The Lunar Orbiter program was a series of five uncrewed

lunar Lunar most commonly means "of or relating to the Moon". Lunar may also refer to: Arts and entertainment * ''Lunar'' (series), a series of video games * "Lunar" (song), by David Guetta * "Lunar", a song by Priestess from the 2009 album ''Prior t ...

orbiter A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, pl ...

missions launched by the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

from 1966 through 1967. Intended to help select

Apollo Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label=Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label= ...

landing sites by mapping the Moon's surface, they provided the first photographs from lunar orbit and photographed both the Moon and Earth. All five missions were successful, and 99 percent of the lunar surface was mapped from photographs taken with a resolution of or better. The first three missions were dedicated to imaging 20 potential crewed lunar landing sites, selected based on Earth-based observations. These were flown at low-inclination orbits. The fourth and fifth missions were devoted to broader scientific objectives and were flown in high-altitude polar orbits. Lunar Orbiter 4 photographed the entire nearside and nine percent of the far side, and Lunar Orbiter 5 completed the far side coverage and acquired medium () and high () resolution images of 36 preselected areas. All of the Lunar Orbiter spacecraft were launched by

Atlas-Agena The Atlas-Agena was an American expendable launch system derived from the SM-65 Atlas missile. It was a member of the Atlas family of rockets, and was launched 109 times between 1960 and 1978. It was used to launch the first five Mariner uncrew ...

-D launch vehicles. The Lunar Orbiters had an ingenious imaging system, which consisted of a dual-lens

camera A camera is an Optics, optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), ...

, a film processing unit, a readout scanner, and a film handling apparatus. Both lenses, a narrow angle high resolution (HR) lens and an wide angle medium resolution (MR) lens, placed their frame exposures on a single roll of

70 mm film 70 mm film (or 65 mm film) is a wide high-resolution film gauge for motion picture photography, with a negative area nearly 3.5 times as large as the standard 35 mm motion picture film format. As used in cameras, the film is wid ...

. The axes of the two cameras were coincident so the area imaged in the HR frames were centered within the MR frame areas. The film was moved during exposure to compensate for the spacecraft velocity, which was estimated by an electro-optical sensor. The film was then processed, scanned, and the images transmitted back to Earth. During the Lunar Orbiter missions, the first pictures of Earth as a whole were taken, beginning with Earth-rise over the lunar surface by Lunar Orbiter 1 in August, 1966. The first full picture of the whole Earth was taken by Lunar Orbiter 5 on 8 August 1967. A second photo of the whole Earth was taken by Lunar Orbiter 5 on 10 November 1967.

Spacecraft and subsystems

The Boeing-Eastman Kodak proposal was announced by NASA on 20 December 1963. The main bus of the Lunar Orbiter had the general shape of a truncated cone, tall and in diameter at the base. The spacecraft was composed of three decks supported by trusses and an arch. The equipment deck at the base of the craft held the battery,

transponder In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend word, blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a T ...

, flight programmer,

inertial reference unit An inertial reference unit (IRU) is a type of inertial sensor which uses gyroscopes (electromechanical, ring laser gyro or MEMS) and accelerometers (electromechanical or MEMS) to determine a moving aircraft’s or spacecraft’s change in rotati ...

(IRU),

Canopus Canopus is the brightest star in the southern constellation of Carina and the second-brightest star in the night sky. It is also designated α Carinae, which is Latinised to Alpha Carinae. With a visual apparent magnitude ...

star tracker A star tracker is an optical device that measures the positions of stars using photocells or a camera. As the positions of many stars have been measured by astronomers to a high degree of accuracy, a star tracker on a satellite or spacecraft may ...

, command decoder, multiplex encoder, traveling-wave tube amplifier (TWTA), and the photographic system. Four solar panels were mounted to extend out from this deck with a total span across of . Also extending out from the base of the spacecraft were a high gain antenna on a boom and a low-gain antenna on a boom. Above the equipment deck, the middle deck held the velocity control engine, propellant, oxidizer, and pressurization tanks, Sun sensors, and micrometeoroid detectors. The third deck consisted of a heat shield to protect the spacecraft from the firing of the velocity control engine. The nozzle of the engine protruded through the center of the shield. Mounted on the perimeter of the top deck were four

attitude control Attitude control is the process of controlling the orientation of an aerospace vehicle with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, etc. Controlling vehicle ...

thrusters. Power of 375 W was provided by the four solar arrays containing 10,856 n/p solar cells which would directly run the spacecraft and also charge the 12 A·h nickel-cadmium battery. The batteries were used during the brief periods of occultation when no solar power was available. Propulsion for major maneuvers was provided by the gimballed velocity control engine, a

hypergolic A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. T ...

