Archaeology is the study of human activity through the recovery and analysis of artifacts and other evidence of material culture. While normally one associates archaeology with the study of ancient civilizations, it can also include research into activities from the present era as well. In recent years there has been an interest in visiting historical hardware in space or even on the Moon in part for scientific reasons but also as potential destinations for future space tourism. The historical and cultural significance of these sites and the potential impact of visitors has sparked a heated debate about how such sites should be protected.

While it will be some time before human archaeologists realistically will have an opportunity to visit a long-abandoned Apollo lunar landing site or some derelict unmanned lunar lander, we already have had a preview of what such an expedition will look like. As part of the second surface EVA on November 20, 1969 during the Apollo 12 lunar landing mission, astronauts Pete Conrad and Al Bean visited the unmanned Surveyor 3 spacecraft which had landed on the Moon 2½ years earlier on April 20, 1967. While the objectives of this visit were more engineering-oriented than archaeological, it does give a foretaste of what future lunar archaeological expeditions could find and how that visit will affect the site.

The Surveyor Spacecraft

This story starts with NASA’s Surveyor program whose primary objectives centered on supporting the upcoming Apollo lunar landing missions. In addition to performing basic engineering and scientific investigations about the nature of the lunar surface and its environment, they would also examine potential landing sites for the first Apollo missions to confirm predictions based on orbital photography. Work began on the Surveyor program in May 1960 under the responsibility of Caltech’s Jet Propulsion Laboratory (JPL) in Pasadena, California (for details on the early history and development of Surveyor, see “Surveyor 1: America’s First Lunar Landing”). Built by Hughes Aircraft Company (whose space division is now part of Boeing), Surveyor was arguably the most advanced lunar spacecraft of its day. The basic 2.4-meter tall structure consisted of a simple 27-kilogram tetrahedral frame made of tubular aluminum alloy members. In each of the three lower corners was a landing leg equipped with an aircraft-style shock absorber and a footpad of crushable honeycomb aluminum. The total span of the legs, once deployed, was 4.3 meters. Rising from the apex of the frame was a mast upon which was mounted a gimballed planar high-gain antenna and a solar panel supplying up to 85 watts of electrical power to the lander’s rechargeable silver-zinc batteries. From the footpads to the top of its mast, Surveyor stood three meters tall.

Buried inside the spacecraft’s frame was a Morton Thiokol-built 91-centimeter diameter TE-M-364 solid propellant rocket motor that would provide between 35.5 to 44.5 kilonewtons of thrust, depending on the motor’s temperature at ignition. This 656-kilogram motor would later be used as the third stage in various Delta launch vehicles models flown in the 1970s and as the final “kick stage” for the Pioneer and Voyager missions to the outer planets. With Surveyor flying a direct descent trajectory towards the lunar surface (instead of first entering lunar orbit as Apollo would do), this retrorocket would be used to negate most of Surveyor’s motion towards the Moon as the lander approached the lunar surface before being jettisoned during descent.

Surveyor also carried a second propulsion system for midcourse corrections and attitude control during the main retrorocket burn as well as for the final descent. This system consisted of three vernier engines fueled by monomethylhydrazine hydrate with MON-10 (a mixture of 90% nitrogen tetroxide and 10% nitric acid) serving as the oxidizer. These engines could be throttled by command of the spacecraft’s flight control subsystem producing between 130 and 460 newtons of thrust each. Yaw, pitch, and descent rate were controlled by selective throttling of the engines while roll was controlled by swiveling a single gimballed vernier. During the trans-lunar coast, Surveyor’s attitude was controlled by a set of six nitrogen gas jets, each providing 270 millinewtons of thrust.

All the temperature sensitive electronics were carried in two thermal boxes mounted to the frame. These compartments were covered with 75 layers of aluminized Mylar insulation and the tops were covered by mirrored glass thermal regulators. Compartment A, which maintained it internal temperature between +4° and +52° C, carried a redundant set of receivers and ten-watt radio transmitters, the batteries, their charge regulators, and some auxiliary equipment. The second box, Compartment B, was designed to maintain the temperature between -15° and +52° C. This compartment carried the computer “brains” of the spacecraft which controlled all aspects of the lander’s operation using a total of just 256 commands. Mounted elsewhere on the frame were star sensors, a pair of radar systems for landing, low-gain antennas, propellant, and helium pressurization tanks.

