gfoclt_c

Index Page gfoclt_c
A B C D E F G H I J K L M N O P Q R S T U V W X
Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input | Detailed_Output Parameters Exceptions Files Particulars Examples | Restrictions Literature_References Author_and_Institution Version Index_Entries
#### Procedure
       void gfoclt_c ( ConstSpiceChar   * occtyp,
                       ConstSpiceChar   * front,
                       ConstSpiceChar   * fshape,
                       ConstSpiceChar   * fframe,
                       ConstSpiceChar   * back,
                       ConstSpiceChar   * bshape,
                       ConstSpiceChar   * bframe,
                       ConstSpiceChar   * abcorr,
                       ConstSpiceChar   * obsrvr,
                       SpiceDouble        step,
                       SpiceCell        * cnfine,
                       SpiceCell        * result )
#### Abstract
       Determine time intervals when an observer sees one target
       occulted by, or in transit across, another.
#### Required_Reading
       FRAMES
       GF
       KERNEL
       NAIF_IDS
       SPK
       TIME
       WINDOWS
#### Keywords
       EVENT
       GEOMETRY
       SEARCH
       WINDOW
#### Brief_I/O
       VARIABLE        I/O  DESCRIPTION
       --------------- ---  -------------------------------------------------
       SPICE_GF_CNVTOL  P   Convergence tolerance.
       occtyp           I   Type of occultation.
       front            I   Name of body occulting the other.
       fshape           I   Type of shape model used for front body.
       fframe           I   Body-fixed, body-centered frame for front body.
       back             I   Name of body occulted by the other.
       bshape           I   Type of shape model used for back body.
       bframe           I   Body-fixed, body-centered frame for back body.
       abcorr           I   Aberration correction flag.
       obsrvr           I   Name of the observing body.
       step             I   Step size in seconds for finding occultation
                            events.
       cnfine          I-O  SPICE window to which the search is restricted.
       result           O   SPICE window containing results.
#### Detailed_Input
       occtyp     indicates the type of occultation that is to be found.
                  Note that transits are considered to be a type of
                  occultation.

                  Supported values and corresponding definitions are:

                     "FULL"               denotes the full occultation
                                          of the body designated by
                                          `back' by the body designated
                                          by `front', as seen from
                                          the location of the observer.
                                          In other words, the occulted
                                          body is completely invisible
                                          as seen from the observer's
                                          location.

                     "ANNULAR"            denotes an annular
                                          occultation: the body
                                          designated by `front' blocks
                                          part of, but not the limb of,
                                          the body designated by `back',
                                          as seen from the location of
                                          the observer.

                     "PARTIAL"            denotes a partial, non-annular
                                          occultation: the body designated
                                          by `front' blocks part, but not
                                          all, of the limb of the body
                                          designated by `back', as seen
                                          from the location of the
                                          observer.

                     "ANY"                denotes any of the above three
                                          types of occultations:
                                          "PARTIAL", "ANNULAR", or
                                          "FULL".

                                          "ANY" should be used to search
                                          for times when the body
                                          designated by `front' blocks
                                          any part of the body designated
                                          by `back'.

                                          The option "ANY" must be used
                                          if either the front or back
                                          target body is modeled as
                                          a point.

                  Case and leading or trailing blanks are not
                  significant in the string `occtyp'.

       front      is the name of the target body that occults---that is,
                  passes in front of---the other. Optionally, you may
                  supply the integer NAIF ID code for the body as a
                  string. For example both "MOON" and "301" are
                  legitimate strings that designate the Moon.

                  Case and leading or trailing blanks are not
                  significant in the string `front'.

       fshape     is a string indicating the geometric model used to
                  represent the shape of the front target body. The
                  supported options are:

                     "ELLIPSOID"     Use a triaxial ellipsoid model
                                     with radius values provided via the
                                     kernel pool. A kernel variable
                                     having a name of the form

                                        "BODYnnn_RADII"

                                     where nnn represents the NAIF
                                     integer code associated with the
                                     body, must be present in the kernel
                                     pool. This variable must be
                                     associated with three numeric
                                     values giving the lengths of the
                                     ellipsoid's X, Y, and Z semi-axes.

