Apollo Expeditions to the Moon: Chapter 12

Ocean of Storms and Fra Mauro

By CHARLES CONRAD, JR., and ALAN B. SHEPARD, JR.

Photo of Apollo 12 astronaut Alan Bean — Apollo 12 Astronaut Alan Bean examines Surveyor III’s camera. The two astronauts walked down to the spacecraft from their own lunar module, which they had landed about 600 feet away. They removed the TV camera and the scoop so that scientists could study the effects on well-known materials of a 31-month lunar sojourn. A third spacecraft, Lunar Orbiter III, made the pinpoint landing possible by its earlier feat of photographing the site in exquisite detail.

Scientific exploration of the Moon began in earnest with the Apollo 12 and 14 missions. Four astronauts worked on the Moon in four-hour shifts, walking from site to site. The Apollo 12 astronauts carried everything: experiments, equipment, tools, sample hags, cameras. The Apollo 14 team had a small equipment cart, and some of the time it was a help. But the missions showed that a man in a pressurized suit had definite limitations on the rugged and perplexing lunar surface. It was more work than it seemed, and in the case of Apollo 14, medical advice from Earth ended one phase of activity. But the two missions produced a wealth of new scientific data and lunar samples, and both laid a firm foundation for the great voyages of lunar exploration to follow.

The sky was cloudy and rain was falling on November 14, 1969, as the Apollo 12 crew prepared for launch. Half a minute after liftoff a lightning strike opened the main circuit breakers in the spacecraft. Quick action by the crew and Launch Control restored power, and Astronauts Charles “Pete” Conrad, Jr., Richard F. Gordon, and Alan L. Bean sped into sunlight above the clouds. “We had everything in the world drop out”, Conrad reported. “We’ve had a couple of cardiac arrests down here too”, Launch Control radioed back.

Their destination was the Ocean of Storms. Four and a half days later, Conrad and Bean entered the lunar module Intrepid and separated from Gordon in the command module Yankee Clipper. Their landing site was about 1300 miles west of where Apollo 11 had landed, on a surface believed covered by debris splashed out from the crater Copernicus some 250 miles away. The exact site was a point where, 31 months before, the unmanned lunar scout Surveyor III had made a precarious automatic landing. The Surveyor site was a natural choice: it was a geologically different surface, it would demonstrate pinpoint landing precision, and it would offer a chance to bring back metal, electronic, and optical materials that had soaked for many months in the lunar environment.

Here is Pete Conrad’s account of the mission:

It was really pioneering in lunar exploration. We had planned our traverses carefully, we covered them, and we stayed on the time line. We had a real-time link with the ground, to help guide our work on the surface. Of course we had practiced a lot beforehand. working with geologists in the field to learn techniques from them while they learned what we could and couldn’t do in the lunar environment.

Our first important task was the precision landing near Surveyor III. When we pitched over just before the landing phase, there it was, looking as if we would land practically on target. The targeting data were just about perfect, but I maneuvered around the crater, landing at a slightly different spot than the one we had planned. In my judgment, the place we had prepicked was a little too rough. We touched down about 600 feet from the Surveyor. They didn’t want us to be nearer than 500 feet because of the risk that the descent engine might blow dust over the spacecraft.

Our second important task- and of course the real reason for going to the Moon in the first place- was to accomplish useful scientific work on the surface. We had to set up the ALSEP and its experiments; we had to do a lot of geologizing; and finally we had to bring back some pieces of the Surveyor, so they could be analyzed for the effects of their exposure.

Al Bean and I made two EVAs, each lasting just under four hours; and we covered the planned traverses as scheduled. We learned things that we could never have found out in a simulation. A simple thing like shoveling soil into a sample bag, for instance, was an entirely new experience. First, you had to handle the shovel differently, stopping it before you would have on Earth, and tilting it to dump the load much more steeply, after which the whole sample would slide off suddenly.

LITTLE CLOUDS AROUND YOUR FEET

And the dust! Dust got into everything. You walked in a pair of little dust clouds kicked up around your feet. We were concerned about getting dust into the working parts of the spacesuits and into the lunar module, so we elected to remain in the suits between our two EVAs. We thought that it would be less risky that way than taking them off and putting them back on again.

