PDS_VERSION_ID                = PDS3
RECORD_TYPE                   = STREAM
OBJECT                        = TEXT
  NOTE                        = "Comments on the MGS Mars Orbiter
    Laser Altimeter (MOLA) Archive Volume MGSL_0002 (ERRATA.TXT)"
  PUBLICATION_DATE            = 1999-04-22
END_OBJECT                    = TEXT
END


COMMENTS ON MGS MOLA ARCHIVE VOLUME MGSL_0002

     This document contains comments and errata concerning the
MGS Mars Orbiter Laser Altimeter (MOLA) Archive Volume MGSL_0002.


1.  MOLA AEDR and PEDR File Names

     The AEDR and PEDR binary data files on MOLA archive volumes
have file names with the extension ".B", instead of the usual
extension of ".DAT" for binary files.

2. Incorrect Values for SPACECRAFT_CLOCK_START_COUNT and 
   SPACECRAFT_CLOCK_STOP_COUNT in AEDR and PEDR Labels

     The attached PDS labels for AEDR and PEDR data files contain
incorrect values for the fields SPACECRAFT_CLOCK_START_COUNT and
SPACECRAFT_CLOCK_STOP_COUNT, due to an error in the processing
software that created the files. This error will be corrected in
future products. The AEDR and PEDR index tables were created from the
data file labels, so the index tables also contain the incorrect
values for these two fields.

3. Incorrect and Missing Values for INTERCHANGE_FORMAT in AEDR Labels

     In the attached PDS labels for AEDR data files, the value for
INTERCHANGE_FORMAT in the MOLA_SCIENCE_MODE_TABLE object is incorrectly
given as ASCII. It should be BINARY. Also in the AEDR labels, the
MOLA_MAINTENANCE_MODE_TABLE object is missing the INTERCHANGE_FORMAT
keyword and value. It should have INTERCHANGE_FORMAT = BINARY.

4. Incorrect Value for ROW_BYTES in AEDR Labels

     The attached PDS labels for AEDR data files have incorrect 
values for ROW_BYTES in the MOLA_SCIENCE_MODE_TABLE object and in the
MOLA_MAINTENANCE_MODE_TABLE object. In both objects the value for 
ROW_BYTES should be 1230.

5.  No Data for Some Orbits 

     PEDR data products do not exist for orbits 373, 375, 413 and 
414. The AEDR data for these orbits consist entirely of noise. 
During these orbits MOLA observed in an off-nadir position while 
the MGS spacecraft was 'tilted', in order to fill in a coverage 
gap at the north pole. The range parameters required for these 
passes were not transmitted in time due to some miscommunication, 
and there were no planetary ranges obtained. Data covering the 
pole were acquired successfully on 10 other orbits.