                     "POINT"         Treat the body as a single point.
                                     When a point target is specified,
                                     the occultation type must be
                                     set to "ANY".

                  At least one of the target bodies `front' and `back' must
                  be modeled as an ellipsoid.

                  Case and leading or trailing blanks are not
                  significant in the string `fshape'.

       fframe     is the name of the body-fixed, body-centered reference
                  frame associated with the front target body. Examples
                  of such names are "IAU_SATURN" (for Saturn) and
                  "ITRF93" (for the Earth).

                  If the front target body is modeled as a point, `fframe'
                  should be left empty or blank.

                  Case and leading or trailing blanks bracketing a
                  non-blank frame name are not significant in the string
                  `fframe'.

       back       is the name of the target body that is occulted
                  by---that is, passes in back of---the other.
                  Optionally, you may supply the integer NAIF ID code
                  for the body as a string. For example both "MOON" and
                  "301" are legitimate strings that designate the Moon.

                  Case and leading or trailing blanks are not
                  significant in the string `back'.

       bshape     is the shape specification for the body designated by
                  `back'. The supported options are those for `fshape'. See
                  the description of `fshape' above for details.

       bframe     is the name of the body-fixed, body-centered reference
                  frame associated with the ``back'' target body.
                  Examples of such names are "IAU_SATURN" (for Saturn)
                  and "ITRF93" (for the Earth).

                  If the back target body is modeled as a point, `bframe'
                  should be left empty or blank.

                  Case and leading or trailing blanks bracketing a
                  non-blank frame name are not significant in the string
                  `bframe'.

       abcorr     indicates the aberration corrections to be applied to
                  the state of each target body to account for one-way
                  light time.  Stellar aberration corrections are
                  ignored if specified, since these corrections don't
                  improve the accuracy of the occultation determination.

                  See the header of the SPICE routine spkezr_c for a
                  detailed description of the aberration correction
                  options. For convenience, the options supported by
                  this routine are listed below:

                     "NONE"     Apply no correction.

                     "LT"       "Reception" case:  correct for
                                one-way light time using a Newtonian
                                formulation.

                     "CN"       "Reception" case:  converged
                                Newtonian light time correction.

                     "XLT"      "Transmission" case:  correct for
                                one-way light time using a Newtonian
                                formulation.

                     "XCN"      "Transmission" case:  converged
                                Newtonian light time correction.

                  Case and blanks are not significant in the string
                  `abcorr'.

       obsrvr     is the name of the body from which the occultation is
                  observed. Optionally, you may supply the integer NAIF
                  ID code for the body as a string.

                  Case and leading or trailing blanks are not
                  significant in the string `obsrvr'.

       step       is the step size to be used in the search. `step' must
                  be shorter than any interval, within the confinement
                  window, over which the specified condition is met. In
                  other words, `step' must be shorter than the shortest
                  occultation event that the user wishes to detect; `step'
                  must also be shorter than the shortest time interval
                  between two occultation events that occur within the
                  confinement window (see below). However, `step' must not
                  be *too* short, or the search will take an unreasonable
                  amount of time.

                  The choice of `step' affects the completeness but not the
                  precision of solutions found by this routine; the
                  precision is controlled by the convergence tolerance. See
                  the discussion of the parameter SPICE_GF_CNVTOL for
                  details.

                  `step' has units of TDB seconds.

       cnfine     is a SPICE window that confines the time period over
                  which the specified search is conducted. `cnfine' may
                  consist of a single interval or a collection of
                  intervals.

                  The endpoints of the time intervals comprising `cnfine'
                  are interpreted as seconds past J2000 TDB.

                  See the Examples section below for a code example
                  that shows how to create a confinement window.
#### Detailed_Output
       cnfine     is the input confinement window, updated if necessary
                  so the control area of its data array indicates the
                  window's size and cardinality. The window data are
                  unchanged.

       result     is a SPICE window representing the set of time
                  intervals, within the confinement period, when the
                  specified occultation occurs.

                  The endpoints of the time intervals comprising `result'
                  are interpreted as seconds past J2000 TDB.

