Main Page Preface - Other Stuff (The Red Shirt topics) (C)
## Table of Contents
       Preface - Other Stuff (The Red Shirt topics) (C)
       Coding and Use Lessons
          Note About HTML Links
          NAIF Documentation
             Required Reading and Users Guides
             Library Source Code Documentation
             API Documentation
             Tutorials
          Text kernels
             Text kernel format
          Kernels for lessons
             Input kernel files
             Output
       Lesson 1: Kernel Management with the Kernel Subsystem
          Relevant Routines
          Requirements and References
          Programming Task
          Code Solution
             First, create a meta text kernel:
             Now the solution source code:
             Run the code example
       Lesson 2: The Kernel Pool
          Relevant Routines
          Requirements and References
          Programming Task
          Code Solution
             Run the code example
       Lesson 3: Coordinate Conversions
          Relevant Routines
          Requirements and References
          Programming Task
          Code Solution
             Run the code example
       Lesson 4: Advanced Time Manipulation Routines
          Relevant Routines
          Requirements and References
          Programming Task
          Code Solution
             Run the code example
       Lesson 5: Error Handling
          Relevant Routines:
          Requirements and References
          Programming Task
          Code Solution
             Run the code example
          Programming Task
          Code Solution
             Run the code example
       Lesson 6: Windows, and Cells
          Relevant Routines
          Requirements and References
          Programming task:
          Code Solution
             Run the code example
       Lesson 7: Utility and Constants Routines
          Relevant Routines
          Requirements and References
          Programming Task
          Code Solution
             Run the code example
          Programming Task
          Code Solution
             Run the code example
Top # Preface - Other Stuff (The Red Shirt topics) (C) October 20, 2008 The extensive scope of the CSPICE system's functionality includes features the average user may not expect or appreciate, features NAIF refers to as "Other Stuff." This workbook includes a set of lessons to introduce the beginning to moderate user to such features. The lessons provide a brief description to several related sets of routines, associated reference documents, a programming task designed to teach the use of the routines, and an example solution to the programming problem. Top # Coding and Use Lessons This workbook contains lessons to demonstrate use of the less celebrated CSPICE routines. `1.` Kernel Management with the Kernel Subsystem `2.` The Kernel Pool `3.` Coordinate Conversions `4.` Advanced Time Manipulation Routines `5.` Error Handling `6.` Windows and Cells `7.` Utility and Constants Routines Top ## Note About HTML Links The HTML version of this lesson contains links pointing to various HTML documents provided with the Toolkit. All of these links are relative and, in order to function, require this document to be in a certain location in the Toolkit HTML documentation directory tree. In order for the links to be resolved, create a subdirectory called ``lessons'' under the ``doc/html'' directory of the Toolkit tree and copy this document to that subdirectory before loading it into a Web browser. Top ## NAIF Documentation The technical complexity of the various CSPICE subsystems mandates an extensive, user-friendly documentation set. The set differs somewhat depending on your choice of development language, FORTRAN, C, IDL, or MATLAB but provides the same information with regards to SPICE operation. The sources for a user needing information concerning the CSPICE System or other NAIF product: `--` Required Readings and Users Guides `--` Library Source Code Documentation `--` API Documentation `--` Tutorials Top ### Required Reading and Users Guides NAIF Required Reading (*.req) documents introduce the functionality of particular CSPICE subsystems:
       cells.req
       ck.req
       cspice.req
       daf.req
       das.req
       ek.req
       ellipses.req
       error.req
       frames.req
       icy.req
       intrdctn.req
       kernel.req
       mice.req
       naif_ids.req
       pck.req
       planes.req
       problems.req
       rotation.req
       scanning.req
       sclk.req
       sets.req
       spc.req
       spk.req
       symbols.req
       time.req
       windows.req
NAIF Users Guides (*.ug) describe the proper use of particular CSPICE tools:
       brief.ug
       chronos.ug
       ckbrief.ug
       commnt.ug
       convert.ug
       inspekt.ug
       mkspk.ug
       msopck.ug
       simple.ug
       spacit.ug
       spkdiff.ug
       spkmerge.ug
       states.ug
       subpt.ug
       tictoc.ug
       tobin.ug
       toxfr.ug
       version.ug
These text documents exist in the 'doc' directory of the main Toolkit directory:
          ../cspice/doc/
HTML format documentation The CSPICE distributions include HTML versions of Required Readings and Users Guides, accessible from the HTML documentation directory:
          ../cspice/doc/html/index.html
Top ### Library Source Code Documentation All SPICELIB and CSPICE source files include usage and design information incorporated in a comment block known as the "header." (Every toolkit includes either the SPICELIB or CSPICE library.) A header consists of several marked sections: `--` Procedure: Routine name and one line expansion of the routine's name. `--` Abstract: A tersely worded explanation describing the routine. `--` Copyright: An identification of the copyright holder for the routine. `--` Required_Reading: A list of CSPICE required reading documents relating to the routine. `--` Brief_I/O: A table of arguments, identifying each as either input, output, or both, with a very brief description of the variable. `--` Detailed_Input & Detailed_Output: An elaboration of the Brief_I/O section providing comprehensive information on argument use. `--` Parameters: Description and declaration of any parameters (constants) specific to the routine. `--` Exceptions: A list of error conditions the routine detects and signals plus a discussion of any other exceptional conditions the routine may encounter. `--` Files: A list of other files needed for the routine to operate. `--` Particulars: A discussion of the routine's function (if needed). This section may also include information relating to "how" and "why" the routine performs an operation and to explain functionality of routines that operate by side effects. `--` Examples: Descriptions and code snippets concerning usage of the routine. `--` Restrictions: Restrictions or warnings concerning use. `--` Literature_References: A list of sources required to understand the algorithms or data used in the routine. `--` Author_and_Institution: The names and affiliations for authors of the routine. `--` Version: A list of edits and the authors of those edits made to the routine since initial delivery to the CSPICE system. The source code for CSPICE products is stored in 'src' sub-directory of the main CSPICE directory:
          ../cspice/src/
Find the CSPICE library source code in:
          ../cspice/src/cspice/
Note: The CSPICE source files have two forms: C files created by the f2c conversion process on a SPICELIB files, indicated with a name of the form "module.c," and wrappers files indicated by names of the form "module_c.c" The f2c converted source code is very difficult to read, refer to the wrapper routines if possible. In some cases, NAIF replaced an f2c converted file with a hand written version. Top ### API Documentation The CSPICE package includes the CSPICE Reference Guide, an index of all CSPICE wrapper APIs with hyperlinks to API specific documentation. Each API documentation page includes cross-links to any other wrapper API mentioned in the document and links to the wrapper source code.
          ...cspice/doc/html/cspice/index.html
Top ### Tutorials A set of Microsoft PowerPoint presentations provide a general overview of the complete CSPICE toolkit. Download the set at:
          http://naif.jpl.nasa.gov/naif/tutorials.html
Access individual files in the 'office/individual_docs/' directory; an archive of all tutorial files is available in the 'office/packages/' directory. Top ## Text kernels Several workbooks use SPICE text kernels. SPICE identifies a text kernel as an ASCII text file containing the mark-up tags the kernel subsystem requires to identify data assignments in that file, and "name=value" data assignments. The subsystem uses two tags:
          \begintext
and
          \begindata
to mark information blocks within the text kernel. The \begintext tag specifies all text following the tag as comment information to be ignored by the subsystem. Things to know: `1.` The \begindata tag marks the start of a data definition block. The subsystem processes all text following this marker as SPICE kernel data assignments until finding a \begintext marker. `2.` The kernel subsystem defaults to the \begintext mode until the parser encounters a \begindata tag. Once in \begindata mode the subsystem processes all text as variable assignments until the next \begintext tag. `3.` Enter the tags as the only text on a line, i.e.:
          \begintext

             ... commentary information on the data assignments ...

