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.help mappa Jun99 "Slalib Package"
.nf
SUBROUTINE slMAPA (EQ, DATE, AMPRMS)
- - - - - -
M A P A
- - - - - -
Compute star-independent parameters in preparation for
conversions between mean place and geocentric apparent place.
The parameters produced by this routine are required in the
parallax, light deflection, aberration, and precession/nutation
parts of the mean/apparent transformations.
The reference frames and timescales used are post IAU 1976.
Given:
EQ d epoch of mean equinox to be used (Julian)
DATE d TDB (JD-2400000.5)
Returned:
AMPRMS d(21) star-independent mean-to-apparent parameters:
(1) time interval for proper motion (Julian years)
(2-4) barycentric position of the Earth (AU)
(5-7) heliocentric direction of the Earth (unit vector)
(8) (grav rad Sun)*2/(Sun-Earth distance)
(9-11) ABV: barycentric Earth velocity in units of c
(12) sqrt(1-v**2) where v=modulus(ABV)
(13-21) precession/nutation (3,3) matrix
References:
1984 Astronomical Almanac, pp B39-B41.
(also Lederle & Schwan, Astron. Astrophys. 134,
1-6, 1984)
Notes:
1) For DATE, the distinction between the required TDB and TT
is always negligible. Moreover, for all but the most
critical applications UTC is adequate.
2) The accuracy of the routines using the parameters AMPRMS is
limited by the routine slEVP, used here to compute the
Earth position and velocity by the methods of Stumpff.
The maximum error in the resulting aberration corrections is
about 0.3 milliarcsecond.
3) The vectors AMPRMS(2-4) and AMPRMS(5-7) are referred to
the mean equinox and equator of epoch EQ.
4) The parameters AMPRMS produced by this routine are used by
slMAPQ and slMAPZ.
Called:
slEPJ MDJ to Julian epoch
slEVP earth position & velocity
slDVN normalize vector
slPRNU precession/nutation matrix
P.T.Wallace Starlink 23 November 1995
Copyright (C) 1995 Rutherford Appleton Laboratory
Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
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.endhelp
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