| ckgr02_c |
|
Table of contents
Procedure
ckgr02_c ( C-kernel, get record, type 02 )
void ckgr02_c ( SpiceInt handle,
ConstSpiceDouble descr [],
SpiceInt recno,
SpiceDouble record [] )
AbstractReturn a specified pointing instance from a CK type 02 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 record 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 2 CK segment.
recno is the number of the individual pointing record to be
returned from the data type 2 segment.
Detailed_Output
record is the pointing record indexed by `recno' in the segment.
The contents are as follows:
record[ 0 ] = start SCLK time of interval
record[ 1 ] = end SCLK time of interval
record[ 2 ] = TDB seconds per tick rate
record[ 3 ] = q0
record[ 4 ] = q1
record[ 5 ] = q2
record[ 6 ] = q3
record[ 7 ] = av0
record[ 8 ] = av1
record[ 9 ] = av2
See the section on data type 2 in the CK Required
Reading for a complete description on how pointing
is obtained from a type 2 record.
Note that the `record' returned by this routine is slightly
different from that returned by the SPICELIB routine
CKR02. The second element of the record returned by that
routine contains the SCLK time at which pointing was
requested, whereas this routine returns the SCLK time of
the right endpoint of the interval for which the constant
angular velocity model is valid.
ParametersNone. Exceptions
1) If the segment is not of data type 2, 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 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 2 segment, see the CK Required Reading. This is a utility routine that may be used to read the individual pointing records that make up a data type 2 segment. It is normally used in combination with cknr02_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 start and end SCLK
time, seconds per tick rate, platform's +Z axis direction,
and angular velocity vector for each pointing instance in
the first segment in a CK file that contains segments of data
type 2.
Use the CK kernel below, available in the Viking Orbiter PDS
archives, as input for the code example.
vo2_swu_ck2.bc
Example code begins here.
/.
Program ckgr02_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"
int main( )
{
SpiceDouble av [3];
SpiceDouble cmat [3][3];
SpiceDouble dcd [2];
SpiceDouble descr [5];
SpiceDouble quat [4];
SpiceDouble record [10];
SpiceDouble sclke;
SpiceDouble sclkr;
SpiceDouble sclks;
SpiceDouble z [3];
SpiceInt icd [6];
SpiceInt handle;
SpiceInt nrec;
SpiceInt i;
SpiceBoolean found;
/.
First load the file. (The file may also be opened by
using cklpf_c).
./
dafopr_c ( "vo2_swu_ck2.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] == 2 )
{
/.
How many records does this segment contain?
./
cknr02_c ( handle, descr, &nrec );
for ( i = 1; i <= nrec; i++ )
{
/.
Get the ith record in the segment.
./
ckgr02_c ( handle, descr, i, record );
/.
Unpack `record' into the start and end time, rate in
TDB seconds/tick, quaternion, and av.
./
sclks = record[0];
sclke = record[1];
sclkr = record[2];
moved_c ( record+3, 4, quat );
moved_c ( record+7, 3, av );
/.
The +Z axis direction is the third row of the
C-matrix.
./
q2m_c ( quat, cmat );
z[0] = cmat[2][0];
z[1] = cmat[2][1];
z[2] = cmat[2][2];
/.
Write out the results.
