THE CAMERA SYSTEMS Developed for lunar and planetary work involved a marriage of photographic and radiotelemetry techniques. By the time it was possible to put cameras into space near the Moon and planets, pictures could be transmitted by radio with very little degradation from the transmission process. To date, all pictures taken by unmanned spacecraft of the Moon and Mars have been returned to Earth by radio-propagation techniques.
Although man had studied the Moon for centuries, no one had ever seen its far side until this decade. It was natural that one of the first things that occurred to man for use of the camera in space was to record the far side to compare it with the visible face. From a scientific point of view, the unknown nature of its crater-pocked surface had also caused considerable interest in the small-scale features, and in determining the texture and composition of the surface.
The first Russian photographs of the Moon obtained with Luna III in October 1959 were crude pictures of a portion of the far side and portrayed the gross similarities and differences between the far and near sides. The U.S. missions concentrated on obtaining the first closeup look at the near side; this was accomplished by Ranger VII in July 1964.
The Moon is particularly difficult to photograph because it is a rather dark body with no atmosphere to diffuse light. Every object photographed is therefore either in bright light or dark shadow, resulting in extremely contrasty pictures. The surface of the Moon also has the strange photometric property of reflecting light selectively in the direction of the light source. Because of these characteristics, pictures taken when the Sun is high would show very little topographic detail; that is, there would be very little contrast due to terrain slope, and the pictures would be dominated by shadow contrast. Pictures taken near lunar sunrise or sunset, however, emphasize slope contrast by eliminating the backscattered light. Thus a spacecraft sent to obtain high-resolution photographs must be aimed within a fairly narrow range of lighting zones.
It was in December 1959 that the National Aeronautics and Space Administration formulated guidelines for a lunar program with objectives that included high-resolution images of the lunar surface. In a guideline letter to the Jet Propulsion Laboratory, inaugurating the effort later known as the Ranger Program, it was stated:
"The lunar reconnaissance mission has been selected with the major objective in mind being the collection of data for use in an integrated lunar-exploration program. Of the several specific experiments reviewed for assignment to the early flights, the transmission of high-resolution pictures of surface detail appears to be the most desirable. It is, therefore, requested that your program be directed to the consideration of a payload containing a picture transmission system which will acquire and transmit a number of images of the lunar surface. The system should have an overall resolution of sufficient capability for it to be possible to detect lunar details whose characteristic dimension is as little as 10 feet."
Nine Ranger missions were flown: seven of the spacecraft carried cameras. Rangers III, IV, and V each carried a camera with a telescope of 40-inch focal length and several other scientific instruments. Rangers Vl through IX were designed solely to obtain closeup photographs; each carried six television cameras of varying focal lengths to provide both wide- and narrow-angle views of the surface on approach. Because of developmental problems, Rangers III through Vl failed to  provide any photographic information Rangers VII, VIII, and IX produced more than 17 000 high-quality photographs, giving man his first close view of the lunar surface. Included in these photographs were detailed images of three different portions of the Moon, two in widely separated mare areas and one inside the crater Alphonsus. Perhaps the last series of pictures was the most striking, for it showed a variety of features that included highland areas, a central peak in the crater, and the floor of this ancient crater. Ranger photographs were hailed by scientists for their clarity and detail, with the last few frames from each mission being as much as a thousand times sharper than any obtained from telescopes on Earth. A number of theories were confirmed, many were rejected, and new theories developed as a result. By far the most dominant topographical feature on the Moon was shown to be the crater, extending in diameter from hundreds of miles down to a few inches, in ever-increasing numbers toward the smaller scale. Past arguments about whether craters had been formed by impact or by volcanic activity were fused into combined theories indicating the probability of both types of formation. Perhaps of most significance was the fact that at high resolution, three widely separated areas on the Moon showed features of a very similar nature.
While the Ranger Program was getting underway, plans were laid for two other programs to extend observations of the Moon with cameras. The Surveyor Program called for soft landing of spacecraft able to observe minute detail on the surface, to view local topography as a man might see it, and to make other scientific measurements. The Lunar Orbiter Program called for putting a camera in orbit about the Moon to observe areas of the surface at extremely high resolution and to survey the entire lunar surface.
On the very first mission, Surveyor I landed successfully and returned some 10 000 pictures before sunset on its first lunar day. included in these pictures were closeups of the spacecraft itself, the soil that had been disturbed by the spacecraft, the features on the distant horizon, rocks and craters nearby, some of the planets and stars, and the setting Sun as it slowly dropped over the horizon. The camera continued to operate into the lunar night and took some pictures with the light of earthshine. During the second lunar day, it returned 899 additional pictures.
Surveyor I was joined by Surveyor III on the Moon after Surveyor II failed to operate properly and crashed onto the surface. Surveyor IV also experienced difficulty, but Surveyors V, Vl, and Vll succeeded in every respect. Surveyor III was significant because, in addition to the camera, it carried a surface sampler which allowed scientists to manipulate the soil under the view of the camera. In a way, this spacecraft represented the placing of man's hands as well as his eyes on the surface of the Moon, for scientists were able to command the sampler on the basis of what they saw, much as a scientist operates in his laboratory.
Surveyor V will be remembered for its first measurements of the constituents on the lunar surface, although it also returned 19 000 photographs. An alpha-backscattering instrument was able to record the elemental composition of the Moon's surface at one location to an accuracy of a few percent, indicating that it is much like many basalts here on Earth. Again the camera served to provide related information on the surface and the placement of the instrument.
Surveyor Vl continued the exploration of the lunar surface with the successful landing near the middle of the Moon as seen from Earth. It repeated the survey of the surrounding terrain and the topography close at hand, transmitting a record 30 065 pictures during the first lunar day. It also gave a second set of readings on the composition of the lunar surface, indicating that the material was essentially the same as that in the region farther east measured by Surveyor V
A series of five Lunar Orbiter spacecraft have successfully photographed, in resolution of about 3 feet, 25 sites that appear to be suitable for manned landings, and from these, 5 potential sites for manned landings have now been selected.
