Py ERFA:docs

- Index
- Modules

### Navigation

- next »
- « previous |
- PyERFA v2.0.1.5 »
- erfa Package »
- nut06a

# nut06a

erfa.nut06a(date1, date2)

  IAU 2000A nutation with adjustments to match the IAU 2006 precession.

  Parameters:
    date1 double array
    date2 double array
  Returns:
    dpsi double array
    deps double array

  Notes

  Wraps ERFA function `eraNut06a`. The ERFA documentation is:

      - - - - - - - - - -
       e r a N u t 0 6 a
      - - - - - - - - - -

      IAU 2000A nutation with adjustments to match the IAU 2006
      precession.

      Given:
         date1,date2   double   TT as a 2-part Julian Date (Note 1)

      Returned:
         dpsi,deps     double   nutation, luni-solar + planetary (Note 2)

      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

             2450123.7           0.0       (JD method)
             2451545.0       -1421.3       (J2000 method)
             2400000.5       50123.2       (MJD method)
             2450123.5           0.2       (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 nutation components in longitude and obliquity are in radians
         and with respect to the mean equinox and ecliptic of date,
         IAU 2006 precession model (Hilton et al. 2006, Capitaine et al.
         2005).

      3) The function first computes the IAU 2000A nutation, then applies
         adjustments for (i) the consequences of the change in obliquity
         from the IAU 1980 ecliptic to the IAU 2006 ecliptic and (ii) the
         secular variation in the Earth's dynamical form factor J2.

      4) The present function provides classical nutation, complementing
         the IAU 2000 frame bias and IAU 2006 precession.  It delivers a
         pole which is at current epochs accurate to a few tens of
         microarcseconds, apart from the free core nutation.

      Called:
         eraNut00a    nutation, IAU 2000A

      References:

         Chapront, J., Chapront-Touze, M. & Francou, G. 2002,
         Astron.Astrophys. 387, 700

         Lieske, J.H., Lederle, T., Fricke, W. & Morando, B. 1977,
         Astron.Astrophys. 58, 1-16

         Mathews, P.M., Herring, T.A., Buffet, B.A. 2002, J.Geophys.Res.
         107, B4.  The MHB_2000 code itself was obtained on 9th September
         2002 from ftp//maia.usno.navy.mil/conv2000/chapter5/IAU2000A.

         Simon, J.-L., Bretagnon, P., Chapront, J., Chapront-Touze, M.,
         Francou, G., Laskar, J. 1994, Astron.Astrophys. 282, 663-683

         Souchay, J., Loysel, B., Kinoshita, H., Folgueira, M. 1999,
         Astron.Astrophys.Supp.Ser. 135, 111

         Wallace, P.T., "Software for Implementing the IAU 2000
         Resolutions", in IERS Workshop 5.1 (2002)

      This revision:  2021 May 11

      Copyright (C) 2013-2023, NumFOCUS Foundation.
      Derived, with permission, from the SOFA library.  See notes at end of file.