PDS_VERSION_ID         = PDS3
LABEL_REVISION_NOTE    = "2025-07-11, N. Putzig, revised"
RECORD_TYPE            = STREAM
OBJECT                 = TEXT
  PUBLICATION_DATE     = 2021-05-03
  INTERCHANGE_FORMAT   = ASCII
  NOTE                 = "Information about the EXTRAS/SURFACE directory"
END_OBJECT             = TEXT
END

Files in the EXTRAS directory are offered as a convenience to the user. They
are not necessary for the use and understanding of the data products in the
archive. They may not have PDS labels and may not be compliant with PDS 
standards.

The EXTRAS/SURFACE directory contains these files:

MOLA_LIMIT_N.TXT
MOLA_LIMIT_S.TXT
PLANUM_AUSTRALE_3D_V1_TIME_AREOID_10125_DELAY.TXT
PLANUM_AUSTRALE_3D_V1_TIME_DATUM.TXT
PLANUM_AUSTRALE_3D_V1_TIME_MEANS.PNG
PLANUM_AUSTRALE_3D_V1_TIME_MEANS.TXT
PLANUM_AUSTRALE_3D_V1_TIME_MOLA_SHARAD_DELAY.PNG
PLANUM_AUSTRALE_3D_V1_TIME_MOLA_SHARAD_DELAY.TXT
PLANUM_BOREUM_3D_V1_TIME_AREOID_10125_DELAY.TXT
PLANUM_BOREUM_3D_V1_TIME_DATUM.TXT
PLANUM_BOREUM_3D_V1_TIME_MEANS.PNG
PLANUM_BOREUM_3D_V1_TIME_MEANS.TXT
PLANUM_BOREUM_3D_V1_TIME_MOLA_SHARAD_DELAY.PNG
PLANUM_BOREUM_3D_V1_TIME_MOLA_SHARAD_DELAY.TXT
PLANUM_BOREUM_3D_V2_TIME_AREOID_10125_DELAY.TXT
PLANUM_BOREUM_3D_V2_TIME_DATUM.TXT
PLANUM_BOREUM_3D_V2_TIME_MOLA_SHARAD_DELAY.TXT
SHARAD_LIMIT_N.TXT
SHARAD_LIMIT_S.TXT

All *DELAY.TXT files define surfaces in the form of columnar ASCII files 
with columns of LINE, SAMPLE, X, Y, and DELAY_TIME, where the delay times 
are relative to the datums given in the accompanying *DATUM.TXT files 
(see below). Each file has a three-line header, giving the surface name, 
the PRODUCT_ID that it corresponds to, and the null value (-9999.99).

   The *MOLA_SHARAD_DELAY.TXT files contains the delay times from the
   radius datum to the surfaces of Planum Boreum and Planum Australe as
   determined by MOLA at latitudes up to the limit of MOLA nadir viewing
   (see MOLA_LIMIT_?.TXT files) and by the SHARAD 3D data volume between
   the MOLA limit and that of SHARAD nadir viewing (see SHARAD_LIMIT_?.TXT).

   The *AREOID_10125_DELAY.TXT files provide the delay times between the
   constant-radius datums of the SHARAD 3D data volumes and a datum 10,125 m
   above the areoid (Martian geoid) as defined by the MOLA team,
   specifically their 16 pixel-per-degree surface available at:
   http://pds-geosciences.wustl.edu/missions/mgs/megdr.html
   The areoid+10125m datum is the same as that used for the individual
   US SHARAD radargrams available at:
   http://pds-geosciences.wustl.edu/missions/mro/sharad.htm
   One would subtract these delay times from each data volume to shift them
   to the areoid+10125m datum.

The *DATUM.TXT files contain a two-line header describing the content 
that follows, which is a single value on the third line specifying the 
reference radius for the DELAY_TIME values. This is the the same radius 
that is given in the DESCRIPTION field of the LBL files for the data 
volumes, except it is specified in meters in the datum files vs. in 
kilometers in the LBL files. 

The *MEANS.TXT files contains a surface of data values in the form of ASCII 
files with columns of LINE, SAMPLE, and MEAN_VALUE, where the mean values
are that of each frame for the first north and south polar 3D time volumes  
as determined in processing subsequent to conversion to reflection strength
but prior to debiasing (carried out by subtracting these mean values from 
each frame). These mean data values may be used to reverse the debiasing if 
desired by the end user. See the 3D_PROCESSING document for more details.
These files are not present for product versions greater than 1 because
the processing did not include the debiasing for those products.

The *.PNG files are screenshots showing the surfaces as displayed in either a 
SeisWare basemap or ProMAX map view. 

The *LIMIT_?.TXT files describe the polygons (quasi-circles) delineating 
the poleward limits of the MOLA and SHARAD-picked surfaces in each 
hemisphere. Each file has a one-line header followed by values of latitude, 
longitude, X, and Y, delineated with commas. These polygons correspond to 
the red (MOLA) and yellow (SHARAD) circles shown on the PNG map views.

All X and Y values are given in meters within polar stereo projections 
centered on the north or south pole of Mars. See label files in the data 
directory for details of the projections.