 In addition to the landing areas, many sites of high scientific interest have been photographed to a resolution of from 3 to 15 feet. The entire front face of the Moon has been covered at a resolution between 175 and 400 feet, providing topographic information that will allow very detailed geologic studies.
Some of the most exciting photographs obtained by Lunar Orbiter were oblique views of the surface. One of the earliest photographs showing the limb of the Moon also revealed the Earth in the distance, clearly showing both the terminator and the cloud coverage over the sunlit portion of the globe. Because there is no atmosphere on the Moon, oblique photographs with the telephoto lens are perfectly clear and distinct, even though features photographed were up to 75 miles away. The views of the steep crater walls and landscapes are very helpful to the- scientific interpretations of topography when used in conjunction with photography obtained from a vertical view.
The series of automated spacecraft containing cameras that have been sent to the vicinity or surface of the Moon have provided detailed knowledge of the surface topography. When combined with other data, photographs have enabled us to examine the relationships between the Moon's topography, its specific mechanical characteristics, and its chemical composition. Photographs allow improved accuracy of mapping for the near side, and for the first time have provided coverage of the far side. Manned landing sites have been selected from photos and from measurements returned by unmanned spacecraft, and are being thoroughly studied both to insure the safety of the astronauts and to achieve the greatest scientific returns from man's visit.
Although much has been done, there are still many potential uses for cameras in exploring the Moon. Because shadowing is necessary to provide topographical detail, many areas of the Moon have not been photographed with high resolution. Under different lighting conditions, new knowledge will be obtained. When man sets foot on the Moon, it is certain that his cameras will return to Earth a wealth of new data.
Because of their greater distances from Earth and because of their atmospheric properties, we know far less about other planets in the solar system from observations by telescope than we know about the Moon. Only one spacecraft has successfully photographed a planet from nearby. This was Mariner IV, which flew by Mars in 1965 and returned 22 pictures. One of these showed an oblique view of the limb of the planet. Perhaps the most striking of the Mariner pictures was one showing many craters and a surface surprisingly like that of the Moon. Elevation changes of thousands of feet were noted and portions of the terrain seemed quite rough.
The future for planetary photography is tremendous. From telescopes on Earth, we know that many of the planets have strikingly different characteristics. The day will surely come when cameras will be flown to the vicinity of these interesting planets, and we will be able to view the results here on Earth. The next planetary mission planned by the United States with emphasis on photography is a pair of missions to Mars in 1969, which will not only provide photographic coverage of most of the surface at resolutions better than we have from Earth, but will also provide closeup looks that will greatly expand our knowledge of Mars.-
ORAN W. NICKS
After centuries of wondering what the other side of the Moon looked like, man finally got his first, engrossing glimpses of it in the fall of 1959.
The first prints of those historic Soviet photos taken by Luna III were not quite as clear as the two shown here. These have enhanced quality, explains WILMOT N. HESS, Director of Science and Applications, Manned Spacecraft Center, NASA, because "they are a combination of various negatives that were screened, combined, and rectified by workers at the University of Arizona's Lunar and Planetary Laboratory.
"Luna III, launched October 4, 1959, was the first space probe to photograph another planetary body and transmit the pictures back to Earth," Hess continues. "The photographs taken covered more than 10 million square kilometers on the far side of the Moon. This meant that about 80 percent of the lunar surface had been covered by photography of various resolutions.
"Features identifiable on the photos here include Tsiolkovsky [dark crater with bright peak at lower right], Mare Moscoviense [dark area at upper right], Mare Australe [large, irregular dark area on lower edge], Mare Fecunditatis with Mare Crisium above it [left edge], Mare Smythii [large dark area with two bright peaks], Mare Marginis [above Mare Smythii], and Mare Humboldtianum [dark area at top left]. Tsiolkovsky and Mare Moscoviense were viewed for the first time on Luna III photography. The Soviets also interpreted the bright area above Tsiolkovsky as a mountain range. (The higher resolution Lunar Orbiter photography has since shown this area to be heavily cratered, but not mountainous.) Luna IlI's photographs indicated that the Moon's far side has no large mare areas and contains much more continental area than the side facing Earth."
"The Soviet space probe Zond III," one of whose pictures is shown on the facing page, says Hess, "was launched on a mission that photographed the 20 percent of the lunar surface that had not previously been viewed. Picture taking began at 1:24 universal time on July 20, 1965, at an altitude of 11570 kilometers. During the following 68 minutes, 25 photos were taken, and the altitude gradually decreased to 9220 kilometers, then increased to 9960 kilometers. The area photographed extended from the western edge of the visible side of the Moon across the far side to the terminator.
"The large photograph shows the equatorial and northern portions of the lunar far side. The large dark area on the right is Mare Orientale, which is....
.....located on the western limb of the Moon when viewed from Earth. (The orientation of cardinal directions is in accordance with the Astronautical Convention adopted by the IAU General Assembly of 1961.) The dark area at the right edge of the picture is the crater Grimaldi, which is on the visible side of the Moon.
"With this Zond III photography and that of the earlier Luna III, only an area at the south polar region of the far side of the Moon remained to be viewed.
"The photography taken by the Zond III camera was of a higher quality than that of Luna lII's camera, and confirmed the initial impressions that the far side of the Moon has fewer large maria and much more continental area than the visible side."
Astronomers were jubilant at the clarity of the thousands of closeup photos of the Moon taken in 1964-1965 by the TV cameras on Rangers Vll, VIII, and IX during the final moments before impact.
Of the four photos shown on these pages and on the two following pages, the one above, taken on July 31, 1964, by Ranger Vll, was "the first high-resolution look at the surface details within faint crater rays," said HARRIS M. SCHURMEIER, former Ranger Project Manager, Jet Propulsion Laboratory. "It shows an area about 12 miles wide, which the International Astronomical Union renamed 'Mare Cognitum' - 'Known Sea'-as a result of this mission. Ranger Vll confirmed that there were lunar areas topographically acceptable as manned landing sites." Of the same picture, GERARD P. KUIPER, Director, Lunar and Planetary Laboratory, University of Arizona, noted: "The photograph shows several clusters of secondary impact craters, found to be bright at full Moon, which are accompanied by short, diffuse ray elements. Some of these clusters belong to Tycho's ray system [prominent center group] and some to Copernicus' [at top, lower left, and lower right]. Evidence indicates that Copernicus and Tycho were both caused by impacts of comets entering the planetary system on parabolic orbits, the secondaries seen on the picture having been caused by associated cometary debris. This photo, in addition, shows numer-...