                  If `result' is non-empty on input, its contents
                  will be discarded before gfoclt_c conducts its
                  search.
#### Parameters
       SPICE_GF_CNVTOL

                  is the convergence tolerance used for finding endpoints
                  of the intervals comprising the result window.
                  SPICE_GF_CNVTOL is used to determine when binary searches
                  for roots should terminate: when a root is bracketed
                  within an interval of length SPICE_GF_CNVTOL, the root is
                  considered to have been found.

                  The accuracy, as opposed to precision, of roots found
                  by this routine depends on the accuracy of the input
                  data. In most cases, the accuracy of solutions will be
                  inferior to their precision.

                  SPICE_GF_CNVTOL is declared in the header file

                     SpiceGF.h
#### Exceptions
       1)  In order for this routine to produce correct results,
           the step size must be appropriate for the problem at hand.
           Step sizes that are too large may cause this routine to miss
           roots; step sizes that are too small may cause this routine
           to run unacceptably slowly and in some cases, find spurious
           roots.

           This routine does not diagnose invalid step sizes, except
           that if the step size is non-positive, the error
           SPICE(INVALIDSTEPSIZE) will be signaled.

       2)  Due to numerical errors, in particular,

              - Truncation error in time values
              - Finite tolerance value
              - Errors in computed geometric quantities

           it is *normal* for the condition of interest to not always be
           satisfied near the endpoints of the intervals comprising the
           result window.

           The result window may need to be contracted slightly by the
           caller to achieve desired results. The SPICE window routine
           wncond_c can be used to contract the result window.

       3)  If name of either target or the observer cannot be translated
           to a NAIF ID code, the error will be diagnosed by a routine
           in the call tree of this routine.

       4)  If the radii of a target body modeled as an ellipsoid cannot
           be determined by searching the kernel pool for a kernel
           variable having a name of the form

              "BODYnnn_RADII"

           where nnn represents the NAIF integer code associated with
           the body, the error will be diagnosed by a routine in the
           call tree of this routine.

       5)  If either of the target bodies `front' or `back' coincides with
           the observer body `obsrvr', the error will be diagnosed by a
           routine in the call tree of this routine.

       6)  If the body designated by `front' coincides with that
           designated by `back', the error will be diagnosed by a routine
           in the call tree of this routine.

       7)  If either of the body model specifiers `fshape' or `bshape'
           is not recognized, the error will be diagnosed by a routine
           in the call tree of this routine.

       8)  If both of the body model specifiers `fshape' and `bshape'
           specify point targets, the error will be diagnosed by a
           routine in the call tree of this routine.

       9)  If a target body-fixed reference frame associated with a
           non-point target is not recognized, the error will be
           diagnosed by a routine in the call tree of this routine.

       10) If a target body-fixed reference frame is not centered at
           the corresponding target body,  the error will be
           diagnosed by a routine in the call tree of this routine.

       11) If the loaded kernels provide insufficient data to
           compute any required state vector, the deficiency will
           be diagnosed by a routine in the call tree of this routine.

       12) If an error occurs while reading an SPK or other kernel file,
           the error will be diagnosed by a routine in the call tree
           of this routine.

       13) If the output SPICE window `result' has insufficient capacity
           to contain the number of intervals on which the specified
           occultation condition is met, the error will be diagnosed
           by a routine in the call tree of this routine.

       14) If a point target is specified and the occultation
           type is set to a valid value other than "ANY", the
           error will be diagnosed by a routine in the call tree
           of this routine.

       15) Invalid occultation types will be diagnosed by a routine in
           the call tree of this routine.

       16) Invalid aberration correction specifications will be
           diagnosed by a routine in the call tree of this routine.

       17) If any input string argument pointer is null, the error
           SPICE(NULLPOINTER) will be signaled.

       18) If any input string argument, other than `fframe' or `bframe',
           is empty, the error SPICE(EMPTYSTRING) will be signaled.
#### Files
       Appropriate SPICE kernels must be loaded by the calling program
       before this routine is called.