          \begindata

             ... data assignments ...
`4.` CSPICE delivery N0059 added to the CSPICE and Icy text kernel parsers the functionality to read non native text kernels, i.e. a Unix compiled library can read a MS Windows native text kernel, a MS Windows compiled library can read a Unix native text kernel. Mice acquires this capability from CSPICE. `5.` With regards to the FORTRAN distribution, as of delivery N0057 the FURNSH call includes a line terminator check, signaling an error on any attempt to read non-native text kernels. Top ### Text kernel format Scalar assignments.
          VAR_NAME_DP  = 1.234
          VAR_NAME_INT = 1234
          VAR_NAME_STR = 'FORBIN'
Please note the use of a single quote in string assignments. Vector assignments. Vectors must contain the same type data.
          VEC_NAME_DP  = ( 1.234   , 45.678  , 901234.5 )
          VEC_NAME_INT = ( 1234    , 456     , 789      )
          VEC_NAME_STR = ( 'FORBIN', 'FALKEN', 'ROBUR'  )

          also

          VEC_NAME_DP  = ( 1.234,
                          45.678,
                          901234.5 )

          VEC_NAME_STR = ( 'FORBIN',
                           'FALKEN',
                           'ROBUR' )
Time assignments.
          TIME_VAL = @31-JAN-2003-12:34:56.798
          TIME_VEC = ( @01-DEC-2004, @15-MAR-2004 )
The at-sign character '@' indicates a time string. The pool subsystem converts the strings to double precision TDB (a numeric value). Please note, the time strings must not contain embedded blanks. WARNING - a TDB string is not the same as a UTC string. The above examples depict direct assignments via the '=' operator. The kernel pool also permits incremental assignments via the '+=' operator. Please refer to the kernels required reading, kernel.req, for additional information. Top ## Kernels for lessons Top ### Input kernel files The following kernels are used in examples provided in these lessons:
          FILE NAME                TYPE  DESCRIPTION
          -----------------------  ----  ----------------------
          naif0008.tls             LSK   Generic LSK
          leapseconds.tls          LSK   The current leapseconds
                                         kernel (naif0008.tls as
                                         of Jan 2006)
          de405s.bsp               SPK   Planet Ephemeris SPK
          pck00008.tpc             PCK   Generic PCK
These SPICE kernels are included in the lesson package available from the NAIF server at JPL:
       ftp://naif.jpl.nasa.gov/pub/naif/toolkit_docs/Lessons/
Top ### Output The code examples listed in this workbook include corresponding outputs for the described inputs. The output of a given example on a particular platform may not exactly match that shown since compilers and math libraries differ between platform architectures. Top # Lesson 1: Kernel Management with the Kernel Subsystem Lesson Goals: This lesson demonstrates use of the kernel subsystem to load, unload, and list loaded kernels. This lesson requires creation of a SPICE meta kernel. Top ## Relevant Routines `--` furnsh_c loads the meta kernel and the SPICE kernels listed within that kernel. `--` ktotal_c retrieves the number of SPICE kernels loaded by the kernel subsystem. `--` kdata_c returns information about each loaded kernel. `--` unload_c removes a kernel and deletes any pool variables defined by that kernel from the kernel subsystem. `--` kclear_c deletes all kernel pool data from the kernel subsystem. Top ## Requirements and References Knowledge of information in the kernels.req document, the mk.ppt and intro_to_kernels.ppt tutorial files. Top ## Programming Task Write a program to load a meta kernel, interrogate the CSPICE system for the names and types of all loaded kernels, then demonstrate the unload functionality and the resulting effects. Top ## Code Solution Top ### First, create a meta text kernel: You can use two versions of a meta kernel with code examples (meta.tm) in this lesson. Either a kernel with explicit path information:
       \begindata

          KERNELS_TO_LOAD = ( 'kernels/spk/de405s.bsp',
                              'kernels/pck/pck00008.tpc',
                              'kernels/lsk/leapseconds.tls')

       \begintext
... or a more generic meta kernel using the PATH_VALUES/PATH_SYMBOLS functionality to declare path names as variables:
       \begintext

       Define the paths to the kernel directory. Use the PATH_SYMBOLS
       as aliases to the paths.

       \begindata

          PATH_VALUES     = ( 'kernels/lsk',
                              'kernels/spk',
                              'kernels/pck' )

          PATH_SYMBOLS    = ( 'LSK', 'SPK', 'PCK' )

          KERNELS_TO_LOAD = ( '$LSK/naif0008.tls',
                              '$SPK/de405s.bsp',
                              '$PCK/pck00008.tpc' )

       \begintext
Top ### Now the solution source code:
       #include <stdlib.h>
       #include <stdio.h>
       #include <strings.h>
       #include "SpiceUsr.h"

       /*
       Define the maximum length for any string, 80
       characters plus one null terminator.
       */
       #define LENOUT 81

       int main( int argc, char **argv )
          {

          /*  Declare the needed variables: */

          SpiceChar     file   [LENOUT];
          SpiceChar     type   [LENOUT];
          SpiceChar     source [LENOUT];

          SpiceInt      i;
          SpiceInt      count;
          SpiceInt      handle;

          SpiceBoolean  found;

          /* Assign the path name of the meta kernel to META. */
          SpiceChar   * META = "meta.tm";

          /*
          Load the meta kernel then use KTOTAL to interrogate the SPICE
          kernel subsystem for the total number of loaded kernel files.
          */
          furnsh_c ( META );
          ktotal_c ("ALL", &count );
          printf( "Kernel count after load: %ld\n", count );

          /*
          Loop over the number of files; interrogate the SPICE system
          with kdata_c for the kernel names and the type. 'found' returns a
          boolean indicating whether any kernel files of the specified
          type were loaded by the kernel subsystem. This example ignores
          checking 'found' as kernels are known to be loaded.
          */
          for (i = 0L; i < count; i++ )
            {
             kdata_c( i, "ALL", LENOUT, LENOUT, LENOUT,
                          file, type, source, &handle, &found );
             printf ( "File %s\n", file );
             printf ( "Type %s\n", type );
             printf ( "Source %s\n", source );
             printf ( "\n" );
            }

          /*
          Unload one kernel then check the count.
          */
          unload_c ( "kernels/spk/de405s.bsp" );
          ktotal_c ( "ALL", &count );

          /*
          The subsystem should report one less kernel.
          */
          printf ( "Kernel count after one unload: %ld\n", count );

          /*
          Now unload the meta kernel. This action unloads all
          files listed in the meta kernel.
          */
          unload_c ( META );

          /*
          Check the count. SPICE should return a count of zero.
          */
          ktotal_c ( "ALL", &count );
          printf ( "Kernel count after meta unload: %ld\n", count );

          exit(0);
          }
Top ### Run the code example First we see the number of all loaded kernels returned from the ktotal_c call:
        Kernel count after load:   4
Now the kdata_c loop returns the name of each loaded kernel, the type of kernel (SPK, CK, TEXT, etc.) and the source of the kernel - the mechanism that loaded the kernel. The source either identifies a meta kernel, or contains an empty string. An empty source string indicates a direct load of the kernel with a furnsh_c call.
       File   meta.tm
       Type   META
       Source

       File   kernels/spk/de405s.bsp
       Type   SPK
       Source meta.tm

       File   kernels/pck/pck00008.tpc
       Type   TEXT
       Source meta.tm

       File   kernels/lsk/naif0008.tls
       Type   TEXT
       Source meta.tm

       Kernel count after one unload :   3
       Kernel count after meta unload:   0
Top # Lesson 2: The Kernel Pool Lesson Goals: The lesson demonstrates the CSPICE system's facility to retrieve different types of data (string, numeric, scalar, array) from the kernel pool. For the code examples, use this generic text kernel (cassini.tm) containing PCK-type data, kernels to load, and example time strings:
       \begintext

       Ring model data.

       \begindata

          BODY699_RING1_NAME     = 'A Ring'
          BODY699_RING1          = (122170.0 136780.0 0.1 0.1 0.5)

          BODY699_RING1_1_NAME   = 'Encke Gap'
          BODY699_RING1_1        = (133405.0 133730.0 0.0 0.0 0.0)

          BODY699_RING2_NAME     = 'Cassini Division'
          BODY699_RING2          = (117580.0 122170.0 0.0 0.0 0.0)

       \begintext

       The kernel pool recognizes values preceded by '@' as time
       values. When read, the kernel subsystem converts these
       representations into double precision ephemeris time.

       Caution: The kernel subsystem interprets the time strings
       identified by '@' as TDB. The same string passed as input
       to @STR2ET is processed as UTC.

       The three expressions stored in the EXAMPLE_TIMES array represent
       the same epoch.

       \begindata

          EXAMPLE_TIMES       = ( @APRIL-1-2004-12:34:56.789,
                                  @4/1/2004-12:34:56.789,
                                  @JD2453097.0242684
                                 )

       \begintext

       Name the kernels to load. Use path symbols.