On the first EVA, the first thing I did was to take the contingency sample. When Al joined me on the surface, we started with the experimental setups. We set out the solar wind experiment and the ALSEP items. We planted the passive seismic experiment, deployed and aligned antennas, laid out the lunar surface magnetometer, and took core samples. Some of the experiments started working right away as planned, sending data back. Others weren’t set to start operating until after we had left.

We were continually describing what we were doing; we kept up a stream of chatter so that people on the ground could follow what was going on if we were to lose the video signal. And we did lose it, too, soon after we landed. That was hard to take.

Photo of Apollo 12 Lunar Module Intrepid — Going its separate way for a landing, the Apollo 12 Lunar Module Intrepid gleams in the sunlight as it pulls ahead of Yankee Clipper, the command module. The view is westward, from a circular orbit 69 miles above the surface, with Intrepid very nearly as high. With the Sun above and behind the camera, the very rough lunar terrain below appears greatly subdued. The circular crater in the middle distance on the right is Herschel. The smooth-floored giant crater Ptolemaeus occupies much of the area to its left.

One strange surface phenomenon was a group of conical mounds, looking for all the world like small volcanoes. They were maybe five feet tall and about fifteen feet in diameter at the base. Both of us really enjoyed working on the surface; we took a lot of kidding later about the way we reacted. But it was exciting; there we were, the third and fourth people on the Moon, doing what we were supposed to do, what we had planned to do, and keeping within schedule. Add to that the excitement of just being there, and I think we could be forgiven for reacting with enthusiasm.

Photo of tracks of Apollo 14 astronauts — Tire tracks trace the path of the Apollo 14 astronauts from their lunar module Antares to the site, some 200 yards to the west, where they set up the Apollo Lunar Surface Experiments Package (ALSEP). On this mission, they had a two-wheeled, light, hand-pulled cart (shown here) to carry their equipment and samples. The Modular Equipment Transporter, or MET, had pneumatic tires, which compacted the soil as they rolled. In this photo, taken in the direction of the Sun, the tracks are brightly backlighted. In general, however, where astronauts worked, the soil scuffed up by their boots was distinctly darker than the undisturbed surface material.

Photo of Lunar Module Intrepid — Astronaut Alan Bean unloads equipment from the Apollo 12 lunar module Intrepid in preparation for the walk to the ALSEP site. The lunar module-surely the clumsiest-looking flying machine ever built-consisted of a descent stage, destined to remain on the Moon, and an ascent stage that later carried the crew and sampies into lunar orbit. Scientific equipment and gear for use an the lunar surface was stowed in four bays of the descent stage. The panel that covered the bay facing Bean folded down to provide a work table.

Our second EVA was heavily scheduled. We were to make visual observations, collect a lot more samples, document photographically the area around the Ocean of Storms, and- if we could- bring back pieces of the Surveyor III spacecraft. We had rehearsed that part with a very detailed mockup before the flight, and were well prepared.

We moved on a traverse, picking up samples and describing them and the terrain around them, as well as documenting the specific sites with photography. We rolled a rock into a crater so that scientists back on Earth could sec if the seismic experiment was working. (It was sensitive enough to pick up my steps as I walked nearby.) Anyway, we rolled the rock and they got a jiggle or two, indicating that experiment was off and running.

TAN DUST ON SURVEYOR

We found some green rocks, and some gray soil that maintained its light color even below the surface, which is not common, and we finally reached the Surveyor crater. I was surprised by its size and its hard surface. We could have landed right there, I believe now, but it would have been a scary thing at the time. The Surveyor was covered with a coating of fine dust, and it looked tan or even brown in the lunar light, instead of the glistening white that it was when it left Earth more than two years earlier. It was decided later that the dust was kicked up by our descent onto the surface, even though we were 600 feet away.

We cut samples of the aluminum tubing, which seemed more brittle than the same material on Earth, and some electrical cables. Their insulation seemed to have gotten dry, hard, and brittle. We managed to break off a piece of glass, and we unbolted the Surveyor TV camera. Then Al suggested that we cut off and take back the sampling scoop, and so we added that to the collection.

