void scs2e_c ( SpiceInt sc,
ConstSpiceChar * sclkch,
SpiceDouble * et )
Convert a spacecraft clock string to ephemeris seconds past
J2000 (ET).
SCLK
TIME
CONVERSION
TIME
Variable I/O Description
-------- --- --------------------------------------------------
sc I NAIF integer code for a spacecraft.
sclkch I An SCLK string.
et O Ephemeris time, seconds past J2000.
sc is a NAIF ID code for a spacecraft, one of whose
clock values is represented by sclkch. The set of
supported spacecraft clocks is listed in the SCLK
Required Reading.
sclkch is a character string representation of the
spacecraft clock value that corresponds to ET, for
the spacecraft specified by the input argument sc.
sclkch is an absolute spacecraft clock time, so
partition information should be included in this
string. The precise format of sclkch is specified
in the SCLK Required Reading.
et is the epoch, specified as ephemeris seconds past
J2000, that corresponds to sclkch.
None.
1) This routine assumes that that an SCLK kernel appropriate
to the spacecraft clock identified by the input argument SC
has been loaded. If an SCLK kernel has not been loaded,
does not contain all of the required data, or contains
invalid data, error diagnoses will be performed by routines
called by this routine. The output argument et will not
be modified.
2) When using SCLK kernels that map SCLK to a time system other
than ET (also called barycentric dynamical time---`TDB'), it
is necessary to have a leapseconds kernel loaded at the time
this routine is called. If a leapseconds kernel is required
for conversion between SCLK and ET but is not loaded, the
error will be diagnosed by routines called by this routine.
The output argument et will not be modified.
The time system that an SCLK kernel maps SCLK to is indicated
by the variable SCLK_TIME_SYSTEM_nn in the kernel, where nn
is the negative of the NAIF integer code for the spacecraft.
The time system used in a kernel is TDB if and only if the
variable is assigned the value 1.
3) Invalid values of sclkch will be diagnosed by routines called
by this routine. The output argument et will not be modified.
None.
This routine is provided as a convenience; it is simply shorthand
for the code fragment
scencd_c ( sc, sclkch, &sclkdp );
sct2e_c ( sc, sclkdp, &et );
1) Find the state (position and velocity) of Jupiter, as seen
from the Galileo spacecraft, at the epoch corresponding to
the SCLK value
2 / 3110578:89:09
The digit "2", followed by the forward slash, indicates that
the time value is in the second mission partition.
During program initialization, load the leapseconds and
SCLK kernels. We will pretend that these files are named
"leapseconds.ker" and "gllsclk.ker". To use this code
fragment, you must substitute the actual names of these
kernel files for the names used here.
/.
Load leapseconds and SCLK kernels:
./
furnsh_c ( "leapseconds.ker" );
furnsh_c ( "gllsclk.ker" );
/.
Load an SPK file (again, a fictitious file)
containing an ephemeris for Jupiter and the
GLL orbiter's trajectory.
./
spklef_c ( "gllspk.ker", &handle );
/.
The Galileo spacecraft ID is -77. Convert our SCLK
string to ephemeris seconds past J2000, which is the
time representation expected by spkez_c.
./
scs2e_c ( -77, "2 / 3110578:89:09", &et );
/.
Find the state of Jupiter (body 599) as seen from Galileo
at time et. To use spkez_c, you must first load an SPK
kernel, using the routine spklef_c.
./
spkez_c ( 599, et, refsys, corr, -77, state, < );
2) Convert a Voyager 2 SCLK value to UTC, using calendar format,
with 3 digits of precision in the seconds component.
Again, your initialization code must load the leapseconds
and SCLK kernels:
/.
Load leapseconds and SCLK kernels:
./
furnsh_c ( "leapseconds.ker" );
furnsh_c ( "vgr2sclk.ker" );
To find the UTC value corresponding to Voyager 2 SCLK
string
11389.20.768
you can use the code fragment
scs2e_c ( -32, "11389.29.768", &et );
et2utc_c ( et, "c", 3, UTCLEN, utc );
where UTCLEN is a constant indicating the available
room in the string utc. A value of 25 characters suffices.
1) An SCLK kernel appropriate to the spacecraft clock identified
by SC must be loaded at the time this routine is called.
2) If the SCLK kernel used with this routine does not map SCLK
directly to barycentric dynamical time, a leapseconds kernel
must be loaded at the time this routine is called.
[1] SPK Required Reading
N.J. Bachman (JPL)
-CSPICE Version 1.1.1, 14-AUG-2006 (EDW)
Replace mention of ldpool_c with furnsh_c.
-CSPICE Version 1.1.0, 08-FEB-1998 (NJB)
References to C2F_CreateStr_Sig were removed; code was
cleaned up accordingly. String checks are now done using
the macro CHKFSTR.
-CSPICE Version 1.0.0, 25-OCT-1997 (NJB)
Based on SPICELIB Version 1.0.2, 10-APR-1992 (NJB) (WLT)
spacecraft_clock string to ephemeris time
Link to routine scs2e_c source file scs2e_c.c
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