Index Page spkw02_c

A B C D E F G H I J K L M N O P Q R S T U V W X

Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input | Detailed_Output Parameters Exceptions Files Particulars Examples | Restrictions Literature_References Author_and_Institution Version Index_Entries

#### Procedure

       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     )

#### Abstract

      Write a type 2 segment to an SPK file.

#### Required_Reading

       NAIF_IDS
       SPC
       SPK

#### Keywords

       EPHEMERIS

#### Brief_I/O

       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.

#### Detailed_Input

       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'.

#### Detailed_Output

       None.

#### Parameters

       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.

#### Exceptions

       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.

#### Files

       A new type 2 SPK segment is written to the SPK file attached
       to handle.

#### Particulars

       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.

#### Examples

       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 );

#### Restrictions

       None.

#### Literature_References

       None.

#### Author_and_Institution

       N.J. Bachman   (JPL)
       K.S. Zukor     (JPL)

#### Version

       -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)

#### Index_Entries

       write spk type_2 data segment

#### Link to routine spkw02_c source file spkw02_c.c

    Wed Apr  5 17:54:44 2017