-...ous small, shallow collapse depressions in the mare floor. Some are nearly linear along well-known structural directions.
"Ranger Vll's records," Kuiper concluded, "were the first to close the gap between Earth-based photography (best resolution, 0.4 kilometer) and fine-structure data derived indirectly from thermal, radio, and radar observations. The overlapping records proved the consistency and reliability of the data."
The Ranger Vlll photograph above shows the sister craters Ritter and Sabine, on the edge of Mare Tranquillitatis. RAYMOND L. HEACOCK, Chief, Lunar and Planetary instruments Section, Jet Propulsion
Laboratory, recalled that "it was one of 7137 photographs that Ranger VIII returned before impacting within 30 kilometers of its target in Mare Tranquillitatis, on February 20, 1965. Taken from an altitude of 243.4 kilometers, it covers approximately 25 square kilometers.
"The resolution," says Heacock, "is about 10 times the best Earth-based resolution, thus revealing considerably greater detail than ever before about the structure of the Hypatia Rilles and the flat-bottomed craters Ritter and Sabine. While the rilles appear to be similar to the graben found on Earth, the cause of the faulting is not revealed. Several north-northwest gouge features are the result of secondary....
....impacts of ejecta derived from the crater Theophilus. "Ranger Vlll impacted within the Apollo landing zone and achieved a terminal resolution of approximately 1.5 meters."
HAROLD C. UREY, Nobel laureate and professor at the University of California, San Diego, said of the Ranger IX photo above: "This picture shows a portion of the floor and crater wall of Alphonsus. The floor is covered with many craters of various sizes, some sharp and hence new, others less distinct and partly filled with fragmented material. The walls have fewer craters, and this probably means that slumping of the wall has filled them. Crevasses are evident, and evidence for slumping exists. The larger crater near the top is undoubtedly collisional in origin. Three craters are surrounded by dark halos and were produced by eruptions from the lunar interior. Exceptionally bright, sharp peaks can be seen on certain mountain tops. Are they possibly metallic objects that resist particle erosion? The crater floor and the smooth area in the walls at the right are usually assumed to be lava. Are they possibly the beds of temporary lakes?"
Ranger IX pictures were seen on TV in the U.S. and Europe as received "live from the Moon."
Concerning Ranger IX's last photograph [shown above], WILLIAM H. PICKERING, Director, Jet Propulsion Laboratory, commented that "it was taken one-quarter second before impact, at 1/3-mile altitude, and shows an area 200 feet from top to bottom and 240 feet from left to right on the floor of the crater Alphonsus.
"The surface," Pickering said, "is dominated with impact craters with very few positive relief features.
The low Sun-elevation angle (10.4°), combined with the surface resolution, would have permitted positive detection of surface blocks on the order of 0.2 to 0.3 meter in diameter.
"Ranger IX, which yielded 5814 Moon-surface pictures, provided confirmation of the dominant role that impact cratering has had in establishing the small-scale topography in both mare and large highland craters. Luna IX and Surveyor I provided additional confirmation of this process.
"The television camera that took this picture had a focal length of 76 mm, a field of view of 2.1°."
"A chill and friendless thing," A. C. Benson called the Moon, and history's first on-the-spot photographs of its bleak surface clearly bore him out.
Early in 1966, a Russian space probe, Luna IX, made the initial soft landing there. One of the pictures that its TV camera took and transmitted to Earth is shown above.
Luna IX landed approximately 100 kilometers northeast of the center of the crater Calaverius on February 3, 1966. The next day, it transmitted its first lunar panorama, part of which appears at left. Of this picture, JACK GREEN, of Douglas Advanced Research Laboratory, said:
"The photograph, with a resolution of some 1.5 to 2 mm at a distance of 1.5 meters, shows: (1) no thick dust; (2) both rounded and angular rock fragments, either concentrated on crater rims or randomly distributed; (3) small ridges and linear open fractures; (4) numerous small craters, some with inner slope angles of over 40°; and (5) a generally cellular-to-granular surface texture
"Not only did Luna IX prove the lunar surface strong enough to support astronauts but it also showed good evidence of pitting on the sides and surfaces of rocks, suggestive of vesiculation. Luna IX photography weakened exotic cotton candy or whisker theories advocating a tenuous lunar surface, and, in my opinion, strengthened more conventional theories of volcanological processes being responsible for shaping the major surface features of the Moon."
 A few months later, in June 1966, the U.S. Surveyor I soft-landed on the Moon. It used many new elements, including throttleable vernier rockets, sensitive velocity- and altitude-sensing radars, and an automatic, closed-loop landing system. During the following 6 weeks it transmitted 11 150 high-resolution pictures back to Earth
Surveyor I's camera system had a variable iris, changeable filters, and a rotating mirror assembly, which allowed the camera to look in almost any direction and take pictures under various lighting conditions, in either black and white or in color. Video pictures with 200-line resolution and with 600-line resolution were possible; the first with a quick-look mode and the capability of transmission with a lowgain antenna; the second for use with the directional antenna and the high data rate.
The bright lunar vista stretching across the bottom of the facing page is part of a spherical mosaic prepared from more than 200 pictures that Surveyor I's camera took on June 13, 1966. One of the spacecraft's three feet protrudes in the foreground.
EUGENE M. SHOEMAKER, Chief, Astrogeology Branch, U.S. Geological Survey, commented on the scene:
"It shows the intricately cratered surface of the Oceanus Procellarum. It is a gently undulating surface pockmarked with craters, ranging from a few centimeters to several hundred meters in diameter, and littered with blocks and fragments, ranging from less than a millimeter to more than a meter across. The craters and the fragmental debris were probably formed by bombardment of the lunar surface by meteoroids and by pieces of the Moon itself, hurled through space from larger craters.
