35
4.18.1
SOLARSYSTEM
short int solarsystem (double tjd, short int body, short int origin,
double *pos, double *vel)
PURPOSE:
Provides the position and velocity vectors of a planet or other
solar system body at a specific time. The origin of coordinates
may be either the barycenter of the solar system or the center
of mass of the Sun.
INPUT
ARGUMENTS:
tjd (double)
TDB Julian date.
body (short int)
Body identification number for the solar system object of
interest; Mercury = 1,...,Pluto = 9, Sun = 10, Moon = 11.
origin (short int)
Origin code; solar system barycenter = 0,
center of mass of the Sun = 1.
OUTPUT
ARGUMENTS:
pos[3] (double)
Position vector of 'body' at tjd; equatorial rectangular
coordinates in AU referred to the mean equator and equinox
of J2000.0.
vel[3] (double)
Velocity vector of 'body' at tjd; equatorial rectangular
system referred to the mean equator and equinox of J2000.0,
in AU/Day.
RETURNED
VALUE:
(short int)
0...Everything OK.
Other values depend upon version in use
Discussion:
Function solarsystem provides positions and velocities for the major bodies of the
solar system. Specifically, this function supplies values for the components of the
position vector
pos
and velocity vector
vel
for body
body
at time
tjd
. The vectors
computed by
solarsystem
are in the equatorial rectangular coordinate system which
is oriented to the mean equator and equinox of standard epoch J2000.0. The vectors are
barycentric if
origin
= 0 and heliocentric if
origin
= 1.
There are two different versions of
solarsystem
supplied in NOVAS-C, each with
its own internal logic. One uses internally-stored data or series expansions, the other uses