       The following data are required:

          - SPK data: the calling application must load ephemeris data
            for the target, source and observer that cover the time
            period specified by the window `cnfine'. If aberration
            corrections are used, the states of target and observer
            relative to the solar system barycenter must be calculable
            from the available ephemeris data. Typically ephemeris data
            are made available by loading one or more SPK files via
            furnsh_c.

          - PCK data: bodies modeled as triaxial ellipsoids must have
            semi-axis lengths provided by variables in the kernel pool.
            Typically these data are made available by loading a text
            PCK file via furnsh_c.

          - FK data: if either of the reference frames designated by
            `bframe' or `fframe' are not built in to the SPICE system,
            one or more FKs specifying these frames must be loaded.

       Kernel data are normally loaded once per program run, NOT every time
       this routine is called.
#### Particulars
       This routine provides a simpler, but less flexible, interface
       than does the CSPICE routine gfocce_c for conducting searches for
       occultation events. Applications that require support for
       progress reporting, interrupt handling, non-default step or
       refinement functions, or non-default convergence tolerance should
       call gfocce_c rather than this routine.

       This routine determines a set of one or more time intervals
       within the confinement window when a specified type of
       occultation occurs. The resulting set of intervals is returned as
       a SPICE window.

       Below we discuss in greater detail aspects of this routine's
       solution process that are relevant to correct and efficient
       use of this routine in user applications.

       The Search Process
       ==================

       The search for occultations is treated as a search for state
       transitions: times are sought when the state of the `back' body
       changes from "not occulted" to "occulted" or vice versa.

       Step Size
       =========

       Each interval of the confinement window is searched as follows:
       first, the input step size is used to determine the time separation
       at which the occultation state will be sampled. Starting at the left
       endpoint of the interval, samples of the occultation state will be
       taken at each step. If a state change is detected, a root has been
       bracketed; at that point, the "root"--the time at which the state
       change occurs---is found by a refinement process, for example, via
       binary search.

       Note that the optimal choice of step size depends on the lengths
       of the intervals over which the occultation state is constant:
       the step size should be shorter than the shortest occultation
       duration and the shortest period between occultations, within
       the confinement window.

       Having some knowledge of the relative geometry of the targets and
       observer can be a valuable aid in picking a reasonable step size.
       In general, the user can compensate for lack of such knowledge by
       picking a very short step size; the cost is increased computation
       time.

       Note that the step size is not related to the precision with which
       the endpoints of the intervals of the result window are computed.
       That precision level is controlled by the convergence tolerance.

       Convergence Tolerance
       =====================

       Once a root has been bracketed, a refinement process is used to
       narrow down the time interval within which the root must lie. This
       refinement process terminates when the location of the root has been
       determined to within an error margin called the "convergence
       tolerance." The convergence tolerance used by this routine is set
       via the parameter SPICE_GF_CNVTOL.

       The value of SPICE_GF_CNVTOL is set to a "tight" value so that the
       tolerance doesn't limit the accuracy of solutions found by this
       routine. In general the accuracy of input data will be the limiting
       factor.

       To use a different tolerance value, a lower-level GF routine such as
       gfocce_c must be called. Making the tolerance tighter than
       SPICE_GF_CNVTOL is unlikely to be useful, since the results are
       unlikely to be more accurate. Making the tolerance looser will speed
       up searches somewhat, since a few convergence steps will be omitted.
       However, in most cases, the step size is likely to have a much
       greater effect on processing time than would the convergence
       tolerance.

       The Confinement Window
       ======================

       The simplest use of the confinement window is to specify a time
       interval within which a solution is sought.

       The confinement window also can be used to restrict a search to
       a time window over which required data (typically ephemeris
       data, in the case of occultation searches) are known to be
       available.

       In some cases, the confinement window be used to make searches
       more efficient. Sometimes it's possible to do an efficient search
       to reduce the size of the time period over which a relatively
       slow search of interest must be performed. See the "CASCADE"
       example program in gf.req for a demonstration.
#### Examples
       The numerical results shown for these examples 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) Find occultations of the Sun by the Moon (that is, solar
          eclipses) as seen from the center of the Earth over the month
          December, 2001.