       \begindata

          PATH_VALUES     = ('kernels/spk',
                             'kernels/pck',
                             'kernels/lsk')

          PATH_SYMBOLS    = ('SPK' , 'PCK' , 'LSK' )

          KERNELS_TO_LOAD = ( '$SPK/de405s.bsp',
                              '$PCK/pck00008.tpc',
                              '$LSK/leapseconds.tls')

       \begintext
Top ## Relevant Routines `--` gipool_c retrieves integer values from the kernel subsystem. `--` gdpool_c retrieves double precision values from the kernel subsystem `--` gcpool_c retrieves character values from the kernel subsystem `--` dtpool_c returns data (name, type, size) describing a kernel pool variable. `--` gnpool_c retrieves the names of kernel pool variables matching a given template. Top ## Requirements and References Knowledge of the material in the kernels.req document and the intro_to_kernels.ppt tutorial file. The main references for pool routines are found in the source files or API documentation for the particular routines. Top ## Programming Task Write a program to retrieve particular string and numeric text kernel variables, both scalars and arrays. Interrogate the kernel pool for assigned variable names. Top ## Code Solution
       #include <stdlib.h>
       #include <stdio.h>
       #include <strings.h>
       #include "SpiceUsr.h"

       /*
       Define the max number of kernel variables
       of concern for this examples.
       */
       #define N_ITEMS   20

       /*
       Define the maximum length for any string, 80
       characters plus one null terminator.
       */
       #define STRLEN 81

       int main( int argc, char **argv )
          {

          /*
          Note, the pool routines return a boolean to 'found'
          signaling whether the requested variable name exists
          in the kernel pool. The code solutions do not check the
          boolean value since the solutions use variables known to
          exist. In general, code should always check the boolean
          value to ensure return of valid data.
          */

          /*
          As usual, type our variables...
          */
          SpiceInt                    i;
          SpiceInt                    j;
          SpiceInt                    dim;
          SpiceInt                    n_var;
          SpiceInt                    n_val;
          SpiceInt                    start;

          SpiceBoolean                found;

          SpiceDouble                 dvars    [N_ITEMS];

          SpiceChar                   cvals    [N_ITEMS][STRLEN];
          SpiceChar                   cvars    [N_ITEMS][STRLEN];
          SpiceChar                   type;
          SpiceChar                   tmplate[12];

          /*
          Load the example kernel containing the kernel variables.
          The kernels defined in KERNELS_TO_LOAD load into the
          kernel pool with this call.
          */
          furnsh_c ( "cassini.tm" );

          /*
          Initialize the start value. This values indicates
          index of the first element to return if a kernel
          variable is an array. start = 0 indicates return everything.
          start = 1 indicates return everything but the first element.
          */
          start = 0;

          /*
          Set the template for the variable names to find. Let's
          look for all variables containing  the string RING.
          Define this with the wildcard template '*RING*'. Note:
          the template '*RING' would match any variable name
          ending with the RING string.
          */
          strcpy ( tmplate, "*RING*");

          /*
          We're ready to interrogate the kernel pool for the
          variables matching the template. gnpool_c tells us:

             1. Does the kernel pool contain any variables that
                match the template (value of found).
             2. If so, how many variables? (value of n_val)
             3. The variable names. (cvals, an array of strings)
          */

          gnpool_c ( tmplate, start, N_ITEMS, STRLEN,
                     &n_val, cvals, &found );

          if ( found )
             {
             printf( "No. variables matching template: %ld\n", n_val);
             }
          else
             {
             puts ( "No kernel variables matched template" );
             exit(0);
             }

          /*
          Okay, now we know something about the kernel pool
          variables of interest to us. Let's find out more...
          */
          for (i=0; i<n_val; ++i )
             {

             /*
             Use dtpool_c to return the dimension and type,
             C (character) or N (numeric), of each pool
             variable name in the cvals array.
             */
             dtpool_c ( cvals[i], &found, &dim, &type );
             printf ( "\n%s\n", cvals[i]);
             printf ( "No. items: %ld Of type: %c\n\n", dim, type );

             /*
             Use the EQSTR routine to test character equality,
             'N' or 'C'.
             */
             if ( type == 'N' )
                {

                /*
                If 'type' equals "N", we found a numeric array.
                In this case any numeric array will be an array
                of double precision numbers ("doubles"). gdpool_c
                retrieves doubles from the kernel pool. 'dvars'
                contains the array of 'n_vars' values.
                */
                gdpool_c ( cvals[i], start, N_ITEMS, &n_var,
                                            dvars  , &found );

                for( j=0; j<n_var; ++j )
                   {
                   printf( "  Numeric value: %f\n", dvars[j] );
                   }

                }
             else if ( type == 'C' )
                {

                /*
                If 'type' equals "C", we found a string array.
                gcpool_c retrieves string values from the
                kernel pool. cvars[i] contains the array of 'n_var'
                values.
                */
                gcpool_c ( cvals[i], start , N_ITEMS,
                           STRLEN  , &n_var, cvars  , &found );

                for( j=0; j<n_var; ++j )
                   {
                   printf( "  String value: %s\n", cvars[j] );
                   }

                }

             }

          puts( " " );

          /*
          Now look at the kernel variable EXAMPLE_TIMES. Extract this
          value as an array of doubles.
          */
          gdpool_c ( "EXAMPLE_TIMES", start, N_ITEMS, &n_var, dvars,
                     &found );

          puts( "EXAMPLE_TIMES");

          for( j=0; j<n_var; ++j )
             {
             printf( "  Time value: %f\n", dvars[j] );
             }

          exit(0);
          }
Top ### Run the code example The program runs and first reports the number of kernel pool variables matching the template, 6.
       No. variables matching template:   6
The program then loops over the dtpool_c 6 times, reporting the name of each pool variable, the number of data items assigned to that variable, and the variable type. Within the dtpool_c loop, a second loop outputs the contents of the data variable using gcpool_c or gdpool_c.
       BODY699_RING1
        No. items: 5 Of type: N

         Numeric value: 122170.000000
         Numeric value: 136780.000000
         Numeric value: 0.100000
         Numeric value: 0.100000
         Numeric value: 0.500000

       BODY699_RING2
        No. items: 5 Of type: N

         Numeric value: 117580.000000
         Numeric value: 122170.000000
         Numeric value: 0.000000
         Numeric value: 0.000000
         Numeric value: 0.000000

       BODY699_RING1_1
        No. items: 5 Of type: N

         Numeric value: 133405.000000
         Numeric value: 133730.000000
         Numeric value: 0.000000
         Numeric value: 0.000000
         Numeric value: 0.000000

       BODY699_RING1_NAME
        No. items: 1 Of type: C

         String value: A Ring

       BODY699_RING2_NAME
        No. items: 1 Of type: C

         String value: Cassini Division

       BODY699_RING1_1_NAME
        No. items: 1 Of type: C

         String value: Encke Gap
Note the final time value differs from the previous values in the final three decimal places despite the intention that all three strings represent the same time. This results from round-off when converting a decimal Julian day representation to the seconds past J2000 ET representation.
       EXAMPLE_TIMES
         Time value: 134094896.789000
         Time value: 134094896.789000
         Time value: 134094896.789753
Top # Lesson 3: Coordinate Conversions Lesson Goals: The CSPICE system provides functions to convert coordinate tuples between Cartesian and various non Cartesian coordinate systems including conversion between geodetic and rectangular coordinates. This lesson presents these coordinate transform routines for rectangular, cylindrical, and spherical systems. Top ## Relevant Routines `--` latrec_c, latitudinal to rectangular `--` latcyl_c, latitudinal to cylindrical `--` latsph_c, latitudinal to spherical `--` reccyl_c, rectangular to cylindrical `--` recgeo_c, rectangular to geodetic `--` reclat_c, rectangular to latitudinal `--` recsph_c, rectangular to spherical `--` recrad_c, rectangular to right ascension - declination `--` sphrec_c, spherical to rectangular `--` sphcyl_c, spherical to cylindrical `--` sphlat_c, spherical to latitudinal `--` cyllat_c, cylindrical to latitudinal `--` cylsph_c, cylindrical to spherical `--` cylrec_c, cylindrical to rectangular `--` georec_c, geodetic to rectangular Top ## Requirements and References Basic knowledge of the standard coordinate systems used in celestial mechanics. The contents of concepts.ppt and derived_quant.ppt tutorial files. Top ## Programming Task Write a program to convert a Cartesian 3-vector representing some location to the other coordinate representations. Use the position of the Moon with respect to Earth in an inertial and non-inertial reference frame as the example vector. Top ## Code Solution
       #include <stdlib.h>
       #include <stdio.h>
       #include <strings.h>
       #include "SpiceUsr.h"

       /* Define the length of the time string, 32
       characters plus 1 for the null terminator.
       */
       #define LENOUT 33

       int main( int argc, char **argv )
          {

          /*
          Type the variables.
          */
          SpiceInt              dim;

          /*
          Define the inertial and non inertial frame names.
          */
          SpiceChar             inrfrm  [] = "J2000";
          SpiceChar             nonfrm  [] = "IAU_EARTH";
          SpiceChar             timstr  [LENOUT];

          SpiceDouble           et;
          SpiceDouble           range;
          SpiceDouble           ra;
          SpiceDouble           dec;
          SpiceDouble           lat;
          SpiceDouble           colat;
          SpiceDouble           lon;
          SpiceDouble           ltime;
          SpiceDouble           flat;
          SpiceDouble           rad   [3];
          SpiceDouble           pos   [3];

