| pck03b |
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Table of contents
Procedure
PCK03B ( PCK, begin a type 3 segment )
SUBROUTINE PCK03B ( HANDLE,
. SEGID, BODY, FRAME,
. FIRST, LAST, CHBDEG )
Abstract
Begin a type 03 PCK segment in the binary PCK file associated with
HANDLE. See also PCK03A and PCK03E.
Required_Reading
PCK
Keywords
PCK
Declarations
IMPLICIT NONE
INCLUDE 'sgparam.inc'
INTEGER HANDLE
CHARACTER*(*) SEGID
INTEGER BODY
CHARACTER*(*) FRAME
DOUBLE PRECISION FIRST
DOUBLE PRECISION LAST
INTEGER CHBDEG
Brief_I/O
VARIABLE I/O DESCRIPTION
-------- --- --------------------------------------------------
HANDLE I The handle of a DAF file open for writing.
SEGID I The string to use for segment identifier.
BODY I The NAIF ID code for the body of the segment.
FRAME I The inertial frame for this segment.
FIRST I The first epoch for which the segment is valid.
LAST I The last epoch for which the segment is valid.
CHBDEG I The degree of the Chebyshev Polynomial used.
Detailed_Input
HANDLE is the file handle of a PCK file that has been
opened for writing.
SEGID is the segment identifier. A PCK segment identifier
may contain up to 40 printing characters. It may also be
blank.
BODY is the SPICE ID code for the body whose orientation
information is to be stored in the PCK segment being
created.
FRAME is the inertial reference frame to which the orientation
data for BODY is relative.
FIRST are the bounds on the ephemeris times, expressed as
LAST seconds past J2000, for which the states can be used
to interpolate a state for BODY.
CHBDEG is the degree of the Chebyshev Polynomial used for
each set of Chebyshev coefficients that are to be stored
in the segment.
Detailed_Output
None.
The data are stored in the PCK segment in the DAF
attached to HANDLE.
See the $Particulars section for details about the
structure of a type 03 PCK segment.
Parameters
This subroutine makes use of parameters defined in the file
'sgparam.inc'.
Exceptions
1) If the degree of the Chebyshev Polynomial to be used for this
segment is negative, the error SPICE(INVALIDARGUMENT) is
signaled.
2) If there is any error in the structure or content of the
inputs other than the degree of the Chebyshev Polynomial, the
error is signaled by a routine in the call tree of this
routine.
3) If a file access error occurs while this routine begins a new
type 03 segment, the error is signaled by a routine in the
call tree of this routine.
Files
None.
Particulars
This routine begins a type 03 segment in the binary PCK file that
is associated with HANDLE. The file must have been opened with
write access.
This routine is one of a set of three routines for creating and
adding data to type 03 PCK segments. These routines are:
PCK03B: Begin a type 03 PCK segment. This routine must be
called before any data may be added to a type 03
segment.
PCK03A: Add data to a type 03 PCK segment. This routine may be
called any number of times after a call to PCK03B to
add type 03 records to the PCK segment that was
started.
PCK03E: End a type 03 PCK segment. This routine is called to
make the type 03 segment a permanent addition to the
PCK file. Once this routine is called, no further type
03 records may be added to the segment. A new segment
must be started.
A type 03 PCK segment consists of coefficient sets for fixed order
Chebyshev polynomials over consecutive time intervals, where the
time intervals need not all be of the same length. The Chebyshev
polynomials represent the orientation of a body specified relative
to an inertial frame by the angles RA, DEC, W and body fixed
angular rates for each axis of the body fixed coordinate system
defined by RA, DEC, and W. All of the angles and the angular rates
of the axes are given in degrees.
The orientation data supplied to the type 03 PCK writer is packed
into an array as a sequence of logical records,
-----------------------------------------------------
| Record 1 | Record 2 | ... | Record N-1 | Record N |
-----------------------------------------------------
with each record has the following format.
------------------------------------------------
| The midpoint of the approximation interval |
------------------------------------------------
| The radius of the approximation interval |
------------------------------------------------
| CHBDEG+1 coefficients for RA |
------------------------------------------------
| CHBDEG+1 coefficients for DEC |
------------------------------------------------
| CHBDEG+1 coefficients for W |
------------------------------------------------
| CHBDEG+1 coefficients for the X-axis rate |
------------------------------------------------
| CHBDEG+1 coefficients for the Y-axis rate |
------------------------------------------------
| CHBDEG+1 coefficients for the Z-axis rate |
------------------------------------------------
Examples
Assume we have the following for each of the examples that
follow.
