Editing Lunar Orbiter program (section)

==Results==
The Lunar Orbiter program consisted of five spacecraft which returned photography of 99 percent of the surface of the Moon (near and [[Far side (Moon)|far side]]) with resolution down to {{convert|1|m|sp=us}}. Altogether the Orbiters returned 2180 high resolution and 882 medium resolution frames.  The micrometeoroid experiments recorded 22 impacts showing the average micrometeoroid flux near the Moon was about two orders of magnitude greater than in interplanetary space, but slightly less than in the near-Earth environment. The radiation experiments confirmed that the design of Apollo hardware would protect the astronauts from average and greater than average short term exposure to solar particle events.

The use of Lunar Orbiters for tracking to evaluate the [[Manned Space Flight Network]] tracking stations and Apollo Orbit Determination Program was successful, with three of the Lunar Orbiters (2, 3, and 5) being tracked simultaneously from August through October 1967. The Lunar Orbiters were all eventually commanded to crash on the Moon before their attitude control fuel ran out so they would not present navigational or communications hazards to later Apollo flights.  The Lunar Orbiter program was managed by NASA [[Langley Research Center]] at a total cost of roughly $200 million.

Doppler tracking of the five orbiters allowed mapping of the gravitational field of the Moon and discovery of [[mass concentration (astronomy)|mass concentrations]] (mascons), or gravitational highs, which were located in the centers of some (but not all) of the lunar maria.<ref>{{cite journal | doi = 10.1126/science.161.3842.680 | title = Mascons: Lunar Mass Concentrations | year = 1968 | author = P. M. Muller, W. L. Sjogren | journal = Science | volume =  161 | issue = 3842  | pages = 680–684 | pmid=17801458| bibcode = 1968Sci...161..680M | s2cid = 40110502 }}</ref>

[[Image:Lunar Orbiter camera (large).jpg|thumb|Lunar Orbiter camera (NASA)]]
Below is the flight log information of the five Lunar Orbiter photographic missions:<ref>Hansen, T.P. (1970). Guide to Lunar Orbiter Photographs. Washington DC: NASA.</ref>
*[[Lunar Orbiter 1]]
**Launched August 10, 1966
**Imaged Moon: August 18 to 29, 1966
**Impact with Moon: October 29, 1966
**Apollo landing site survey mission
*[[Lunar Orbiter 2]]
**Launched November 6, 1966
**Imaged Moon: November 18 to 25, 1966
**Impact with Moon: October 11, 1967
**Apollo landing site survey mission
*[[Lunar Orbiter 3]]
**Launched February 5, 1967
**Imaged Moon: February 15 to 23, 1967
**Impact with Moon: October 9, 1967
**Apollo landing site survey mission
*[[Lunar Orbiter 4]]
**Launched May 4, 1967
**Imaged Moon: May 11 to 26, 1967
**Impact with Moon: Approximately October 31, 1967
**Lunar mapping mission
*[[Lunar Orbiter 5]]
**Launched August 1, 1967
**Imaged Moon: August 6 to 18, 1967
**Impact with Moon: January 31, 1968
**Lunar mapping and hi-res survey mission

===Data availability===
The Lunar Orbiter orbital photographs were transmitted to Earth as analog data after onboard scanning of the original film into a series of strips. The data were written to magnetic tape and also to film. The film data were used to create hand-made mosaics of Lunar Orbiter frames.  Each LO exposure resulted in two photographs: medium-resolution frames recorded by the 80-mm focal-length lens and high-resolution frames recorded by the 610-mm focal length lens.  Due to their large size, HR frames were divided into three sections, or sub-frames. Large-format prints ({{convert|16|x|20|in}}) from the mosaics were created and several copies were distributed across the U.S. to NASA image and data libraries known as [https://www.lpi.usra.edu/library/RPIF/ Regional Planetary Information Facilities].  The resulting outstanding views were of generally very high spatial resolution and covered a substantial portion of the lunar surface, but they suffered from a "venetian blind" striping, missing or duplicated data, and frequent saturation effects that hampered their use.  For many years these images have been the basis of much of lunar scientific research.  Because they were obtained at low to moderate Sun angles, the Lunar Orbiter photographic mosaics are particularly useful for studying the morphology of lunar topographic features.