Then we headed back to the Intrepid. We retrieved the solar- wind experiment, stowed it and the sample bags in the Intrepid, got in, buttoned it up, and started repressurization. Altogether we brought back about 75 pounds of rocks, and 15 pounds of Surveyor hardware. We also brought back the 25-pound color TV camera from Intrepid so that its failure could be investigated.

While we were busy on the surface, Dick Gordon was busy in lunar orbit. The Yankee Clipper was a very sophisticated observation and surveying spacecraft. One of the experiments that Dick performed was multispectral photography of the lunar surface, which gave scientists new data with which to interpret the composition of the Moon.

After Al and I got back to Yankee Clipper following lunar liftoff and rendezvous, all three of us worked on the photography schedule. We were looking specifically for good coverage of proposed future landing sites, especially Fra Mauro, which was then scheduled for Apollo 13. That’s a rough surface, and we wanted to get the highest resolution photos we could so that the crew of the Apollo 13 mission would have the best training information they could get.

We changed the plane of our lunar orbit to cover the sites better, and we also elected to stay an extra day in lunar orbit so that we could complete the work without feeling pressured. We took hundreds of stills, and thousands of feet of motion-picture film of the Fra Mauro site, and of the Descartes and Lalande craters, two other proposed landing sites.

Meantime the experiments we had left on the lunar surface were busy recording and transmitting data. They all worked well, with one exception, and were really producing useful data. One unexpected result came from the seismic experiment recording the impact of Intrepid on the surface after we had jettisoned it. The entire Moon rang like a gong, vibrating and resonating for almost on hour after the impact. The best guess was that the Moon was composed of rubble a lot deeper below its surface than anybody had assumed. The internal structure, being fractured instead of a solid mass, could bounce the seismic energy from piece to piece for quite a while.

The same phenomenon was observed at two ALSEP stations when the Apollo 14 crew jettisoned their lunar module Antares and programmed it to crash between the Apollo 12 and 14 sites.

With every mission after Apollo 12, additional seismic calibrations were obtained by aiming the Saturn S-IVB stage to impact a selected point on the Moon after separation from the spacecraft. The seismic vibrations from these impacts lasted about three hours.

Photo of S-band antenna — Color telecasts, live from the Apollo 14 site, came by way of the erectable S-band antenna shown here. The S-band of radio frequencies (between 1550 and 5200 megahertz) was used for high-data-rate space transmissions. The gold-colored parabolic reflector, which opened just like an umbrella, provided a higher gain than the lunar module’s own steerable antenna. Note how featureless the lunar surface appears in the area just above the astronaut’s shadow. This illustrates the visibility problem that the astronauts faced in walking down-Sun.

Apollo 13 was supposed to land in the Fra Mauro area. The explosion on board wiped out that mission, and it became instead a superb example of a crew’s ability to turn a very risky situation into a safe return to Earth.

So the Fra Mauro site was reassigned to Apollo 14, because scientists gave that area a high priority. The following account is by Alan B. Shepard, Jr., the first American into space and of the original seven astronauts.

The Fra Mauro hills stand a couple of hundred of miles to the cast of the Apollo 12 landing site. I was selected to command this mission, my first since the original Mercury flight in 1961. With me to the lunar surface went Edgar D. Mitchell in Antares, while Stuart A. Roosa was the command module pilot of Kitty Hawk.

CHOOSING A SMOOTHER SPOT

The targeting data for the Apollo 14 landing site were every bit as good as the data for Apollo 12; but we had to fly around for a little while for the same reason they had to. The landing site was rougher, on direct observation, than the photos had been able to show. So I looked for a smoother area, found one, and landed there.

Our first EVA was similar to those before; we got out, set up the solar-wind experiment and the flag, and deployed the ALSEP. The latter had two new experiments. One was called the “thumper.” Ed Mitchell set up an array of geophones, and then walked out along a planned survey line with a device that could be placed against the surface and fired, to create a local impact of known size. Thirteen of the 21 charges went off, registering good results. The other different experiment we had was a grenade launcher, with four grenades to be fired off by radio command some time after we had left the Moon. They were designed to impact at different distances from the launcher, to get a pattern of seismic response to the impact explosions.

While Ed and I were working on our first EVA. Stu was doing the photographic part of the orbital science experiments. One job was to get detailed photographic coverage of the proposed site for the Apollo 15 mission, near the Descartes crater.

