EnVision CK files
==============================================================================

   This ``aareadme.txt'' file describes the contents of the kernels/ck
   directory of the EnVision SPICE Kernel Dataset.

   It was last modified on June 5, 2025 by Alfredo Escalante, ESAC/ESA.


Contact Information
-----------------------------------------------------------------------------

   If you have any questions regarding this file contact the
   ESA SPICE Service (ESS) at ESAC:

           Alfredo Escalante Lopez
           (+34) 91-8131-429
           spice@cosmos.esa.int


References and required readings
-----------------------------------------------------------------------------

   1. ``Frames Required Reading'', NAIF Document

   2. ``C-Kernel Required Reading'', NAIF Document

   3. ``SCLK Required Reading'', NAIF Document

   4. ``TIME Required Reading'', NAIF Document

   5. ``EnVision SCLK file naming conventions,'' aareadme.txt
      file in kernels/sclk directory.


Brief Summary
-----------------------------------------------------------------------------

   This directory contains the SPICE C-Kernel files for the EnVision
   spacecraft, its structures, and science instruments. Particularly,
   it contains data for the following EnVision frames:

       Frame Name              Relative to            NAIF ID
      -------------------     -------------------    ---------
      ENVISION_SPACECRAFT     J2000                    -668000


File naming conventions
-----------------------------------------------------------------------------

   EnVision spacecraft CK:

      The naming scheme for the EnVision spacecraft CK is:

         envision_INST_TYPE[_DESC][_ID]_[YYMMDD_YYMMDD]_[SCLK]_vNN.bc

      where

         INST     instrument/structure/sensor identifier (required):
         
                     sc          for the EnVision spacecraft planning or
                                 measured frame;

         TYPE      Data type, where a reference to the originator of the
                   data, the type of data and the and the reference period
                   is provided. The different types are:

                   default  S/C default attitude covering the full mission.
                            This is a test attitude and should only be used
                            by the EnVision SOC for planning analysis.

                      attc  S/C predicted attitude during cruise covering
                            until end of a commanding cycle from Flight
                            Dynamics.

                      attm  MTP S/C predicted attitude covering special
                            activities during GAMs or instrument checkouts
                            from Flight Dynamics.

                      meas  S/C measured as-flown attitude from the
                            housekeeping telemetry.

                      cmmd  S/C measured commanded attitude from the
                            housekeeping telemetry.

                      plan  S/C predicted attitude covering special
                            planning activities from the uplink group of
                            the Science Operations Center.

                       ptr  S/C test attitude covering planning exercise
                            periods and created by Science Operations Center
                            Uplink Group.

         DESC      description of the original reference file (optional);

                      e.g.  ET1_2031_northVOI_ML008

         YYMMDD    coverage start and stop times in TDB (optional);

         SCLK      reference to the SCLK used to create the CK (optional):

                       sYYMMDD: SCLK version YYMMDD for type ``step''
                       tYYMMDD: SCLK version YYMMDD for type ``stretch''
                       fYYMMDD: SCLK version YYMMDD for type ``fictional''

         NN        CK version number -- 2 digits (required).


      See [5] for further details on the SCLK types available to EnVision.

   If multiple versions of a C-Kernel file are provided, always use the latest 
   version (unless earlier version is needed for some special reasons.)


Other directory contents
-----------------------------------------------------------------------------

   aareadme.txt         This file.


Particulars
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   Nothing to report.


Kernel File Details
-----------------------------------------------------------------------------
   
   The most detailed description of the data in a binary CK file is
   provided in metadata included inside the comment area of the file.
   This information can be viewed using the utility programs COMMNT and
   SPACIT included in the NAIF Toolkit.


End of aareadme file.