thrust Marquardt Corp. rocket motor. Three axis stabilization and attitude control were provided by four nitrogen gas jets. Navigational knowledge was provided by five

sun sensor A sun sensor is a navigational instrument used by spacecraft to detect the position of the sun. Sun sensors are used for attitude control, solar array pointing, gyro updating, and fail-safe recovery. In addition to spacecraft, sun sensors fin ...

s, the Canopus star sensor, and the inertial navigation system. Communications were via a 10 W transmitter and the directional one meter diameter high-gain antenna for transmission of photographs, and a 0.5 W transmitter and omnidirectional low-gain antenna for other communications. Both transmitters operated in the

S band The S band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a part of the microwave band of the electromagnetic spectrum covering frequencies from 2 to 4 gigahertz (GHz). Thus it crosses the convention ...

at about 2295 MHz. Thermal control was maintained by a multilayer aluminized

Mylar BoPET (biaxially-oriented polyethylene terephthalate) is a polyester film made from stretched polyethylene terephthalate (PET) and is used for its high tensile strength, chemical and dimensional stability, transparency, reflectivity, gas and aro ...

and

Dacron Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foo ...

thermal blanket which enshrouded the main bus, special paint, insulation, and small heaters. The camera used two lenses to simultaneously expose a wide-angle and a high-resolution image on the same film. The wide-angle, medium resolution mode used an 80 mm F 2.8 Xenotar lens manufactured by

Schneider Kreuznach Schneider Kreuznach () is the abbreviated name of the company Jos. Schneider Optische Werke GmbH, which is sometimes also simply referred to as Schneider. They are a manufacturer of industrial and photographic optics. The company was founded on ...

of West Germany. The high-resolution mode used a 610 mm F 5.6 Panoramic lens manufactured by the Pacific Optical Company. The photographic film was developed in-orbit with a semidry process, and then it was scanned by a

photomultiplier A photomultiplier is a device that converts incident photons into an electrical signal. Kinds of photomultiplier include: * Photomultiplier tube, a vacuum tube converting incident photons into an electric signal. Photomultiplier tubes (PMTs for sh ...

for transmission to Earth. This system was adapted under permission of the NRO from the

SAMOS Samos (, also ; el, Σάμος ) is a Greece, Greek island in the eastern Aegean Sea, south of Chios, north of Patmos and the Dodecanese, and off the coast of western Turkey, from which it is separated by the -wide Mycale Strait. It is also a se ...

E-1 reconnaissance camera, built by Kodak for a short-lived USAF near-realtime satellite imaging project. Originally, the Air Force had offered NASA several spare cameras from the

KH-7 GAMBIT BYEMAN codenamed GAMBIT, the KH-7 (Air Force Program 206) was a reconnaissance satellite used by the United States from July 1963 to June 1967. Like the older CORONA system, it acquired imagery intelligence by taking photographs and returning ...

program, but then authorities became concerned over security surrounding the classified cameras, including the possibility of images of the Moon giving away their resolution. Some proposals were made that NASA not publish the orbital parameters of the Lunar Orbiter probes so that the resolution of the images could not be calculated through their altitude. In the end, NASA's existing camera systems, while lower resolution, proved to be adequate for the needs of the mission.

Potential backup

As a backup for Lunar Orbiter program, NASA and the NRO cooperated on the Lunar Mapping and Survey System (LM&SS), based on the

KH-7 BYEMAN codenamed GAMBIT, the KH-7 (Air Force Program 206) was a reconnaissance satellite used by the United States from July 1963 to June 1967. Like the older CORONA system, it acquired imagery intelligence by taking photographs and returnin ...

reconnaissance satellite. Replacing the Lunar Module in the

Saturn V Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, with multistage rocket, three stages, and powered with liquid-propellant r ...

, Apollo astronauts would operate LM&SS remotely in lunar orbit. NASA canceled the project in the summer of 1967 after the complete success of the Lunar Orbiters.

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 ''The Far Side'' is a single-panel comic created by Gary Larson and syndicated by Chronicle Features and then Universal Press Syndicate, which ran from December 31, 1979, to January 1, 1995 (when Larson retired as a cartoonist). Its surrealis ...

) with resolution down to . 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 The Manned Space Flight Network (abbreviated MSFN, pronounced "''misfin''") was a set of tracking stations built to support the American Mercury, Gemini, Apollo, and Skylab space programs. There were two other NASA space communication networks a ...

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 concentrations (mascons), or gravitational highs, which were located in the centers of some (but not all) of the lunar maria. Below is the flight log information of the five Lunar Orbiter photographic missions: *

Lunar Orbiter 1 The 1966 Lunar Orbiter 1 robotic spacecraft mission, part of NASA's Lunar Orbiter program, was the first American spacecraft to orbit the Moon. It was designed primarily to photograph smooth areas of the lunar surface for selection and verifica ...