The only true scientific instrument carried by the initial batch Surveyors was a slow-scan television camera. The camera was mounted in a 1.65-meter tall mast attached to the spacecraft’s framework. The camera pointed up into a movable mirror that allowed the camera to view 360° of azimuth and from 60° below to 50° above the normal plane of the camera. The 7.6-kilogram camera package was canted at a 16° angle to offer a clear view of the surface between two of the footpads out to the lunar horizon 2½ kilometers away. The camera was fitted with a 25 to 100 mm zoom lens that offered a field of view of between 25.3° and 6.4°. The aperture could be set between f/4 and f/22 and the lens could be focused from 1.2 meters to infinity. A shutter was also included so that various integration times could be used to obtain the ideal exposure. While the nominal exposure time was 150 milliseconds, exposures as long as about thirty minutes could be accommodated. The typical resolution of the camera was one millimeter at a distance of four meters. By combining a series of images taken in a stepwise fashion at various azimuth and elevation angles, panoramic mosaics of the spacecraft and the surrounding terrain could be created.

The Surveyor 3 Mission

Unlike the first two Surveyors, Surveyor 3 carried an additional experiment: a remote controlled mechanical arm formally known as the Soil Mechanics Surface Sampler (SMSS). The SMSS consisted of a simple tubular aluminum pantograph with a 13-centimeter long, five-centimeter wide scoop attached to the end. One electric motor on the SMSS allowed the pantograph to extend outwards from 58 to 150 centimeters while another opened and closed the door on the scoop. A third motor allowed movement through 112° of azimuth while a fourth provided 42° of motion in elevation. Used in conjunction with Surveyor’s slow-scan television camera, the SMSS would be operated remotely in near-real time by an operator on the Earth to provide information on the mechanical properties of the lunar soil up to a depth of half a meter. The SMSS would give scientists their first chance to touch the surface of the Moon. With the SMSS and other modifications made to the spacecraft based on earlier experience, the total launch mass of Surveyor 3 was 1,036 kilograms – the heaviest so far in the series.

The primary objectives of the Surveyor 3 mission were to land in the equatorial Apollo landing zone east of Surveyor 1 (so that a landing out of the local vertical could be demonstrated) and then return television images of the surface. The secondary objectives included obtaining information on the bearing strength, radar reflectivity and thermal properties of the lunar surface as well as observe the effects of the SMSS on the lunar surface material using the television camera. The landing site ultimately chosen for the Surveyor 3 mission was in Oceanus Procellarum at 3.33° South, 23.17° West. The area had been imaged by NASA’s Lunar Orbiter 1 and 3 missions (see “Lunar Orbiter 1: America’s First Lunar Satellite”) and was eventually designated as “Site 7” for a future Apollo landing.

With Surveyor 3 tucked inside its launch shroud, Atlas-Centaur 12 successfully lifted off from Cape Kennedy’s Launch Complex 36B at 3:05:01 AM EST (7:05:01 GMT) on April 17, 1967. After a brief coast in a low Earth parking orbit (the first “operational” Centaur flight to do so), the Centaur stage reignited to send Surveyor 3 towards the Moon. Following a mid-course correction the day after launch, Surveyor 3 safely landed at 2.94° South, 23.34° West at 00:04:16 GMT on April 20 just 2.8 kilometers from its post-midcourse correction target point. Initial images returned shortly after landing revealed that Surveyor 3 had come down on the inner slope of an old 200-meter crater resulting in a noticeable 12° tilt to the local vertical. The subdued crater had rocks in a range of sizes present with blocks up to four meters long. All in all, it was considered a safe site for future Apollo lunar landings.

The day after landing, a pyrotechnic locking pin was fired freeing the SMSS to begin its first movements as it was observed via Surveyor’s slow-scan television camera. Over the coming days, the SMSS would perform a total of eight bearing tests, dig four small trenches and conduct 14 impact tests where the arm was dropped onto the surface from some predetermined height. With much effort, the SMSS was used to pick up a small rock and unsuccessfully attempted to break it in the scoop’s jaw in order to test its strength. The arm was also used to pick up and deposit a small amount of lunar soil on Surveyor’s landing pad so that it could be imaged through the television camera’s multiple color filters. All together, the SMSS responded to 5,879 commands during just over 18 hours of operation while Surveyor’s camera returned 6,326 television images during its first lunar day.

Shortly after local sunset on May 1, 1967, Surveyor 3 was placed into hibernation. Unlike the earlier Surveyor 1, ground controllers never regained contact with the lander after local sunrise two weeks later to attempt operations during a second lunar day. Despite the lack of extended mission operations, the Surveyor 3 mission was a complete success (for a full account of this mission, see “Surveyor 3: Touching the Face of the Moon”). Over the following eight months, NASA launched four more Surveyors with three of them successfully landing on the Moon. These missions clearly demonstrated that the mare sites chosen for the first Apollo lunar landing would be safe. Surveyor 7, which landed about 30 kilometers north of the rim of Tycho on January 10, 1968, showed that even scientifically interesting highland sites could be safely reached by later Apollo flights (see “Surveyor 7: The Mission to Tycho”).

