NUM00A Subroutine

  1. astro_module.f90
  2. astro_module
  3. NUM00A

public subroutine NUM00A(date1, date2, rmatn)

Form the matrix of nutation for a given date, IAU 2000A model.

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 operates in the sense V(true) = RMATN * V(mean), where the p-vector V(true) is with respect to the true equatorial triad of date and the p-vector V(mean) is with respect to the mean equatorial triad of date.

  3. A faster, but slightly less accurate result (about 1 mas), can be obtained by using instead the NUM00B routine.

Reference

  • Explanatory Supplement to the Astronomical Almanac, P. Kenneth Seidelmann (ed), University Science Books (1992), Section 3.222-3 (p114).

History

  • IAU SOFA revision: 2006 November 13

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):: rmatn

nutation matrix

Calls

proc~~num00a~~CallsGraph proc~num00a NUM00A proc~pn00a PN00A proc~num00a->proc~pn00a proc~nut00a NUT00A proc~pn00a->proc~nut00a proc~pn00 PN00 proc~pn00a->proc~pn00 proc~faom03 FAOM03 proc~nut00a->proc~faom03 proc~faju03 FAJU03 proc~nut00a->proc~faju03 proc~fasa03 FASA03 proc~nut00a->proc~fasa03 proc~fae03 FAE03 proc~nut00a->proc~fae03 proc~fame03 FAME03 proc~nut00a->proc~fame03 proc~fal03 FAL03 proc~nut00a->proc~fal03 proc~fapa03 FAPA03 proc~nut00a->proc~fapa03 proc~faf03 FAF03 proc~nut00a->proc~faf03 proc~fave03 FAVE03 proc~nut00a->proc~fave03 proc~fama03 FAMA03 proc~nut00a->proc~fama03 proc~faur03 FAUR03 proc~nut00a->proc~faur03 proc~obl80 OBL80 proc~pn00->proc~obl80 proc~numat NUMAT proc~pn00->proc~numat proc~bp00 BP00 proc~pn00->proc~bp00 proc~pr00 PR00 proc~pn00->proc~pr00 proc~rxr RXR proc~pn00->proc~rxr proc~rx RX proc~numat->proc~rx proc~ir IR proc~numat->proc~ir proc~rz RZ proc~numat->proc~rz proc~bp00->proc~pr00 proc~bp00->proc~rxr proc~bp00->proc~rx proc~ry RY proc~bp00->proc~ry proc~bp00->proc~ir proc~bp00->proc~rz proc~bi00 BI00 proc~bp00->proc~bi00

Contents

Source Code

NUM00A

Source Code

    subroutine NUM00A ( date1, date2, rmatn )

    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) :: rmatn !! nutation matrix

    real(wp) :: dpsi, deps, epsa, &
                rb(3,3), rp(3,3), rbp(3,3), rbpn(3,3)

    !  Obtain the required matrix (discarding other results).
    call PN00A ( date1, date2, &
                 dpsi, deps, epsa, rb, rp, rbp, rmatn, rbpn )

    end subroutine NUM00A