          Use light time corrections to model apparent positions of Sun
          and Moon. Stellar aberration corrections are not specified
          because they don't affect occultation computations.

          We select a step size of 3 minutes, which means we
          ignore occultation events lasting less than 3 minutes,
          if any exist.

          Use the meta-kernel shown below to load the required SPICE
          kernels.

             KPL/MK

             File name: standard.tm

             This meta-kernel is intended to support operation of SPICE
             example programs. The kernels shown here should not be
             assumed to contain adequate or correct versions of data
             required by SPICE-based user applications.

             In order for an application to use this meta-kernel, the
             kernels referenced here must be present in the user's
             current working directory.

             \begindata

                KERNELS_TO_LOAD = ( 'de421.bsp',
                                    'pck00008.tpc',
                                    'naif0009.tls'  )

             \begintext

          Example code begins here.

             #include <stdio.h>
             #include "SpiceUsr.h"

             int main()
             {
                /.
                Local constants
                ./

                #define TIMFMT          "YYYY MON DD HR:MN:SC.###### (TDB)::TDB"
                #define MAXWIN          200
                #define TIMLEN          41

                /.
                Local variables
                ./
                SPICEDOUBLE_CELL      ( cnfine, MAXWIN );
                SPICEDOUBLE_CELL      ( result, MAXWIN );

                SpiceChar             * win0;
                SpiceChar             * win1;
                SpiceChar               begstr [ TIMLEN ];
                SpiceChar               endstr [ TIMLEN ];

                SpiceDouble             et0;
                SpiceDouble             et1;
                SpiceDouble             left;
                SpiceDouble             right;
                SpiceDouble             step;

                SpiceInt                i;

                /.
                Load kernels.
                ./
                furnsh_c ( "standard.tm" );

                /.
                Obtain the TDB time bounds of the confinement
                window, which is a single interval in this case.
                ./
                win0 = "2001 DEC 01 00:00:00 TDB";
                win1 = "2002 JAN 01 00:00:00 TDB";

                str2et_c ( win0, &et0 );
                str2et_c ( win1, &et1 );

                /.
                Insert the time bounds into the confinement
                window.
                ./
                wninsd_c ( et0, et1, &cnfine );

                /.
                Select a 3-minute step. We'll ignore any occultations
                lasting less than 3 minutes.  Units are TDB seconds.
                ./
                step = 180.0;

                /.
                Perform the search.
                ./
                gfoclt_c ( "any",
                           "moon",    "ellipsoid",  "iau_moon",
                           "sun",     "ellipsoid",  "iau_sun",
                           "lt",      "earth",      step,
                           &cnfine,   &result                 );

                if ( wncard_c(&result) == 0 )
                {
                   printf ( "No occultation was found.\n" );
                }
                else
                {
                   for ( i = 0;  i < wncard_c(&result); i++ )
                   {
                      /.
                      Fetch and display each occultation interval.
                      ./
                      wnfetd_c ( &result, i, &left, &right );

                      timout_c ( left,  TIMFMT, TIMLEN, begstr );
                      timout_c ( right, TIMFMT, TIMLEN, endstr );

                      printf ( "Interval %ld\n"
                               "   Start time: %s\n"
                               "   Stop time:  %s\n",
                               i, begstr, endstr      );
                   }
                }

                return ( 0 );
             }

          When this program was executed on a PC/Linux/gcc platform, the
          output was:

             Interval 0
                Start time: 2001 DEC 14 20:10:14.195952 (TDB)
                Stop time:  2001 DEC 14 21:35:50.317994 (TDB)

       2) Find occultations of Titan by Saturn or of Saturn by
          Titan as seen from the center of the Earth over the
          last four months of 2008. Model both target bodies as
          ellipsoids. Search for every type of occultation.

          Use light time corrections to model apparent positions of
          Saturn and Titan. Stellar aberration corrections are not
          specified because they don't affect occultation computations.

          We select a step size of 15 minutes, which means we
          ignore occultation events lasting less than 15 minutes,
          if any exist.

          Use the meta-kernel shown below to load the required SPICE
          kernels.

