Lunar Orbiter program

• 1. Mapping The Moon For Apollo

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  The United States launched five uncrewed spacecraft to the Moon between 1966 and 1967. These missions aimed to map the lunar surface for Apollo landing site selection. NASA needed detailed images of potential crewed landing areas before sending astronauts. The first three missions focused on imaging twenty specific sites chosen from Earth-based observations. These flights operated in low-inclination orbits to capture close-up views. The fourth and fifth missions targeted broader scientific goals instead. They flew in high-altitude polar orbits to cover the entire near side and parts of the far side. Lunar Orbiter 4 photographed the whole nearside plus nine percent of the dark hemisphere. Lunar Orbiter 5 completed the far side coverage while acquiring medium and high resolution images of thirty-six preselected areas. All five missions succeeded in mapping ninety-nine percent of the lunar surface with resolutions better than one meter.

• 2. Engineering A Truncated Cone Bus

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  Boeing and Eastman Kodak developed a truncated cone bus for these spacecraft. The main body stood about two meters tall and measured roughly one point four meters in diameter at its base. Four solar panels extended outward from the equipment deck with a total span across of nearly six meters. The equipment deck held batteries, transponders, flight programmers, and inertial reference units. It also contained Canopus star trackers and command decoders. A traveling-wave tube amplifier supported communications systems. Four attitude control thrusters mounted on the perimeter of the top deck managed orientation. Power reached three hundred seventy-five watts via solar arrays containing ten thousand eight hundred fifty-six n/p cells. These cells directly ran the spacecraft and charged a twelve amp-hour nickel-cadmium battery. Propulsion came from a gimballed velocity control engine using hypergolic thrust from Marquardt Corp rocket motors. Three axis stabilization relied on nitrogen gas jets. Thermal control used multilayer aluminized Mylar blankets to protect the craft.

• 3. Five Successful Launches Between 1966 And 1967

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  Lunar Orbiter 1 launched on the 10th of August 1966, and imaged the Moon from August 18 through 29 that same year. It impacted the lunar surface on the 29th of October 1966, after completing its survey mission. Lunar Orbiter 2 followed on the 6th of November 1966, imaging the Moon between November 18 and 25 before crashing into the surface on the 11th of October 1967. The third spacecraft launched the 5th of February 1967, and operated until the 9th of October 1967 when it crashed as planned. Lunar Orbiter 4 lifted off the 4th of May 1967, and finished its mapping duties by late October of that year. The final mission, Lunar Orbiter 5, launched the 1st of August 1967, and remained operational until the 31st of January 1968. All five missions returned photography covering ninety-nine percent of the Moon's surface. Altogether they sent back two thousand one hundred eighty high resolution frames plus eight hundred eighty-two medium resolution frames. Each spacecraft was eventually commanded to crash into the Moon to avoid becoming navigational hazards for future Apollo flights.

• 4. Film Processing Onboard A Spacecraft

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  Kodak created an onboard film development process that scanned images from seventy millimeter film for transmission back to Earth. The camera used two lenses simultaneously exposing wide-angle and high-resolution images onto a single roll of sixty-five millimeter Kodak Bimat film. An eighty millimeter F 2.8 Xenotar lens manufactured by Schneider Kreuznach handled medium resolution shots. A six hundred ten millimeter F 5.6 Panoramic lens made by Pacific Optical Company captured high detail views. The film moved during exposure to compensate for spacecraft velocity estimated by an electro-optical sensor. After exposure, the film underwent processing using a semidry process before scanning began. A photomultiplier then scanned the developed images as analog video signals. Receiving stations on Earth transferred these video images back onto film for final processing at Kodak facilities in Rochester. This system adapted permissions from the NRO allowed use of SAMOS E-1 reconnaissance camera technology originally built for USAF near-realtime satellite imaging projects.

• 5. Discovering Mascons And First Earth Pictures

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  During the Lunar Orbiter missions, the first pictures of Earth as a whole were taken starting with Earth-rise over the lunar surface by Lunar Orbiter 1 in August 1966. Lunar Orbiter 5 captured the first full picture of the entire Earth on the 8th of August 1967. A second photo of the complete globe followed on the 10th of November 1967. Doppler tracking of the five orbiters enabled mapping of the Moon's gravitational field and discovery of mass concentrations known as mascons. These gravitational highs appeared located in centers of some but not all lunar maria. Micrometeoroid experiments recorded twenty-two impacts showing average flux near the Moon was about two orders of magnitude greater than interplanetary space. Radiation experiments confirmed Apollo hardware design would protect astronauts from short-term solar particle events. The program managed by NASA Langley Research Center cost roughly two hundred million dollars total.

• 6. Digitizing Lost Analog Tapes In The 2000s

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  In 2000 the Astrogeology Research Program of the US Geological Survey received funding to scan archival LO positive film strips at twenty-five micrometer resolution. This project aimed to produce a global mosaic using the best available frames largely matching coverage from Bowker and Hughes 1971 atlas. Frames were constructed from scanned film strips digitally controlled and map-projected without original striping issues. Only fifteen percent of available photographic frames got scanned due to emphasis on global mosaic construction. Data from missions three four and five contributed to this effort. Sites like the Apollo 12 landing area and Marius Hills received special attention for scientific interest. In 2007 the Lunar Orbiter Image Recovery Project began converting images directly from original Ampex FR-900 analog video recordings to digital format. First restored images appeared in late 2008 with vastly improved resolution over 1960s releases. Almost all recovered images underwent digital processing before submission to NASA's Planetary Data System. The task addressed venetian blind striping missing data duplication effects that hampered earlier use.