KPL/SCLK

STEREO-BEHIND Science Spacecraft Clock Kernel (SCLK)
===========================================================================

     This file is a SPICE spacecraft clock (SCLK) kernel containing
     information required for time conversions involving the on-board
     STEREO-BEHIND spacecraft clock.
 
Version
--------------------------------------------------------

     STEREO-BEHIND Science SCLK Kernel Version:

     Version 0.1 -- September 16, 2004 -- Deane Sibol

        This kernel is static and will only be updated for leap seconds.
        The SCLK value is based on the raw STEREO_UTC reported from the
        spacecraft.  The clock rate assumes no drift from the parallel
        time system (TDT). Clock drift rate will be accounted for in the
        UTCF which is applied on the spacecraft to yield STEREO_UTC.
        The clock coefficients indicate the clock starts on the following
        epoch:

                   1/1451606400:0                 (SCLK)
                   01-JAN-2004-00:01:04.184       (TDT) 

        The end of the first partition is currently defined as the value
        in ticks of the rollover of the spacecraft clock (STEREO_UTC).
 
Usage
--------------------------------------------------------

     This file is used by the SPICE system as follows: programs that
     make use of this SCLK kernel must 'load' the kernel, normally
     during program initialization.  Loading the kernel associates
     the data items with their names in a data structure called the
     'kernel pool'.  The SPICELIB routine FURNSH loads text kernel
     files, such as this one, into the pool as shown below:

        FORTRAN:

                  CALL FURNSH ( SCLK_kernel_name )

        C:

                  furnsh_c ( SCLK_kernel_name );

     Once loaded, the SCLK time conversion routines will be able to
     access the necessary data located in this kernel for their 
     designed purposes.

References
--------------------------------------------------------
 
         1.   "SCLK Required Reading"

Inquiries
--------------------------------------------------------

     If you have any questions regarding this file or its usage, 
     contact:

           Scott Turner
           (443)778-1693
           Scott.Turner@jhuapl.edu

Kernel Data
--------------------------------------------------------

     The first block of keyword equals value assignments define the
     type, parallel time system, and format of the spacecraft clock.

     The STEREO-BEHIND Science spacecraft clock is represented by the SPICE
     type 1 SCLK kernel.  It uses TDT, Terrestrial Dynamical Time,
     as its parallel time system.

        \begindata

        SCLK_KERNEL_ID         = ( @2004-09-16T17:00:00 )
        SCLK_DATA_TYPE_235     = ( 1 )
        SCLK01_TIME_SYSTEM_235 = ( 2 ) 

        \begintext

     In a particular partition of the STEREO-BEHIND spacecraft clock,
     the clock read-out consists of two separate stages:

                           1/17314125:231

     The first stage, a 32 bit field, represents the spacecraft
     clock seconds count.  The second, an 8 bit field, represents
     a count of 1/256ths of a second of the spacecraft clock.

     The following keywords and their values establish this structure:

        \begindata

        SCLK01_N_FIELDS_235     = ( 2 )
        SCLK01_MODULI_235       = ( 4294967296  256 )
        SCLK01_OFFSETS_235      = (          0    0 )
        SCLK01_OUTPUT_DELIM_235 = ( 2 )

        \begintext

     This concludes the invariant portion of the SCLK kernel data.  The
     remaining sections of the kernel may require updates as the clock
     correlation coefficients evolve in time.  The first section below
     establishes the clock partitions.  The data in this section consists
     of two parallel arrays, which denote the start and end values in 
     ticks of each partition of the spacecraft clock.

     SPICE utilizes these two arrays to map from spacecraft clock ticks,
     determined with the usual modulo arithmetic, to encoded SCLK--the
     internal, monotonically increasing sequence used to tag various 
     data sources with spacecraft clock.

        \begindata

        SCLK_PARTITION_START_235 = ( 3.71611238400E+11 )
                                     
        SCLK_PARTITION_END_235   = ( 1.09951162777500E+12 )

        \begintext

     The remaining section of the SCLK kernel defines the clock correlation
     coefficients.  Each line contains a 'coefficient triple':

         Encoded SCLK at which Rate is introduced.
         Corresponding TDT Epoch at which Rate is introduced.
         Rate in TDT (seconds) / most significant clock count (~seconds).

     In this Science SCLK kernel, the encoded SCLK does -NOT- map to a Mission
     Elapsed Time (MET).  (For this, see the Operations SCLK kernel.)
     Instead, the encoded SCLK in this SCLK kernel maps to a representation
     of STEREO_UTC.

     SPICE uses linear extrapolation to convert between the parallel time
     system and encoded SCLK.  The triples are stored in the array defined
     below:

        \begindata

        SCLK01_COEFFICIENTS_235 = ( 

        0     @01-JAN-2004-00:01:04.184     1.00000000000

)        
        \begintext