             KPL/MK

             File name: gfoclt_ex2.tm

             This meta-kernel is intended to support operation of SPICE
             example programs. The kernels shown here should not be
             assumed to contain adequate or correct versions of data
             required by SPICE-based user applications.

             In order for an application to use this meta-kernel, the
             kernels referenced here must be present in the user's
             current working directory.

             The names and contents of the kernels referenced
             by this meta-kernel are as follows:

                File name                     Contents
                ---------                     --------
                de421.bsp                     Planetary ephemeris
                sat288.bsp                    Satellite ephemeris for
                                              Saturn
                pck00008.tpc                  Planet orientation and
                                              radii
                naif0009.tls                  Leapseconds

             \begindata

                KERNELS_TO_LOAD = ( 'de421.bsp',
                                    'sat288.bsp',
                                    'pck00008.tpc',
                                    'naif0009.tls'  )

             \begintext

             End of meta-kernel

         Example code begins here.

            #include <stdio.h>
            #include <string.h>
            #include "SpiceUsr.h"

            int main()
            {
               /.
               Local constants
               ./
               #define TIMFMT          "YYYY MON DD HR:MN:SC.###### (TDB)::TDB"
               #define MAXWIN          200
               #define TIMLEN          41
               #define LNSIZE          81
               #define NTYPES          4

               /.
               Local variables
               ./
               SPICEDOUBLE_CELL      ( cnfine, MAXWIN );
               SPICEDOUBLE_CELL      ( result, MAXWIN );

               SpiceChar             * back;
               SpiceChar             * bframe;
               SpiceChar             * front;
               SpiceChar             * fframe;
               SpiceChar               line   [ LNSIZE ];
               SpiceChar             * obsrvr;

               SpiceChar             * occtyp [ NTYPES ] =
                                       {
                                          "FULL",
                                          "ANNULAR",
                                          "PARTIAL",
                                          "ANY"
                                       };

               SpiceChar             * templt [ NTYPES ] =
                                       {
                                          "Condition: # occultation of # by #",
                                          "Condition: # occultation of # by #",
                                          "Condition: # occultation of # by #",
                                          "Condition: # occultation of # by #"
                                       };

               SpiceChar               timstr [ TIMLEN ];
               SpiceChar               title  [ LNSIZE ];
               SpiceChar             * win0;
               SpiceChar             * win1;

               SpiceDouble             et0;
               SpiceDouble             et1;
               SpiceDouble             finish;
               SpiceDouble             start;
               SpiceDouble             step;

               SpiceInt                i;
               SpiceInt                j;
               SpiceInt                k;

               /.
               Load kernels.
               ./
               furnsh_c ( "gfoclt_ex2.tm" );

               /.
               Obtain the TDB time bounds of the confinement
               window, which is a single interval in this case.
               ./
               win0 = "2008 SEP 01 00:00:00 TDB";
               win1 = "2009 JAN 01 00:00:00 TDB";

               str2et_c ( win0, &et0 );
               str2et_c ( win1, &et1 );

               /.
               Insert the time bounds into the confinement
               window.
               ./
               wninsd_c ( et0, et1, &cnfine );

               /.
               Select a 15-minute step. We'll ignore any occultations
               lasting less than 15 minutes. Units are TDB seconds.
               ./
               step = 900.0;

               /.
               The observation location is the Earth.
               ./
               obsrvr = "Earth";

               /.
               Loop over the occultation types.
               ./
               for ( i = 0;  i < NTYPES;  i++ )
               {
                  /.
                  For each type, do a search for both transits of
                  Titan across Saturn and occultations of Titan by
                  Saturn.
                  ./
                  for ( j = 0;  j < 2;  j++ )
                  {
                     if ( j == 0 )
                     {
                        front  = "TITAN";
                        fframe = "IAU_TITAN";
                        back   = "SATURN";
                        bframe = "IAU_SATURN";
                     }
                     else
                     {
                        front  = "SATURN";
                        fframe = "IAU_SATURN";
                        back   = "TITAN";
                        bframe = "IAU_TITAN";
                     }