"The pitted appearance of the lunar surface [which one observer has likened to that of a World War I battlefield] is enhanced by the presence of long shadows, extending away from the spacecraft's foot and the more prominent blocks, due to the low angle of incidence of the rays of the evening Sun."
Surveyor l's TV camera had a zoom lens with focal lengths ranging from 25 to 100 millimeters. One of its most effective near-view photos is reproduced at right above.
STEPHEN E. DWORNIK, Surveyor Program Scientist, NASA, reported: "This photograph shows a 12- by 18-inch block located about 13 feet from the camera. It is subangular in shape, with facets slightly rounded at the edges and corners. The lighter colored part of the rock is the more resistant to erosion, and therefore distinctive. Granularity of the block is not evident, but it shows mottling. Intersecting fracture planes resemble cleavage planes produced during static flow of rock under high shock pressure. The edges of the fractures also exhibit a rounding. No fracturing or crevicing is evident in the lighter- colored part of the block.
"The block lies near many smaller blocks," Dwornik added, "and it is likely that all the blocks and fragments in the photograph are of the same origin. Both the smaller fragments and the block itself are partly submerged by the younger, finer material composing the lunar surface. The grain size of the lunar surface material cannot be determined because it is below the resolution of the camera."
On June 2, 1966, some 63 1/2 hours after being launched from Cape Kennedy, Surveyor I sat its 596-pound weight down on the Moon without apparent difficulty. It had landed on a dark, relatively smooth, bare surface north of the crater Flamsteed, in Oceanus Procellarum. The geographic coordinates of the site, encircled by hills and low mountains, were 2.41° S, 43.34° W.
In reference to the mosaic view above, A. R. LUEDECKE, then Deputy Director, Jet Propulsion Laboratory, wrote, "The ridge of surface material pushed up during landing by the outward motion of the footpad, 12 inches in diameter, is well outlined by shadow, for the Sun was approximately 10° above the horizon when the pictures in the mosaic were taken. The contrast in texture and albedo between the undisturbed surface and that disturbed by the footpad is noticeable, particularly above the footpad. Both of these features indicate that the lunar surface material at the Surveyor I site is not hard rock but a structure disturbed appreciably when subjected to the rather low loads of the order of 5 pounds per square inch.
"This photograph is a mosaic of separate frames [narrow-angle, 6° field of view] taken by the Surveyor television system. Most of the frames were digitized, processed on a computer to correct for system-frequency response, and then converted back to image form." It was a technique used throughout that mission and the Surveyor missions that followed.
"The lunar material seen in the picture on the opposite page is primarily material thrown out from beneath a Surveyor I footpad during landing," said EDWARD N. SHIPLEY, of Bellcomm, inc., although some of the original surface layer, which is lighter in color, is visible. The darker color of the subsurface material was unexpected, and there is currently no widely accepted explanation for it.
"Geometrical analysis," Shipley continued, "shows that the bottom of the footpad's depression is between 1 and 2 inches below the undisturbed lunar...
....surface. Additional data from the spacecraft telemetry give the magnitude of the forces exerted on the surface during landing. The size of the depression, compared with the magnitude of the impact forces, provides a quantitative measurement of the strength of the lunar surface material. From this information, further analysis has shown that there is no danger that either an Apollo spacecraft landing on the Moon or an astronaut walking on it would sink hazardously into the surface."
"This remarkable self-portrait [above] of Surveyor I is one of 144 pictures taken during its first 24 hours of operation on the Moon," said W. E. GIBERSON, formerly Surveyor Project Manager, Jet Propulsion Laboratory. It was one of the earliest of the 600 line high-resolution television pictures that the spacecraft took. initial photographs were made in the system's 200-line scanning mode.
"At upper left," continued Giberson, "is footpad 3 (12 inches in diameter), attached to the landing gear and shock absorber. Below the footpad are one of the spacecraft's omni-directional antenna booms,...
...its helium pressurization tank (14 inches in diameter), and the tank's valves, regulator, and lines.
"Details as small as a fiftieth of an inch can be seen. Most of the lunar surface particles are even smaller."
Surveyor I landed on the Moon at a vertical velocity of approximately 10 feet per second, rebounded about 2 1/2 inches, then came to rest. its footpads, in the process, slightly disturbed the surface, as shown in the picture at top left.
"This photograph was taken on June 13, 1966, at 19:45:35 GMT," wrote HOWARD H. HAGLUND, Surveyor Project Manager, Jet Propulsion Laboratory. "The Sun at the time was 10° above the western horizon. The view is of the outboard edge of footpad 2 of Surveyor 1, and of the lunar surface material beyond it.
"The arc of lighter-colored material nearest the footpad is part of the ridge pushed up by the pad. It shows lumps, or 'clods,' up to an inch in diameter, produced by the pad pressure during landing. These are apparently made up of fine particles (less than one-fiftieth inch in diameter).
"The photograph is scientifically interesting in that it shows that the lunar surface material is cohesive. Its mechanical properties are roughly similar to those of damp garden soil."
Describing the picture at top right, THOMAS GOLD, Director, Cornell University's Center for Radiophysics and Space Research, said: "The sharp cut in the lunar surface material directly underneath Surveyor I was caused during the landing by a thin heat shield, which cut into the soil as a cookie cutter would. When the springing of Surveyor's legs restored the spacecraft to its normal height, the 'cookie cutter' was withdrawn.
"The picture demonstrates," said Gold, "that the material is fine grained and cohesive to the extent that it can be cut and leave a vertical face. Clumps thrown out at impact are clearly visible, so it is a crumbly, crunchy surface.
"A dry material in vacuum has such properties only if it is composed of particles mostly smaller than 0.01 millimeter. A coarser aggregate, like sand, would slide and leave only incline slopes, never vertical ones.
"The picture strengthens the case that the porous overlay known to cover most of the Moon consists of cohesive, fine rock dust, and not either sand or solid, bubbly lava."
Surveyor l's camera had a lens of variable focal length and could be pointed by radio command from Earth. This allowed scientists to choose their subject and the most suitable light and lens setting for photographing it. Surveyor's scanning of its horizon, affording man his first look around the landscape of another world, provided the views on this page and the three following pages.