          /*
          Load the needed kernels using a furnsh_c call on the
          meta kernel.
          */
          furnsh_c ( "meta.tm" );

          /*
          Prompt the user for a time string. Convert the
          time string to ephemeris time J2000 (ET).
          */
          prompt_c ( "Time of interest: ", LENOUT, timstr );
          str2et_c ( timstr, &et );

          /*
          Access the kernel pool data for the triaxial radii of the
          Earth, 'rad[0]' holds the equatorial radius, 'rad[2]'
          the polar radius.
          */
          bodvrd_c ( "Earth", "RADII", 3, &dim, rad);

          /*
          Calculate the flattening factor for the Earth.

                   equatorial_radius - polar_radius
          flat =   ________________________________

                         equatorial_radius
          */

          flat = (rad[0] - rad[2])/rad[0];

          /*
          Make the spkpos_c call to determine the apparent position of
          the Moon w.r.t. to the Earth at 'et' in the inertial frame.
          */
          spkpos_c ( "MOON", et, inrfrm, "LT+S","EARTH", pos, &ltime);

          /*
          Show the current frame and time.
          */
          printf ( " Time : %s\n"         , timstr );
          printf ( "  Inertial Frame: %s\n", inrfrm );

          /*
          First convert the position vector
          X = pos[0], Y = pos[1], Z = pos[2], to RA/DEC.
          */
          recrad_c ( pos, &range, &ra, &dec );
          printf ( "   Range/Ra/Dec\n" );
          printf ( "    Range: %f\n", range        );
          printf ( "    RA   : %f\n", ra * dpr_c() );
          printf ( "    DEC  : %f\n", dec* dpr_c() );

          /*
          ...latitudinal coordinates...
          */
          reclat_c ( pos, &range, &lon, &lat );
          printf ( "   Latitudinal\n" );
          printf ( "    Rad  : %f\n", range);
          printf ( "    Lon  : %f\n", lon * dpr_c() );
          printf ( "    Lat  : %f\n", lat * dpr_c() );

          /*
          ...spherical coordinates use the colatitude,
          the angle from the Z axis.
          */
          recsph_c ( pos, &range, &colat, &lon );
          printf ( "   Spherical\n");
          printf ( "    Rad  : %f\n", range           );
          printf ( "    Lon  : %f\n", lon   * dpr_c() );
          printf ( "    Colat: %f\n", colat * dpr_c() );

          /*
          Make the spkpos_c call to determine the apparent position of
          the Moon w.r.t. to the Earth at 'et' in the non-inertial,
          body fixed, frame.
          */
          spkpos_c ( "MOON", et, nonfrm, "LT+S","EARTH", pos, &ltime);

          puts ( " " );
          printf ( "  Non-inertial Frame: %s\n", nonfrm );

          /*
          ...latitudinal coordinates...
          */
          reclat_c ( pos, &range, &lon, &lat );
          printf ( "   Latitudinal\n" );
          printf ( "    Rad  : %f\n", range         );
          printf ( "    Lon  : %f\n", lon * dpr_c() );
          printf ( "    Lat  : %f\n", lat * dpr_c() );

          /*
          ...spherical coordinates...
          */
          recsph_c ( pos, &range, &colat, &lon );
          printf ( "   Spherical\n" );
          printf ( "    Rad  : %f\n", range           );
          printf ( "    Lon  : %f\n", lon   * dpr_c() );
          printf ( "    Colat: %f\n", colat * dpr_c() );

          /*
          ...finally, convert the position to geodetic coordinates.
          */
          recgeo_c ( pos, rad[0], flat, &lon, &lat, &range );
          printf ( "   Geodetic\n" );
          printf ( "    Rad  : %f\n", range         );
          printf ( "    Lon  : %f\n", lon * dpr_c() );
          printf ( "    Lat  : %f\n", lat * dpr_c() );
          puts ( " " );

          exit(0);
          }
Top ### Run the code example Input a time/date at which to calculate the Moon's position. (the 'TDB' tag indicates a Barycentric Dynamical Time value).
       Time of interest: Feb 3 2002 TDB
Examine the Moon position in the J2000 inertial frame, display the time and frame:
        Time : Feb 3 2002 TDB
         Inertial Frame: J2000
Convert the Moon Cartesian coordinates to right ascension declination.
          Range/Ra/Dec
           Range: 369340.815193
           RA   : 203.643686
           DEC  : -4.979010
Latitudinal. Note the difference in the expressions for longitude and right ascension though they represent a measure of the same quantity. The RA/DEC system measures RA in the interval [0,2Pi). Latitudinal coordinates measures longitude in the interval (-Pi,Pi].
          Latitudinal
           Rad  : 369340.815193
           Lon  : -156.356314
           Lat  : -4.979010
Spherical. Note the difference between the expression of latitude in the Latitudinal system and the corresponding Spherical colatitude. The spherical coordinate system uses the colatitude, the angle measure away from the positive Z axis. Latitude is the angle between the position vector and the x-y (equatorial) plane with positive angle defined as toward the positive Z direction
          Spherical
           Rad  : 369340.815193
           Lon  : -156.356314
           Colat: 94.979010
The same position look-up in a body fixed (non-inertial) frame, IAU_EARTH.
         Non-inertial Frame: IAU_EARTH
Latitudinal coordinates return the geocentric latitude.
          Latitudinal
           Rad  : 369340.815193
           Lon  : 70.986950
           Lat  : -4.989675
Spherical.
          Spherical
           Rad  : 369340.815193
           Lon  : 70.986950
           Colat: 94.989675
Geodetic. The cartographic lat/lon.
          Geodetic
           Rad  : 362962.836755
           Lon  : 70.986950
           Lat  : -4.990249
Top # Lesson 4: Advanced Time Manipulation Routines Lesson Goals: Introduce the routines used for advanced manipulation of time strings. Understand the concept of ephemeris time (ET) as used in CSPICE. Top ## Relevant Routines `--` str2et_c converts time strings to ephemeris time (ET). `--` timout_c formats a time string output. `--` tpictr_c creates a format template for use in timout_c. `--` tsetyr_c sets the reference century/year for two digit representation of the year. Top ## Requirements and References Knowledge of the time.req document, the time.ppt, lsk_and_sclk.ppt, and other_functions.ppt tutorial files. Also, examine the header of timout_c for a list of the string markers used by timout_c and tpictr_c to describe time string format. Always keep in mind str2et_c assumes 'UTC' unless indicated otherwise. Top ## Programming Task Demonstrate the advanced functions of the time utilities with regard to formatting of time strings for output. Formatting options include altering calendar representations of the time strings. Convert time-date strings between different CSPICE-supported formats. Top ## Code Solution Caution: Be sure to assign sufficient string lengths for time formats/pictures.
       #include <stdlib.h>
       #include <stdio.h>
       #include <strings.h>
       #include "SpiceUsr.h"

       /*
       Define the maximum length for any string, 80
       characters plus one null terminator.
       */
       #define STRLEN 256

       int main( int argc, char **argv )
          {

          /* Declare the needed variables: */

          SpiceDouble            et;
          SpiceDouble            et1;
          SpiceDouble            et2;

          SpiceBoolean           ok;

          SpiceChar              error [STRLEN];
          SpiceChar              pictr [STRLEN];
          SpiceChar              timstr[STRLEN];

          /*
          Assign the LSK variable to the name of the leapsecond,
          kernel and create an arbitrary time string.
          */
          SpiceChar            * CALSTR   =
                                 "Mar 15, 2003 12:34:56.789 AM PST";

          SpiceChar            * LSK      =
                                 "/kernels/gen/lsk/leapseconds.tls";

          SpiceChar            * AMBIGSTR =
                                 "Mar 15, 79 12:34:56";

          /* Load the leapseconds kernel. */

          furnsh_c ( LSK );
          printf   ( "Original time string       : %s\n", CALSTR );

          /*
          Convert the time string to the number of ephemeris
          seconds past the J2000 epoch. This is the most common
          internal time representation used by the CSPICE
          system; CSPICE refers to this as ephemeris time (ET).
          */
          str2et_c ( CALSTR, &et );
          printf   ( "Corresponding ET           : %f\n", et     );

          /*
          Make a picture of an output format. Describe a Unix-like
          time string then send the picture and the 'et' value through
          timout_c to format and convert the ET representation of the
          time string into the form described in timout_c. The
          '::UTC-7' token indicates the time zone for the 'timstr'
          output - PDT. 'PDT' is part of the output, but not a time
          system token.
          */
          timout_c ( et,
                     "Wkd Mon DD HR:MN:SC PDT YYYY ::UTC-7",
                     STRLEN,
                     timstr );
          printf   ( "Time in string format 1    : %s\n", timstr );

