Surveyor 3

• 1. Introduction

  ›

  Surveyor 3 is the only spacecraft that humans have ever visited on another world. In November 1969, Apollo 12 astronauts Pete Conrad and Alan Bean walked up to this American uncrewed lander on the Moon and carried pieces of it back to Earth. It had arrived there in 1967 as the third lander of the Surveyor program, and only the second to land successfully. How did it get down in one piece? What did its scoop and camera reveal? And why did a few parts that came home with the astronauts spark a debate about bacteria on the Moon?

  1712

• 2. Bouncing Down

  ›

  Surveyor 3 left Earth on the 17th of April 1967 and touched the Moon on the 20th of April. Its destination was the Mare Cognitum portion of the Oceanus Procellarum, and it came down inside a small crater that was later named Surveyor.

  At 14 feet above the surface, the engines were supposed to shut off. They did not, because highly reflective rocks in the crater had confused the lander's descent radar. The engines kept running, and the lander bounced twice. The first bounce reached about 35 feet, and the second about 11 feet. On the third contact with the surface, Surveyor 3 settled into the soft landing that was intended all along. Now it could put to work the feature that set it apart from every earlier Surveyor, an electric arm carrying a scoop.

  13689

• 3. Digging the Moon

  ›

  A scoop on an electric-motor-driven arm let Surveyor 3 dig trenches up to 7 inches deep in the lunar soil. Soil from those trenches was set in front of the television cameras, photographed, and radioed to Earth.

  Engineers called the device the soil mechanics surface sampler. They built it to dig, scrape and trench the surface, and to carry lunar material in front of the camera so its properties could be judged.

  The scoop measured roughly 120 mm long and 50 mm wide. It had a container, a sharpened blade, and an electric motor to open and close the container. A small footpad on the scoop door gave it a flat surface to press against the ground. The scoop could hold up to 100 cm3 of granular material.

  The pantograph arm carrying it could extend about 1.5 m or retract close to the spacecraft. Motors swung it from +40 to -72 degrees in azimuth and raised it by 130 mm. It could also be dropped onto the surface, driven by gravity and a spring.

  Over ten separate occasions, the sampler worked for a total of 18 hours and 22 minutes. It performed seven bearing tests, four trench tests, and thirteen impact tests. Penetrations in the bearing tests measured 38-50 mm.

  The thirteen impact tests could not reveal the soil's density, because the torque spring had a small spring constant. Motor currents and applied forces were also not recorded, because of the state of the telemetry after landing, though estimates were still possible. Even so, the mechanism and its electronics proved more than adequate for the work. The sampler hung just below the television camera, whose own record of the mission ran to thousands of frames.

  81116

• 4. Eyes on the Moon

  ›

  Among the 6,315 pictures the television camera sent home were the first images showing what Earth looks like from the Moon's surface. Others showed the spacecraft itself, panoramic surveys of the terrain, the digger at work, and an eclipse of the Sun by the Earth on the 24th of April.

  The camera held a vidicon tube behind lenses of 25 and 100 millimeter focal length, along with shutters, an iris, and clear, red, green and blue filters. The assembly was inclined about 16 degrees to the spacecraft's central axis and mounted under a mirror that could swing horizontally and vertically. That mirror gave frame-by-frame coverage through the full 360 degrees of azimuth, from +40 degrees above the camera's reference plane to -65 degrees below it.

  Everything the camera did depended on commands from Earth, including its choice between a 200-line mode and a 600-line mode. The 200-line mode scanned one frame every 61.8 seconds and traveled over an omnidirectional antenna. Sending each of those pictures took 20 seconds and a bandwidth of 1.2 kHz. The 600-line mode used a directional antenna and could scan as often as once every 3.6 seconds. Each of those pictures needed about one second to be read from the vidicon and 220 kHz of bandwidth, with digital picture transmission.

  A long-persistence phosphor coated the slow-scan monitor that displayed the pictures on Earth. Its persistence was chosen to match the maximum frame rate. One frame of identification arrived with each photo, the picture appeared in real time, and a video magnetic-tape recorder kept the data. The camera's hardware would eventually be examined back on Earth, long after its last transmission.

  1826

• 5. The Long Night

  ›

  The first lunar nightfall arrived on the 3rd of May 1967, and Surveyor 3 was shut down because its solar panels no longer produced electricity. Lunar dawn came after 14 terrestrial days, about 336 hours. The lander could not be reactivated, because of the extremely cold temperatures it had experienced.

  Surveyor 1 had fared differently. It was reactivated twice after lunar nights, but then never again. The silent Surveyor 3 would sit in its crater for more than two years before anyone came to it.

  168

• 6. Walking to Surveyor

  ›

  Surveyor 3 became famous after Apollo 12 chose its crater as the landing target for the Lunar Module. On the 19th of November 1969, the crew set down within walking distance of the old probe. Conrad and Bean examined the spacecraft and took several pictures of it.

  A scoop, two aluminum tubes, a length of cable and the television camera came off the lander. One tube was unpainted and came from a strut supporting the radar altimeter and Doppler velocity sensor. The other was coated with inorganic white paint. The cable segment was wrapped in aluminized plastic film. The scoop came from the soil mechanics surface sampler.

  Together the parts weighed about 10 kg. They were meant for studying the long-term effects of the harsh lunar environment on human-made objects and materials.

  In 2009, the Lunar Reconnaissance Orbiter photographed the Surveyor 3 site in detail, and astronaut foot tracks around the lander were visible. In 2011, the orbiter returned at a lower altitude to take higher-resolution photographs.

  71231617

• 7. Back in the Lab

  ›

  The returned camera had endured 947 days in vacuum, including 32 two-week lunar nights with temperatures dropping below -200 F, and it was in good condition. Most major components were functional and undamaged. Temperature extremes, micrometeorite strikes, and manufacturing errors had left some changes. The recovered scoop was also in good condition, with little change beyond some sun-induced fading of its paint.

  The camera now sits on permanent display in the National Air and Space Museum in Washington, D.C. The scoop is on display at JPL. A different question hung over the camera, though: whether anything living had come home inside it.

  117112

• 8. The Bacteria Claim

  ›

  A widely repeated claim holds that Streptococcus mitis, a common bacterium, accidentally contaminated Surveyor's camera before launch. According to the claim, the bacteria lay dormant in the harsh lunar environment for two and a half years and were detected after Apollo 12 brought the camera to Earth. Some have cited this as credence for interplanetary panspermia, the idea that life can travel between worlds.

  The claim also led NASA to adopt strict abiotic procedures for probes bound for Mars and other bodies suspected of conditions suitable for life. Most dramatically, the Galileo probe was deliberately destroyed at the end of its mission by crashing it into Jupiter, to avoid contaminating the moon Europa with bacteria from Earth. The Cassini probe also impacted Saturn at the end of its mission in 2017.

  Independent investigators have challenged the Streptococcus mitis claim. They point to two possibilities for the contamination: a container that was not airtight, or the handling of samples in the clean room after Apollo 12.

  13141511