"A surface born in violence!" exclaimed RALPH B. BALDWIN, a noted astronomer, referring m the lunar scene above. "Prominently displayed on this Surveyor view of a mare is a small crater, perhaps 3 meters across, dug by the impact of a small meteorite. Scattered essentially at random over the surface are numerous rocks ejected from other, larger craters.
"In the distance," Baldwin pointed out, "is a strange wall of rocks. Study shows that these rocks lie, in part, on the near wall of a crater some hundreds of meters in diameter and, in part, in a sort....
....of raylike extension of the crater wall They were thrown out when the crater was formed. It is not known whether they represent true subsurface, stony materials, or are pulverized materials consolidated by the shock waves from the violent impact."
A telephoto view of the rocks referred to is shown above. BENJAMIN MILWITZKY, Surveyor Program Manager, NASA, said of it, "This remarkable photo shows a field of large rocks several hundred feet from the spacecraft. They range from about 3 to 6 feet in diameter, and appear to have been excavated from beneath the lunar surface and hurled outward by the impact of a large meteorite.
"Ejecta of this type are brighter than the undisturbed mare surface, and may contribute to the 'rays,' radiating from large impact craters, seen through Earth-based telescopes.
"The fact that the rocks came to rest on the surface," Milwitzky continued, "suggests that the surface, at least in this area, must have appreciable bearing strength, adequate to support manned spacecraft This evidence is consistent with data from Surveyor's landing-gear strain gages and pictures of its footprints. The large rocks, on the other hand, represent a significant hazard, which the astronauts will have to avoid by carefully maneuvering their spacecraft during its descent"
One of Surveyor l's most interesting telephoto views [at top] was of a mountain range about 16 miles northeast of the spacecraft. E. C. MORRIS, of the U.S. Geological Survey, described it as follows:
"The landing site was within a large, ancient crater, more than 60 miles in diameter, buried by mare material. "The mountain range shown here is part of the rim of this nearly buried crater. The highest peak rises more than 1300 feet above the lunar surface, but only the upper 600 feet project above the near horizon, which is little more than a mile away. The observable crest of the range extends approximately 3 miles along the horizon."
 The mosaic of TV pictures below forms a broad vista of the rim of a low crater several hundred yards distant from the landing site of Surveyor 1.
ZDENEK KOPAL, of the University of Manchester, in England, made the following points about it: "What makes this photograph unique is the vantage point from which it was taken. The crater, one of hundreds of thousands of this type on the Moon, is much akin to the well-known Meteor Crater in Arizona; namely, caused by the impact of an outside mass.
"However, from the shape of the ramparts (and boulders dispersed around them), we may conjecture that the crater itself is likely to be of secondary, rather than primary, origin. Also, whereas the Meteor Crater is probably not more than 100 000 years old, this lunar one may well be 10 times older. So slow are the grinding processes of cosmic obliteration on the Moon!"
The pictures on these pages were taken toward the close of two different lunar days in 1966, by Surveyor I (above), in mid-June, and by Russia's Luna Xlll (opposite), the day after Christmas.
"As the Sun approaches the lunar horizon," GEORGE H. SUTTON, University of Hawaii, said of the photos above, "lengthening shadows emphasize the pockmarked and rubble-strewn character of the surface. Raised rims of several craters and angular outlines of many surface fragments stand out sharply. In addition to giving a clear impression of the nature of the lunar surface, the long shadows in such pictures, taken at low Sun angles, can be measured to determine shapes and sizes of surface irregularities, obtaining accurate estimates of the size distribution of fragments and the shapes of craters."
The photographs have additional value. "Comparison of the craters in them with craters obtained in Earth-bound experiments of high-speed impacts in simulated lunar materials," Sutton continued, "permits estimation of the mechanical properties of the Moon's surface."
The pair of Luna Xlll photographs shown on page 61 are the last two pictures o[ a 360° panoramic view of the Moon's surface.
"The horizon appears to slope because of the tilt of the television camera," explained JOHN A. O'KEEFE, Assistant Chief, Laboratory for Theoretical Studies, Goddard Space Flight Center, NASA. "In the lower left and center of the top picture is a beam that was extended from the spacecraft to implant a penetrometer, measuring soil resistance to penetration. At left center in the bottom picture is the rounded end of one of the 'petals' that covered Luna XlII's instruments through the landing, and then unfolded.
"Note the change in the texture of the landscape about 3° below the horizon," O'Keefe added. "This is stated to be the rim of a crater in which Luna Xlll rests. And note the blocks beyond, toward the horizon."
"Alone on a desolate plain of the Moon's Sea of Storms (Oceanus Procellarum), Surveyor I stands quietly, its job well done, wrote HOMER E. NEWELL, Associate Administrator, NASA, in describing the photograph above. "Here is a picture of its own making. Surveyor casts a lengthening shadow as the long lunar day nears its end.
"The mosaic of approximately 52 photographs shows the rough texture of the Moon's cratered and pitted surface, on which rocks and boulders may be seen scattered here and there. Surface temperatures, which at lunar noon had risen to 235° F, are now falling slowly, a mere hint of the approaching plunge to 250° below zero after sunset."
[One should not be misled by the sinusoidal appearance of the lunar horizon in the mosaic. This occurred because Surveyor l's camera was tilted, in order to observe the spacecraft's feet better. Thus, when the camera was pointed in the direction of the tilt, the horizon appeared higher than it was. When the camera was pointed in the opposite direction, it looked slightly upward and the horizon appeared lower. In reality, the vicinity was largely flat.]
Surveyor I survived the 14 earthly days of its first lunar night, took and transmitted 10 388 pictures during its first lunar day, 812 the second, and sent its last photograph on July 13, 1966, as the Sun was setting on the Moon.
"Because of battery failure," Newell continued, "presumably caused by the bitter cold of the lunar night, Surveyor I can no longer send earthward pictures of its lonely vigil. However, with solar power,  its radio continued to function during each lunar day for 8 months after landing, answering simple questions about the status of the spacecraft.