HANDLE is the handle of a PCK file opened with write
access.
SEGID is a character string of no more than 40 characters
which provides a pedigree for the data in the PCK
segment.
BODY is the SPICE ID code for the body whose orientation
data is to be placed into the file.
REFFRM is the name of the SPICE inertial reference frame
the orientation data is relative to.
FIRST is the starting epoch, in seconds past J2000, for
the orientation data to be placed into the segment.
LAST is the ending epoch, in seconds past J2000, for
the orientation data to be placed into the segment.
Example 1:
For this example, we also assume that:
N is the number of type 03 records that we want to
put into a segment in PCK file.
RECRDS contains N type 03 records packaged for the PCK
file.
ETSTRT contains the initial epochs for each of the
records contained in RECRDS, where
ETSTRT(I) < ETSTRT(I+1), I = 1, N-1
ETSTRT(1) <= FIRST, ETSTRT(N) < LAST
ETSTRT(I+1), I = 1, N-1, is the ending epoch for
record I as well as the initial epoch for record
I+1.
Then the following code fragment demonstrates how to create a
type 03 PCK segment if all of the data for the segment is
available at one time.
C
C Begin the segment.
C
CALL PCK03B ( HANDLE, SEGID, BODY, REFFRM,
. FIRST, LAST, CHBDEG )
C
C Add the data to the segment all at once.
C
CALL PCK03A ( HANDLE, N, RECRDS, ETSTRT )
C
C End the segment, making the segment a permanent addition
C to the PCK file.
C
CALL PCK03E ( HANDLE )
Example 2:
In this example we want to add type O3 PCK records, as
described above in the $Particulars section, to the segment
being written as they are generated. The ability to write the
records in this way is useful if computer memory is limited. It
may also be convenient from a programming perspective to write
the records one at a time.
For this example, assume that we want to generate N type 03 PCK
records, one for each of N time intervals, writing them all to
the same segment in a PCK file. Let
N be the number of type 03 records that we want to
generate and put into a segment in an PCK file.
RECORD be an array with enough room to hold a single type
03 record, i.e. RECORD should have dimension at
least 6 * (CHBDEG + 1 ) + 2.
START be an array of N times that are the beginning
epochs for each of the intervals of interest. The
times should be in increasing order and the start
time for the first interval should equal the
starting time for the segment.
START(I) < START(I+1), I = 1, N-1
START(1) = FIRST
STOP be an array of N times that are the ending epochs
for each of the intervals of interest. The times
should be in increasing order and the stop time for
interval I should equal the start time for interval
I+1, i.e., we want to have continuous coverage in
time across all of the records. Also, the stop time
for the last interval should equal the ending time
for the segment.
STOP(I) < STOP(I+1), I = 1, N-1
STOP(I) = START(I+1), I = 1, N-1
STOP(N) = LAST
GENREC( TIME1, TIME2, RECORD )
be a subroutine that generates a type 03 PCK record
for a time interval specified by TIME1 and TIME2.
Then the following code fragment demonstrates how to create a
type 03 PCK segment if all of the data for the segment is not
available at one time.
C
C Begin the segment.
C
CALL PCK03B ( HANDLE, SEGID, BODY, REFFRM,
. FIRST, LAST, CHBDEG )
C
C Generate the records and write them to the segment in the
C PCK file one at at time.
C
DO I = 1, N
CALL GENREC ( START(I), STOP(I), RECORD )
CALL PCK03A ( HANDLE, 1, RECORD, START(I) )
END DO
C
C End the segment, making the segment a permanent addition
C to the PCK file.
C
CALL PCK03E ( HANDLE )
Restrictions
1) The binary PCK file must be open with write access.
2) Only one segment may be written to a particular PCK file at a
time. All of the data for the segment must be written and the
segment must be ended before another segment may be started in
the file.
Literature_References
None.
Author_and_Institution
J. Diaz del Rio (ODC Space)
K.R. Gehringer (JPL)
B.V. Semenov (JPL)
E.D. Wright (JPL)
Version
SPICELIB Version 1.0.2, 03-JUN-2021 (JDR)
Edited the header to comply with NAIF standard.
SPICELIB Version 1.0.1, 10-FEB-2014 (EDW) (BVS)
Minor edits to $Procedure; clean trailing whitespace.
Corrected order of header sections to conform to NAIF
standard.
Removed comments from the $Declarations section.
SPICELIB Version 1.0.0, 06-MAR-1995 (KRG)
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Fri Dec 31 18:36:37 2021