spkw03_c |

Table of contents## Procedurespkw03_c ( Write SPK segment, type 3 ) void spkw03_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 ) ## AbstractWrite a type 3 segment to an SPK file. ## Required_ReadingNAIF_IDS SPC SPK ## KeywordsEPHEMERIS ## Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- MAXDEG P Maximum degree of Chebyshev expansions. TOLSCL P Scale factor used to compute time bound tolerance. handle I Handle of SPK file open for writing. body I NAIF code for ephemeris object. center I NAIF code for the center of motion of the body. frame I Reference frame name. first I Start time of interval covered by segment. last I End time of interval covered by segment. segid I Segment identifier. intlen I Length of time covered by record. n I Number of records in segment. polydg I Chebyshev polynomial degree. cdata I Array of Chebyshev coefficients. btime I Begin time of first record. ## Detailed_Inputhandle is the DAF handle of an SPK file to which a type 3 segment is to be added. The SPK file must be open for writing. body is the NAIF integer code for an ephemeris object whose state relative to another body is described by the segment to be created. center is the NAIF integer code for the center of motion of the object identified by `body'. frame is the NAIF name for a reference frame relative to which the state information for `body' is specified. first, last are the start and stop times of the time interval over which the segment defines the state of body. segid is the segment identifier. An SPK segment identifier may contain up to 40 characters. intlen is the 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 is the number of sets of Chebyshev polynomial coefficients for coordinates and their derivatives (number of logical records) to be stored in the segment. There is one set of Chebyshev coefficients for each time period. polydg is the degree of each set of Chebyshev polynomials used to represent the ephemeris information. `polydg' must not exceed MAXDEG (see -Parameters below). cdata is a time-ordered array of `n' sets of Chebyshev polynomial coefficients to be placed in the segment of the SPK file. Each set has size setsz = 6*(polydg+1). The coefficients are stored in `cdata' in order as follows: the (degree + 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 derivative with respect to time of the first coordinate, the coefficients for the derivative with respect to time of the second coordinate, the coefficients for the derivative with respect to time of the third coordinate, the coefficients for the first coordinate for the second logical record, ... and so on. btime is the begin time (seconds past J2000 TDB) of first set of Chebyshev polynomial coefficients (first logical record). ## Detailed_OutputNone. The routine writes to the SPK file referred to by `handle' a type 03 SPK segment containing the data in `cdata'. See the -Particulars section for details about the structure of a type 03 SPK segment. ## ParametersThe parameters below are declared in the Fortran include file spk03.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 3 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 ## Exceptions1) If the number of sets of coefficients is not positive, the error SPICE(NUMCOEFFSNOTPOS) is signaled by a routine in the call tree of this routine. 2) If the interval length is not positive, the error SPICE(INTLENNOTPOS) is signaled by a routine in the call tree of this routine. 3) If the name of the reference frame is not recognized, the error SPICE(INVALIDREFFRAME) is signaled by a routine in the call tree of this routine. 4) If segment stop time is not greater then the begin time, the error SPICE(BADDESCRTIMES) is signaled by a routine in the call tree of this routine. 5) 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 by a routine in the call tree of this routine. See the -Parameters section above for a description of the tolerance. 6) If the input degree `polydg' is less than 0 or greater than MAXDEG, the error SPICE(INVALIDDEGREE) is signaled by a routine in the call tree of this routine. 7) If the last non-blank character of `segid' occurs past index 40, or if `segid' contains any nonprintable characters, an error is signaled by a routine in the call tree of this routine. 8) If any of the `frame' or `segid' input string pointers is null, the error SPICE(NULLPOINTER) is signaled. 9) If any of the `frame' or `segid' input strings has zero length, the error SPICE(EMPTYSTRING) is signaled. ## FilesA new type 3 SPK segment is written to the SPK file attached to handle. ## ParticularsThis routine writes an SPK type 3 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. The ephemeris data supplied to the type 3 SPK writer is packed into an array as a sequence of records. 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 | +--------------------------------------+ | Coeff set for X velocity component | +--------------------------------------+ | Coeff set for Y velocity component | +--------------------------------------+ | Coeff set for Z velocity 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. ## ExamplesThe numerical results shown for this example may differ across platforms. The results depend on the SPICE kernels used as input, the compiler and supporting libraries, and the machine specific arithmetic implementation. 1) This example demonstrates how to create an SPK type 3 kernel containing only one segment, given a set of Chebyshev coefficients and their associated epochs. Example code begins here. /. Program spkw03_ex1 ./ #include "SpiceUsr.h" int main( ) { /. Define the segment identifier parameters. ./ #define SPK3 "spkw03_ex1.bsp" #define REF "J2000" #define BODY 3 #define CENTER 10 #define CHBDEG 2 #define NRECS 4 #define RECSIZ ( 6*(CHBDEG+1) ) /. Local variables. ./ SpiceChar * ifname; SpiceChar * segid; SpiceDouble first; SpiceDouble intlen; SpiceDouble last; SpiceInt handle; SpiceInt ncomch; /. Define the coefficients. ./ SpiceDouble recrds [NRECS][RECSIZ] = { {1.0101, 1.0102, 1.0103, 1.0201, 1.0202, 1.0203, 1.0301, 1.0302, 1.0303, 1.0401, 1.0402, 1.0403, 1.0501, 1.0502, 1.0503, 1.0601, 1.0602, 1.0603}, {2.0101, 2.0102, 2.0103, 2.0201, 2.0202, 2.0203, 2.0301, 2.0302, 2.0303, 2.0401, 2.0402, 2.0403, 2.0501, 2.0502, 2.0503, 2.0601, 2.0602, 2.0603}, {3.0101, 3.0102, 3.0103, 3.0201, 3.0202, 3.0203, 3.0301, 3.0302, 3.0303, 3.0401, 3.0402, 3.0403, 3.0501, 3.0502, 3.0503, 3.0601, 3.0602, 3.0603}, {4.0101, 4.0102, 4.0103, 4.0201, 4.0202, 4.0203, 4.0301, 4.0302, 4.0303, 4.0401, 4.0402, 4.0403, 4.0501, 4.0502, 4.0503, 4.0601, 4.0602, 4.0603} }; /. Set the start and end times of interval covered by segment, and the length of time covered by logical record. ./ first = 100.0; last = 500.0; intlen = 100.0; /. `ncomch' is the number of characters to reserve for the kernel's comment area. This example doesn't write comments, so set to zero. ./ ncomch = 0; /. Internal file name and segment ID. ./ ifname = "Type 3 SPK internal file name."; segid = "SPK type 3 test segment"; /. Open a new SPK file. ./ spkopn_c ( SPK3, ifname, ncomch, &handle ); /. Write the segment. ./ ## RestrictionsNone. ## Literature_ReferencesNone. ## Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) E.D. Wright (JPL) K.S. Zukor (JPL) ## Version-CSPICE Version 2.0.1, 13-AUG-2021 (JDR) Edited the header to comply with NAIF standard. Added complete example code from existing fragment. Extended "polydg" and "cdata" arguments description to provide the size of the Chebyshev polynomials sets. Moved the details of the SPK structure from "cdata" argument description to -Particulars section. Added entry #5 in -Exceptions section. -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, 08-MAR-2002 (EDW) Corrected section header typo: Example to -Examples. -CSPICE Version 1.0.0, 23-JUN-1999 (NJB) (KSZ) ## Index_Entrieswrite SPK type_3 data segment |

Fri Dec 31 18:41:13 2021