                     /.
                     Perform the search. The target body shapes
                     are modeled as ellipsoids.
                     ./
                     gfoclt_c ( occtyp[i],
                                front,    "ellipsoid",  fframe,
                                back,     "ellipsoid",  bframe,
                                "lt",     obsrvr,       step,
                                &cnfine,  &result               );

                     /.
                     Display the results.
                     ./
                     printf ( "\n" );

                     /.
                     Substitute the occultation type and target
                     body names into the title string:
                     ./
                     repmc_c ( templt[i], "#", occtyp[i], LNSIZE, title );
                     repmc_c ( title,     "#", back,      LNSIZE, title );
                     repmc_c ( title,     "#", front,     LNSIZE, title );

                     printf ( "%s\n", title );

                     if ( wncard_c(&result) == 0 )
                     {
                        printf ( " Result window is empty: "
                                 "no occultation was found.\n" );
                     }
                     else
                     {
                        printf ( " Result window start, stop times:\n" );

                        for ( k = 0;  k < wncard_c(&result);  k++ )
                        {
                           /.
                           Fetch the endpoints of the kth interval
                           of the result window.
                           ./
                           wnfetd_c ( &result, k, &start, &finish );

                           /.
                           Call strncpy with a length of 7 to include
                           a terminating null.
                           ./
                           strncpy ( line, "  #  #", 7 );

                           timout_c ( start,  TIMFMT, TIMLEN, timstr );

                           repmc_c  ( line, "#", timstr, LNSIZE, line );

                           timout_c ( finish, TIMFMT, TIMLEN, timstr );

                           repmc_c  ( line, "#", timstr, LNSIZE, line );

                           printf ( "%s\n", line );
                        }
                     }
                     /.
                     We've finished displaying the results of the
                     current search.
                     ./
                  }
                  /.
                  We've finished displaying the results of the
                  searches using the current occultation type.
                  ./
               }
               printf ( "\n" );

               return ( 0 );
            }

          When this program was executed on a PC/Linux/gcc platform, the
          output was:

             Condition: FULL occultation of SATURN by TITAN
              Result window is empty: no occultation was found.

             Condition: FULL occultation of TITAN by SATURN
              Result window start, stop times:
               2008 OCT 27 22:08:01.627053 (TDB)  2008 OCT 28 01:05:03.375236 (TDB)
               2008 NOV 12 21:21:59.252262 (TDB)  2008 NOV 13 02:06:05.053051 (TDB)
               2008 NOV 28 20:49:02.402832 (TDB)  2008 NOV 29 02:13:58.986344 (TDB)
               2008 DEC 14 20:05:09.246177 (TDB)  2008 DEC 15 01:44:53.523002 (TDB)
               2008 DEC 30 19:00:56.577073 (TDB)  2008 DEC 31 00:42:43.222909 (TDB)

             Condition: ANNULAR occultation of SATURN by TITAN
              Result window start, stop times:
               2008 OCT 19 21:29:20.599087 (TDB)  2008 OCT 19 22:53:34.518737 (TDB)
               2008 NOV 04 20:15:38.620368 (TDB)  2008 NOV 05 00:18:59.139978 (TDB)
               2008 NOV 20 19:38:59.647712 (TDB)  2008 NOV 21 00:35:26.725908 (TDB)
               2008 DEC 06 18:58:34.073268 (TDB)  2008 DEC 07 00:16:17.647040 (TDB)
               2008 DEC 22 18:02:46.288289 (TDB)  2008 DEC 22 23:26:52.712459 (TDB)

             Condition: ANNULAR occultation of TITAN by SATURN
              Result window is empty: no occultation was found.

