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.help moon Jun99 "Slalib Package"
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SUBROUTINE slMOON (IY, ID, FD, PV)
- - - - -
M O O N
- - - - -
Approximate geocentric position and velocity of the Moon
(single precision).
Given:
IY i year
ID i day in year (1 = Jan 1st)
FD r fraction of day
Returned:
PV r(6) Moon position & velocity vector
Notes:
1 The date and time is TDB (loosely ET) in a Julian calendar
which has been aligned to the ordinary Gregorian
calendar for the interval 1900 March 1 to 2100 February 28.
The year and day can be obtained by calling slCAYD or
slCLYD.
2 The Moon 6-vector is Moon centre relative to Earth centre,
mean equator and equinox of date. Position part, PV(1-3),
is in AU; velocity part, PV(4-6), is in AU/sec.
3 The position is accurate to better than 0.5 arcminute
in direction and 1000 km in distance. The velocity
is accurate to better than 0.5"/hour in direction and
4 m/s in distance. (RMS figures with respect to JPL DE200
for the interval 1960-2025 are 14 arcsec and 0.2 arcsec/hour in
longitude, 9 arcsec and 0.2 arcsec/hour in latitude, 350 km and
2 m/s in distance.) Note that the distance accuracy is
comparatively poor because this routine is principally intended
for computing topocentric direction.
4 This routine is only a partial implementation of the original
Meeus algorithm (reference below), which offers 4 times the
accuracy in direction and 30 times the accuracy in distance
when fully implemented (as it is in slDMON).
Reference:
Meeus, l'Astronomie, June 1984, p348.
Called: slS2C6
P.T.Wallace Starlink 8 December 1994
Copyright (C) 1995 Rutherford Appleton Laboratory
Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
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