He was asked also to get a number of other photos of the lunar surface, in areas that had not been well-covered in earlier missions. Stu produced some great photos of the surface, rotating the command module Kitty Hawk to compensate for the motion of the image. He photographed the area around Lansberg B, which had been the predicted impact site of the Apollo 13 S-IVB stage. It was calculated that the impact could have produced a crater about 200 feet in diameter, and scientists wanted good pictures of the area so they could search for the brand-new crater on the Moon.

Stu also found them another new crater on the back side of the Moon. It was serendipity; he was shooting other pictures and suddenly this very bright, young crater came into view directly under Kitty Hawk. So he swung the camera around, pushed the button, and then went back to his original assignment.

A LUNAR RICKSHAW

Ed and I worked on the surface for 4 hours and 50 minutes during our first EVA; after the return to Antares, a long rest period, and then resulting, we began the second EVA. This time we had the MET- modularized equipment transporter, although we called it the lunar rickshaw- to carry tools, cameras, and samples so we could work more effectively and bring back a larger quantity of samples.

A picture of the Apollo 14 EVA map — The planned traverse route for the second EVA is shown by a fine black line an this map of the Apollo 14 site. The heavier white line is the traverse actually covered. The craters and boulders encountered are plotted, as are the locations of the emplaced experiments. Such maps are essential for an understanding of the sample sources and the experiment data.

Our planned traverse was to take us from Antares more or less due east to the rim of Cone crater. That traverse had been chosen because scientists wanted samples and rocks from the crater’s rim. The theory is that the oldest rocks from deep under the Moon’s surface were thrown up and out of the crater by the impact, and that the ones from the extreme depth of the crater were to be found on the rim.

On our way to the crater, one of the first things Ed did was to take a magnetometer reading at the first designated site. When he read the numbers over the air, there was some excitement back at Houston because the readings were about triple the values gotten on Apollo 12. They were also higher than the values Stu was reading in the Kitty Hawk, and so it seemed that the Moon’s magnetic field varied spatially.

A picture of a well-stocked tool rack — The well-stocked tool rack at left, which fitted neatly on the rickshaw, was at least better than traipsing about carrying everything, including samples already collected. But it proved to be a drag in deep dust, easier to carry than to tow. The problem of doing on-the-spot lunar geologising in an efficient way awaited the electric Rover.

Our first sampling began a little further on, in a rock field with boulders about two or three feet along the major dimension. These were located in the centers of a group of three craters, each about sixty feet across. Like the bulk of the samples brought back, these were documented samples. That means photographing the soil or rocks, describing them and their position over the voice link to Mission Control, and then putting the sample in a numbered bag, identifying the bag at the same time on the voice hookup.

Apollo 14 tried an experiment to do something constructive about the dust that plagued all of the missions. NASA engineers wanted to check out some of the finishes proposed for the Rover and other pieces of operating equipment. I had a group of samples - material chips with different finishes - and I dusted them with the surface dust, shook them off, and then brushed one set to try to determine the abrasive effects, if any, of such dust removal. The other set was left unbrushed as a control sample. All this was of course recorded with the closeup camera.

The mapped traverse was to take us nearly directly to the rim of Cone crater, a feature about 1000 feet in diameter. As we approached. the boulders got larger, up to four and five feet in size. And at this time, the going started to get rough for us. The terrain became more steep as we approached the rim, and the increased grade accentuated the difficulty of walking in soft dust.

THE HUNT FOR THE RIM OF CONE

Another problem was that the ruggedness and unevenness of the terrain made it very hard to navigate by landmarks, which is the way a man on foot gets around. Ed and I had difficulty in agreeing on the way to Cone, just how far we had traveled, and where we were. We did some more sampling, and then moved on toward Cone, into terrain that had almost continuous undulations, and very small flat areas. Soon after that, the surface began to slope upward even more steeply, and it gave us the feeling that we were starting the last climb to the rim of Cone. We passed a rock which had a lot of glass in it, and reported to Houston that it was too big to pick up.

We continued, changing our suit cooling rated to match our increased work output as we climbed. and stopping a couple of times briefly to rest. For a while, we picked up the cart and carried it, preferring to move this way because it was a little faster.

