KPL/SCLK

MER-2 SCLK File Implementing Approximate LST at EP55A2 Landing Site
===========================================================================

     This file is a SPICE spacecraft clock (SCLK) kernel that implements 
     Approximate Local Solar Time (ALST) accepted by the MER project. 
     This file contains information required to convert between ALST at 
     the MER-2 landing site EP55A2 and Ephemeris Time (ET) using SPICE SCLK 
     time conversion routines/tools.


References
--------------------------------------------------------

         2.   Ken Fujii, "MER LST - Continuous Time Option", 09/06/01

         1.   SCLK Required Reading Document
 
 
Implementation Details
--------------------------------------------------------

     Per [1], the MER-2 ALST starts at "True" LST0 - 10 local minutes
     and runs at a constant rate of 1.02749127 ET seconds in 1 local 
     Martian second.

     To implement correct counting of these fields in the SCLK 
     subsystem, the ALST0 is computed as "True" LST0 for the midnight 
     of SOL 1 shifted by 10 minutes, which at the EP55A2 landing site 
     corresponds to ET 126409039.0. 

     The second-to-second rate given above translates to the SCLK rate 
     of 8.877524572800E+04 ET seconds in 1 local day, which appears 
     in the COEFFICIENTS keyword below.

     The ID for this clock is chosen to be 254900 to indicate that 
     this is NOT a actual SCLK for the MER-2 but rather a convenient 
     way to implement ALST using SCLK subsystem of SPICE.


ALST Format
--------------------------------------------------------

     The ALST string, the conversion for which is provided by this SCLK
     file, consists of four fields:

          DDD:HR:MN:SC

     where:

          DDD  -- count of ALST (SOL) days
          HR   -- count of ALST hours
          MN   -- count of ALST minutes
          SC   -- count of ALST seconds


Usage
--------------------------------------------------------
 
     This file must be loaded into the user's program by a call to the
     FURNSH subroutine
 
          CALL FURNSH( 'this_file_name' )
 
     in order to use the SPICELIB SCLK family of subroutines to convert
     MER-2 ALST at the landing site EP55A2 to ET and vice versa.

     Once loaded, the SCE2S/sce2s_c.f routines can be used to convert 
     an ET time to an ALST string in the format DDD:HR:MN:SC:

          CALL SCE2S( -254900, ET,         ALST )
          sce2s_c   ( -254900, et, maxlen, alst )
 
     and the routines SCS2E/scs2e_c can be used for backward conversion --
     from ALST in DDD:HR:MN:SC format to ET:

          CALL SCS2E( -254900, ALST,  ET )
          scs2e_c   ( -254900, alst, &et )
   

Production/History of this SCLK file
--------------------------------------------------------
 
     This file was generated manually using the MER ALST definition 
     provided in [1] and the ALST0 reference point computed for the 
     landing site EP55A2.
 
 
Inquiries
--------------------------------------------------------
 
     If you have any questions regarding this file contact NAIF  at JPL
 
           Charles H. Acton, Jr
           (818) 354-3869
           Chuck.Acton@jpl.nasa.gov
 
           Boris V. Semenov
           (818) 354-8136
           Boris.Semenov@jpl.nasa.gov
 

Kernel DATA
--------------------------------------------------------

     \begindata

	 SCLK_KERNEL_ID               = ( @2001-12-02/10:00 )

	 SCLK_DATA_TYPE_254900        = ( 1 )
	 SCLK01_TIME_SYSTEM_254900    = ( 2 )
	 SCLK01_N_FIELDS_254900       = ( 4 )
	 SCLK01_MODULI_254900         = ( 24855 24 60 60 )
	 SCLK01_OFFSETS_254900        = ( 1     0  0  0  )
	 SCLK01_OUTPUT_DELIM_254900   = ( 2 )

	 SCLK_PARTITION_START_254900  = ( 0.0000000000000E+00 )

	 SCLK_PARTITION_END_254900    = ( 1.0995116277750E+12 )

	 SCLK01_COEFFICIENTS_254900   = ( 
	     0.0000000000000E+00     126409039.0    8.877524572800E+04 
				  )

     \begintext