          /*
          Create another picture, this time combine a calendar,
          2 digit year , with Julian Day format.
          */
          timout_c ( et,
                     "Wkd Mon DD HR:MN ::UTC-7 YR (JULIAND.##### JDUTC)",
                     STRLEN,
                     timstr );
          printf   ( "Time in string format 2    : %s\n", timstr );

          /*
          Why create a picture by hand when CSPICE can do it for you?
          Input a string to tpictr_c with the format of interest.
          'ok' returns a boolean indicating whether an error
          occurred while parsing the picture string, if so,
          an error diagnostic message returns in 'error'. In this
          example, no need exists to check the error flag since
          the picture string is known as correct..
          */
          tpictr_c ( "12:34:56.789 P.M. PDT January 1, 2006",
                     STRLEN,
                     STRLEN,
                     pictr,
                     &ok,
                     error);

          /*
          Confirm the tpictr_c call succeeded. Report the error string
          if not.
          */
          if( !ok )
             {
             printf( "\nError in TPICTR call:\n" );
             printf( "%s\n", error );
             exit(1);
             }

          timout_c ( et, pictr, STRLEN, timstr );
          printf   ("Time in string format 3    : %s\n", timstr );

          /*
          Two digit year representations often cause problems due to
          the ambiguity of the century. The routine tsetyr_c gives the
          user the ability to set a default range for 2 digit year
          representation. SPICE uses 1969AD as the default start
          year so the numbers inclusive of 69 to 99 represent years
          1969AD to 1999AD, the numbers inclusive of 00 to 68 represent
          years 2000AD to 2068AD.

          The defined time string AMBIGSTR contains a two-digit
          year. Since the SPICE base year is 1969, the time
          subsystem interprets the string as 1979.
          */
          str2et_c ( AMBIGSTR, &et1 );

          /*
          Set 1980 as the base year causes CSPICE to interpret the time
          string's "79" as 2079.
          */
          tsetyr_c ( 1980 );
          str2et_c ( AMBIGSTR, &et2 );

          /*
          Calculate the number of years between the two ET
          representations, ~100.
          */
          printf ( "Years between evaluations  : %f\n",
                                (et2 - et1)/jyear_c() );

          exit(0);
          }
Top ### Run the code example
       Original time string      : Mar 15, 2003 12:34:56.789 AM PST
       Corresponding ET          : 100989360.974561
       Time in string format 1   : Sat Mar 15 01:34:56 PDT 2003
       Time in string format 2   : Sat Mar 15 01:34 03 (2452713.85760 JDUTC)
       Time in string format 3   : 01:34:56.789 A.M. PDT March 15, 2003
       Years between evaluations : 100.000000
Top # Lesson 5: Error Handling Lesson Goal: This lesson introduces the basics of the error subsystem and its various the response modes: DEFAULT, RETURN, ABORT, RETURN, IGNORE, the error output modes: SHORT, LONG, EXPLAIN TRACEBACK, DEFAULT, ALL, NONE, and the error traceback message. Top ## Relevant Routines: `--` failed_c returns TRUE if a CSPICE error signaled. `--` reset_c resets the error subsystem to the state prior to an error signal - WARNING, this call resets only the error subsystem, the rest of the CSPICE system is unchanged. `--` erract_c sets the reaction of the error subsystem to an error. `--` errch_c inserts a character/string into an error message. `--` errdp_c inserts a double precision value into an error message. `--` errint_c inserts an integer value into an error message. `--` errdev_c sets the device for error output. `--` errprt_c sets the error message items for output on an error signal. `--` sigerr_c signals a CSPICE error with a given short message. `--` setmsg_c sets the long message corresponding to sigerr_c. `--` return_c returns TRUE if a routine should return to caller on entry. Top ## Requirements and References Knowledge of material in the error.req document and the exceptions.ppt tutorial file. Comprehension of the catch/throw concept. Top ## Programming Task Show the behavior of the various error modes by writing a program to signal an error, check for an error signal, set the long and short error strings, set error behavior (DEFAULT, RETURN, ABORT, RETURN). Top ## Code Solution
       #include <stdlib.h>
       #include <stdio.h>
       #include <strings.h>
       #include "SpiceUsr.h"

       /*
       Define the maximum length for any string, 80
       characters plus one null terminator.
       */
       #define STRLEN 81

       void doerr();

       int main( int argc, char **argv )
          {

          /*  Declare the needed variables: */

          SpiceChar      errcon[STRLEN];
          SpiceBoolean   doloop        = SPICETRUE;

          /*
          Check into the error subsystem to create a traceback
          showing the call tree. A chkout_c must balance every
          chkin_c.
          */
          chkin_c ( "ERRSYSC" );

          /*
          Before we start, what's the initial (default)
          error state? erract_c both sets the state and
          reports the state.
          */
          erract_c ( "GET", STRLEN, errcon );
          printf   ( "Default error state: %s\n", errcon );

          /*
          Now start an input loop so we can try different
          settings for error response.
          */
          do
             {

             /* Again use ERRACT to retrieve the current error mode. */
             erract_c ( "GET", STRLEN, errcon );
             printf   ( "Current error state: %s\n", errcon );

             /*
             Okay, input one of the response settings strings
             then set the error subsystem response to that value.
             */
             prompt_c ( "Set error condition (DEFAULT, REPORT, "
                        "ABORT, RETURN, IGNORE) :",
                         STRLEN,
                         errcon );
             erract_c ( "SET", STRLEN, errcon );

             /* Cause an error signal. */
             doerr();

             /*
             Check for an error signal via a call to FAILED.
             At this point we see an important difference
             between the error mode's response to an error
             signal.
             */
             if ( !failed_c() )
                {
                puts( "No error signal noted." );
                }
             else
                {
                puts( "Error signal noted." );
                }

             }
          while ( doloop );

          /*
          Check out of the error subsystem tho' we'll
          never hit this call.
          */
          chkout_c ( "ERRSYSC" );
          exit(0);
          }

       /* This subroutine initiates a SPICE error signal. */

       void doerr ()
          {

          /* Check into the error subsystem as before. */

          chkin_c ("DOERR");

          /*
          Let's signal an error. The string passed by setmsg_c
          is the long error message. You may place markers in the
          long message string then later substitute other data
          items for those markers.
          */
          setmsg_c ( "A truly horrendous event occurred "
                     "during execution of this program. "
                     "Data added to long error message string: "
                     "A double #, an int #, and a string #." );

          /*
          Now substitute other data into the long message string.
          Note the substitutions work on the first found marker.
          */
          errdp_c  ( "#", 186282.397 );
          errint_c ( "#", 666        );
          errch_c  ( "#", "A STRING" );

          /*
          SIGERR causes the error signal with the string passed
          from SETMSG. Set the error flag in the SPICE error
          subsystem and execute the proper error response.
          */
          sigerr_c ( "OOPS(SOMETHINGBAD)" );

          chkout_c ( "DOERR" );

          }
Top ### Run the code example o- Demo the DEFAULT mode:
       Default error state: DEFAULT
       Current error state: DEFAULT
The subsystem is in error state DEFAULT. Let the subsystem run to the error signal in DEFAULT mode:
       Set error condition (DEFAULT,REPORT,ABORT,RETURN,IGNORE):default
What subsystem reaction occurs in this state?
       ===================================================================

       Toolkit version: N0060

       OOPS(SOMETHINGBAD) --

       A truly horrendous event occurred during execution of this program.
       Data added to long error message string: A double
       1.8628239700000E+05, an int 666, and a string A STRING.

       A traceback follows.  The name of the highest level module is
       first. ERRSYSF --> DOERR

       Oh, by the way:  The SPICELIB error handling actions are
       USER-TAILORABLE.  You can choose whether the Toolkit aborts or
       continues when errors occur, which error messages to output, and
       where to send the output.  Please read the ERROR "Required Reading"
       file, or see the routines ERRACT, ERRDEV, and ERRPRT.

       ===================================================================
Notice we see no error signal status line. The program quit when it signaled an error. The program output the error messages, an additional information blurb ("Oh by the way"), the Toolkit version, and the traceback list. o- Rerun the program in REPORT mode:
        Default error state: DEFAULT
        Current error state: DEFAULT
       Set error condition (DEFAULT, REPORT, ABORT, RETURN, IGNORE) :report

       ===================================================================

       Toolkit version: N0060

       OOPS(SOMETHINGBAD) --

       A truly horrendous event occurred during execution of this program.
       Data added to long error message string: A double
       1.8628239700000E+05, an int 666, and a string A STRING.