A photo of astronaut Shepard holding a core tube section — Apollo 14 Astronaut Shepard fits a core tube section to the extension handle in preparation for taking a vertical sample of the subsurface material. Core tubes were among the handtools carried on the MET.

And then came what had to be one of the most frustrating experiences on the traverse. We thought we were nearing the rim of Cone, only to find we were at another and much smaller crater still some distance from Cone. At that point, I radioed Houston that our positions were doubtful, and that there was probably quite a way to go yet to reach Cone.

About then, there was a general concurrence that maybe that was about as far as we should go, even though Ed protested that we really ought to press on and look into Cone crater. But in the end, we stopped our traverse short of the lip and turned for the walk back to Antares.

Later estimates indicated we were perhaps only 30 feet or so below the rim of the crater, and yet we were just not able to define it in that undulating and rough country.

One of the rocks we sampled in that area was a white breccia (a rock made up of pieces of stone embedded in a matrix). The white coloring came from the very high percentage of feldspar that was in the breccia. That rock, and others in the area, were believed to approach 4.6 billion years in age.

A photo of astronaut Beam removing hot fuel capsule — Beam cautiously removes hot fuel capsule from its graphite cask in order to insert it into the Radioisotope Thermoelectric Generator (RTG) at his right. The temperature of the capsule, which was filled with plutonium-238, is about 1350° F.

A photo of the Radioisotope Thermoelectric Generator — The RTG was the powerhouse for the entire experiment package. The temperature difference between the fuel capsule and the finned outer housing was converted into electrical power by 442 lead telluride thermocouples. Starting at about 74 watts, the output to the central station will continue for years at a slowly diminishing rate.

We stopped at Weird crater, for more sampling and some panoramic photography, and then continued the return traverse. At the Triplet craters, more than three-quarters of the way back to Antares, we stopped again. Ed’s job there was to drive some core tubes; I was to dig a trench to check the stratification of the surface. But the core material was granular and slipped out of the tube every time Ed lifted it clear of the surface. I wasn’t having any better luck with my trenching, because the side walls kept collapsing. I did get enough of a trench dug so that I could observe some stratification of the surface materials, seeing their color shift into the darker browns and near blacks, and then into a surprisingly light-colored layer underneath the darkest one.

That was it, Antares was in sight, as it had been throughout much of the traverse, and our long Moon walk was almost over. I went on past Antares to the ALSEP site to check antenna alignment because of reports from Houston that a weak signal was being received. Ed took some more samples from a nearby field of boulders.

A photo of the Lunar Surface Magnetometer — With its three gold-covered booms outspread, the Lunar Surface Magnetometer can measure the three orthogonal components of the magnetic field. Periodically, the fluxgate sensors at the ends of the booms are flipped over mechanically to check the calibration. An astronaut initially oriented the instrument by means of the shadowgraph shown at the base of the X-axis (right) boom and the bubble level on the sunshade.

A photo of the Laser Ranging Retroreflector — The Laser Ranging Retroreflector (LRRR) is a completely passive array of small fused-silica corner cubes that reflect incident light precisely back toward its sources. When the source is a pulsed ruby Laser at a large telescope, the distance from the LRRR to the ground station can be routinely measured within 6 inches. The three LRRR arrays on the Moon permit long-term studies of subtle Earth and Moon motions.

At that, our surface tasks were done, with the exception of recovering the solar-wind experiment and getting back into Antares for the return flight. We had covered a distance of about two miles and collected many samples during four and one-half hours on the surface in the second EVA. I also threw a makeshift javelin, and hit a couple of golf shots.

A photo of an antenna attached to atop the sunshield — The top surface of the central station in an aluminum honeycomb sunshield. Before deployment, the antenna and several ALSEP experiments were attached to the brackets atop the sunshield with quick-release bolts. When raised, the sunshield and insulating side curtains provide thermal protection for the electronics. A leveling head on the antenna mast permitted the astronaut to aim the helical S-band antenna earthward.

