Lunar Orbiter(glossary entry)
A series of five unmanned spacecraft that were sent to photographically survey the Moon's surface from lunar orbit in the mid 1960's, in preparation for the manned Apollo Moon landings. Each spacecraft carried a Medium and a High Resolution camera, with the images being recorded on film which was developed in orbit then electronically scanned and relayed back to Earth.
All of these missions returned interesting data, but the most frequently referenced is Lunar Orbiter IV, which attempted a complete survey of the Moon's nearside. The images from Lunar Orbiter IV, supplemented with those from some of the earlier missions, were systematically compiled and annotated in NASA SP-206 (Bowker and Hughes). Kosofsky and El-Baz also published a selection of some of the most striking images, explaining their geologic implications.
- A growing collection of high resolution digital scans of Lunar Orbiter images, taken directly from the films reconstructed from the video transmissions, is available on-line courtesy of the USGS Lunar Orbiter Digitization Project. This includes seperate sections for what the USGS calls Global and (Very) High Resolution images. These were actually taken with the same set of two Lunar Orbiter cameras (80- and 610-mm focal lengths operating at f/5.6, implying aperture diameters of 14 and 109 mm), and the only fundamental difference between them is that the "(Very) High Resolution" images were taken from closer to the lunar surface (~40-200 km) than the "Global" ones (~2000-3000 km). The USGS scans are distributed as TIFF image files in a "*.gz" zipped format. You may need to install special software to extract the TIFF images from the compressed files.
- For a detailed description of the five missions Lunar Orbiter see the Wikipedia articles or the NSSDC website. When operating at an altitude of 40 km, the Lunar Orbiter High Resolution camera was capable of a ground resolution of about 1 m. The most familiar images, however, were taken by Lunar Orbiter IV which photographed from altitudes of 2700 km and above, and hence achieved a resolution of only about 60 m. The NSSDC has detailed descriptions of the photographic experiments on Lunar Orbiters I, II, III, IV and V.
- For brief summary of the dates and kinds of observations made on each mission, as well as an extensive collection of digitally scanned 16x20 inch photographic prints, visit the LPI Lunar Orbiter Photo Gallery. These pages include links to the higher resolution scans available from the USGS (when available), although some of the links are erroneous/broken. If the availability of a high resolution scan is indicated, but the link to it doesn't work, then you need to go directly to the USGS site(s) mentioned above.
- Support information (date/time, spacecraft position, camera angle, etc.) for all Lunar Orbiter images is available in PDF files on the LPI site (under TWP-70-047) and, independently, in NSSDC 71-13 (Lunar Orbiter Photographic Supporting Data) provided by Arizona State University on their Space Exploration Resources website. With the support data it is a relatively easy matter to "calibrate" the images using the freeware LTVT software, making possible the identification of features, measurement of sizes and distances, and interpretation of shadow lengths. The essential support data for the images in Bowker and Hughes is also available in spreadsheet format on the LTVT download page.
- Selected USGS scans of frames taken with the Lunar Orbiter high resolution cameras, reassembled into their original full-frame format are also available on the LTVT website
- A new Lunar Orbiter Image Recovery Project at NASA's Ames Research Center in California has begun to digitally recover new versions of the Lunar Orbiter images directly from the analog magnetic tapes on which the transmissions from the Moon were originally recorded. By providing slightly higher resolution and an adjustable tonal range, the new digital reconstructions promise to unlock detail that has not been visible in the photographic reconstructions prepared in, and used since, the 1960's. Background information and preliminary results can be viewed on the project website. Assuming the restoration proceeds successfully, the resulting higher-than-ever quality images are supposed to be made promptly available through NASA'a free and publicly accessible Planetary Data System.
- Fisher, E. A. et al (2017). Evidence for surface water ice in the lunar polar regions using reflectance measurements from the Lunar Orbiter Laser Altimeter and temperature measurements from the Diviner Lunar Radiometer Experiment. - Icarus Vol 292, Pages 74–85, August 2017.
- Byrne, C. J. et al (2011). Restoration of Very High Resolution Lunar Orbiter Images – 42nd LPSC Conference (Mar), 2011.
- Epps, A. D. & Sandler, M. (2011). Recovering Lunar Orbiter Framelets from Digitized Magnetic Tape Record – 42nd LPSC Conference (Mar), 2011.
- Wingo, D. R. et al (2011). Analysis of Lunar Orbiter Images Recovered from Analog Tape – 42nd LPSC Conference (Mar), 2011.
- Bruce K. Byers. 1977. DESTINATION MOON: A History of the Lunar Orbiter Program. Washington, D.C. (NASA TECHNICAL MEMORANDUM: NASA TM X-3487)
- Thomas P. Hansen. 1970. Guide to lunar orbiter photographs. NASA SP-242.
- Leon J. Kosofsky and Farouk El-Baz. 1970. The Moon as Viewed by Lunar Orbiter (297 MB PDF download). NASA SP-200.
- See also Mark Wade's extensive list of references.