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Boeing Lunar Orbiter 1–5

Boeing · Lunar Photographic Mapping Orbiters (Apollo Prep) · USA · Early Jet (1946–1969)

The Lunar Orbiter Program was a NASA series of five robotic spacecraft — Boeing's NASA Apollo-era reconnaissance missions to photograph the Moon + map potential Apollo landing sites. Boeing developed the Lunar Orbiter at Seattle in 1963-1966; launched 5 spacecraft on Atlas-Agena boosters from Cape Canaveral in 1966-1967. All 5 missions were successful. The programme directly enabled Apollo 11's July 1969 lunar landing by mapping suitable landing sites + characterising the lunar surface in unprecedented detail.

Each Lunar Orbiter (Boeing-built) was a ~390 kg spacecraft with film-based photographic system, S-band telemetry, + small thrust system. Dimensions 1.65 m × 1.5 m × 1.6 m. Power: 4 solar panels (~375 W at Moon distance). Cameras: a unique hybrid film-photo + on-orbit film-developer + electronic-scanner — the camera exposed 70 mm film, on-board developed it with Bimat process (a NASA-Eastman Kodak chemical development), then electronically scanned the negative + transmitted the image to Earth via S-band radio. Coverage: 99% of the lunar surface at medium resolution + 98% of the Moon's near side at very-high resolution (~1 m / pixel — sufficient to identify boulders + craters that would threaten Apollo landings).

Lunar Orbiter missions: Lunar Orbiter 1 (10 August 1966, mapped Apollo landing sites + provided the first photo of Earth from the Moon — the iconic 'Earthrise' image that preceded the more-famous Apollo 8 1968 version), Lunar Orbiter 2-3 (1966-1967, continued Apollo site mapping), Lunar Orbiter 4-5 (1967, scientific mapping of remaining lunar surface + polar regions). All 5 spacecraft were intentionally impacted on the Moon at end of mission. The programme cost ~$200 million (1966 dollars) — a successful + efficient Apollo precursor + a major Boeing space-systems contract. The Lunar Orbiter images remained the principal lunar-surface reference until the 2009-present Lunar Reconnaissance Orbiter (LRO) provided modern digital coverage.

For Kids — a shorter, friendlier version

The Lunar Orbiter Program was a set of five robot spacecraft that flew to the Moon in 1966 and 1967. NASA hired Boeing to build them. The mission was to take pictures of the Moon and find safe spots for the Apollo astronauts to land.

Each Lunar Orbiter was about as big as a small car. The spacecraft used a strange but clever camera system. Real film took the photos, then a small machine on board developed the film. The pictures were then scanned and sent back to Earth by radio.

All five missions worked perfectly. Together, they took photos of 99% of the Moon. That was a huge step at the time. Without those photos, the Apollo 11 astronauts would not have known where it was safe to land in 1969.

The Lunar Orbiters even helped scientists find weird gravity bumps on the Moon called mascons. The spacecraft also took the first picture of Earth rising over the Moon, which became one of the most famous photos in space history. After their missions, all five Lunar Orbiters were crashed on purpose into the Moon.

Fun Facts

Five Lunar Orbiter spacecraft flew to the Moon in 1966 and 1967.
Together they took pictures of 99% of the Moon's surface.
Their photos helped NASA pick safe landing spots for the Apollo astronauts.
Each spacecraft used real film and developed the photos in space.
They discovered weird heavy spots on the Moon called mascons.
All five spacecraft were crashed on purpose into the Moon after their missions.

Kids’ Questions

Why did the Lunar Orbiters use real film instead of digital cameras?

Digital cameras did not exist yet in the 1960s. The Lunar Orbiter used a clever system that took photos on film, developed the film right on the spacecraft, and then scanned the photos to send them home by radio. It was the best way to get sharp Moon photos at that time.

Why were the spacecraft crashed into the Moon?

NASA crashed them on purpose so they would not get in the way of future spacecraft going to the Moon. The crashes also helped scientists study how the Moon's surface reacted. The Lunar Orbiters had run out of fuel and were no longer useful.

Variants

Lunar Orbiter 1-5 (1966-1967): Five identical spacecraft. All missions successful.

Notable Operators

NASA (1966-1967): Sole operator. Apollo lunar-landing reconnaissance.

Frequently Asked Questions

How did the film-camera + telemetry system work?

Each Lunar Orbiter carried two cameras (medium- + high-resolution) loaded with 70 mm Eastman Kodak film. After photographing the lunar surface during orbital passes, the film advanced through an onboard processor that used Bimat — a single-bath chemical developer — to develop the negatives entirely in-spacecraft. The developed negatives then ran through a flying-spot photomultiplier scanner that converted the image to an analog electrical signal, modulated on S-band radio + transmitted to Earth ground stations. Earth-station film recorders reconstructed the image from the analog signal. The system was a remarkable engineering achievement — film + chemicals + cameras + scanner + transmitter all working autonomously in vacuum + radiation. The total transmitted-image area equalled ~12,000 modern A4 pages of high-resolution lunar surface photography.

Sources

Wikipedia — Lunar Orbiter Program