The Apollo 12 Mission

As JPL was wrapping up the Surveyor program, NASA was pushing forward with an aggressive series of unmanned and then manned test flights of Apollo hardware. A spectacularly successful series of five manned Apollo missions over nine months culminating with the lunar landing of Apollo 11 on July 20, 1969 finally met the late President Kennedy’s mandate to land men on the Moon and safely return them to Earth before the end of the decade. With the Apollo program’s primary goal met, the focus turned towards plans for the Apollo 12 mission.

The all-Navy primary crew for the Apollo 12 mission consisted of Commander Charles “Pete” Conrad, Jr. as the Commander, Commander Richard F. Gordon, Jr. as the Command Module Pilot (CMP) and Commander Alan L. Bean as the Lunar Module Pilot (LMP). The crew’s previous assignment had been as the backup crew for the Apollo 9 mission flown in March of 1969 (see “Apollo 9: Giving the “Spider” Its Wings”). Pete Conrad, 39 years old, was part of NASA’s second group of astronauts announced in September 1962. Conrad had previously flown as the pilot on the Gemini 5 long duration mission in August 1965 (see “Eight Days or Bust: The Mission of Gemini 5”) and as the command pilot on the Gemini 11 mission 13 months later (see “Gemini 11: Preparing for Apollo”) for a total of almost 11 days in orbit. Dick Gordon was part of NASA’s third group of astronauts chosen in October 1963. Forty years of age, he had previously flown as Conrad’s pilot on the Gemini 11 mission in September 1966 logging two hours and 41 minutes of EVA time. The last member of the crew, 37 year old Al Bean, was part of NASA’s third group of astronauts like Gordon. This would be his first spaceflight.

Building on the experience gained during the Apollo 11 mission, the lunar surface objectives for Apollo 12 were significantly expanded. The stay time on the surface was increased by ten hours to a total of 31½ hours. This extra time allowed for a pair of 3½-hour surface EVAs to be performed instead of the single 2½-hour EVA of Apollo 11. With so much additional time on the surface, Conrad and Bean could conduct much more science. As part of the first EVA, the Apollo 12 crew would deploy the first ALSEP (Apollo Lunar Surface Experiments Package) – a collection of a half dozen instruments powered by a SNAP-27 RTG (Radioisotope Thermal Generator) which would continue to transmit data after the astronauts had departed for home. Tasks for the second EVA included a 2¼-hour geologic traverse of up to a couple of kilometers in length around the vicinity of the Lunar Module (LM), Intrepid. Small impact craters and other targets of geologic interest would be photographed and sampled along the way.

Mission planners spent much time selecting a landing site for Apollo 12. Still wishing to choose a fairly conservative (i.e. bland) site, the target would be one of the other half dozen equatorial mare landing sites in order to maximize safety. Since Apollo 11 had come down 6.9 kilometers from the center of its landing ellipse due to navigation issues, one of the tasks for Apollo 12 was to demonstrate a precision lunar landing. Proving such a capability would be required for future missions to more interesting sites where more precise targeting was essential for crew safety and meeting science objectives. A number of changes were made to the LM landing procedures and software to improve the accuracy of navigating through the Moon’s lumpy gravitational field. After much debate, Site 7 was chosen because of the presence of Surveyor 3 (which presented an obvious target to gauge navigation accuracy) and despite the roughness of the area compared to other sites being considered.

If Apollo 12 landed within about a kilometer of Surveyor 3, Conrad and Bean would visit the long-silent Surveyor during the mission’s second surface EVA traverse as part of a secondary objective of the mission. The plan was for the astronauts to enter the crater where Surveyor 3 landed (informally dubbed “Surveyor Crater”) collecting samples along the way. Al Bean was tasked with photographing Surveyor and its vicinity as Conrad read off a target checklist. Conrad would then use a pair of modified bolt cutters to remove the Surveyor’s television camera, a sample of camera cabling and a piece of polished aluminum tubing. These items would then be dropped untouched into a special environmental sample container for return to Earth. The astronauts would also inspect the mirrors used for thermal control on the spacecraft’s electronics boxes to determine the amount of any debonding and collect some samples, if possible. The plan was to spend about a half an hour performing Surveyor-related activities. An inspection of the components after they are returned to Earth would allow engineers to assess the effects of 31 months exposure to the lunar surface environment.

