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.help earth Jun99 "Slalib Package"
.nf
SUBROUTINE slERTH (IY, ID, FD, PV)
- - - - - -
E R T H
- - - - - -
Approximate heliocentric position and velocity of the Earth
Given:
IY I year
ID I day in year (1 = Jan 1st)
FD R fraction of day
Returned:
PV R(6) Earth 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 Earth heliocentric 6-vector is mean equator and equinox
of date. Position part, PV(1-3), is in AU; velocity part,
PV(4-6), is in AU/sec.
3 Max/RMS errors 1950-2050:
13/5 E-5 AU = 19200/7600 km in position
47/26 E-10 AU/s = 0.0070/0.0039 km/s in speed
4 More precise results are obtainable with the routine slEVP.
P.T.Wallace Starlink 23 November 1994
Copyright (C) 1995 Rutherford Appleton Laboratory
Copyright (C) 1995 Association of Universities for Research in Astronomy Inc.
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