Table of contents
CSPICE_CKCOV finds the coverage window for a specified object in a
specified CK file.
Given:
ckfnm the name(s) of SPICE CK files.
[n,c1] = size(ckfnm); char = class(ck)
or
[1,n] = size(ckfnm); cell = class(ck)
idcode the CK ID code of an object, normally a spacecraft
structure or instrument, for which pointing data are expected
to exist in the specified CK file.
[1,1] = size(idcode); int32 = class(idcode)
needav a flag indicating whether only segments having
angular velocity are to be considered when determining
coverage.
[1,1] = size(needav); logical = class(needav)
When `needav' is true, segments without angular velocity
don't contribute to the coverage window; when `needav' is
false, all segments for `idcode' may contribute to the
coverage window.
level the string defining the level (granularity) at which
the coverage is examined.
[1,c2] = size(level); char = class(level)
or
[1,1] = size(level); cell = class(level)
Allowed values and corresponding meanings are:
'SEGMENT' The output coverage window contains
intervals defined by the start and stop
times of segments for the object
designated by `idcode'.
'INTERVAL' The output coverage window contains
interpolation intervals of segments for
the object designated by `idcode'. For type
1 segments, which don't have
interpolation intervals, each epoch
associated with a pointing instance is
treated as a singleton interval; these
intervals are added to the coverage
window.
All interpolation intervals are
considered to lie within the segment
bounds for the purpose of this summary:
if an interpolation interval extends
beyond the segment coverage interval,
only its intersection with the segment
coverage interval is considered to
contribute to the total coverage.
tol a tolerance value expressed in ticks of the spacecraft clock
associated with `idcode'.
[1,1] = size(tol); double = class(tol)
Before each interval is inserted into the coverage window,
the interval is intersected with the segment coverage
interval, then if the intersection is non-empty, it is
expanded by `tol': the left endpoint of the intersection
interval is reduced by `tol' and the right endpoint is
increased by `tol'. Adjusted interval endpoints, when
expressed as encoded SCLK, never are less than zero ticks.
Any intervals that overlap as a result of the expansion are
merged.
The coverage window returned when tol > 0 indicates the
coverage provided by the file to the CK readers cspice_ckgpav
and cspice_ckgp when that value of `tol' is passed to them as
an input.
timsys the name of the time system to use in the output coverage
window.
[1,c3] = size(timsys); char = class(timsys)
or
[1,1] = size(timsys); cell = class(timsys)
`timsys' may have the values:
'SCLK' Elements of `cover' are expressed in encoded
SCLK ("ticks"), where the clock is associated
with the object designated by `idcode'.
'TDB' Elements of `cover' are expressed as seconds
past J2000 TDB.
room a parameter specifying the maximum number of intervals that
can be accommodated by the dynamically allocated workspace
window used internally by this routine.
[1,1] = size(room); int32 = class(room)
It's not necessary to compute an accurate estimate of how
many intervals will be returned in `cover'; rather, the
user can pick a size considerably larger than what's
really required.
cover_i an optional input describing a either an empty window or a
window array created from a previous cspice_ckcov call.
[2m,1] = size(cover_i), double = class(cover_i)
or
[0,0] = size(cover_i), double = class(cover_i)
Inclusion of this window argument results in an output window
consisting of a union of the data retrieved from the `ck'
kernels and the data in `cover_i'.
the call:
[cover] = cspice_ckcov( ckfmn, idcode, needav, level, ...
tol, timsys, room, cover_i )
or
[cover] = cspice_ckcov( ckfnm, idcode, needav, level, ...
tol, timsys, room )
returns:
cover the window containing the coverage for `idcode' available
from `ckfnm'.
[2p,1] = size(cover), double = class(cover)
or
[0,1] = size(cover), double = class(cover)
When the coverage level is 'INTERVAL', this is the set
of time intervals for which data for `idcode' are present
in the file `ckfnm', merged with the set of time intervals
present in `cover_i' if provided on input. The merged
coverage is represented as the union of one or more
disjoint time intervals. The array `cover' contains the
pairs of endpoints of these intervals.
Each window defined as a pair of endpoints such that:
window 1 = cover(1:2)
window 2 = cover(3:4)
window 3 = cover(5:6)
...
window p = cover(2p-1,2p)
When the coverage level is 'SEGMENT', `cover' is computed
in a manner similar to that described above, but the coverage
intervals used in the computation are those of segments
rather than interpolation intervals within segments.
When `tol' is > 0, the intervals comprising the coverage
window for `idcode' are expanded by `tol' and any intervals
overlapping as a result are merged. The resulting window is
returned in `cover'. The expanded window in no case
extends beyond the segment bounds in either direction by
more than `tol'.
