Table of contents
CSPICE_CKGR02 returns a specified pointing instance from a CK type 02
segment. The segment is identified by a CK file handle and segments
descriptor.
Given:
handle the handle of the binary CK file containing the desired
segment.
[1,1] = size(handle); int32 = class(handle)
The file should have been opened for read or write access,
by cspice_cklpf, cspice_dafopr or cspice_dafopw.
descr the packed descriptor of the data type 2 CK segment.
[5,1] = size(descr); double = class(descr)
recno the number of the individual pointing record to be returned
from the data type 2 segment.
[1,1] = size(recno); int32 = class(recno)
the call:
[record] = cspice_ckgr02( handle, descr, recno )
returns:
record the pointing record indexed by `recno' in the segment.
[10,1] = size(record); double = class(record)
The contents are as follows:
record( 1 ) = start SCLK time of interval
record( 2 ) = end SCLK time of interval
record( 3 ) = tdb seconds per tick rate
record( 4 ) = q1
record( 5 ) = q2
record( 6 ) = q3
record( 7 ) = q4
record( 8 ) = av1
record( 9 ) = av2
record( 10 ) = av3
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.
None.
Any numerical results shown for this example may differ between
platforms as the results depend on the SPICE kernels used as input
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.
function ckgr02_ex1()
%
% First load the file. (The file may also be opened by
% using cspice_cklpf).
%
[handle] = cspice_dafopr( 'vo2_swu_ck2.bc' );
%
% Begin forward search. Find the first array.
%
cspice_dafbfs( handle );
[found] = cspice_daffna;
%
% Get segment descriptor.
%
% Unpack the segment descriptor into its double precision
% and integer components.
%
[dcd, icd] = cspice_dafgs( 2, 6 );
[descr] = cspice_dafps( dcd, icd );
%
% The data type for a segment is located in the third
% integer component of the descriptor.
%
if ( icd(3) == 2 )
%
% How many records does this segment contain?
%
[nrec] = cspice_cknr02( handle, descr );
for i=1:nrec
%
% Get the ith record in the segment.
%
[record] = cspice_ckgr02( handle, descr, i );
%
% Unpack `record' into the start and end time, rate in
% TDB seconds/tick, quaternion, and av.
%
sclks = record(1);
sclke = record(2);
sclkr = record(3);
quat = record(4:7);
av = record(8:10);
%
% The +Z axis direction is the third row of the
% C-matrix.
%
[cmat] = cspice_q2m( quat );
z = cmat(:,3);
%
% Write out the results.
%
fprintf( 'Record: %1d\n', i )
fprintf( ' Start encoded SCLK: %20.6f\n', sclks )
fprintf( ' End encoded SCLK : %20.6f\n', sclke )
fprintf( ' TDB Seconds/tick : %20.6f\n', sclkr )
fprintf( ' +Z axis : %12.8f %12.8f %12.8f\n', z )
fprintf( ' Angular velocity : %12.8f %12.8f %12.8f\n', av )
fprintf( '\n' )
end
end
When this program was executed on a Mac/Intel/Octave6.x/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 : -0.37100754 -0.58030627 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 : -0.36011140 -0.57851153 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 : -0.34654725 -0.57947579 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 : -0.52790086 -0.78142544 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 : -0.53591430 -0.75336795 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 : -0.52897927 -0.75383975 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 : -0.52739277 -0.75283638 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 : -0.54702960 -0.69406245 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 : -0.55111040 -0.67525183 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 : -0.55538431 -0.66374748 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 : -0.55830213 -0.65303671 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 : -0.56718006 -0.65737847 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 : -0.57392845 -0.63511679 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 : -0.57600983 -0.62488782 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.
For 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 cspice_cknr02, which gives the number
of pointing instances stored in a segment.
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.
5) If any of the input arguments, `handle', `descr' or `recno',
is undefined, an error is signaled by the Matlab error
handling system.
6) If any of the input arguments, `handle', `descr' or `recno',
is not of the expected type, or it does not have the expected
dimensions and size, an error is signaled by the Mice
interface.
The CK file specified by `handle' should be open for read or write
access.
1) The binary CK file containing the segment whose descriptor was
passed to this routine must be opened for read or write access
by cspice_cklpf, cspice_dafopr or cspice_dafopw.
CK.REQ
DAF.REQ
MICE.REQ
None.
J. Diaz del Rio (ODC Space)
-Mice Version 1.0.0, 01-NOV-2021 (JDR)
get CK type_2 record
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