A photo of Suprathermal Ion Detector and its accompanying Cold Cathode Gauge — A wavy golden ribbon connects the Apollo 14 Suprathermal Ion Detector and its accompanying Cold Cathode Gauge with the ALSEP central station some 50 feet away. This pair of instruments was also emplaced at the Apollo 12 and 16 sites. The wide range of the three Ion Detector look angles permits study of the directional characteristics of the flow of ions an both sides of the Earth’s magnetospheric tail.

After liftoff there were still experiments left to do. The first of these was another seismic event, generated by the impact of the jettisoned Antares on the Moon. Again the Moon responded with that resonant ringing for some time after the event. Once we were on our way back to Earth, we did a series of four experiments in weightlessness. One was a simple metal casting experiment, to see what the effects of zero gravity would be on the purity or the homogeneity of the mass. The materials included some pure samples, and others with crystals or fibers for strengthening. As you might expect, the materials turned out to be more homogeneous under zero-gravity conditions. We measured heat flow and convection in some samples and, sure enough, zero gravity changed those characteristics also. We did some electrophoretic separations, which are techniques used by the pharmaceutical industry to make vaccines, in the belief that maybe zero-gravity conditions could simplify a complex and expensive process. Finally, we did some fluid transfer experiments, simply trying to pour a fluid from one container to another in zero gravity. The surface tension works against you there, and so it was much easier when the containers being used were equipped with baffles that the fluid could cling to, as it were.

A photo of the Passive Seismic Experiment — The Passive Seismic Experiment is completely hidden by its many-layered shroud of aluminized Mylar. The top of the thermal shroud is the platform for the bubble level and Sun compass that the astronaut used to orient the experiment initially. An internal set of leveling motors keeps the seismometers constantly level within a few seconds of arc. Seismic motions are recorded on Earth with a magnification factor of 10 million. The network created by the four ALSEPs that have this experiment enables seismologists to locate moonquakes in three dimensions, and to study the seismic velocities and propagation characteristics of subsurface materials.

That was our mission. Our return was routine, our landing on target, and our homecoming as joyous as those before.

I look back now on the flights carrying Pete’s crew and my crew as the real pioneering explorations of the Moon. Neil, Buzz, and Mike in Apollo 11 proved that man could get to the Moon and do useful scientific work, once he was there. Our two flights- Apollo 12 and 14- proved that scientists could select a target area and define a series of objectives, and that man could get there with precision and carry out the objectives with relative ease and a very high degree of success. And both of our flights. as did earlier and later missions, pointed up the advantage of manned space exploration. We all were able to make minor corrections or major changes at times when they were needed, sometimes for better efficiency, and sometimes to save the mission.

A photo of astronaut Mitchell looking at a map on his way to Cone crater — Like any tourist in a strenge place, Ed Mitchell consults a map on his way to Cone crater. He was photographed by his companion, Alan Shepard, during the second Apollo 14 EVA. During their 9 hours on the lunar surface, these tourists collected 95 pounds of lunar samples to bring home. Their main complaint during their stay was the way the lunar dust stuck to their suits almost up to their knees.

Apollo 12 and 14 were the transition missions. After us came the lunar rover, wheels to extend greatly the distance of the traverse and the quantity of samples that could be carried back to the lunar module. And on the last flight, a trained scientist who was also an astronaut went along on the mission.

I’d like to look on that last flight as just a temporary hold in the exploration of space.

A photo of the US flag on the Moon from the top view — The flag flutters an the Moon in the genuine wind of a rocket exhaust as the ascent stage of the Apollo 14 lunar module Antares lifts off from the Moon. Pieces of the gold-coated insulating foil turn off the descent stage by the blast were also sent flying. Who knows how many thousands of years will pass before a wind of vaporized rock from some nearby meteorite impact once more sets this flag flapping?

A photo of Apollo 14 command service module Kitty Hawk — In the blackness of space, the Apollo 14 command-service module Kitty Hawk gleams brilliantly as it draws near the camera in the lunar module Antares. The single-orbit rendezvous procedure, used for the first time in lunar orbit on this mission, brought the two craft together in two hours. After crew transfer, Antares was guided to lunar impact at a point between the Apollo 12 and 14 sites. The resulting seismic signal, recorded by both instruments, lasted 1½ hours.