The interval endpoints contained in `cover' are encoded
spacecraft clock times if `timsys' is 'SCLK'; otherwise the
times are converted from encoded spacecraft clock to seconds
past J2000 TDB.
`cover' returns an empty set if `ckfnm' lacks coverage for
`idcode' and `cover_i' is not provided on input. `cover'
can overwrite `cover_i'.
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) Display the interval-level coverage for each object in a
specified CK file. Use tolerance of zero ticks. Do not
request angular velocity. Express the results in the TDB time
system.
Find the set of objects in the file. Loop over the contents
of the ID code set: find the coverage for each item in the
set and display the coverage.
Example code begins here.
function ckcov_ex1( )
%
% Local constants.
%
MAXIV = 100000;
WINSIZ = 2 * MAXIV;
MAXOBJ = 1000;
LEVEL = { 'SEGMENT', 'INTERVAL' };
%
% Load a leapseconds kernel and the SCLK corresponding to the
% input CK. Prompt the user for the file names.
%
% Note, neither cspice_ckcov or cspice_ckobj require these
% kernels to function. We need these data for output time
% conversion.
%
LSK = input( 'Name of leapseconds kernel > ', 's' );
SCLK = input( 'Name of SCLK kernel > ', 's' );
cspice_furnsh( LSK )
cspice_furnsh( SCLK )
%
% Get the name of the CK file.
%
CK = input( 'Name of CK file > ', 's' );
%
% Find the set of objects in the CK file.
%
ids = cspice_ckobj( CK, MAXOBJ );
%
% Find the coverage for 'INTERVAL' and 'SEGMENT' levels.
%
for l=1:numel(LEVEL)
%
% We want to display the coverage for each object. Loop over
% the contents of the ID code set, find the coverage for
% each item in the set, and display the coverage.
%
for i=1:numel(ids)
%
% Extract the coverage data for object `ids(i)'.
%
cover = cspice_ckcov( CK, ids(i), 0, LEVEL(l), ...
0.0, 'TDB', WINSIZ );
[row,col]= size(cover);
%
% Display a simple banner.
%
fprintf( '========================================\n')
fprintf( '%s level coverage for object %d\n', ...
char(LEVEL(l)), ids(i) )
%
% `cover' has dimension 2Nx1, where 'row' has the value
% 2N with each window defined as a pair of endpoints
% such that:
%
% window 1 = cover(1:2)
% window 2 = cover(3:4)
% window 3 = cover(5:6)
% ...
% window N = cover(2N-1,2N)
%
% Loop from 1 to 1row' with stepsize 2.
%
for j=1:2:row
%
% Convert the endpoints to TDB calendar format time
% strings and display them. Pass the endpoints in an
% array, so cspice_timout returns an array of time
% strings.
%
% Recall a vectorized input has dimension 1xM so
% transpose the `cover' slice.
%
timstr = cspice_timout( cover(j:j+1)', ...
'YYYY MON DD HR:MN:SC.### (TDB) ::TDB' );
fprintf('Interval: %d\n' , (j+1)/2 )
fprintf(' Start: %s\n' , timstr(1,:) )
fprintf(' Stop: %s\n\n', timstr(2,:) )
end
end
end
%
% Empty the kernel pool.
%
cspice_kclear
When this program was executed on a Mac/Intel/Octave6.x/64-bit
platform, using the LSK file named naif0010.tls, the SCLK file
named cas00145.tsc and the CK file named 08052_08057ra.bc, the
output was:
Name of leapseconds kernel > naif0010.tls
Name of SCLK kernel > cas00145.tsc
Name of CK file > 08052_08057ra.bc
========================================
SEGMENT level coverage for object -82000
Interval: 1
Start: 2008 FEB 21 00:01:07.771 (TDB)
Stop: 2008 FEB 26 00:01:04.752 (TDB)
========================================
INTERVAL level coverage for object -82000
Interval: 1
Start: 2008 FEB 21 00:01:07.771 (TDB)
Stop: 2008 FEB 23 22:53:30.001 (TDB)
Interval: 2
Start: 2008 FEB 23 22:58:13.999 (TDB)
Stop: 2008 FEB 24 02:22:25.913 (TDB)
Interval: 3
Start: 2008 FEB 24 02:27:49.910 (TDB)
Stop: 2008 FEB 24 19:46:33.470 (TDB)
Interval: 4
Start: 2008 FEB 24 19:49:33.469 (TDB)
Stop: 2008 FEB 25 04:25:21.250 (TDB)
Interval: 5
Start: 2008 FEB 25 04:29:33.248 (TDB)
Stop: 2008 FEB 25 15:23:44.971 (TDB)
Interval: 6
Start: 2008 FEB 25 15:24:12.971 (TDB)
Stop: 2008 FEB 25 20:25:04.843 (TDB)
Interval: 7
Start: 2008 FEB 25 20:25:48.843 (TDB)
Stop: 2008 FEB 26 00:01:04.752 (TDB)
This routine provides an API via which applications can determine
the coverage a specified CK file provides for a specified
object.