./
printf( "Record: %2d\n", (int)i );
printf( " Start encoded SCLK: %20.6f\n", sclks );
printf( " End encoded SCLK : %20.6f\n", sclke );
printf( " TDB Seconds/tick : %20.6f\n", sclkr );
printf( " +Z axis : %12.8f %12.8f %12.8f\n",
z[0], z[1], z[2] );
printf( " Angular velocity : %12.8f %12.8f %12.8f\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
Start encoded SCLK: 32380393707.000015
End encoded SCLK : 32380395707.000015
TDB Seconds/tick : 0.001000
+Z axis : 0.62277152 -0.29420673 0.72498141
Angular velocity : 0.00000000 0.00000000 0.00000000
Record: 2
Start encoded SCLK: 32380402605.999947
End encoded SCLK : 32380404605.999947
TDB Seconds/tick : 0.001000
+Z axis : 0.62172600 -0.27894910 0.73187716
Angular velocity : 0.00000000 0.00000000 0.00000000
Record: 3
Start encoded SCLK: 32380412542.000053
End encoded SCLK : 32380414542.000053
TDB Seconds/tick : 0.001000
+Z axis : 0.62183610 -0.26307233 0.73764003
Angular velocity : 0.00000000 0.00000000 0.00000000
Record: 4
Start encoded SCLK: 32827264875.000000
End encoded SCLK : 32827266875.000000
TDB Seconds/tick : 0.001000
+Z axis : 0.82984105 -0.44796078 0.33270853
Angular velocity : 0.00000000 0.00000000 0.00000000
Record: 5
Start encoded SCLK: 32827403805.999992
End encoded SCLK : 32827405805.999992
TDB Seconds/tick : 0.001000
+Z axis : 0.80812500 -0.44911178 0.38109395
Angular velocity : 0.00000000 0.00000000 0.00000000
Record: 6
Start encoded SCLK: 32827412705.000042
End encoded SCLK : 32827414705.000042
TDB Seconds/tick : 0.001000
+Z axis : 0.81120505 -0.43593555 0.38975193
Angular velocity : 0.00000000 0.00000000 0.00000000
Record: 7
Start encoded SCLK: 32827417284.000038
End encoded SCLK : 32827419284.000038
TDB Seconds/tick : 0.001000
+Z axis : 0.81313834 -0.42861613 0.39382008
Angular velocity : 0.00000000 0.00000000 0.00000000
Record: 8
Start encoded SCLK: 33793314593.000053
End encoded SCLK : 33793316593.000053
TDB Seconds/tick : 0.001000
+Z axis : 0.79860617 -0.37840751 0.46801275
Angular velocity : 0.00000000 0.00000000 0.00000000
Record: 9
Start encoded SCLK: 33793332478.000046
End encoded SCLK : 33793334478.000046
TDB Seconds/tick : 0.001000
+Z axis : 0.77861783 -0.39171670 0.49021658
Angular velocity : 0.00000000 0.00000000 0.00000000
Record: 10
Start encoded SCLK: 33793341463.000061
End encoded SCLK : 33793343463.000061
TDB Seconds/tick : 0.001000
+Z axis : 0.76852381 -0.39797437 0.50098659
Angular velocity : 0.00000000 0.00000000 0.00000000
Record: 11
Start encoded SCLK: 33793350363.000034
End encoded SCLK : 33793352363.000034
TDB Seconds/tick : 0.001000
+Z axis : 0.75779934 -0.40484364 0.51170478
Angular velocity : 0.00000000 0.00000000 0.00000000
Record: 12
Start encoded SCLK: 33984028250.000000
End encoded SCLK : 33984030250.000000
TDB Seconds/tick : 0.001000
+Z axis : 0.77099184 -0.39926339 0.49614546
Angular velocity : 0.00000000 0.00000000 0.00000000
Record: 13
Start encoded SCLK: 33984046134.999992
End encoded SCLK : 33984048134.999992
TDB Seconds/tick : 0.001000
+Z axis : 0.75024440 -0.41218993 0.51694564
Angular velocity : 0.00000000 0.00000000 0.00000000
Record: 14
Start encoded SCLK: 33984055121.000053
End encoded SCLK : 33984057121.000053
TDB Seconds/tick : 0.001000
+Z axis : 0.73947359 -0.41886863 0.52699894
Angular velocity : 0.00000000 0.00000000 0.00000000
Record: 15
Start encoded SCLK: 33984220835.999966
[...]
Warning: incomplete output. Only 100 out of 875 lines have been
provided.
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_2 record |
Fri Dec 31 18:41:02 2021