SOHO_EPHEMERIS(3)
NAME
soho_ephemeris, soho_latitude, soho_longitude, soho_obs_dist
-- positional and physical ephemeris of Sun as observed from
SOHO
SYNOPSIS
#include <soi_time.h>
#include <soi_ephem.h>
int soho_ephemeris (TIME obs_time, double *r_sun_soho,
double *soho_lat, double *soho_lon, double *vr,
double *vn, double *vw, TIME *mod_time)
double soho_latitude (TIME obs_time)
double soho_longitude (TIME obs_time)
double soho_obs_dist (TIME obs_time)
DESCRIPTION
soho_ephemeris interpolates the tabulated positional ephem-
eris of SOHO to the requested observation time, returning
the Sun--SOHO distance in Astronomical Units, the helio-
graphic coordinates of SOHO in degrees, and the components
of the SOHO heliocentric velocity in m/s. The normal time
step of the ephemeris tables is 10 minutes, so linear inter-
polation is used. The most recent modification time of the
ephemeris table is also returned.
The functions soho_latitude, soho_longitude, and
soho_obs_dist simply return the corresponding elements of
the ephemeris for a given time, with no status information;
they are convenience functions to avoid having to provide
the full set of arguments required by soho_ephemeris.
FILES
~CM/tables/ephemeris/summary
/usr/local/lib/libastro.a
SEE ALSO
solephem(3), carrington_rots(3)
DIAGNOSTICS
Return values:
0 normal
1 requested observation time within one time step beyond last entry in
table
-1 requested observation time outside range of table
-2 ephemeris table could not be read
If the return value is negative, the ephemeris values
returned are those for the Earth (calculated) rather than
SOHO. Values for times within one time-step of the last
tabulated value are simply continued, not extrapolated.
BUGS
There is no provision for gaps in the table. Since gaps are
marked by zero values for all ephemerides, the function will
return garbage values within a time step of any gap. No
warning is returned.
The ephemeris values change discontinuously at the end of
the tabulated range, but with a warning at least.