The robot scouts of Apollo
NASA’s Surveyor programme sent seven uncrewed spacecraft toward the Moon between 1966 and 1968, five of which landed successfully. Their purpose was practical: to show that a spacecraft could make a controlled landing on the Moon, and to examine the ground it landed on. One fear of the time was that the Moon might be covered with such a deep layer of loose dust that a heavy craft would sink. Surveyor was designed to find out.
Surveyor 1 made the first American soft landing in June 1966. Surveyor 3, the third in the series, came ten months later.
Launch and landing
Surveyor 3 was launched on 17 April 1967 on an Atlas-Centaur rocket and reached the Moon on 20 April. It targeted an area in the Oceanus Procellarum region on the Moon’s near side, and one of the aims was to test a site resembling places proposed for Apollo landings.
The landing did not go exactly as planned. Normally, the spacecraft’s main descent engines were meant to shut off just before touchdown. In this case, a radar problem meant the engines kept firing after the first contact, and the craft lifted off again and bounced. By most accounts it touched down in total three times, before settling inside a shallow crater. The spacecraft survived intact, which was a useful demonstration of how robust the design was.
What Surveyor 3 did on the surface
Surveyor 3 carried a television camera and, unlike the first Surveyor, a mechanical scoop on a short arm, called the surface sampler. With this, controllers on Earth could dig trenches, press the scoop into the soil, drop it, and examine how the ground responded.
The results were reassuring. The lunar soil, though fine and powdery, had enough strength to support a spacecraft and astronauts. Engineers compared its behaviour to damp sand or similar granular material. The camera sent back thousands of images, with figures of over six thousand frequently cited, including views of the landscape, the spacecraft’s own footpads, and the digging operations.
Later in April, the camera also photographed the Earth passing in front of the Sun, a lunar view of a solar eclipse. These were unusual pictures at the time, and they showed the glow around the Earth’s edge.
Working life was limited by the lunar night, which is about two weeks long and extremely cold. Surveyor 3 operated through the first lunar day and then ceased to respond. Its mission was judged a success.
The Apollo 12 visit
Surveyor 3’s story did not end there. In November 1969, Apollo 12 astronauts Charles “Pete” Conrad and Alan Bean landed on the Moon in a pinpoint landing in the same area, on the Ocean of Storms. NASA had picked the site partly because Surveyor 3 was nearby, so that the astronauts could demonstrate they could land accurately.
After landing, they walked to the crater, a distance of roughly 180 metres, and examined the older spacecraft. They saw that it had changed. It had taken on a tan colour because it was covered in a fine layer of dust, probably thrown up by the Apollo landing and settled onto it.
The astronauts removed pieces from the probe, including the television camera, parts of the scoop, and some tubing and cable. These were returned to Earth. Engineers could then study how materials had weathered after about thirty-one months on the Moon, exposed to vacuum, radiation, extreme temperatures and micrometeoroids. The camera is now held in the Smithsonian’s National Air and Space Museum collection.
A claim that bacteria had survived on the returned camera drew a lot of attention. It was later questioned, and the generally favoured view is that contamination occurred during handling on Earth, rather than that life survived on the Moon.
Why Surveyor 3 mattered
Surveyor 3 was one of the quiet successes of 1967, a year that included the Apollo 1 fire and other setbacks. It confirmed that landing was feasible, offered close-up information about the soil, and provided a rare chance to examine hardware that had been exposed to the lunar environment. The pictures of the Moon taken from orbit by Lunar Orbiter had shown potential sites, and the Surveyors helped check whether those sites were safe.
For the Apollo programme, Surveyor 3 was a probe that returned a second time, brought back by humans who had come to meet it.