| spkw13_c |
|
Table of contents
Procedure
spkw13_c ( Write SPK segment, type 13 )
void spkw13_c ( SpiceInt handle,
SpiceInt body,
SpiceInt center,
ConstSpiceChar * frame,
SpiceDouble first,
SpiceDouble last,
ConstSpiceChar * segid,
SpiceInt degree,
SpiceInt n,
ConstSpiceDouble states[][6],
ConstSpiceDouble epochs[] )
AbstractWrite a type 13 segment to an SPK file. Required_ReadingNAIF_IDS SPC SPK TIME KeywordsEPHEMERIS FILES Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- handle I Handle of an SPK file open for writing. body I NAIF code for an ephemeris object. center I NAIF code for center of motion of body. frame I Reference frame name. first I Start time of interval covered by segment. last I End time of interval covered by segment. segid I Segment identifier. degree I Degree of interpolating polynomials. n I Number of states. states I Array of states. epochs I Array of epochs corresponding to states. MAXDEG P Maximum allowed degree of interpolating polynomial. Detailed_Input
handle is the file handle of an SPK file that has been
opened for writing.
body is the NAIF integer code for an ephemeris object
whose state relative to another body is described
by the segment to be created.
center is the NAIF integer code for the center of motion
of the object identified by body.
frame is the NAIF name for a reference frame
relative to which the state information for body
is specified.
first,
last are, respectively, the start and stop times of
the time interval over which the segment defines
the state of body.
segid is the segment identifier. An SPK segment
identifier may contain up to 40 characters.
degree is the degree of the Hermite polynomials used to
interpolate the states. All components of the
state vectors are interpolated by polynomials of
fixed degree.
n is the number of states in the input state vector
array.
states contains a time-ordered array of geometric states
( x, y, z, dx/dt, dy/dt, dz/dt, in kilometers and
kilometers per second ) of body relative to center,
specified relative to frame.
epochs is an array of epochs corresponding to the members
of the state array. The epochs are specified as
seconds past J2000, TDB.
Detailed_OutputNone. See -Particulars for a description of the effect of this routine. Parameters
MAXDEG is the maximum allowed degree of the interpolating
polynomial. If the value of MAXDEG is increased,
the SPICELIB routine SPKPVN must be changed
accordingly. In particular, the size of the
record passed to SPKRnn and SPKEnn must be
increased, and comments describing the record size
must be changed.
Exceptions
If any of the following exceptions occur, this routine will return
without creating a new segment.
1) If `frame' is not a recognized name, the error
SPICE(INVALIDREFFRAME) is signaled by a routine in the call
tree of this routine.
2) If the last non-blank character of `segid' occurs past index 40,
the error SPICE(SEGIDTOOLONG) is signaled by a routine in the
call tree of this routine.
3) If `segid' contains any nonprintable characters, the error
SPICE(NONPRINTABLECHARS) is signaled by a routine in the call
tree of this routine.
4) If `degree' is not at least 1 or is greater than MAXDEG, the
error SPICE(INVALIDDEGREE) is signaled by a routine in the
call tree of this routine.
5) If `degree' is not odd, the error SPICE(INVALIDDEGREE) is
signaled by a routine in the call tree of this routine.
6) If the number of states `n' is not at least (degree+1)/2, the
error SPICE(TOOFEWSTATES) is signaled by a routine in the call
tree of this routine.
7) If `first' is greater than or equal to `last', the error
SPICE(BADDESCRTIMES) is signaled by a routine in the call tree
of this routine.
8) If the elements of the array `epochs' are not in strictly
increasing order, the error SPICE(TIMESOUTOFORDER) is
signaled by a routine in the call tree of this routine.
9) If the first epoch, epochs[0], is greater than `first', the
error SPICE(BADDESCRTIMES) is signaled by a routine in the
call tree of this routine.
10) If the last epoch, epochs[n-1], is less than `last', the error
SPICE(BADDESCRTIMES) is signaled by a routine in the call tree
of this routine.
11) If any of the `frame' or `segid' input string pointers is
null, the error SPICE(NULLPOINTER) is signaled.
12) If any of the `frame' or `segid' input strings has zero
length, the error SPICE(EMPTYSTRING) is signaled.
FilesA new type 13 SPK segment is written to the SPK file attached to HANDLE. ParticularsThis routine writes an SPK type 13 data segment to the open SPK file according to the format described in the type 13 section of the SPK Required Reading. The SPK file must have been opened with write access. Examples
The numerical results shown for this example may differ across
platforms. The results depend on the SPICE kernels used as
input, the compiler and supporting libraries, and the machine
specific arithmetic implementation.