       A traceback follows.  The name of the highest level module is
       first. ERRSYSF --> DOERR

       ===================================================================
        Error signal noted.
        Current error state: REPORT
       Set error condition (DEFAULT, REPORT, ABORT, RETURN, IGNORE) :
The error output ceases after the traceback then returns into the calling routine. Note the error signal marker indicates detection of the signal. The subsystem in REPORT mode does not print the information blurb. The CSPICE system can continue to run after an error signal with the error state set to REPORT - this mode flags an error then allows the program to continue the run. It may happen that the cause of the error condition causes instability in the CSPICE system. o- Rerun to test ABORT mode:
       Default error state: DEFAULT
       Current error state: DEFAULT
       Set error condition (DEFAULT,REPORT,ABORT,RETURN,IGNORE) :abort
How does the subsystem respond in ABORT mode?
       ===================================================================

       Toolkit version: N0060

       OOPS(SOMETHINGBAD) --

       A truly horrendous event occurred during execution of this program.
       Data added to long error message string: A double
       1.8628239700000E+05, an int 666, and a string A STRING.

       A traceback follows. The name of the highest level module is first.
       ERRSYSF --> DOERR

       ===================================================================
ABORT responds quite like DEFAULT except the error output does not include the information blurb shown in the DEFAULT output. All execution stops when the error signals. o- Run the program to demo the RETURN mode:
       Default error state: DEFAULT
       Current error state: DEFAULT
       Set error condition (DEFAULT,REPORT,ABORT,RETURN,IGNORE) :return
RETURN mode provides the highest measure of flexibility to deal with error signals. On output:
       ===================================================================

       Toolkit version: N0060

       OOPS(SOMETHINGBAD) --

       A truly horrendous event occurred during execution of this program.
       Data added to long error message string: A double
       1.8628239700000E+05, an int 666, and a string A STRING.

       A traceback follows. The name of the highest level module is first.
       ERRSYSF --> DOERR

       ===================================================================
        Error signal noted.
        Current error state: RETURN
The subroutine signals an error then returns similar to REPORT mode. However, this mode includes another property. If we make another pass through the command loop:
       Set error condition (DEFAULT, REPORT, ABORT, RETURN, IGNORE):return
       Error signal noted.
       Current error state: RETURN
We see no error output. The main property of the RETURN mode is to allow program execution to continue but immediately return from all CSPICE routines that check the state of the return_c function. This mode restricts program flow after an error signal. o- And the final mode to test, IGNORE:
       Default error state: DEFAULT
       Current error state: DEFAULT
       Set error condition (DEFAULT,REPORT,ABORT,RETURN,IGNORE) :ignore
       No error signal noted.
       Current error state: IGNORE
       Set error condition (DEFAULT,REPORT,ABORT,RETURN,IGNORE) :
No error output, no error signal. IGNORE mode prevents expression of all error subsystem functions; the subsystem does not set RETURN or FAILED. While using IGNORE mode the user cannot identify an error signal. Carefully consider program requirements before any use of IGNORE mode. Top ## Programming Task Write an interactive program to return a state vector based on a user's input. Code the program with the capability to recover from user input mistakes, inform the user of the mistake, then continue to run. Top ## Code Solution
       #include <stdlib.h>
       #include <stdio.h>
       #include <strings.h>
       #include "SpiceUsr.h"

       /*
       Define the maximum length for any string, 80
       characters plus one null terminator.
       */
       #define STRLEN 81

       int main( int argc, char **argv )
          {

          /*  Declare the needed variables: */

          SpiceChar              targ [STRLEN];

          /*
          Set a flag to start/stop and continue the
          inquiry loop.
          */
          SpiceBoolean           doloop = SPICETRUE;

          SpiceDouble            state[6];
          SpiceDouble            ltime;

          /*
          The RETURN mode signals an error then returns to the
          caller. Just what we need. REPORT mode performs almost
          the same function as RETURN, however RETURN mode
          sets the return_c() value to TRUE and so the program does
          not execute those CSPICE routines that check the return_c()
          value. Consider REPORT mode useful for debugging.
          */
          erract_c ( "SET", STRLEN, "RETURN" );

          /*
          Load the data we need for state evaluation.
          */
          furnsh_c ( "meta.tm" );

          /*
          Start our input query loop to the user.
          */

          while ( doloop )
             {

             /*
             For simplicity, we request only one input.
             The program calculates the state vector from
             Earth to the user specified target (TARG) in the
             J2000 frame, at ephemeris time zero, using
             aberration correction LT+S (light time plus
             stellar aberration).
             */
             prompt_c ( "Target: ", STRLEN, targ );

             if (  eqstr_c( targ, "NONE" ) )
                {

                /*
                An exit condition. If the user inputs NONE
                for a target name, set the loop to stop...
                */
                doloop = SPICEFALSE;

                }
             else
                {

                /*
                ...otherwise evaluate the state between the Earth
                and the target.
                */
                spkezr_c ( targ, 0., "J2000", "LT+S", "EARTH", state,
                           &ltime );

                /*
                What if the program can't perform the evaluation?
                Since we set the error subsystem to REPORT we know
                a failed spkezr_c call sets the failed_c flag to
                SPICETRUE then returns control to the calling routine.
                The CSPICE system also outputs an error message
                informing the user of the problem's cause.

                Examine the state of failed_c() to determine if we
                output a state vector or not.
                */

                if ( ! failed_c() )
                   {
                   printf ( "R : %17.5f %17.5f %17.5f\n",
                            state[0] , state[1], state[2] );
                   printf ( "V : %17.5f %17.5f %17.5f\n",
                            state[3] , state[4], state[5] );
                   printf ( "LT: %f\n", ltime );
                   }
                else
                   {

                   /*
                   Problem. Something went wrong. Reset the error
                   subsystem for another pass.
                   */
                   reset_c();

                   }

                }

             }

          exit(0);
          }
Top ### Run the code example Now run the code with various inputs to observe behavior. Begin the run using known astronomical bodies. Recall the CSPICE default units are kilometers, kilometers per second, kilograms, and seconds. The 'R' marker identifies the (X,Y,Z) position of the body in kilometers, the 'V' marker identifies the velocity of the body in kilometers per second, and the 'LT' marker identifies the one-way light time between the bodies at the requested evaluation time.
       Target: Moon
       R :     -291584.61659     -266693.40236      -76095.64756
       V :           0.64353          -0.66608          -0.30132
       LT: 1.342311

       Target: Mars
       R :   234536077.41914  -132584383.59557   -63102685.70619
       V :          30.95976          28.93646          13.11449
       LT: 923.001080

       Target: Pluto barycenter
       R : -1451304742.83853 -4318174144.40632  -918251433.58736
       V :          35.03838           3.06560          -0.01514
       LT: 15501.258293

       Target: Puck

       ===================================================================

       Toolkit version: N0060

       SPICE(SPKINSUFFDATA) --

       Insufficient ephemeris data has been loaded to compute the state
       of 715 (PUCK) relative to 0 (SOLAR SYSTEM BARYCENTER) at the
       ephemeris epoch 2000 JAN 01 12:00:00.000.

       A traceback follows.  The name of the highest level module is
       first.
       spkezr_c --> SPKEZR --> SPKEZ --> SPKAPP --> SPKSSB --> SPKGEO

       ===================================================================
Perplexing. What happened? The kernel files named in meta.tm did not include ephemeris data for Puck. When the SPK subsystem tried to evaluate Puck's position, the evaluation failed due to lack of data, so an error signaled. The above error signifies an absence of state information at ephemeris time 2000 JAN 01 12:00:00.000 (the requested time, ephemeris time zero). Since the program set the error mode to RETURN, program execution continues. Try another look-up.
       Target: Casper

       ===================================================================
       Toolkit version: N0060

       SPICE(IDCODENOTFOUND) --

       The target, 'Casper', is not a recognized name for an ephemeris
       object. The cause of this problem may be that you need an updated
       version of the SPICE Toolkit. Alternatively you may call SPKEZ
       directly if you know the SPICE ID codes for both 'Casper' and
       'EARTH'

       A traceback follows.  The name of the highest level module is
       first.
       spkezr_c --> SPKEZR