             Condition: PARTIAL occultation of SATURN by TITAN
              Result window start, stop times:
               2008 OCT 19 20:44:30.326771 (TDB)  2008 OCT 19 21:29:20.599087 (TDB)
               2008 OCT 19 22:53:34.518737 (TDB)  2008 OCT 19 23:38:26.250580 (TDB)
               2008 NOV 04 19:54:40.339331 (TDB)  2008 NOV 04 20:15:38.620368 (TDB)
               2008 NOV 05 00:18:59.139978 (TDB)  2008 NOV 05 00:39:58.612935 (TDB)
               2008 NOV 20 19:21:46.689523 (TDB)  2008 NOV 20 19:38:59.647712 (TDB)
               2008 NOV 21 00:35:26.725908 (TDB)  2008 NOV 21 00:52:40.604703 (TDB)
               2008 DEC 06 18:42:36.100544 (TDB)  2008 DEC 06 18:58:34.073268 (TDB)
               2008 DEC 07 00:16:17.647040 (TDB)  2008 DEC 07 00:32:16.324244 (TDB)
               2008 DEC 22 17:47:10.776722 (TDB)  2008 DEC 22 18:02:46.288289 (TDB)
               2008 DEC 22 23:26:52.712459 (TDB)  2008 DEC 22 23:42:28.850542 (TDB)

             Condition: PARTIAL occultation of TITAN by SATURN
              Result window start, stop times:
               2008 OCT 27 21:37:16.970175 (TDB)  2008 OCT 27 22:08:01.627053 (TDB)
               2008 OCT 28 01:05:03.375236 (TDB)  2008 OCT 28 01:35:49.266506 (TDB)
               2008 NOV 12 21:01:47.105498 (TDB)  2008 NOV 12 21:21:59.252262 (TDB)
               2008 NOV 13 02:06:05.053051 (TDB)  2008 NOV 13 02:26:18.227357 (TDB)
               2008 NOV 28 20:31:28.522707 (TDB)  2008 NOV 28 20:49:02.402832 (TDB)
               2008 NOV 29 02:13:58.986344 (TDB)  2008 NOV 29 02:31:33.691598 (TDB)
               2008 DEC 14 19:48:27.094229 (TDB)  2008 DEC 14 20:05:09.246177 (TDB)
               2008 DEC 15 01:44:53.523002 (TDB)  2008 DEC 15 02:01:36.360243 (TDB)
               2008 DEC 30 18:44:23.485898 (TDB)  2008 DEC 30 19:00:56.577073 (TDB)
               2008 DEC 31 00:42:43.222909 (TDB)  2008 DEC 31 00:59:17.030568 (TDB)

             Condition: ANY occultation of SATURN by TITAN
              Result window start, stop times:
               2008 OCT 19 20:44:30.326771 (TDB)  2008 OCT 19 23:38:26.250580 (TDB)
               2008 NOV 04 19:54:40.339331 (TDB)  2008 NOV 05 00:39:58.612935 (TDB)
               2008 NOV 20 19:21:46.689523 (TDB)  2008 NOV 21 00:52:40.604703 (TDB)
               2008 DEC 06 18:42:36.100544 (TDB)  2008 DEC 07 00:32:16.324244 (TDB)
               2008 DEC 22 17:47:10.776722 (TDB)  2008 DEC 22 23:42:28.850542 (TDB)

             Condition: ANY occultation of TITAN by SATURN
              Result window start, stop times:
               2008 OCT 27 21:37:16.970175 (TDB)  2008 OCT 28 01:35:49.266506 (TDB)
               2008 NOV 12 21:01:47.105498 (TDB)  2008 NOV 13 02:26:18.227357 (TDB)
               2008 NOV 28 20:31:28.522707 (TDB)  2008 NOV 29 02:31:33.691598 (TDB)
               2008 DEC 14 19:48:27.094229 (TDB)  2008 DEC 15 02:01:36.360243 (TDB)
               2008 DEC 30 18:44:23.485898 (TDB)  2008 DEC 31 00:59:17.030568 (TDB)
#### Restrictions
       The kernel files to be used by gfoclt_c must be loaded (normally via
       the CSPICE routine furnsh_c) before gfoclt_c is called.
#### Literature_References
      None.
#### Author_and_Institution
      N. J. Bachman  (JPL)
      L. S. Elson    (JPL)
      E. D. Wright   (JPL)
#### Version
       -CSPICE Version 1.0.0, 07-APR-2009 (NJB) (LSE) (EDW)
#### Index_Entries
       GF occultation search
#### Link to routine gfoclt_c source file gfoclt_c.c

    Thu Apr 16 08:58:13 2009