1) Suppose that you have a time-ordered array of geometric states
of a new object that follows Phobos, with a delay of 1 hour,
in its orbit around Mars and are prepared to produce a segment
of type 13 in an SPK file. Create a new SPK file with this
segment. Use an existing SPK to create the input data for the
SPK segment.
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File: spkw13_ex1.tm
This meta-kernel is intended to support operation of SPICE
example programs. The kernels shown here should not be
assumed to contain adequate or correct versions of data
required by SPICE-based user applications.
In order for an application to use this meta-kernel, the
kernels referenced here must be present in the user's
current working directory.
The names and contents of the kernels referenced
by this meta-kernel are as follows:
File name Contents
--------- --------
mar097.bsp Mars satellite ephemeris
naif0012.tls Leapseconds
\begindata
KERNELS_TO_LOAD = ( 'mar097.bsp',
'naif0012.tls' )
\begintext
End of meta-kernel
Example code begins here.
/.
Program spkw13_ex1
./
#include <stdio.h>
#include <math.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local parameters.
./
#define SPKNAM "spkw13_ex1.bsp"
#define DEGREE 3
#define MARS 499
#define NEPOCS 800
#define NOBJ 403
/.
Local variables.
./
SpiceChar * ifname;
SpiceChar * segid;
SpiceDouble delta;
SpiceDouble et;
SpiceDouble epochs [NEPOCS];
SpiceDouble lt;
SpiceDouble state [6];
SpiceDouble states [NEPOCS][6];
SpiceDouble step;
SpiceDouble time;
SpiceInt i;
SpiceInt handle;
/.
Load the input SPK file.
./
furnsh_c ( "spkw13_ex1.tm" );
/.
Convert the input UTC to ephemeris time
./
str2et_c ( "2018 Apr 03 08:35", &et );
/.
Create the time-ordered array of geometric states,
at unequal time steps.
./
time = et;
step = 60.0;
delta = 10.0;
for ( i = 0; i < NEPOCS; i++ )
{
spkezr_c ( "PHOBOS", time, "J2000", "NONE", "MARS",
states[i], < );
epochs[i] = time + 3600.0;
time = time + step + sin( halfpi_c ( ) * i / 2.0 ) * delta;
}
/.
Open a new SPK file, with 5000 characters reserved
for comments.
./
ifname = "Test SPK type 13 internal filename.";
spkopn_c ( SPKNAM, ifname, 5000, &handle );
/.
Create a segment identifier.
./
segid = "MY_SAMPLE_SPK_TYPE_13_SEGMENT";
/.
Write the segment.
./
spkw13_c ( handle, NOBJ, MARS, "J2000",
epochs[0], epochs[NEPOCS-1], segid, DEGREE,
NEPOCS, states, epochs );
/.
Close the new SPK file.
./
spkcls_c ( handle );
/.
Compute the state of Phobos as seen from Mars,
12 hours after the input UTC time.
./
et = et + 43200.0;
spkezr_c ( "PHOBOS", et, "J2000", "NONE", "MARS",
state, < );
printf( "Phobos as seen from Mars\n" );
printf( " Epoch (s): %19.5f\n", et );
printf( " Position (km): %13.5f %13.5f %13.5f\n",
state[0], state[1], state[2] );
printf( " Velocity (km/s): %13.5f %13.5f %13.5f\n",
state[3], state[4], state[5] );
printf( "\n" );
/.
Load the newly created kernel, and compute the state
of the new object as seen from Mars, 13 hours after
the input UTC time.
./
furnsh_c ( SPKNAM );
et = et + 3600.0;
spkezr_c ( "403", et, "J2000", "NONE", "MARS",
state, < );
printf( "Object 403 as seen from Mars\n" );
printf( " Epoch (s): %19.5f\n", et );
printf( " Position (km): %13.5f %13.5f %13.5f\n",
state[0], state[1], state[2] );
printf( " Velocity (km/s): %13.5f %13.5f %13.5f\n",
state[3], state[4], state[5] );
return ( 0 );
}
When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:
Phobos as seen from Mars
Epoch (s): 576059769.18566
Position (km): -7327.26277 2414.32655 5207.10638
Velocity (km/s): -0.94289 -1.89473 -0.39671
Object 403 as seen from Mars
Epoch (s): 576063369.18566
Position (km): -7327.26277 2414.32655 5207.10638
Velocity (km/s): -0.94289 -1.89473 -0.39671
Note that after run completion, a new SPK file exists in
the output directory.
RestrictionsNone. Literature_ReferencesNone. Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) Version
-CSPICE Version 1.0.1, 10-AUG-2021 (JDR)
Edited the header to comply with NAIF standard.
Added complete example to the -Examples section.
-CSPICE Version 1.0.0, 15-FEB-2000 (NJB)
Index_Entrieswrite SPK type_13 ephemeris data segment |
Fri Dec 31 18:41:13 2021