Lunar Orbiter Digital Data Archive
U.S. Geological Survey, Astrogeology Program, Flagstaff, AZ
December 1, 2009

This document describes Lunar Orbiter digitized film strips ('framelets')
as provided within the Lunar Orbiter Archive located at:

http://pdsmaps.wr.usgs.gov/PDS/public/lunar_orbiter/LO_Archive.html

These data are presented in raw (byte-stream, 8-bit, no header) image
format. No digital processing enhancements (such as filtering) have
been applied.

The image array dimensions for each raw film strip file are:

 970 samples x 16550 lines.

Strips are located within 'frame' directories as described here:

LO[n]_0001/extras/scanned_strips/[r]_resolution/frame_[nnn]/

Where [n]   = 3,4, or 5
      [r]   = medium or high
      [nnn] = 3 digit frame number

Filenames within each 'frame' directory follow this form:

lo[n]r[r]f[nnn]s[sss][i].raw

Where [n]   = 3,4, or 5
      [r]   = 0 (Medium)
            = 1 (High)
      [nnn] = 3 digit frame number
      [sss] = 3 digit strip number
      [i] (if present)
            = x (strip also identified as sss+1)
                (sss+1 does not exist)
            = a,b,c,... (indicates rare cases of strip or scan versions)

File retrieval:
Individual scanned strips (*.raw files) can be downloaded via ordinary
means within a web browser ("Save Link/Target as") or other ftp protocol
(anonymous command line ftp, WinSCP, etc). Additionally, each 'frame'
directory contains a text file (*.lst) where each line entry defines the
URL path for each scanned strip located within the directory. This text
file can be retrieved and then used for bulk download within retrieval
tools such as wget, cURL, NcFTP, etc..

For example, after retrieving the following text file from the LO archive:

ftp://pdsimage2.wr.usgs.gov/data/lunar_orbiter/pds/LO3_0001/extras/scanned_strips/medium_resolution/frame_153/lo3_frame_153_medium_url.lst

The following single 'wget' command will retrieve all .raw files from the
specific 'frame' directory and place each file at the user local working
directory.

wget -i lo3_frame_153_medium_url.lst


Digitization and Processing Notes:

Strips from only the highest quality and most complete film canisters
were scanned for each Lunar Orbiter (LO) frame.  Film canisters were
selected from the Flagstaff Regional Planetary Information Facility
inventory and supplemented with canisters from the collection at the
Lunar and Planetary Institute, Houston, Texas.

Scanning was performed on a CreoScitex Pro II scanner, operated by
proprietary software running on a Macintosh (OS9).  Each film strip
within a frame was cut from the selected film canister at a measured
length.  It was then placed on the scan plate within a template and
scanned at 25 microns with emulsion side down.  Scanning density and
resolution were tested and set to ensure the best representation of
all image data on the film.   Scanning resolutions of 8, 25, 50, and
100 microns were tested for preservation of fine detail in the film
and suppression of scan spots, scan lines, and film grain.  It was
determined that a 25-micron scanning resolution was best.  Also,
input minimum and maximum values of the film density were determined
for a representative collection of film strips with a broad range of
average brightness.  The scanner and software then mapped these
input density settings to an 8 bit output density range of 0 to 255
and recorded the digital output as Tagged Interchange File Format 
(TIFF) images.  Data in TIFF format were used in further processing
but were are included in the formal data archive.

The scanned 25-micron multi-strip template data were then ported to 
a Linux system running USGS in-house Integrated Software for Imagers
and Spectrometers (ISIS, v.2).  In ISIS, the data were converted to
raw single-band 'cube' files and processed to extract individual data 
strips for each Lunar Orbiter subframe.  Digitized film strips were 
then visually inspected for quality and archived here at 25-micron
in individual strips for each scanned LO frame or subframe.

The quality of the digital film strip data was determined by
visual inspection and comparison to 16x20-inch prints of Lunar
Orbiter subframe mosaics from our RPIF data library and as printed
in Lunar Orbiter Photographic Atlas [Bowker & Hughes, 1971, NASA SP
208].  Following verification that the data were free of noise or
anomalies introduced at scanning, the noise-free, full-density image
strips were stored and staged for input into the final archive.