Several atlases and books featuring Lunar Orbiter photographs have been published. Perhaps the most definitive was that of [https://www.lpi.usra.edu/resources/lunar_orbiter/book/lopam.pdf Bowker and Hughes] (1971); it contained 675 photographic plates with approximately global coverage of the Moon. In part because of high interest in the data and in part because that atlas is out of print, the task was undertaken at the [https://www.lpi.usra.edu/ Lunar and Planetary Institute] to scan the large-format prints of Lunar Orbiter data.<ref>Jeffrey J. Gillis, Paul D. Spudis, Mary Ann Hager, Mary Noel, Debra Rueb, and James Cohen, [https://www.lpi.usra.edu/meetings/LPSC99/pdf/1770.pdf Digitized Lunar Orbiter IV Images:  A Preliminary Step to Recording the Global Set of Lunar Oribter Images in Bowker & Hughes], Lunar and Planetary Science XXX, Abstract #1770(1999)</ref>  These were made available online as the [https://www.lpi.usra.edu/resources/lunar_orbiter/ Digital Lunar Orbiter Photographic Atlas of the Moon].<ref>Jeffrey J. Gillis, Debra Rueb, James Cohen, and Mary Ann Hager, [https://www.lpi.usra.edu/meetings/LPSC2000/pdf/1815.pdf The Lunar Orbiter Photographic Atlas Digital Archive], Lunar and Planetary Science XXXI, Abstract #1815 (2000)</ref>

===Data recovery and digitization===
[[Image:Comparison between original and LOIRP result.jpg|thumb|A detail of an original image at the top, compared to a reprocessed version at the bottom created by [[LOIRP]].]]
In 2000, the [[Astrogeology Research Program]] of the US Geological Survey in Flagstaff, Arizona was funded by NASA (as part of the [https://astrogeology.usgs.gov/Projects/LunarOrbiterDigitization/ Lunar Orbiter Digitization Project] {{Webarchive|url=https://web.archive.org/web/20171123151046/https://astrogeology.usgs.gov/Projects/LunarOrbiterDigitization/ |date=2017-11-23 }}) to scan at 25 micrometer resolution archival LO positive film strips that were produced from the original data.<ref>L.R. Gaddis, T. Sucharski, T. Becker, and A. Gitlin, [https://www.lpi.usra.edu/meetings/lpsc2001/pdf/1892.pdf Cartographic Processing of Digital Lunar Orbiter Data], Lunar and Planetary Science XXXII (2001).</ref>  The goal was to produce a [http://www.mapaplanet.org/explorer-bin/explorer.cgi?map=Moon&layers=moon_lo&west=-180&south=-90&east=180&north=90&center=0&defaultcenter=on&grid=none&stretch=auto&projection=SIMP&advoption=NO&info=NO&resolution=2 global mosaic] of the Moon using the best available [[Lunar Orbiter]] frames (largely the same coverage as that of Bowker and Hughes, 1971).  The frames were constructed from scanned film strips; they were digitally constructed, geometrically controlled, and map-projected without the stripes that had been noticeable in the original photographic frames.  Because of its emphasis on construction of a global mosaic, this project only scanned about 15% of the available Lunar Orbiter photographic frames.  Data from Lunar Orbiter missions [[Lunar Orbiter 3|III]], [[Lunar Orbiter 4|IV]] and [[Lunar Orbiter 5|V]] were included in the global mosaic.<ref>T. Becker, L. Weller, L. Gaddis, D. Cook, B. Archinal, M. Rosiek, C. Isbell, T. Hare, R. Kirk, [https://www.lpi.usra.edu/meetings/lpsc2008/pdf/2357.pdf Lunar Orbiter Mosaic of the Moon], Lunar and Planetary Science XXXIX (2008).</ref>

In addition, the USGS digitization project created frames from very high resolution Lunar Orbiter images for several 'sites of scientific interest.'  These sites had been identified in the 1960s when the Apollo landing sites were being selected.  Frames for sites such as the [[Apollo 12]] landing site, the [[Marius (crater)|Marius]] Hills, and the Sulpicius Gallus rille have been released.<ref>L. Weller, T. Becker, B. Archinal, A. Bennett, D. Cook, L. Gaddis, D. Galuszka, R. Kirk, B. Redding, D. Soltesz, [https://www.lpi.usra.edu/meetings/lpsc2007/pdf/2092.pdf USGS Lunar Orbiter Digitization Project: Updates and Status], Lunar and Planetary Science XXXVIII (2007).</ref>

In 2007, the [[Lunar Orbiter Image Recovery Project]] (LOIRP) began a process to convert the Lunar Orbiter Images directly from the original [[Ampex]] FR-900 analog video recordings of the spacecraft data to digital image format, a change which provided vastly improved resolution over the original images released in the 1960s.  The first of these restored images were released in late 2008.<ref>{{cite news|url=http://www.collectspace.com/news/news-111408a.html |title=Repaired data drives restoring the Moon |publisher=collectSPACE.com |date=November 14, 2008 |access-date=2008-12-24}}</ref> Almost all of the Lunar Orbiter images had been successfully recovered {{as of|February 2014}} and were undergoing digital processing before being submitted to NASA's [[Planetary Data System]].<ref>[http://www.moonviews.com/2014/02/ LOIRP Moon Views], February 2014</ref>

{{multiple image
| align = center
| image1 = First View of Earth from Moon.jpg
| width1 = 400
| alt1 = 
| caption1 = 
| image2 = First View of Earth from Moon - reprocessed.png
| width2 = 75
| alt2 = 
| caption2 = 
| footer = The first image of Earth taken from the Moon. On the left the original and on the right a digitally restored version created by [[LOIRP]].
}}