       ===================================================================
An easy to understand error. The SPICE system does not contain information on a body named 'Casper.' Another look-up, this time, something easy.
       Target: Venus
       R :   -80970027.54053  -139655772.57390   -53860125.95820
       V :          31.16969         -27.00018         -12.31622
       LT: 567.655074
The look-up succeeded despite two errors in our run. The CSPICE system can respond to error conditions (not system errors) in much the same fashion as languages with catch/throw instructions. Top # Lesson 6: Windows, and Cells Lesson Goal: This lesson introduces the concepts of the SPICE data types 'cell' and 'window'. A 'cell' is a data structure designed to provide easy and safe manipulation of typed array data. A C SPICE cell consists of a C structure. A user should create cells by use of the appropriate CSPICE calls. NAIF recommends against manual creation of cells. A 'window' is a type of cell containing ordered, double precision values describing a collection of zero or more intervals. We define an interval, 'i', as all double precision values bounded by and including an ordered pair of numbers,
          [ a , b ]
             i   i
where
          a    <   b
           i   -    i
The intervals within a window are both ordered and disjoint. That is, the beginning of each interval is greater than the end of the previous interval:
          b  <  a
           i     i+1
A common use of the windows facility is to calculate the intersection set of a number of time intervals. Top ## Relevant Routines `--` wncomd_c determines the compliment of a window with respect to a defined interval. `--` wncond_c contracts a window's intervals. `--` wndifd_c : Calculate the difference between two windows; i.e. every point existing in the first but not the second. `--` wnelmd_c returns TRUE or FALSE if a value exists in a window. `--` wnexpd_c expands the size of the intervals in a window. `--` wnextd_c extracts a window's endpoints . `--` wnfetd_c retrieves a specified interval from a window. `--` wnfild_c fills gaps between intervals in a window. `--` wnfltd_c filter/removes small intervals from a window. `--` wnincd_c determines if an interval exists within a window. `--` wninsd_c inserts an interval into a window. `--` wnintd_c calculates the intersection of two windows. `--` wnreld_c compares two windows. Comparison operations available, equality '=', inequality '<>', subset '<=' and '>=', proper subset '<' and '>'. `--` wnsumd_c creates a window summary. `--` wnunid_c calculates the union of two windows. `--` wnvald_c validates/creates a window from a cell array. Top ## Requirements and References Knowledge of cells.req, and windows.req documents, as well as the other_functions.ppt tutorial file. Top ## Programming task: Given the times of line-of-sight for a vehicle from a ground station and the times for an acceptable Sun-station-vehicle phase angle, write a program to determine the time intervals common to both configurations. Top ## Code Solution
       #include <stdio.h>
       #include "SpiceUsr.h"
       #include <stdlib.h>
       #include <string.h>

       #define MAXSIZ       8

       /*
       Define the maximum length for a UTC string, 25
       characters plus one null terminator.
       */
       #define UTCLEN       26

       int main( int argc, char **argv )
          {

          /*
          Define our variable types.

          Define the cells to use as windows.
          The windows can hold 8 data values i.e.
          four intervals.
          */

          SPICEDOUBLE_CELL ( loswin, MAXSIZ );
          SPICEDOUBLE_CELL ( phswin, MAXSIZ );
          SPICEDOUBLE_CELL ( sched , MAXSIZ );

          SpiceInt         i;
          SpiceInt         small;
          SpiceInt         large;

          SpiceChar        utcstr[2][UTCLEN];

          /*
          Define sets of time intervals. For the purposes of this
          tutorial program, define time intervals representing
          an unobscured line of sight between a ground station
          and some  body.
          */
          SpiceChar   los   [MAXSIZ][UTCLEN] =
                        { "Jan 1, 2003 22:15:02", "Jan 2, 2003  4:43:29",
                          "Jan 4, 2003  9:55:30", "Jan 4, 2003 11:26:52",
                          "Jan 5, 2003 11:09:17", "Jan 5, 2003 13:00:41",
                          "Jan 6, 2003 00:08:13", "Jan 6, 2003  2:18:01"
                        };

          /*
          A second set of intervals representing the times for which
          an acceptable phase angle exits between the ground station,
          the body and the Sun.
          */
          SpiceChar   phase [MAXSIZ][UTCLEN] =
                        { "Jan 2, 2003 00:03:30", "Jan 2, 2003 19:00:00",
                          "Jan 3, 2003  8:00:00", "Jan 3, 2003  9:50:00",
                          "Jan 5, 2003 12:00:00", "Jan 5, 2003 12:45:00",
                          "Jan 6, 2003 00:30:00", "Jan 6, 2003 23:00:00"
                        };

          SpiceDouble      left;
          SpiceDouble      right;
          SpiceDouble      meas;
          SpiceDouble      avg;
          SpiceDouble      stddev;
          SpiceDouble      los_et [MAXSIZ];
          SpiceDouble      phs_et [MAXSIZ];

          /* Load our meta kernel for the leapseconds data. */
          furnsh_c ( "meta.tm" );

          /*
          Windows consist of double precision values, convert the
          time tags defined in the LOS and PHASE arrays to
          double precision ET. Store the double values in the
          loswin and phswin arrays.
          */
          for ( i=0; i < MAXSIZ; ++i )
             {
             str2et_c ( los[i]  , &los_et[i] );
             str2et_c ( phase[i], &phs_et[i] );
             }

          /*
          Initialize the cells from the double precision arrays,
          then validate the cells as windows.

          Since we use 4 intervals, set the window to accept 8 (MAXSIZ)
          data values ( 4 * 2 = 8 ). Since we require no more than
          8 data values, assign a window size of 8.
          */

          memmove ( (SpiceDouble*)loswin.data,
                    los_et,
                    MAXSIZ * sizeof(SpiceDouble) );

          memmove ( (SpiceDouble*)phswin.data,
                    phs_et,
                    MAXSIZ * sizeof(SpiceDouble) );

          wnvald_c ( MAXSIZ, MAXSIZ, &loswin );
          wnvald_c ( MAXSIZ, MAXSIZ, &phswin );
          wnvald_c ( MAXSIZ, MAXSIZ, &sched  );

          /*
          The issue for consideration, at what times do line of
          sight events coincide with acceptable phase angles?
          Perform the set operation AND on loswin, phswin,
          place the results in the window 'sched'.
          */

          wnintd_c ( &loswin, &phswin, &sched );

          puts   ( " " );
          printf ( "No. data values in sched            : %d\n",
                                                   (int)card_c(&sched) );
          printf ( "Space available for values in sched : %d\n",
                                                   (int)size_c(&sched) );

          /*
          Output the results. The number of intervals in 'sched'
          is half the number of data points (the cardinality).
          Use a call to card_c to retrieve the window's cardinality.
          */
          puts ( " " );
          puts ( "Time intervals meeting defined criterion.");

          for ( i=0; i < card_c(&sched)/2 ; ++i )
             {

             /*
             Extract from the derived 'sched' the values defining the
             time intervals, [small, large].
             */
             wnfetd_c ( &sched, i, &left, &right );

             /*
             Convert the ET values to UTC for human comprehension.
             */
             et2utc_c ( left , "C", 3, UTCLEN, utcstr[0] );
             et2utc_c ( right, "C", 3, UTCLEN, utcstr[1] );

             /*
             Output the UTC string and the corresponding index
             for the interval.
             */
             printf ( " %d  %s %s\n", (int)i, utcstr[0], utcstr[1] );

             }

          puts ( " " );
          puts ( "Summary of sched window" );

          wnsumd_c ( &sched, &meas, &avg, &stddev, &small, &large );

          /*
          Summarize the 'sched' window.
          */
          printf( "o Total measure of sched    : %12.5f\n", meas   );
          printf( "o Average measure of sched  : %12.5f\n", avg    );
          printf( "o Standard deviation of\n "                     );
          printf(  " the measures in sched     : %12.5f\n", stddev );

          /*
          The values for small and large refer to the indexes of the
          values in the window ('sched'). The shortest interval is

                [ SPICE_CELL_ELEM_D( &sched, small),
                  SPICE_CELL_ELEM_D( &sched, small+1) ];

          the longest is

                [ SPICE_CELL_ELEM_D( &sched, large),
                  SPICE_CELL_ELEM_D( &sched, large+1) ];

          Output the indexes for the shortest and longest
          intervals. As C bases an array index on 0, the interval
          index is half the array index.
          */
          printf ( "o Index of shortest interval: %d\n", (int)small/2 );
          printf ( "o Index of longest interval : %d\n", (int)large/2 );