**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 The 1966 Lunar Orbiter 2 robotic spacecraft mission, part of the Lunar Orbiter Program, was designed primarily to photograph smooth areas of the lunar surface for selection and verification of safe landing sites for the Surveyor and Apollo mi ...

**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 The Lunar Orbiter 3 was a spacecraft launched by NASA in 1967 as part of the Lunar Orbiter Program. It was designed primarily to photograph areas of the lunar surface for confirmation of safe landing sites for the Surveyor and Apollo missions. ...

**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 Lunar Orbiter 4 was a robotic U.S. spacecraft, part of the Lunar Orbiter program, Lunar Orbiter Program, designed to orbit the Moon, after the three previous orbiters had completed the required needs for Project Apollo, Apollo mapping and site s ...

**Launched May 4, 1967 **Imaged Moon: May 11 to 26, 1967 **Impact with Moon: Approximately October 31, 1967 **Lunar mapping mission *

Lunar Orbiter 5 Lunar Orbiter 5, the last of the "Lunar Orbiter series", was designed to take additional Apollo and Surveyor landing site photography and to take broad survey images of unphotographed parts of the Moon's far side. It was also equipped to collec ...

**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 () from the mosaics were created and several copies were distributed across the U.S. to NASA image and data libraries known a
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 o
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 th
Lunar and Planetary Institute
to scan the large-format prints of Lunar Orbiter data. These were made available online as th
Digital Lunar Orbiter Photographic Atlas of the Moon

Data recovery and digitization

In 2000, the

Astrogeology Research Program The Astrogeology Science Center is the entity within the United States Geological Survey concerned with the study of planetary geology and planetary cartography. It is housed in the Shoemaker Building in Flagstaff, Arizona. The Center was establ ...

of the US Geological Survey in Flagstaff, Arizona was funded by NASA (as part of th
Lunar Orbiter Digitization Project
) to scan at 25 micrometer resolution archival LO positive film strips that were produced from the original data. The goal was to produce
global mosaic
of the Moon using the best available

Lunar Orbiter The Lunar Orbiter program was a series of five uncrewed lunar orbiter missions launched by the United States from 1966 through 1967. Intended to help select Apollo landing sites by mapping the Moon's surface, they provided the first photographs ...

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 III, IV and V were included in the global mosaic. 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 Hills, and the Sulpicius Gallus rille have been released. In 2007, the

Lunar Orbiter Image Recovery Project The Lunar Orbiter Image Recovery Project (LOIRP) is a project to digitize the original analog data tapes from the five Lunar Orbiter spacecraft that were sent to the Moon in 1966 and 1967; it is funded by NASA, SkyCorp, SpaceRef Interactive, an ...

(LOIRP) began a process to convert the Lunar Orbiter Images directly from the original

Ampex Ampex is an American electronics company founded in 1944 by Alexander M. Poniatoff as a spin-off of Dalmo-Victor. The name AMPEX is a portmanteau, created by its founder, which stands for Alexander M. Poniatoff Excellence.AbramsoThe History ...

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. Almost all of the Lunar Orbiter images have been successfully recovered as of February 2014 and are undergoing digital processing before being submitted to NASA's

Planetary Data System The Planetary Data System (PDS) is a distributed data system that NASA uses to archive data collected by Solar System missions. The PDS is an active archive that makes available well documented, peer reviewed planetary data to the research communi ...

.LOIRP Moon Views
February 2014

References

External links

B.K. Byers, 1977, DESTINATION MOON: A history of the Lunar Orbiter Program (PDF), NASA TM X-3487 DESTINATION MOON: A history of the Lunar Orbiter Program (PDF) 1977, NASA TM X-3487
The above links lead to a whole book on the Lunar Orbiter program. For the HTML one, scroll down to see the table of contents link. *T.P. Hansen, 197
Guide to Lunar Orbiter Photographs (PDF), NASA SP-242Guide to Lunar Orbiter Photographs (PDF) 1970, NASA SP-242
National Space Science Data Center (NSSDC)

Lunar and Planetary Institute
Digital Lunar Orbiter Photographic Atlas of the Moon
Lunar and Planetary Institute
Lunar Orbiter Photo Gallery
Over 2,600 high- and moderate-resolution photographs
Lunar Orbiter Digitization Project
USGS Astrogeology Science Center

USGS Astrogeology Science Center, NASA Planetary Data System Archive
Lunar Orbiter Image Recovery Project (LOIRP) Overview
* NASA Documentary from 1967. {{DEFAULTSORT:Lunar Orbiter Program Missions to the Moon