| ckgr03_c |
|
Table of contents
Procedure
ckgr03_c ( C-kernel, get record, type 03 )
void ckgr03_c ( SpiceInt handle,
ConstSpiceDouble descr [],
SpiceInt recno,
SpiceDouble record [] )
AbstractReturn a specified pointing instance from a CK type 03 segment. The segment is identified by a CK file handle and segment descriptor. Required_ReadingCK DAF KeywordsPOINTING Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- handle I The handle of the CK file containing the segment. descr I The segment descriptor. recno I The number of the pointing instance to be returned. record O The pointing record. Detailed_Input
handle is the handle of the binary CK file containing the
desired segment. The file should have been opened
for read or write access, by cklpf_c, dafopr_c or dafopw_c.
descr is the packed descriptor of the data type 3 CK segment.
recno is the number of the discrete pointing instance to be
returned from the data type 3 segment.
Detailed_Output
record is the pointing instance indexed by `recno' in the
segment. The contents are as follows:
record[ 0 ] = clkout
record[ 1 ] = q0
record[ 2 ] = q1
record[ 3 ] = q2
record[ 4 ] = q3
record[ 5 ] = av0 |
record[ 6 ] = av1 |-- Returned optionally
record[ 7 ] = av2 |
`clkout' is the encoded spacecraft clock time associated
with the returned pointing values.
The quantities q0 - q3 are the components of the
quaternion that represents the C-matrix that transforms
vectors from the inertial reference frame of the
segment to the instrument frame at time `clkout'.
The quantities `av0', `av1', and `av2' represent the
angular velocity vector, and are returned only if
the segment contains angular velocity data. The
components of the angular velocity vector are
specified relative to the inertial reference
frame of the segment.
ParametersNone. Exceptions
1) If the segment is not of data type 3, the error
SPICE(CKWRONGDATATYPE) is signaled by a routine in the call tree of
this routine.
2) If `recno' is less than one or greater than the number of records in
the specified segment, the error SPICE(CKNONEXISTREC) is signaled by
a routine in the call tree of this routine.
3) If the specified handle does not belong to any DAF file that
is currently known to be open, an error is signaled by a
routine in the call tree of this routine.
4) If `descr' is not a valid descriptor of a segment in the CK
file specified by `handle', the results of this routine are
unpredictable.
FilesThe CK file specified by `handle' should be open for read or write access. ParticularsFor a detailed description of the structure of a type 3 segment, see the CK required reading. This is a utility routine that may be used to read the individual pointing instances that make up a type 3 segment. It is normally used in conjunction with cknr03_c, which gives the number of pointing instances stored in a segment. 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) The following code example extracts the SCLK time, boresight
vector, and angular velocity vector for each pointing instance
in the first segment in a CK file that contains segments of
data type 3.
Use the CK kernel below, available in the Venus Express PDS
archives, as input for the code example.
VEX_BOOM_V01.BC
Example code begins here.
/.
Program ckgr03_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local variables.
./
SpiceDouble quat [4];
SpiceDouble av [3];
SpiceDouble bore [3];
SpiceDouble cmat [3][3];
SpiceDouble dcd [2];
SpiceDouble descr [5];
SpiceDouble record [8];
SpiceDouble sclkdp;
SpiceInt i;
SpiceInt icd [6];
SpiceInt handle;
SpiceInt nrec;
SpiceBoolean avseg;
SpiceBoolean found;
/.
First load the file (it may also be opened by using
cklpf_c).
./
dafopr_c ( "VEX_BOOM_V01.BC", &handle );
/.
Begin forward search. Find the first array.
./
dafbfs_c ( handle );
daffna_c ( &found );
/.
Get segment descriptor.
./
dafgs_c ( descr );
/.
Unpack the segment descriptor into its double precision
and integer components.
./
dafus_c ( descr, 2, 6, dcd, icd );
/.
The data type for a segment is located in the third
integer component of the descriptor.
./
if ( icd[2] == 3 )
{
/.