A photo of Apollo 14 command module splahes down into the South Pacific ocean — At its journey’s end, the Apollo 14 command module splashes down into the sparkling South Pacific, some 900 miles south of Samoa. The parachutes collapse as they are freed of their load. On this occasion, the command module remained right side up in the water after landing. Like a kayak, a command module was just as stable in the water when it was upside-down (stable two). If it toppled over to an inverted position, as happened on other splashdowns, the crew could right it by means of inflatable airbags.

A photo of astronauts Mitchell,Shepard,and Roosa, and a frogman on a raft — Astronauts Mitchell, Shepard, and Roosa, and a recovery team frogman wait aboard the raft Lily Pad for a helicopter pickup. With the hatch open, the command module was vulnerable to swamping, along with its priceless load of lunar samples and film, which is why frogmen routinely lashed an inflated flotation collar around a spacecraft.

A photo of scientists examining samples brought from the Apollo 14 mission — The veritable pay dirt of the Apollo expeditions is the collection of lunar samples that is now available for the most detailed examination and analysis. Scientists have long been aware that our understanding of the nature and history of the solar system has been biased in unknown ways by the fact that all of the study material comes from one planet. Although meteorites are fascinating samples of the material of the solar system at large, there is never any direct evidence of the source of an individual meteorite. Now, within a few years, mankind has assembled the material of another world, recording where each piece came from and what was nearby. Here, scientists at the Lunar Receiving Laboratory work with an Apollo 14 sample in a sterile nitrogen atmosphere.

ALSEP: Scientific Station on the Moon

Although the Apollo astronauts could stay on the lunar surface for only a few days, scientists wished to make some kinds of observations over a period of weeks or even years, if possible. The solution was to have the astronauts set up an unmanned, automatic scientific station called ALSEP (Apollo Lunar Surface Experiments Package). An ALSEP was emplaced at each landing site, beginning with Apollo 12.

A picture of a group of geophysical instruments surrounding the central station — An ALSEP is a group of geophysical instruments arrayed about a central station, as in the accompanying sketch. Each ALSEP has a different set of experiments. Power is supplied by a Radioisotope Thermoelectric Generator. Radio communication for the transmission of experiment data and the receipt of instrument adjustment commands is maintained through a rod-shaped antenna pointed in the Earth’s general direction.

Each ALSEP can send about 9 million instrument readings a day. With five ALSEPs operating simultaneously, a staggering amount of information has already accumulated. An unexpected bonus has been the unusually long lifetimes of the ALSEP units. Originally designed for one year of reliable operation, all were still sending useful data five years after Apollo 12.

A picture of the Suprathermal Ion Detector Experiment (SIDE) — The Suprathermal Ion Detector Experiment (SIDE) measures the energy and mass of the positive ions that result from the ionization of gases near the lunar surface by the solar wind or ultraviolet radiation. The Cold Cathode Gauge Experiment (CCGE) measures changes in the extremely low concentrations of gas in the lunar atmosphere. The electronics for the CCGE are housed in the SIDE.

A picture of the Solar-Wind Spectrometer — The Solar-Wind Spectrometer experiment uses seven Faraday-cup sensors to measure the energy spectra of charged particles that strike it from various directions. Because the Moon, unlike the Earth, is not protected from the solar-wind plasma by a magnetic shield, the instrument can detect subtle variations in the wind’s intensity and direction.

A picture Lunar Surface Magnetometer — Lunar Surface Magnetometers, operating at three ALSEP stations, have simultaneously measured the global response of the Moon to fluctuations in large-scale solar and terrestrial magnetic fields. By considering these responses in conjunction with the freespace magnetic data from the lunar satellite, Explorer 35, scientists have estimated rock temperatures (which affect electrical conductivity) deep in the lunar interior.

A picture of the Passive Seismic Experiment — The Passive Seismic Experiment uses four extremely sensitive seismometers to measure lunar surface vibrations, free oscillations, and tidal variations in surface tilt. Three long-period seismometers are mounted orthogonally to measure wave motions with periods between ½ and 250 seconds, while the short-period seismometer measures vertical motions with periods between 1/20 and 20 seconds. The electronics are housed in the ALSEP central station. The thermal shroud isolates the sensor and a patch of ground 5 feet in diameter from the temperature extremes of the lunar day and night.