In order to reach Surveyor 3 at Site 7, Apollo 12 had to liftoff during a limited launch window extending from 11:22 AM to 2:28 PM EST on November 14, 1969. Since even a one-day delay in launch would result in the solar elevation angle at Site 7 being too high for a safe landing, a backup launch window running from 2:09 to 5:27 PM EST on November 16 would be used to land at Site 5 located at 41.90° W, 1.68° N in the western part of Oceanus Procellarum. Compared to the mare of Site 7, this was a more lightly cratered and younger site with a possible mantling of ejecta from Kepler Crater. If both windows were missed, launch windows existed a month later on December 14 and 15 to reach Sites 7 and 5, respectively.

The Visit to Surveyor 3

Apollo 12 lifted off in the rain from Kennedy Space Center’s LC-39A at the beginning of its launch window at 11:22:00 AM EST (16:22:00 GMT) on November 14, 1969. In order to get an on-time launch, Mission Rule I-404 was suspended which prevented liftoff during a rainstorm. Despite a lightning strike about 36 seconds after launch, Apollo 12 made it safely into its Earth parking orbit. After all systems were checked to make sure the lightning had not caused any damage, the S-IVB stage of Saturn V AS-507 reignited halfway through the second revolution of the Earth as planned to send Apollo 12 on its way to the Moon.

After the CSM, Yankee Clipper, extracted the LM, Intrepid, from the spent S-IVB stage, the pair of spacecraft continued on their translunar coast. Apollo 12 slipped into lunar orbit at 03:47:23 GMT on November 18. The following day, Yankee Clipper and Intrepid undocked and the LM began its descent to the lunar surface. As Intrepid pitched over to make its final approach for landing, Pete Conrad spotted Surveyor Crater and exclaimed, “Hey, there it is! There it is! Son of a gun, right down the middle of the road!” as Al Bean continued to read out data from the flight computer. Intrepid landed at 06:54:36 GMT on November 19 just beyond the rim of Surveyor Crater only 155 meters from Surveyor 3. Apollo 12 had made the second successful manned landing on the lunar surface and had demonstrated the ability to make a precision landing.

The first surface EVA started at 11:33 GMT just over 4½ hours after landing. After Bean joined Conrad on the surface a half hour later, the two astronauts set about familiarizing themselves with the new environment, collecting contingency samples and setting up the ALSEP, among other tasks. The slightly longer than planned EVA 1 was completed after 3 hours and 56 minutes successfully meeting nearly all its objectives. The only notable issue was the loss of the color television camera which was to be used to provide live coverage of the EVA as well as help survey the landing site for geologists back on Earth. As Conrad was moving the camera from its mount on the LM (where it transmitted the crew’s first steps on the Moon) to a tripod, he accidentally pointed the camera at the Sun burning out its vidicon tube in the process. After the EVA, Conrad and Bean recharged their PLSS life support packs, were debriefed by Mission Control, ate and got some much needed sleep.

While Conrad and Bean were scheduled for 8½ hours of rest, they were up and preparing for their second day of work an hour early. Two hours ahead of schedule, EVA 2 started at 03:54:45 GMT on November 20. At Conrad’s suggestion, the pair of moonwalkers immediately set out on their geologic traverse. After passing the ALSEP deployed the previous day (whose seismometer picked up the astronaut’s footsteps), the crew proceeded to their targets at craters informally dubbed “Head”, “Bench”, “Sharp” and “Halo” where surface and core samples were collected after being carefully photographed to document their geologic context.

Conrad and Bean had reached the southern rim of Surveyor Crater at about 06:06 GMT about two hours into their planned traverse. By this point, Mission Control had given permission to extend the EVA by another 30 minutes to give the astronauts plenty of time to complete their remaining tasks. While during EVA 1 Conrad perceived Surveyor (which was in the shadow on the far side of the Surveyor Crater at the time) to be on a nearly vertical slope, from the new, fully sunlit perspective, the slope did not seem anywhere near as steep. The astronauts carefully made their way down the 12° slope of the crater making sure that the lunar soil was not too loose. After they confirmed their firm footing, they made their way to Surveyor 3 as Bean took photographs as they approached.

After reaching Surveyor 3 at 06:22 GMT, Al Bean took a series of photographs of selected components as Pete Conrad read off their checklist. The astronauts noted that all the white painted and shiny metal surfaces of the lander had a tan-like color. When rubbed hard enough, this light coating of brown material seemed to come off suggesting it was dust which had been deposited over the previous 30 months on the surface. Despite the slope, the crew had a firm footing and were unable to make Surveyor slide or tip when they pushed on it. The marks left by the Surveyor’s footpads and SMSS were photographed and surface sample secured so that Surveyor’s findings could be correlated with detailed analysis back on Earth.