Does the segment contain `av' data?
./
avseg = ( icd[3] == 1 );
/.
How many records does this segment contain?
./
cknr03_c ( handle, descr, &nrec );
for ( i = 1; i <= nrec; i++ )
{
/.
Get the ith pointing instance in the segment.
./
ckgr03_c ( handle, descr, i, record );
/.
Unpack `record' into the time, quaternion, and av.
./
sclkdp = record[0];
moved_c ( record+1, 4, quat );
if ( avseg )
{
moved_c ( record+5, 3, av );
}
/.
The boresight vector is the third row of the
C-matrix.
./
q2m_c ( quat, cmat );
bore[0] = cmat[2][0];
bore[1] = cmat[2][1];
bore[2] = cmat[2][2];
/.
Write out the results.
./
printf( "Record: %2d\n", (int)i );
printf( " SCLK time : %24.6f\n", sclkdp );
printf( " Boresight : %13.9f %13.9f %13.9f\n",
bore[0], bore[1], bore[2] );
if ( avseg )
{
printf( " Angular velocity: %13.9f %13.9f %13.9f\n",
av[0], av[1], av[2] );
}
printf( "\n" );
}
}
return ( 0 );
}
When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:
Record: 1
SCLK time : 2162686.710986
Boresight : -0.999122830 0.000000000 0.041875654
Angular velocity: 0.000000000 0.000000000 0.000000000
Record: 2
SCLK time : 54160369751.715164
Boresight : -0.999122830 0.000000000 0.041875654
Angular velocity: 0.000000000 1.176083393 0.000000000
Record: 3
SCLK time : 54160454948.487686
Boresight : 0.000000000 0.000000000 1.000000000
Angular velocity: 0.000000000 0.000000000 0.000000000
Record: 4
SCLK time : 299264885854.937805
Boresight : 0.000000000 0.000000000 1.000000000
Angular velocity: 0.000000000 0.000000000 0.000000000
Record: 5
SCLK time : 2366007685832.532227
Boresight : 0.000000000 0.000000000 1.000000000
Angular velocity: 0.000000000 0.000000000 0.000000000
Record: 6
SCLK time : 4432750485810.126953
Boresight : 0.000000000 0.000000000 1.000000000
Angular velocity: 0.000000000 0.000000000 0.000000000
Record: 7
SCLK time : 6505155594828.757812
Boresight : 0.000000000 0.000000000 1.000000000
Angular velocity: 0.000000000 0.000000000 0.000000000
Record: 8
SCLK time : 8571898394806.352539
Boresight : 0.000000000 0.000000000 1.000000000
Angular velocity: 0.000000000 0.000000000 0.000000000
Record: 9
SCLK time : 10638641194783.947266
Boresight : 0.000000000 0.000000000 1.000000000
Angular velocity: 0.000000000 0.000000000 0.000000000
Record: 10
SCLK time : 12705383994761.541016
Boresight : 0.000000000 0.000000000 1.000000000
Angular velocity: 0.000000000 0.000000000 0.000000000
Record: 11
SCLK time : 14777789103780.169922
Boresight : 0.000000000 0.000000000 1.000000000
Angular velocity: 0.000000000 0.000000000 0.000000000
Record: 12
SCLK time : 16844531903757.763672
Boresight : 0.000000000 0.000000000 1.000000000
Angular velocity: 0.000000000 0.000000000 0.000000000
Record: 13
SCLK time : 18911274703735.359375
Boresight : 0.000000000 0.000000000 1.000000000
Angular velocity: 0.000000000 0.000000000 0.000000000
Restrictions
1) The binary CK file containing the segment whose descriptor was
passed to this routine must be opened for read or write access
by cklpf_c, dafopr_c or dafopw_c.
Literature_ReferencesNone. Author_and_InstitutionJ. Diaz del Rio (ODC Space) Version-CSPICE Version 1.0.0, 01-NOV-2021 (JDR) Index_Entriesget CK type_3 record |
Fri Dec 31 18:41:02 2021