"Surveyor I stands physically on the Moon, an enduring monument to its creators, a solitary artifact of men who live on another body of the solar system, a quarter of a million miles away, but its true resting place is in the pages of history, where even now is being inscribed man's conquest of space."
"The performance of Surveyor I met or exceeded expectations in all areas," commented ROBERT J. PARKS, Assistant Laboratory Director for Lunar and Planetary Projects, Jet Propulsion Laboratory. "After its successful soft landing, a planned series of 200-line pictures was transmitted, using an omni antenna. The high-gain antenna positioning equipment was then exercised for the first time. It responded immediately, and was properly positioned. The switchover to the 600-line mode was then accomplished. It was in this mode that the many high-quality photographs were obtained.
"In the 600-line mode, during the first lunar day, nearly complete coverage of the surrounding area was obtained under a wide variety of Sun-angle and shadow conditions.
"Toward the end of the first lunar day," Parks concluded, "as the shadows lengthened, the Surveyor camera obtained the fascinating silhouette self-portrait at right above. This picture symbolizes in a very dramatic way the highly successful performance of all elements of the mission."
"The solar corona in the photograph at top right was observed by Surveyor I, 16 minutes after sunset on the Moon on June 14, 1966," remarked GORDON NEWKIRK, of the High Altitude Observatory. "A bright coronal streamer is visible as a thin pencil of light extending out of the brighter inner corona, against which the lunar horizon is silhouetted. Halation in the optical system produces an apparent depression of the horizon immediately below the brightest portion of the corona. The faint disk in the upper-right corner and the bar extending to the lower-right corner are the omni-directional antenna and its support structure, visible in the light of earthshine.
"This photograph demonstrated the feasibility of making observations of the solar corona from lunar-based observatories. With little or no modification, the Surveyor cameras can investigate the outer corona and inner zodiacal light, which are inaccessible to ground-based observatories
"The fact that the corona is visible after sunset demonstrates that little or no residual atmosphere exists on the Moon. Detailed photometric comparison of these Surveyor observations with those made on the ground the same day will allow an exact upper limit of such a residual lunar atmosphere to be established."
In reference m the photograph at bottom right, LEONARD D. JAFFE, Surveyor Project Scientist, Jet Propulsion Laboratory, said, "This photograph was made during the lunar night, using light provided by the Earth. It shows a footpad and adjacent parts of Surveyor I against the darker background of the lunar surface. The indentation made by the footpad in the surface is also visible.
"As evidenced by this picture, it is possible to get useful photographs on the Moon at night, using earthshine for illumination. The surface is bright enough for human vision.
"The bright spot at the left," added Jaffe, "is a reflection of the Earth in the optical system. The small circular dish with radial stripes is a calibrated photometric target mounted on the spacecraft leg.
It permits accurate determination of the light intensity and surface brightness.
"This photograph was taken by Surveyor l's television system on June 14, 1966, at 16:35 Greenwich mean time. The iris aperture (which provided nominal focal ratios ranging from f/4 to f/22) was f/4. The exposure time (150 milliseconds in the normal mode) was 4 minutes."
Surveyor III bounced twice on landing, April 20, 1967, and slid down one steep wall of a crater. The multiple landings arose from a failure of its vernier engines to shut off as programmed. The mosaic above shows the surface disturbances made by its three legs (1, 2, 3) and one of the thrusting vernier rocket engines (V) at the end of the first bounce. Footpad 2 hit the surface first, followed by I and 3. All three rebounded, but 2 hit again (2') while I and 3 were still in the air.
"These surface disturbances," explained SIDNEY A. BATTERSON, Dynamic Loads Division, Langley Research Center, NASA, "are located approximately 14 meters upslope and in an easterly direction from the final resting place of the spacecraft." Impact marks of similar shape and depth were observed where Surveyor III finally came to a halt and where Surveyor I landed.
"Since the landing sites are hundreds of kilometers apart," Batterson concluded, "and since Surveyor I landed on a relatively flat plane, whereas Surveyor III landed on the wall of a crater, the similarity in the behavior of the surface material at both sites suggests that the material is quite homogeneous over very large areas of the lunar surface."
Surveyor IlI's television camera could not view the lunar surface outside the crater within which the spacecraft had landed, but the sloping walls of the crater allowed it to view nearby features more clearly than would have been possible on flat terrain. The spacecraft took 6315 pictures between April 20 and May 3, 1967.
This Surveyor, unlike its predecessors, carried a remotely controlled surface sampler, a device for digging and otherwise manipulating the surface material in the view of the television camera. The sampler made 8 bearing tests and 14 impact tests on the lunar surface, dug 4 trenches, and picked up 3 objects. One of these, a small rock [see opposite page, top right], was gripped by the sampler's scoop with a pressure of at least 100 pounds per square inch without apparently crushing or breaking it.
"Through the camera eye of Surveyor III," commented S. C. SHALLON, Chief Surveyor Program Scientist, Hughes Aircraft Co., "we see at top right a lunar surface capable of supporting both men and their spacecraft in future exploration of the Moon.
"This photograph was transmitted from the Moon by Surveyor III on April 26, 1967. The circular impression was made by one of the three footpads on the last bounce of a three-bounce landing. The surface impression at bottom left was made by the 'scooper,' a digging device shown in an extended position here. These surface impressions appear similar to those that might be made in damp, finegrained soil on Earth.
"We know, of course, that the lunar surface cannot be damp, because of the near-vacuum conditions there. But the results of the scooper's experiments, as viewed through Surveyor lIl's camera, together with other measurements made by the spacecraft, indicate that the Moon's surface does indeed have a consistency similar to that of damp, fine-grained terrestrial soil."
"The dark, longitudinal area seen in the photograph at bottom right," explained MAURICE C. CLARY, Lunar and Planetary instruments Section, Jet Propulsion Laboratory, "is a furrow in the lunar surface that resulted from a single trenching operation....
....by Surveyor lIl's soil-mechanics surface sampler. Some of the lunar fragments along the length of the trench resemble terrestrial rocks. Further manipulation of the surface sampler, which included closing its scoop door on one of these objects, proved that most of the fragments were aggregates of more finely divided particles, similar to clods. That was not true of all, however, as the photograph at top right on the facing page reveals.
