Table of contents
CSPICE_CKGR03 returns a specified pointing instance from a CK type 03
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.
help, handle
LONG = Scalar
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 3 CK segment.
help, descr
DOUBLE = Array[5]
recno the number of the discrete pointing instance to be returned
from the data type 3 segment.
help, recno
LONG = Scalar
the call:
cspice_ckgr03, handle, descr, recno, record
returns:
record the pointing instance indexed by `recno' in the segment.
help, record
DOUBLE = Array[8]
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.
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 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.
PRO ckgr03_ex1
;;
;; First load the file (it may also be opened by using
;; cspice_cklpf).
;;
cspice_dafopr, 'VEX_BOOM_V01.BC', handle
;;
;; Begin forward search. Find the first array.
;;
cspice_dafbfs, handle
cspice_daffna, found
;;
;; Get segment descriptor.
;;
;; Unpack the segment descriptor into its double precision
;; and integer components.
;;
cspice_dafgs, 2L, 6L, dcd, icd
cspice_dafps, dcd, icd, descr
;;
;; The data type for a segment is located in the third
;; integer component of the descriptor.
;;
if ( icd[2] eq 3L ) then begin
;;
;; Does the segment contain `av' data?
;;
avseg = ( icd[3] eq 1L )
;;
;; How many records does this segment contain?
;;
cspice_cknr03, handle, descr, nrec
for i=1L, nrec do begin
;;
;; Get the ith pointing instance in the segment.
;;
cspice_ckgr03, handle, descr, i, record
;;
;; Unpack `record' into the time, quaternion, and av.
;;
sclkdp = record[0]
quat = record[1:4]
if ( avseg ) then begin
av = record[5:7]
endif
;;
;; The boresight vector is the third row of the
;; C-matrix.
;;
cspice_q2m, quat, cmat
bore = cmat[*,2]
;;
;; Write out the results.
;;
print, format='(A,I2)', 'Record: ', i
print, format='(A,F25.6)', ' SCLK time :', sclkdp
print, format='(A,3F14.9)', ' Boresight :', bore
if ( avseg ) then begin
print, format='(A,3F14.9)', ' Angular velocity:', av
endif
print
endfor
endif
END
When this program was executed on a Mac/Intel/IDL8.x/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
For 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 cspice_cknr03, which gives the number of
pointing instances stored in a segment.
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.
5) If any of the input arguments, `handle', `descr' or `recno',
is undefined, an error is signaled by the IDL 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 Icy
interface.
7) If the output argument `record' is not a named variable, an
error is signaled by the Icy 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
ICY.REQ
None.
J. Diaz del Rio (ODC Space)
-Icy Version 1.0.0, 01-NOV-2021 (JDR)
get CK type_3 record
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