, eo )

    implicit none

    real(wp),intent(in) :: date1 !! TDB as a 2-part...
    real(wp),intent(in) :: date2 !! ...Julian Date (Note 1)
    real(wp),dimension(30),intent(inout) :: 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)     unchanged
                                                   !! (23)     unchanged
                                                   !! (24)     unchanged
                                                   !! (25)     unchanged
                                                   !! (26)     unchanged
                                                   !! (27)     unchanged
                                                   !! (28)     unchanged
                                                   !! (29)     unchanged
                                                   !! (30)     unchanged
    real(wp),intent(out) :: eo !! equation of the origins (ERA-GST)

    integer :: j
    real(wp) :: pvh(3,2), pvb(3,2), r(3,3), x, y, s

    !  Earth barycentric & heliocentric position/velocity (au, au/d).
    call EPV00 ( date1, date2, pvh, pvb, j )

    !  Form the equinox based BPN matrix, IAU 2006/2000A.
    call PNM06A ( date1, date2, r )

    !  Extract CIP X,Y.
    call BPN2XY ( r, x, y )

    !  Obtain CIO locator s.
    s = S06 ( date1, date2, x, y )

    !  Compute the star-independent astrometry parameters.
    call APCI ( date1, date2, pvb, pvh, x, y, s, astrom )

    !  Equation of the origins.
    eo = EORS ( r, s )

    end subroutine APCI13