Table of contents
CSPICE_CKMETA returns (depending upon the user's request) the ID code of
either the spacecraft or spacecraft clock associated with a C-Kernel ID
code.
Given:
ckid the ID code for some object whose attitude and possibly
angular velocity are stored in some C-kernel.
[1,1] = size(ckid); int32 = class(ckid)
meta a character string that indicates which piece of meta data to
fetch.
[1,c1] = size(meta); char = class(meta)
or
[1,1] = size(meta); cell = class(meta)
Acceptable values are 'SCLK' and 'SPK'. The routine is case
insensitive. Leading and trailing blanks are insignificant.
However, blanks between characters are regarded as being
significant.
the call:
[idcode] = cspice_ckmeta( ckid, meta )
returns:
idcode if `meta' is 'SCLK' then the value returned in `idcode' is
the ID code of the spacecraft clock used for converting ET to
TICKS and TICKS to ET for the C-kernel used to represent the
attitude of the object with ID code `ckid'.
[1,1] = size(idcode); int32 = class(idcode)
If `meta' is 'SPK' then the value returned in `idcode' is the
ID code of the spacecraft on which the platform indicated
by `ckid' is mounted.
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) Suppose you would like to look up the attitude of an object
in a C-kernel but have ET and seconds as your input time and
tolerance.
Use the meta-kernel shown below to load the required SPICE
kernels.
KPL/MK
File name: ckmeta_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
-------------------- -----------------------
cas00071.tsc CASSINI SCLK
naif0012.tls Leapseconds
04153_04182ca_ISS.bc CASSINI image navigated
spacecraft CK
\begindata
KERNELS_TO_LOAD = ( 'naif0012.tls',
'cas00071.tsc'
'04153_04182ca_ISS.bc' )
\begintext
End of meta-kernel
Example code begins here.
function ckmeta_ex1()
%
% Local parameters.
%
% -- The code for CASSINI spacecraft reference frame is
% -82000.
%
% -- The reference frame we want is J2000.
%
REF = 'J2000';
CKID = -82000;
%
% Initial values.
%
et = [141162208.034340]';
sectol = [0.5]';
%
% First load the CK, LSK and SCLK files.
%
cspice_furnsh( 'ckmeta_ex1.tm' );
%
% Get the SCLK identifier of the spacecraft clock required
% to convert from `et' to `ticks'.
%
[idcode] = cspice_ckmeta( CKID, 'SCLK' );
%
% Convert `et' and et+sectol to spacecraft clock ticks.
%
[ticks] = cspice_sce2c( idcode, et );
[tick2] = cspice_sce2c( idcode, et+sectol );
%
% Compute the tolerance in spacecraft clock ticks.
%
tol = tick2 - ticks;
%
% Look the attitude up.
%
[cmat, av, clkout, found] = cspice_ckgpav( CKID, ticks, tol, REF );
fprintf( 'Input ET: %19.6f\n', et )
if ( found )
[etout] = cspice_sct2e( idcode, clkout );
fprintf( 'Attitude found at ET: %19.6f\n', etout )
else
fprintf( 'No attitude found at ET.\n' )
end
%
% It's always good form to unload kernels after use,
% particularly in Matlab due to data persistence.
%
cspice_kclear
When this program was executed on a Mac/Intel/Octave6.x/64-bit
platform, the output was:
Input ET: 141162208.034340
Attitude found at ET: 141162208.034586
This is a utility routine for mapping C-kernels to associated
spacecraft clocks.
An association of an SCLK ID and spacecraft ID with a CK frame
class ID may be made by placing in a text kernel the kernel
variable assignments
CK_<ck_frame_class_ID_code>_SCLK = <ID code of SCLK>
CK_<ck_frame_class_ID_code>_SPK = <SPK ID code>
See the Frames Required Reading section on CK frames.
1) If the variable `meta' is not recognized to be one of the
inputs 'SPK' or 'SCLK', the error SPICE(UNKNOWNCKMETA)
is signaled by a routine in the call tree of this routine.
2) If `ckid' is greater than -1000, the associated SCLK and SPK
IDs must be in the kernel pool. If they are not present
a value of zero is returned for the requested item. Zero
is never the valid ID of a spacecraft clock.
3) If any of the input arguments, `ckid' or `meta', is undefined,
an error is signaled by the Matlab error handling system.
4) If any of the input arguments, `ckid' or `meta', is not of the
expected type, or it does not have the expected dimensions and
size, an error is signaled by the Mice interface.
None.
None.
CK.REQ
FRAMES.REQ
MICE.REQ
None.
J. Diaz del Rio (ODC Space)
-Mice Version 1.0.0, 21-JUN-2021 (JDR)
Map C-kernel ID to SCLK and SPK ID
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