"In the photograph," Clary continued, "the majority of the lunar-surface material displaced during formation of the trench appears at the left. This is due to the slope of Surveyor IlI's landing site."
"The area [1 by 2 inches] where Surveyor IlI's surface-sampler scoop contacted the Moon's soil was slightly depressed, and some of the adjacent soil was cracked and slightly lifted, said ELMER M. CHRISTENSEN, of Jet Propulsion Laboratory, in regard to the photo at top left. "This and other Surveyor tests- surface-sampler operations, landing imprints, landing loads; vernier-engine firings, attitude-control jet firings, and deposition of small amounts of soil on the spacecraft-have revealed the lunar soil to be fine grained, granular, and slightly cohesive, with greater strength and density 6 inches below the top surface
''At the Surveyor landing sites," Christensen declared, "the soil is amazingly uniform, much more so than at terrestrial areas so widely separated. Because of programs like Surveyor, man will explore the Moon, walking and driving his machines, with significantly fewer restrictions than on Earth."
"During bearing-test operations on May 1, 1967," recounted F. I. ROBERSON, Lunar and Planetary Sciences, Jet Propulsion Laboratory, "an object that appeared brighter than the surrounding surface was observed. A careful scraping action by the surface sampler dislodged the partially buried fragment. By alternately taking television frames and commanding the sampler, we brought the scoop slowly into position and closed the scoop door on the object. The result, shown at top right, was this photo of a lunar rock being picked up in the edge of the scoop's jaw.
"The soil-mechanics surface-sampler experiment, including picking up this rock, marked the first time in history that man has manipulated by remote control the surface of a celestial body other than Earth.
"This rock test also provided the first conclusive evidence that objects observed on the Moon through Surveyor's TV camera that looked like rocks were indeed rocks, and not clumps of dirt."
"The value of the data transmitted by the various successfully landed Surveyor spacecraft is considerably augmented," declares EWEN A. WHITAKER, Lunar and Planetary Laboratory, University of Arizona, "when actual locations of these craft can be found on Orbiter photographs of their respective landing areas.
"Such pinpointing permits (1) precise control of distances in the Surveyor panoramas, with consequent accurate estimates of the dimensions of craters, rocks, etc.; (2) extrapolation of small-scale surface structure to other areas of similar appearance in Orbiter photographs; and (3) an independent check on landed-position coordinates determined from tracking data.
"The chosen landing point for Surveyor III was 43° W, 3° S, situated in a telescopically smooth mare area southeast of the crater Lansberg. This area had been photographed by Orbiter III shortly beforehand. An inspection of the Surveyor panoramas showed that the spacecraft had come to rest on the inner eastern slope of a crater, the angle of tilt being about 15°. From the disposition of several small craters and rocks [marked A, B, and C above], it was possible to draw a very rough plan of the neighborhood. Comparison of this plan with the Orbiter III photographs eventually allowed the pinpointing of the Surveyor III location.
"The photograph opposite is an enlargement of an Orbiter III high-resolution frame of the Surveyor III landing-point neighborhood [with craters A and C, and rocks B, marked]. The small white triangle represents the area enclosed by the spacecraft's footpads, and is correctly oriented. The rim of the 200-meter-diameter 'soft' crater defines Surveyor's horizon."
Surveyor V, first of its spacecraft family to obtain information about the chemical nature of the Moon's surface, landed in Mare Tranquillitatis on September 11, 1967. The 50-picture mosaic of its landing site [above] is described in this way by R. J. DANKANYIN, Manager, Surveyor Scientific Payload Systems, Hughes Aircraft Company:
"The spacecraft is on a 20° slope in a crater about 11 meters long, 9 meters wide, and 1.5 meters deep. The top edge of the crater is clearly discernible...
....about one-third of the way down from the top of the picture. The camera is actually about one-half meter above the edge of the crater, so the picture appears as though one were standing in the crater, looking toward and over the far side. Most of the small craters nearby are a few meters wide. The lunar horizon is about a kilometer away."
The spacecraft slid about 3 feet in landing, and the photograph its camera took of the slide mark [above] yielded useful information. FRANK B. SPERLING, of Jet Propulsion Laboratory, said of it:
"The outstanding feature in this picture is the surface trench formed by the footpad during the landing process. The footpad first impacted just to the left of the rock, or clump, shown near the right margin. It penetrated the surface by approximately 4 inches while sliding 3 to 4 inches downhill. The spacecraft then rebounded to a height of 4 to 5 inches, still moving farther downslope. The bright area to the right of the leg marks the footpad's reimpact, with little penetration because of the greatly reduced impact energy. From there it slid to its final position.
"Lunar material was thrown out during this process, and some was deposited on top of the footpad. Also, some material crumbled from the walls of the first footpad imprint, obscuring its flattened bottom.
"Scientifically this picture is significant because it facilitates estimates of the frictional forces that acted between the footpad and the lunar surface."
One, high-quality Surveyor V photo [below], as JAMES, D. CLOUD, Assistant Surveyor Program Manager, Hughes Aircraft Co., pointed out, shows how "the camera was used for visual engineering evaluation of the spacecraft's condition as well as for scientific purposes. Visible [upper left] is part of the small crater, 8 inches in diameter, 1 inch deep, formed when the vernier engines were static fired. Also visible are the large, spherical helium tank [top], the smaller nitrogen tank [with vertical black band], and the alpha-scattering electronic compartment [far left] ."
"Surveyor V carried an instrument to determine the principal chemical elements of the lunar-surface material," explained ANTHONY TURKEVICH, Enrico Fermi institute and Chemistry Department, University of Chicago. "After landing, upon command from Earth, the instrument was lowered by a nylon cord to the surface of the Moon [left, above]. The results of the measurements were telemetered back to Earth.
"Both photographs above were taken by Surveyor V's television camera. The right-hand one shows the chemical analyzer slightly displaced by the restarting of the spacecraft's vernier engines, 2 days after landing. The displacement enabled it to analyze a second sample of lunar-surface material.
