NUM00B Subroutine

  1. astro_module.f90
  2. astro_module
  3. NUM00B

public subroutine NUM00B(date1, date2, rmatn)

Form the matrix of nutation for a given date, IAU 2000B 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. The present routine is faster, but slightly less accurate (about 1 mas), than the NUM00A 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~~num00b~~CallsGraph proc~num00b NUM00B proc~pn00b PN00B proc~num00b->proc~pn00b proc~nut00b NUT00B proc~pn00b->proc~nut00b proc~pn00 PN00 proc~pn00b->proc~pn00 proc~obl80 OBL80 proc~pn00->proc~obl80 proc~numat NUMAT proc~pn00->proc~numat proc~bp00 BP00 proc~pn00->proc~bp00 proc~rxr RXR proc~pn00->proc~rxr proc~pr00 PR00 proc~pn00->proc~pr00 proc~rx RX proc~numat->proc~rx proc~ir IR proc~numat->proc~ir proc~rz RZ proc~numat->proc~rz proc~bp00->proc~rxr proc~bp00->proc~pr00 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

NUM00B

Source Code

    subroutine NUM00B ( 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 PN00B ( date1, date2, &
                 dpsi, deps, epsa, rb, rp, rbp, rmatn, rbpn )

    end subroutine NUM00B