PDS_VERSION_ID                = PDS3
RECORD_TYPE                   = STREAM
OBJECT                        = TEXT
  NOTE                        = "Comments on the MRO SPICE Archive"
  PUBLICATION_DATE            = 2022-09-01
END_OBJECT                    = TEXT
END


COMMENTS ON THE MRO SPICE DATA ARCHIVE
======================================

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


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

   All SPICE text kernel files (LSK, PCK, SCLK, IK, FK) provided in
   this data set 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 in the archived data sets.

   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 data sets 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 data sets 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 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:

      "MRO SPACECRAFT"
      "MRO SOLAR ARRAYS"
      "MRO HIGH GAIN ANTENNA"
      "HIGH RESOLUTION IMAGING SCIENCE EXPERIMENT (HIRISE)"
      "MARS CLIMATE SOUNDER"
      "SHALLOW RADAR"
      "COMPACT RECONNAISSANCE IMAGING SPECTROMETER FOR MARS"
      "CONTEXT CAMERA"
      "MARS COLOR IMAGER"
      "OPTICAL NAVIGATION (CAMERA) EXPERIMENT"


4. 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.


5. 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.


6. MRO Reconstructed CK Files for Sep 2014 - Dec 2014 
--------------------------------------------------------

   During the period from July 2014 till April 2015 reconstructed MRO 
   CK production pipeline run by NAIF used an out of date SCLK kernel 
   (v00055). SCLK v00056 delivered Sep 5, 2014 introduced a new partition 
   with a jump of ~75 milliseconds on Sep 1, 2014. All reconstructed CKs 
   generated since that time (September 2014 to March 2015) had internal 
   encoded SCLK time tags in error by 75 milliseconds. Due to this timing
   error, using the reconstructed CKs with the latest SCLK resulted in 
   attitude error of ~0.07 mrad in pitch, up to 0.15 mrad in roll (<0.015 
   mrad baseline), and 0.05 mrad in yaw (<0.015 mrad baseline). All weekly 
   reconstructed CKs covering September 2014 - March 2015 were re-generated
   at the end of March 2015 with the latest SCLK and included in the archive
   as v2 files in release 33. For the period September-December 2014 these 
   v2 CKs fully supersede the CKs added to the archive in releases 31 
   and 32.


6. Incorrectly named MCS CK
--------------------------------------------------------

   The MCS CK 

      mro_mcs_psp_211101_211101.bc 

   name has incorrect end date. To match its time coverage, this date 
   should be 211130 instead of 211101.


End of errata.