ATIC13 Subroutine

  1. astro_module.f90
  2. astro_module
  3. ATIC13

public subroutine ATIC13(ri, di, date1, date2, rc, dc, eo)

Transform star RA,Dec from geocentric CIRS to ICRS astrometric.

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. Iterative techniques are used for the aberration and light deflection corrections so that the routines ATIC13 (or ATICQ) and ATCI13 (or ATCIQ) are accurate inverses; even at the edge of the Sun's disk the discrepancy is only about 1 nanoarcsecond.

  3. The available accuracy is better than 1 milliarcsecond, limited mainly by the precession-nutation model that is used, namely IAU 2000A/2006. Very close to solar system bodies, additional errors of up to several milliarcseconds can occur because of unmodeled light deflection; however, the Sun's contribution is taken into account, to first order. The accuracy limitations of the SOFA routine EPV00 (used to compute Earth position and velocity) can contribute aberration errors of up to 5 microarcseconds. Light deflection at the Sun's limb is uncertain at the 0.4 mas level.

  4. Should the transformation to (equinox based) J2000.0 mean place be required rather than (CIO based) ICRS coordinates, subtract the equation of the origins from the returned right ascension: RA = RI - EO. (The ANP routine can then be applied, as required, to keep the result in the conventional 0-2pi range.)

History

  • IAU SOFA revision: 2017 March 12

Arguments

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

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

CIRS geocentric Dec (radians)
real(kind=wp), intent(in) :: date1

TDB as a 2-part...
real(kind=wp), intent(in) :: date2
real(kind=wp), intent(out) :: rc

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

ICRS astrometric Dec (radians)
real(kind=wp), intent(out) :: eo

equation of the origins (ERA-GST, Note 4)

Calls

proc~~atic13~~CallsGraph proc~atic13 ATIC13 proc~apci13 APCI13 proc~atic13->proc~apci13 proc~aticq ATICQ proc~atic13->proc~aticq 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~zp ZP proc~aticq->proc~zp proc~ab AB proc~aticq->proc~ab proc~c2s C2S proc~aticq->proc~c2s proc~s2c S2C proc~aticq->proc~s2c proc~ldsun LDSUN proc~aticq->proc~ldsun proc~trxp TRXP proc~aticq->proc~trxp proc~anp ANP proc~aticq->proc~anp 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~pdp PDP proc~ab->proc~pdp proc~c2ixys C2IXYS proc~apci->proc~c2ixys proc~apcg APCG proc~apci->proc~apcg proc~ld LD proc~ldsun->proc~ld proc~rxp RXP proc~trxp->proc~rxp proc~tr TR proc~trxp->proc~tr 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~ld->proc~pdp proc~pxp PXP proc~ld->proc~pxp 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~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

Contents

Source Code

ATIC13

Source Code

    subroutine ATIC13 ( ri, di, date1, date2, rc, dc, eo )

    implicit none

    real(wp),intent(in) :: ri !! CIRS geocentric RA (radians)
    real(wp),intent(in) :: di !! CIRS geocentric Dec (radians)
    real(wp),intent(in) :: date1 !! TDB as a 2-part...
    real(wp),intent(in) :: date2 !! ...Julian Date (Note 1)
    real(wp),intent(out) :: rc !! ICRS astrometric RA (radians)
    real(wp),intent(out) :: dc !! ICRS astrometric Dec (radians)
    real(wp),intent(out) :: eo !! equation of the origins (ERA-GST, Note 4)

    !  Star-independent astrometry parameters
    real(wp) :: astrom(30)

    !  Star-independent astrometry parameters.
    call APCI13 ( date1, date2, astrom, eo )

    !  CIRS to ICRS astrometric
    call ATICQ ( ri, di, astrom, rc, dc )

    end subroutine ATIC13