The mission of the Surveyor 5 lunar spacecraft began at 3:57 a.m. EDT Sept. 8, 1967.
It lifted off from Cape Canaveral’s Launch Complex 36B aboard an Atlas-Centaur two-stage rocket.
The Surveyor 5 lander weighed 2,218 pounds and carried instruments to test lunar soft-landing technology, collect surface data, and support safe human landings.
It was one of several unmanned spacecraft built to prove precision soft-landing technology essential for Apollo.
The lander stood about 10 feet tall on a lightweight, three-legged aluminum frame with crushable footpads built to absorb impact.
A central mast supported a solar array of 792 cells, supplying 85 watts of electrical power.
Near the mast were a high-gain antenna for detailed data and images, and an omnidirectional antenna for continuous Earth communication.
As it approached the moon, Surveyor 5 began its landing sequence, which was a two-stage automated process.
First, a large solid-fuel retrorocket fired at approximately 39,000 feet above the moon’s surface to slow the spacecraft’s descent.
Once jettisoned, three gimbaled vernier engines (small, steerable thrusters) handled the final approach.
Guided by a radar altimeter, the engines enabled a controlled descent toward the surface.
However, an unexpected helium regulator valve leak forced NASA flight controllers to shut the engines off early, causing the spacecraft to free-fall the final 42 feet to the lunar surface at a speed of 7.4 miles per hour.
Surveyor 5 safely landed Sept. 10 at 8:46 p.m. EDT in Mare Tranquillitatis (the Sea of Tranquility) which is a broad, flat plain on the moon formed by ancient volcanic lava flows.
The spacecraft touched down inside a small, rimless crater approximately 30 by 40 feet in diameter and 4 feet deep, situated at a 20-degree slope at coordinates 1.4551°N, 23.1943°E.
One of its footpads landed near the crater rim, while the other two settled lower on the slope.
Surveyor 5’s vidicon television camera recorded the lander’s touchdown and its effect on the lunar surface.
This provided NASA engineers with data used to develop the descent and lift-off procedures for the Apollo Lunar Module’s engines.
After landing, Surveyor 5 slid slightly downhill; an event captured in images showing furrows in the soft regolith, aka loose, rocky material covering the lunar surface.
The panoramic view provided by the Surveyor 5 lander allowed NASA to assess the area around the crater and to study the lunar surface in detail.
Developed by NASA’s Jet Propulsion Laboratory and Caltech, the onboard alpha-scattering instrument was activated about 11.5 hours after landing via commands sent from NASA’s Deep Space Network station near Madrid, Spain.
These commands lowered the alpha-scattering instrument about 30 inches to make contact with the lunar surface on a nylon line.
The instrument’s gold-and-white sensor head, measuring 7-by-6-by-5 inches and weighing five pounds, contained six Curium-242 sources that bombarded the moon’s soil with alpha particles.
Built-in detectors then measured the energy of the scattered particles to identify the chemical makeup of the regolith.
The results showed that the soil was rich in elements such as silicon, aluminum, iron, magnesium, calcium, and titanium.
These elements confirmed that the dark, flat Mare Tranquillitatis region was formed by ancient volcanic activity.
Surveyor 5’s radar reflectivity measurements, which processed the lunar surface texture and composition data at the landing site, validated Mare Tranquillitatis as a safe region for the first crewed landing, which would be the Apollo 11 mission.
About 53 hours after landing, on Sept. 13, 1967, NASA controllers briefly fired one of Surveyor 5’s vernier engines for half a second to observe how the thrust would disturb nearby lunar soil.
NASA announced that the firing created no new cratering and did not generate any significant dust cloud.
Thermal data collected by Surveyor 5 recorded surface temperatures ranging from 234 degrees Fahrenheit during the lunar day to minus 274 degrees at night.
Its television camera transmitted 19,118 photographs to Earth during its mission, which concluded with its final data transmission at 11:30 p.m. EST Dec. 16, 1967.
Surveyor 5 became the fifth spacecraft from Earth to make a successful soft landing on the moon, following Luna 9 (1966), Surveyor 1 (1966), Luna 13 (1966), and Surveyor 3 (1967).
Surveyor 4 was launched July 14, 1967, at 7:53 a.m. EST from Cape Canaveral’s Launch Complex 36A.
As it approached the moon July 17, all radio contact was lost during its descent; just 2.5 minutes before landing. NASA concluded that the spacecraft likely exploded or suffered catastrophic failure, possibly due to the explosion of the solid-fuel retrorocket.
The Apollo 11 lunar module, Eagle, touched down in the southwestern region of the Sea of Tranquility July 20, 1969, at coordinates 0.67416°N, 23.47314°E.
Eagle’s landing site is approximately 15.5 miles southeast from where Surveyor 5 touched down.
The data received from Surveyor 5 played a significant role in Apollo 11’s historic landing in the Sea of Tranquility and its “giant leap” into the history books.
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