          exit (0);
          }
Top ### Run the code example The output window has the name SCHED (schedule). Output the amount of data held in SCHED compared to the maximum possible amount.
        No. data values in SCHED            :   6
        Space available for values in SCHED :   8
List the time intervals for which a line of sight exists during the time of a proper phase angle.
       Time intervals meeting defined criterion.
        0  2003 JAN 02 00:03:30.000 2003 JAN 02 04:43:29.000
        1  2003 JAN 05 12:00:00.000 2003 JAN 05 12:45:00.000
        2  2003 JAN 06 00:30:00.000 2003 JAN 06 02:18:01.000
Finally, an analysis of the SCHED data. The measure of an interval [a,b] (a <= b) equals b-a. Real values output in units of seconds.
       Summary of sched window
       o Total measure of sched    :  25980.00001
       o Average measure of sched  :   8660.00000
       o Standard deviation of
         the measures in sched     :   5958.55022
       o Index of shortest interval: 1
       o Index of longest interval : 0
Top # Lesson 7: Utility and Constants Routines Lesson Goals: CSPICE provides several routines to perform commonly needed tasks. Among these: `--` convert values between unit expressions `--` determine the equality of strings `--` indicate whether a file exists `--` identify the toolkit version CSPICE also includes a set of functions that return constant values often used in astrodynamics, time calculations, and geometry. Top ## Relevant Routines `--` convrt_c converts between measurements units `--` tkvrsn_c returns the current version of the toolkit `--` eqstr_c returns a boolean describing the equality of two strings. The comparison is case insensitive and ignores spaces. `--` exists_c returns a boolean indicating the existence of a file. `--` clight_c : velocity of light in a vacuum, kilometers per second `--` dpr_c : number of degrees per radian (180/Pi) `--` rpd_c : number radians per degree (Pi/180) `--` spd_c : number of seconds per day (60*60*24) `--` b1900_c : Julian Date of the epoch Besselian Date 1900.0 `--` b1950_c : Julian date of the epoch Besselian Date 1950.0 `--` j1900_c : Julian date of 1900 JAN 0.5 this corresponds to calendar date 1899 DEC 31 12:00:00 `--` j1950_c : Julian date of 1950 JAN 1.0 this corresponds to calendar date 1950 JAN 01 00:00:00 `--` j2000_c : Julian date of 2000 JAN 1.5 (2000 JAN 01 12:00:00) `--` j2100_c : Julian date of 2100 JAN 1.5, this corresponds to calendar date 2100 JAN 01 12:00:00 `--` twopi_c : double precision value of 2 * Pi `--` pi_c : double precision value of Pi `--` halfpi_c : double precision value of 0.5 * Pi `--` jyear_c : seconds per Julian year (365.25 Julian days) `--` tyear_c : seconds per tropical year (approximately the number of seconds from one spring equinox to the next) Top ## Requirements and References The references used to define or calculate the constants functions are found in the source code file and/or the API reference. Also reference the other_functions.ppt tutorial file. Top ## Programming Task Write an interactive program to convert values between various units. Demonstrate the flexibility of the unit conversion routine, the string equality function, and show the version ID function. Top ## Code Solution
       #include <stdio.h>
       #include <stdlib.h>
       #include <string.h>
       #include "SpiceUsr.h"

       #define UTCLEN       32

       void tostan ( SpiceChar * alias );

       int main( int argc, char **argv )
          {

          /*
          Define the few variables needed for data input
          and output.
          */

          SpiceChar           funits [UTCLEN];
          SpiceChar           tunits [UTCLEN];
          SpiceChar           fromstr[UTCLEN];
          SpiceDouble         fvalue;
          SpiceDouble         tvalue;

          /*
          Define the tkvrsn_c return value.
          */
          ConstSpiceChar     * vers;

          /*
          Display the Toolkit version string with a
          tkvrsn_c call.
          */
          vers = tkvrsn_c( "TOOLKIT" );
          printf( "\n Convert demo program compiled against "
                     "CSPICE Toolkit %s\n\n", vers );

          /*
          The user first inputs the name of a unit of measure.
          Send the name through TOSTAN for de-aliasing.
          */
          prompt_c ( "From Units : ", UTCLEN, funits );
          tostan   ( funits );

          /*
          Input a double precision value to express in a new
          unit format.
          */
          prompt_c ( "From Value : ", UTCLEN, fromstr );
          prsdp_c ( fromstr, &fvalue );

          /*
          Now the user inputs the name of the output units.
          Again we send the units name through TOSTAN for
          de-aliasing.
          */
          prompt_c ( "To Units   : ", UTCLEN, tunits );
          tostan ( tunits );

          convrt_c ( fvalue, funits, tunits, &tvalue );
          printf ( "%f %s\n", tvalue, tunits );

          exit(0);
          }

       void tostan ( SpiceChar * alias )
          {

          /*
          As a convenience, let's alias a few common terms
          to their appropriate counterpart. Use eqstr_c
          to compare strings. The comparison ignores
          letter case and trailing/leading spaces.
          */

          if ( eqstr_c ( alias, "meter" ) )
             {

             /*
             First, a 'meter' by any other name is a
             'METER' and smells as sweet ...
             */
             strcpy ( alias, "METERS");

             }
          else if ( eqstr_c ( alias, "klicks"     ) ||
                    eqstr_c ( alias, "kilometers" ) ||
                    eqstr_c ( alias, "kilometer"  )   )
             {

             /*
             ... 'klicks' and 'KILOMETERS' and
             'KILOMETER' identifies 'KM'....
             */
             strcpy ( alias, "KM");

             }
          else if ( eqstr_c ( alias, "secs") )
             {

             /*
             ... 'secs' to 'SECONDS'.
             */
             strcpy ( alias, "SECONDS");

             }
          else if ( eqstr_c ( alias, "miles") )
             {

             /*
             ... and finally 'miles' to 'STATUTE_MILES'.
             Normal people think in statute miles.
             Only sailors think in nautical miles - one
             minute of arc at the equator.
             */
             strcpy ( alias, "STATUTE_MILES");

             }

          /*
          Much better. Now return. If the input matched
          none of the aliases, this routine did nothing.
          */

          }
Top ### Run the code example Run a few conversions through the application to ensure it works. The intro banner gives us the Toolkit version against which the application was linked:
        Convert demo program compiled against CSPICE Toolkit CSPICE_N0060

       From Units : klicks
       From Value : 3
       To Units   : miles
       1.864114 STATUTE_MILES
Now we know. Three kilometers equals 1.864 miles. Legend states Pheidippides ran from the Marathon Plain to Athens. The modern marathon race (inspired by this event) spans 26.2 miles. How far in kilometers?
        Convert demo program compiled against CSPICE Toolkit CSPICE_N0060

       From Units : miles
       From Value : 26.2
       To Units   : km
       42.164813 km
Top ## Programming Task Write a program to output CSPICE constants and use those constants to calculate some rudimentary values. Top ## Code Solution
       #include <stdlib.h>
       #include <stdio.h>
       #include <strings.h>
       #include "SpiceUsr.h"

       int main( int argc, char **argv )
          {

          /*
          All the functions have the same calling sequence:

             VALUE = function_name();
             some_procedure( function_name() );
             printf ( "%19.12f\n", function_name() );

          First a simple example using the seconds per day
          constant...
          */
          printf ("Number of (S)econds (P)er (D)ay           : %19.12f\n",
                                                           spd_c() );

          /*
          ...then show the value of degrees per radian, 180/Pi...
          */
          printf ("Number of (D)egrees (P)er (R)adian        : %19.16f\n",
                                                           dpr_c() );

          /*
          ...and the inverse, radians per degree, Pi/180.
          It is obvious dpr_c() equals 1.0/rpd_c(), or more simply
          dpr_c() * rpd_c() equals 1.0.
          */
          printf("Number of (R)adians (P)er (D)egree        : %19.16f\n",
                                                           rpd_c() );

          /*
          What's the value for the astrophysicist's favorite
          physical constant (in a vacuum)?
          */
          printf ("Speed of light in KM per second           : %19.12f\n",
                                                         clight_c() );

          /*
          How long (in Julian days) from the J2000 epoch to the
          J2100 epoch?
          */
          printf ("Number of days between epochs J2000  \n"        );
          printf ("  and J2100                               : %19.12f\n",
                                             j2100_c() - j2000_c()  );

          /*
          Redo the calculation returning seconds...
          */
          printf ("Number of seconds between epochs\n"             );
          printf ("  J2000 and J2100                         : %19.5f\n",
                                 spd_c() * (j2100_c() - j2000_c() ) );

          /*
          ...then tropical years.
          */
          printf ( "Number of tropical years between\n"             );
          printf ( "  epochs J2000 and J2100                 : %19.12f\n",
                 ( spd_c() / tyear_c() ) * (j2100_c() - j2000_c() ) );

          /*
          Finally, how can I convert a radian value to degrees.
          */
          printf ("Number of degrees in Pi/2 radians of arc  : %19.16f\n",
                                               halfpi_c() * dpr_c() );

          /*
          and degrees to radians.
          */
          printf ("Number of radians in 250 degrees of arc   : %19.16f\n",
                                                        250. * rpd_c() );

          exit(0);
          }
Top ### Run the code example
       Number of (S)econds (P)er (D)ay           :  86400.000000000000
       Number of (D)egrees (P)er (R)adian        : 57.2957795130823229
       Number of (R)adians (P)er (D)egree        :  0.0174532925199433
       Speed of light in KM per second           : 299792.457999999984
       Number of days between epochs J2000
         and J2100                               :  36525.000000000000
       Number of seconds between epochs
         J2000 and J2100                         :    3155760000.00000
       Number of tropical years between
         epochs J2000 and J2100                  :    100.002135902909
       Number of degrees in Pi/2 radians of arc  : 90.0000000000000000
       Number of radians in 250 degrees of arc   :  4.3633231299858242