PDS_VERSION_ID                = PDS3
RECORD_TYPE                   = STREAM
OBJECT                        = TEXT
  NOTE                        = "Comments on the MGS SPICE Archive"
  PUBLICATION_DATE            = 2013-01-07
END_OBJECT                    = TEXT
END


COMMENTS ON THE MGS SPICE DATA ARCHIVE
======================================

   This document contains comments and errata concerning the MGS SPICE
   Data Archive.


0. SPICE for TES
----------------

   The set of kernels included in the data set is not sufficient to
   compute derived geometry parameters for the TES instrument. 
   Specifically the data set is lacking:

      -- FOV definitions for the TES detectors in the TES IK file

      -- additional frames that would allow incorporating TES scanning
         mirror rotation in the FK file

      -- CK files capturing TES scanning mirror position as a function
         of time


1. Text Kernel File Format
--------------------------

   All SPICE text kernel files (LSK, PCK, SCLK, IK, FK) provided on
   these volumes have lines terminated by only <LF> (UNIX convention.)
   This is dictated by NAIF's archiving approach to include a
   consistent set of UNIX binary (IEEE architecture) and text (<LF>
   only for end of line marker) kernels on the archive volumes.

   However, the format of the text kernels is specified in their
   associated labels as ASCII (INTERCHANGE_FORMAT = ASCII.) This is a
   violation of the PDS standard stating that lines in ASCII files must
   be delimited by the combination of <CR><LF>. This line termination
   treatment is standard practice for SPICE volumes in the PDS.


2. Use of SPACECRAFT_NAME in the Labels
---------------------------------------

   PDS labels for SPICE kernels provided in this data set contain the
   deprecated keyword SPACECRAFT_NAME instead of the keyword
   INSTRUMENT_HOST_NAME. This is standard practice for SPICE volumes in
   the PDS and is dictated by NAIF's archiving approach to make SPICE
   archives for more recent missions consistent with SPICE archives for
   older missions, for which use of SPACECRAFT_NAME was legitimate.


3. Values of the VOLUME_SET_ID/VOLUME_ID Keyword in VOLDESC.CAT
---------------------------------------------------------------
 
   VOLUME_SET_ID and VOLUME_ID from VOLDESC.CAT are not used
   appropriately suggesting that there are multiple MGS SPICE Data
   volume sets each containing only one volume.
 
 
4. E-Kernel embedded labels
---------------------------
 
   Some E-Kernel text files have embedded labels which differ from the
   detached (.lbl) labels. Examples include DATA_SET_ID, START_TIME and
   PRODUCT_CREATION_TIME keyword values.


5. Values of INSTRUMENT_NAME in the Labels
------------------------------------------

   PDS labels for SPICE kernels provided in this data do not set the
   keyword INSTRUMENT_NAME to "SPICE KERNELS", that is the name of the
   instrument described by the instrument catalog file SPICE_INST.CAT
   provided in the data set. Instead this keyword is set to either
   "N/A" or the name(s) of the instrument(s) or structure(s), the
   geometric parameters of which a particular kernel file provides.
   While this error does prevent the individual data products from
   being associated with the "SPICE KERNELS" instrument, it does not
   affect usability of the SPICE data provided in this data set in any
   way because the SPICE toolkit does not use any information from the
   PDS label to access the data.

   The other side of this error is that the data set does not include
   instrument catalog files for the following instruments named in
   the INSTRUMENT_NAME keyword in the PDS labels:

      "MAGNETOMETER/ELECTRON REFLECTOMETER"
      "MARS ORBITER CAMERA"
      "MARS ORBITER LASER ALTIMETER"
      "MGS HIGH GAIN ANTENNA"
      "MGS HORIZON SENSOR ASSEMBLY"
      "MGS NADIR DECK"
      "MGS SOLAR ARRAYS"
      "THERMAL EMISSION SPECTROMETER"


6. Missing FILE_RECORDS Keyword in the Binary Kernel Labels
-----------------------------------------------------------

   All labels for binary SPICE kernels provided in this data set are
   missing the FILE_RECORDS keyword, which is required because these
   labels have the RECORD_TYPE keyword set to FIXED_LENGTH. While this
   error violates the PDS standards, it does not affect usability of
   the SPICE data provided in this data set in any way because the
   SPICE toolkit does not use any information from the PDS labels to
   access the data.


7. Incorrect SCLK Values in the Comment Area of CK Files
--------------------------------------------------------

   The values of the SPACECRAFT_CLOCK_START_COUNT and/or
   SPACECRAFT_CLOCK_STOP_COUNT keywords in the copy of the PDS label
   embedded at the top of the comment area of CK files are incorrect
   for all CK files that contain more than one segment. The values of
   these keywords provided in the detached PDS labels are correct.


8. No Label the HGA CK "mgs_hga_ext6.bc" Internal Comments
----------------------------------------------------------

   The internal comments in the HGA CK file "mgs_hga_ext6.bc" do not 
   include a copy of the label.