1) If the input file has transfer format, the error
SPICE(INVALIDFORMAT) is signaled by a routine in the call tree
of this routine.
2) If the input file is not a transfer file but has architecture
other than DAF, the error SPICE(INVALIDARCHTYPE) is signaled
by a routine in the call tree of this routine.
3) If the input file is a binary DAF file of type other than CK,
the error SPICE(INVALIDFILETYPE) is signaled by a routine in
the call tree of this routine.
4) If the CK file cannot be opened or read, an error is signaled
by a routine in the call tree of this routine. The output
window will not be modified.
5) If the size of the output window argument `cover' is
insufficient to contain the actual number of intervals in the
coverage window for `idcode', an error is signaled by a
routine in the call tree of this routine.
6) If `tol' is negative, the error SPICE(VALUEOUTOFRANGE) is
signaled by a routine in the call tree of this routine.
7) If `level' is not recognized, the error SPICE(INVALIDOPTION)
is signaled by a routine in the call tree of this routine.
8) If `timsys' is not recognized, the error SPICE(NOTSUPPORTED)
is signaled by a routine in the call tree of this routine.
9) If a time conversion error occurs, the error is signaled by a
routine in the call tree of this routine.
10) If the output time system is TDB, the CK subsystem must be
able to map `idcode' to the ID code of the associated spacecraft
clock. If this mapping cannot be performed, an error is
signaled by a routine in the call tree of this routine.
11) If the input CK type is not one of the supported CK types, the
error SPICE(NOTSUPPORTED) is signaled by a routine in the call
tree of this routine. This problem may indicate the version of
the SPICE Toolkit being used is outdated and a new version is
required.
12) If any of the input arguments, `ckfnm', `idcode', `needav',
`level', `tol', `timsys', `room' or `cover_i', is undefined,
an error is signaled by the Matlab error handling system.
13) If any of the input arguments, `ckfnm', `idcode', `needav',
`level', `tol', `timsys', `room' or `cover_i', is not of the
expected type, or it does not have the expected dimensions and
size, an error is signaled by the Mice interface.
This routine reads a C-kernel.
If the output time system is 'TDB', then a leapseconds kernel
and an SCLK kernel for the spacecraft clock associated with
`idcode' must be loaded before this routine is called.
If the ID code of the clock associated with `idcode' is not
equal to
idcode / 1000
then the kernel variable
CK_<idcode>_SCLK
must be present in the kernel pool to identify the clock
associated with `idcode'. This variable must contain the ID code
to be used for conversion between SCLK and TDB. Normally this
variable is provided in a text kernel loaded via cspice_furnsh.
1) When this routine is used to accumulate coverage for `idcode'
provided by multiple CK files, the inputs `needav', `level', `tol',
and `timsys' must have the same values for all files in order
for the result to be meaningful.
CK.REQ
DAF.REQ
MICE.REQ
TIME.REQ
WINDOWS.REQ
None.
J. Diaz del Rio (ODC Space)
E.D. Wright (JPL)
-Mice Version 1.3.0, 26-NOV-2021 (EDW) (JDR)
Changed argument names "ck" and "cov" to "ckfnm" and "cover" for
consistency with other routines.
Edited the header to comply with NAIF standard. Modified existing
example to prompt the user for the required input data and hardcoded
the coverage levels within the code. Extended -Index_Entries.
Added -Parameters, -Exceptions, -Files, -Restrictions,
-Literature_References and -Author_and_Institution sections, and
completed -Particulars section.
Eliminated use of "lasterror" in rethrow.
Removed reference to the function's corresponding CSPICE header from
-Required_Reading section.
Updated description of argument "room".
-Mice Version 1.2.1, 10-MAR-2015 (EDW)
Edited -I/O section to conform to NAIF standard for Mice
documentation.
-Mice Version 1.2.0, 03-APR-2012 (EDW)
Edits to Example code and comments. No change to Example code
functionality.
Renamed the argument "size" to "room". "size" is a Matlab function
name and it's seriously dumb to use a function name word as an
argument name.
Edited -I/O section to conform to NAIF standard for Mice
documentation.
Explicitly described ID variables as "CK IDs."
-Mice Version 1.1.0, 29-DEC-2008 (EDW)
Edited description of "size"; "size" now defines the maximum
number of intervals for the internal workspace window.
The "cover_i" argument may now have the empty array value, [],
on input.
Added range restriction on size.
Corrected misspellings.
-Mice Version 1.0.0, 18-JUN-2007 (EDW)
get coverage window for ck_object
get coverage start and stop time for ck_object
get coverage start and stop time for CK frame
get coverage start and stop time for CK instrument
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