void spkw02_c ( SpiceInt handle,
SpiceInt body,
SpiceInt center,
ConstSpiceChar * frame,
SpiceDouble first,
SpiceDouble last,
ConstSpiceChar * segid,
SpiceDouble intlen,
SpiceInt n,
SpiceInt polydg,
ConstSpiceDouble cdata [],
SpiceDouble btime )
Write a type 2 segment to an SPK file.
NAIF_IDS
SPC
SPK
EPHEMERIS
Variable I/O Description
-------- --- --------------------------------------------------
MAXDEG P Maximum degree of Chebyshev expansions.
TOLSCL P Scale factor used to compute time bound tolerance.
handle I Handle of an SPK file open for writing.
body I Body code for ephemeris object.
center I Body code for the center of motion of the body.
frame I The reference frame of the states.
first I First valid time for which states can be computed.
last I Last valid time for which states can be computed.
segid I Segment identifier.
intlen I Length of time covered by logical record.
n I Number of coefficient sets.
polydg I Chebyshev polynomial degree.
cdata I Array of Chebyshev coefficients.
btime I Begin time of first logical record.
handle DAF handle of an SPK file to which a type 2 segment
is to be added. The SPK file must be open for
writing.
body NAIF integer code for an ephemeris object whose
state relative to another body is described by the
segment to be created.
center NAIF integer code for the center of motion of the
object identified by `body'.
frame NAIF name for a reference frame relative to which
the state information for `body' is specified.
first,
last Start and stop times of the time interval over
which the segment defines the state of `body'.
segid Segment identifier. An SPK segment identifier may
contain up to 40 characters.
intlen Length of time, in seconds, covered by each set of
Chebyshev polynomial coefficients (each logical
record). Each set of Chebyshev coefficients must
cover this fixed time interval, `intlen'.
n Number of sets of Chebyshev polynomial coefficients
for coordinates (number of logical records) to be
stored in the segment. There is one set of
Chebyshev coefficients for each time period.
polydg Degree of each set of Chebyshev polynomials, i.e. the
number of Chebyshev coefficients per coordinate minus
one. `polydg' must not exceed MAXDEG (see Parameters
below).
cdata Array containing all the sets of Chebyshev
polynomial coefficients to be placed in the
segment of the SPK file. The coefficients are
stored in `cdata' in order as follows:
the (polydg + 1) coefficients for the first
coordinate of the first logical record
the coefficients for the second coordinate
the coefficients for the third coordinate
the coefficients for the first coordinate for
the second logical record, ...
and so on.
The logical data records are stored contiguously:
+----------+
| Record 1 |
+----------+
| Record 2 |
+----------+
...
+----------+
| Record N |
+----------+
The contents of an individual record are:
+--------------------------------------+
| Coeff set for X position component |
+--------------------------------------+
| Coeff set for Y position component |
+--------------------------------------+
| Coeff set for Z position component |
+--------------------------------------+
Each coefficient set has the structure:
+--------------------------------------+
| Coefficient of T_0 |
+--------------------------------------+
| Coefficient of T_1 |
+--------------------------------------+
...
+--------------------------------------+
| Coefficient of T_POLYDG |
+--------------------------------------+
Where T_n represents the Chebyshev polynomial
of the first kind of degree n.
btime Begin time (seconds past J2000 TDB) of first set
of Chebyshev polynomial coefficients (first
logical record). `first' is an appropriate value
for `btime'.
None.
The parameters below are declared in the Fortran include file
spk02.inc, which is part of the Fortran SPICE Toolkit (aka
SPICELIB). The values of those parameters are used in CSPICE code
generated by running f2c on SPICELIB source code. They are not
directly referenced by code in this module.
MAXDEG is the maximum allowed degree of the input
Chebyshev expansions.
The value of MAXDEG is 27.
TOLSCL is a tolerance scale factor (also called a
"relative tolerance") used for time coverage bound
checking. TOLSCL is unitless. TOLSCL produces a
tolerance value via the formula
TOL = TOLSCL * max( abs(first), abs(last) )
where `first' and `last' are the coverage time
bounds of a type 2 segment, expressed as seconds
past J2000 TDB.
The resulting parameter TOL is used as a tolerance
for comparing the input segment descriptor time
bounds to the first and last epoch covered by the
sequence of time intervals defined by the inputs
to spkw02_c:
btime
intlen
n
The value of TOLSCL is 1.e-13.
1) If the number of sets of coefficients is not positive
SPICE(NUMCOEFFSNOTPOS) is signaled.
2) If the interval length is not positive, SPICE(INTLENNOTPOS) is
signaled.
3) If the integer code for the reference frame is not recognized,
SPICE(INVALIDREFFRAME) is signaled.
4) If the start time of the first record exceeds the descriptor
begin time by more than a computed tolerance, or if the end time
of the last record precedes the descriptor end time by more than
a computed tolerance, the error SPICE(COVERAGEGAP) is signaled.
See the Parameters section above for a description of the
tolerance.
5) If the input degree `polydg' is less than 0 or greater than
MAXDEG, the error will be diagnosed by a routine in the call
tree of this routine.
6) If the last non-blank character of `segid' occurs past index 40,
or if `segid' contains any nonprintable characters, the error will
be diagnosed by a routine in the call tree of this routine.
7) The error SPICE(EMPTYSTRING) is signaled if either input string
does not contain at least one character, since the input strings
cannot be converted to a Fortran-style string in this case.
8) The error SPICE(NULLPOINTER) is signaled if either input string
pointer is null.
A new type 2 SPK segment is written to the SPK file attached
to handle.
This routine writes an SPK type 2 data segment to the designated
SPK file, according to the format described in the SPK Required
Reading.
Each segment can contain data for only one target, central body,
and reference frame. The Chebyshev polynomial degree and length
of time covered by each logical record are also fixed. However,
an arbitrary number of logical records of Chebyshev polynomial
coefficients can be written in each segment. Minimizing the
number of segments in an SPK file will help optimize how the SPICE
system accesses the file.
Suppose that you have sets of Chebyshev polynomial coefficients
in an array CDATA pertaining to the position of the moon (NAIF ID
= 301), relative to the Earth-moon barycenter (NAIF ID = 3), in
the J2000 reference frame, and want to put these into a type 2
segment in an existing SPK file. The following code could be used
to add one new type 2 segment. To add multiple segments, put the
call to spkw02_c in a loop.
#include "SpiceUsr.h"
.
.
.
/.
First open the SPK file and get a handle for it.
./
spkopa_c ( spknam, &handle );
/.
Create a segment identifier.
./
segid = "MY_SAMPLE_SPK_TYPE_2_SEGMENT";
/.
Write the segment.
./
spkw02_c ( handle, 301, 3, "J2000",
first, last, segid, intlen,
n, polydg, cdata, btime );
/.
Close the file.
./
spkcls_c ( handle );
None.
None.
N.J. Bachman (JPL)
K.S. Zukor (JPL)
-CSPICE Version 2.0.0, 09-JAN-2014 (NJB)
Relaxed test on relationship between the time bounds of the
input record set (determined by `btime', `intlen', and `n') and
the descriptor bounds `first' and `last'. Now the descriptor
bounds may extend beyond the time bounds of the record set by a
ratio computed using the parameter TOLSCL (see Parameters above
for details). Added checks on input polynomial degree.
-CSPICE Version 1.0.0, 21-JUL-1999 (NJB) (KSZ)
write spk type_2 data segment
Link to routine spkw02_c source file spkw02_c.c
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