After securing the photographs of Surveyor, Conrad proceeded to use the bolt cutters to remove Surveyor’s television camera as well as samples of cabling and an unpainted aluminum tube near the landing strut for Leg 2. The moonwalkers tried to flex the sheet metal on the top of the pair of Surveyor’s thermally controlled electronics boxes in hopes of debonding part of the mirrors mounted on them. Unfortunately, the mirrors only shed fine slivers of glass, so no samples were gathered as hoped. As a bonus, Conrad was able to cut the scoop from the end of Surveyor’s SMSS and slip it into his sample bag. After spending 33 minutes at Surveyor 3, Conrad and Bean then proceeded out of Surveyor Crater and back to Intrepid to wrap up EVA 2 after a 1.8 kilometer traverse. The EVA ended after 3 hours and 49 minutes bringing the mission’s total to 7 hours and 45 minutes – almost three times longer than the Apollo 11 EVA.

Coming Home

With the recovered Surveyor parts and 34 kilograms of lunar samples stowed, Intrepid lifted off the lunar surface on time at 14:25:47 GMT on November 20 to begin the journey home. Intrepid and Yankee Clipper docked 3½ hours later. After Conrad and Bean (along with their samples) rejoined Dick Gordon in the CSM, the LM was jettisoned and deliberately impacted the lunar surface 72 kilometers east southeast of the Apollo 12 landing site to provide a test of the ASLEP seismometer left behind.

After completing their tasks in lunar orbit, Yankee Clipper ignited its main engine at 20:49:16 GMT on November 21 for the Trans Earth Injection to begin the trip back to Earth. The Apollo 12 CM safely splashed down in the Pacific at 20:58:25 GMT on November 24 ending the highly successful ten-day mission. The crew along with their CM and returned samples were placed into quarantine and transferred to the Lunar Receiving Laboratory in Houston for evaluation. After being declared devoid of any biological hazards, the crew was free to go and the returned samples were released to investigators.

Engineers and scientists at Hughes, which had built the Surveyors, were tasked with examining the spacecraft components returned from the lunar surface. A total of 36 studies by 80 investigators were made. Despite exposure to 32 day-night cycles on the lunar surface, the components of Surveyor 3 were in remarkably good condition. While the surface paint was darkened by a thin coating of lunar dust as well as radiation exposure, no failures or serious adverse environmental effects were found. Most of the dust on the spacecraft, which can have deleterious effects on thermal control, was deposited during Surveyor’s initial landing but there was also evidence that the landing of Apollo 12 sandblasted the lander despite the 155-meter distance. Such dust contamination will be an issue in any future investigation of lunar hardware.

Probably one of the more publicized findings from the examination of the returned Surveyor components came from the microbe survival analysis. A common bacterium, Streptococcus mitis, was isolated from a sample of foam taken from the interior of the television camera. The evidence suggested that the bacterium was deposited there before launch and had survived inside the camera despite 2½ years exposure to the lunar environment. Nothing was found on a sample of cable. The conclusion that the bacterium had survived its exposure on the Moon has been questioned in recent years. It has been suggested that the sample could have been contaminated after the camera’s return. Better procedures will be needed for future studies of biological contamination of spacecraft. These and other lessons from Apollo 12 will be vital for planning future visits to historic extraterrestrial landing sites and minimizing the impact of such visits.

Follow Drew Ex Machina on Facebook.

Related Video

Here is an excellent NASA documentary about the Apollo 12 mission entitled “Apollo 12: Pinpoint for Science.”

Related Reading

“Surveyor 3: Touching the Face of the Moon”, Drew Ex Machina, April 17, 2017 [Post]

General References

David Baker, The History of Manned Space Flight, Crown Publishers, 1981

Richard W. Orloff and David M. Harland, Apollo: The Definitive Sourcebook, Springer-Praxis, 2006

Surveyor III Preliminary Science Results, PD-125, JPL, May 15, 1967

Surveyor III: A Preliminary Report, SP-146, NASA, June 1967

Apollo 12 Press Kit, NASA Press Release 69-148, November 5, 1969

Apollo 12 Technical Debriefing, NASA, December 1, 1969

Apollo 12 Mission Report, MSC-01855, Johnson Space Center, March 1970

Test and Evaluation of the Surveyor III Television Camera Returned from the Moon by Apollo XII – Volumes 1 & 2, Hughes Aircraft Co., December 31, 1970

Apollo 12 Preliminary Science Report, SP-235, NASA, 1970

Analysis of Surveyor 3 Material and Photographs Returned by Apollo 12, NASA, 1972