spkw02_c |

## Procedurevoid 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 ) ## AbstractWrite a type 2 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 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_Inputhandle 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_OutputNone. ## ParametersThe 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 ## Exceptions1) 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. ## FilesA new type 2 SPK segment is written to the SPK file attached to handle. ## ParticularsThis 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. ## ExamplesSuppose 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 ## RestrictionsNone. ## Literature_ReferencesNone. ## Author_and_InstitutionN.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_Entrieswrite spk type_2 data segment |

Wed Apr 5 17:54:44 2017