Lunar Reconnaissance Orbiter Science Targeting Meeting (2009)
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COORDINATING LOIRP ENHANCED LUNAR ORBITER AND LUNAR RECONNAISSANCE ORBITER HIGH RESOLUTION IMAGES FOR SELECTED SCIENCE AND EXPLORATION TARGETS. D. R. Wingo1 and C. A. Lundquist2, 1Skycorp Incorporated, NASA Ames Research Park, Building 596, Moffett Field, CA 94035 (
[email protected]), 2University of Alabama in Huntsville, 500 North Sparkman Drive, Huntsville, AL 35899
Introduction: The Lunar Orbiter Image Recovery Project (LOIRP), located at the NASA Ames Research Park is in the process of digitizing the original analog tapes of the Lunar Orbiter (LO) image database. This new resource of 43 year old LO images are being digitized in a manner that will foster their utility for comparison with the output of the Lunar Reconnaissance Orbiter Camera (LROC) In order to meet on of the LROC’s main exploration goals of ascertaining the hazards of small meteors for crew operations, the oldest and highest resolution datasets must be used. The LOIRP recovered images from the five Lunar Orbiters meet this criterion.[1] LO 35mm Film vs Analog Tape Derived Quality: The five LO spacecraft, who’s missions were flown in the period of August 1966 to August of 1967 are still to this day the highest resolution visible light images taken of the lunar surface in the near side equatorial region of the Moon as well as other selected regions.[2] The LO spacecraft used SO-243 70 millimeter film coupled to a 610mm optical system for high resolution imaging. The SO-243 film, with a granularity for LO of 286 lines/mm provided images with four lines per meter on the lunar surface.[3] The LO spacecraft, flying at a periselene altitude of ~40 km on the near side equatorial region photographed several thousand square kilometers at this resolution. The existing imagery in the Planetary Data System (PDS) and other archives are based upon a 35mm film reconstruction of the LO 70mm film. The 70mm film was electronically scanned on the spacecraft, transmitted to the Earth as an analog signal, demodulated, and reconstructed through three generations of equipment to arrive at the 35mm filmsets. These filmsets have subsequently been scanned by various efforts over the years to arrive at our current datasets. While these digital datasets are the best that can be derived from the 35mm film, the film itself was not the best representation of the quality of the data. A group of ~1500 2” analog tapes were made in parallel with the 35mm film from the predetected (before baseband conversion and demodulation) analog data stream. In 2008 LOIRP project successfully restored an Ampex FR-900A tape drive of the same type that originally recorded these images. We have also successfully reconstructed the LO demodulator and have confirmed
the higher dynamic range of the analog tape based data.[4] The following image shows a comparison between the LPI LO-III-162-H3 and the LOIRP image recovered from the undemoulated analog tapes:
LOIRP (top) vs GRE Copernicus Uplift Image The reason for the striking difference in the grey scale values in the above images is that during the reconstruction process, the whitest whites and blackest blacks were clipped due limitations in the 35mm film based Ground Reconstruction Equipment (GRE).[5] This is shown below:
Dynamic Range Clipping of LO 35mm Film The above gray step data is derived from the calibration blocks on each framelet of LO data and represent the difference in dynamic range between the 35mm GRE film and the analog data on the 2” LO tapes. As can be readily seen above, as well as in the full images, the increased dynamic range brings out subtle details (shadows emanating from boulders on the central uplift of Copernicus for example) that are simply impossible to see on the 35mm film, no matter how expertly reprocessed and digitized.
Lunar Reconnaissance Orbiter Science Targeting Meeting (2009)
LOIRP Images as Applied to LROC Mission Goals: One of the six primary goals of the LROC camera is “Meter-scale coverage overlapping with Apollo era Panoramic images (1-2 m/pixel) to document the number of small impacts since 1971-1972, to ascertain hazards for future surface operations and interplanetary travel”.[6] The LOIRP image database, as it is digitized will allow a direct mapping of the LROC images to the corresponding LO images. The LOIRP software team are currently working with Apple computer to develop the software and methodology for automated creation of LO images from the analog tapes. A follow on to this will be to develop the automated means of integrating LROC images with our reprocessed LO database and targeting known impacts that occurred after the LO missions. One example of a significant historical impact was recorded on May 13, 1972 by the seismic array placed on the Moon by the Apollo missions. The impact coordinates derived from the seismic data are 1.1 N latitude and 16.9 W longitude with an uncertainty of 0.2 degrees.[7] The area of this impact was imaged by the LO imaging system to ~1 meter resolution and would be a perfect calibration target for the LROC imaging system. It is estimated that this impactor created a crater on the order of 50-100 meters, which was below the threshold of detection from Clementine. Images of this area have not been released by other nations so this will be a great test and an ideal calibration test for the LROC camera. Other impacts, such as the one personally witnessed by astronaut Dr. Harrison Schmidt during the Apollo 17 mission could also be reimaged.[8] The LOIRP project is, as of this writing, digitizing images from LO missions I,II, and III. This includes the Apollo landing sites as well as the area of the impact identified by the Apollo seismographs. Automated methods for identifying differences between the LO other missions are being developed that will seamlessly integrate with the LROC imaging products. By using a known post LO impact, along with others surely to be found, it is expected that the risk to the crew of small impactors can be quantified. Additionally, with the multispectral capability of the LROC camera, and with known lunar regolith color maturation rates, the number of impacts in the recent geological epoch can be estimated with a much higher confidence than before the LROC mission, when coupled with the LO analog tape dataset. References: [1] Wingo, D.R., Cowing, K Abstract 2517 LPS XD, [2] Lunar Orbiter Catalog (1970) (TWP-70-047) October, [3][4] Ibid [1][5][6] http://lunar.gsfc.nasa.gov/lroc.html, accessed 4/22/09,
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[7] Latham, G.V, Ewing, M, Press, F, Sutton, G. et al, (1972) NASA SP 315, , [8] Schmidt H, Personal Communication. etc. References should then appear in numerical order in the reference list, and should use the following abbreviated style: [1] Author A. B. and Author C. D. (1997) JGR, 90, 1151–1154. [2] Author E. F. et al. (1997) Meteoritics & Planet. Sci., 32, A74. [3] Author G. H. (1996) LPS XXVII, 1344–1345. [4] Author I. J. (2002) LPS XXXIII, Abstract #1402.