"The instrument under discussion is a cubical box, approximately 6 inches on a side, sitting on a 12-inch white plate. The box has an opening in the bottom through which alpha particles from the radioactive element curium, provided by the Argonne National Laboratory of the Atomic Energy Commission, are directed toward the lunar surface underneath. A few of these alpha particles are scattered back; some of them produce protons by nuclear reactions in the lunar material. From the number and energy of the scattered alpha particles and protons, the chemical composition of the lunar surface can be deduced.
"In this way," Turkevich continued, "it was determined that the most abundant elements at the mare site where Surveyor V landed were oxygen, silicon, and aluminum, in decreasing order. This is the order. of abundance of the chemical elements on the crust of the Earth. The relative amounts of the elements resemble those in terrestrial basalts. This similarity suggests that the lunar material on the surface of the mare has been subjected to a geochemical process of differentiation similar to that undergone by the material of the Earth's crust."
Surveyor V was carrying a magnet on footpad 2 [top left, opposite page] when it slid downslope upon landing. JANE NEGUS DE WYS, of Jet Propulsion Laboratory, commented on the picture as follows:
"The permanent magnet [500-gauss strength] is at left in the photo, the unmagnetized control bar at right. A relatively small amount of iron material is seen adhering to the magnetic pole faces.
"Laboratory studies of impact in powders of different rock types and impact in powdered basalt with additions of powdered iron in varying amounts were used to interpret the pictures of the magnet that landed on the Moon. The closest resemblance was to the finely powdered basalt with no addition of powdered iron. This was in agreement with the alpha-scattering data. Since the magnet and alphascattering data indicate basalt, the lunar surface material in this area is of volcanic origin.
"The two general theories of lunar-crater formation are (1) meteoritic bombardment and (2) volcanic or gaseous emission.
"If all lunar craters and pulverization of the surface material were due to meteoritic impact," Mrs. de Wys concluded, "some addition of magnetic iron to the lunar-surface material would be expected. The magnet on the Moon does not indicate such an addition. Therefore, the extent of meteoritic bombardment and its role in lunar-surface morphology should perhaps be reexamined in the light of this evidence."
The dark semicircle in the lunar surface, located in the center of the photograph above, is a small, manmade crater, caused by a brief pulse of exhaust from one vernier engine. It was the result of a test that Surveyor performed in behalf of the manned lunar landing program. JAMES H. TURNOCK, Apollo Program, NASA, wrote:
"This successful experiment was performed at the request of the Apollo Program to determine by extrapolation what the effects on the lunar surface will be from the exhaust of the lunar module's descent engine. We wondered whether large clouds of dust would be raised, which would impair the astronauts' visibility. This information could not be obtained during a Surveyor landing, since the engines are cut off about 14 feet above the surface.
"Therefore, on September 13, 1967, about 53 hours after Surveyor V's landing, its engines were ignited and allowed to burn for 0.6 second. The resulting crater formed beneath engine 3, shown here, is about 8 inches in diameter and a little over an inch deep. That is about what we expected, and indicates that the engine-exhaust effects on the lunar surface should be no problem for Apollo. This, therefore, represents another important data point that the Surveyor Program provided for Apollo."
Surveyor VI landed on the flat surface of Sinus Medii, at 1.40° W, 0.49° N, on November 10, 1967, at 01:01:05 GMT. It came to rest near a mare ridge, visible in the lunar vista above.
In the course of its mission, this spacecraft took more than 30 000 photographs. It also took them from two slightly differing perspectives. At one point, its vernier engines were restarted and it was made to hop 8 feet. It then took fresh measurements and pictures from its new location (opposite page) .
Though Surveyor Vi and its three successful predecessors landed at lunar locations that were thousands of kilometers apart, the sites chosen for them to investigate proved to be strikingly alike, and promising for manned landings.
"The mosaic at the top of this page is the first view of a lunar wrinkle ridge from the surface of the Moon," declared JOHN B. ADAMS, of Jet Propulsion Laboratory. "Wrinkle ridges are low, sinuous features on the maria that have been observed for many years through telescopes, and, more recently, in Lunar Orbiter photographs.
"In this view from Surveyor Vi, in Sinus Medii, the ridge extends northeast along the horizon. Each frame in the mosaic covers a field of view of 6°. Notable features are the gentle slopes along the ridge flank facing the camera and the abundance of rock blocks on the ridge relative to the mare material near the spacecraft [foreground]. Blocks up to I meter in diameter are prominent around the two subdued craters on the ridge [right of center].
"From this photo and others," said Adams, "it is thought that craters that were formed on the ridge excavated more solid rock than did similar-sized craters in the flat mare. This suggests a thinner mantle of particulate rock on the ridge. The origin of the ridge is still a subject of debate, although wrinkle ridges in general are thought to have formed by deformation of the mare material.
"The terrain photographed by Surveyor Vi in Sinus Medii does not appear to be excessively hazardous for landing spacecraft. Although the region is highly cratered, most slopes are gentle, and there are few rocks-compared, for example, to the rock-strewn terrain in Oceanus Procellarum seen by Surveyor I. Sinus Medii is one of several prime sites for future manned landings."
After having been commanded to hop from its original landing position, Surveyor Vi took additional pictures, of which the scene above is one.
"This view of the lunar surface to the southeast of Surveyor VI was taken shortly before sunset," explained JACK N. LINDSLEY, of the Jet Propulsion Laboratory. "Long shadows cast by the late-afternoon Sun accentuate the irregularities of the Moon's surface in the Sinus Medii area. Although there are many craters and depressions, which appear as dark areas because they are filled with shadows, due to the low Sun angle, there are very few rocks of significant size. The shadow that appears on the bottom edge of the picture about 2 inches inward from the lower left corner is caused by the rim of a depression left by one of the spacecraft's feet when it first landed.
"The nearest area shown in the picture is about 12 feet from the camera, and the horizon is about one-half mile distant. A large crater is located near the horizon, to the right of the picture's center.
"The picture is a mosaic made from 20 individual wide-angle pictures taken by Surveyor VI's television camera, and covers 120° of the panorama. These 20 pictures are part of a series of 120 pictures taken to provide complete, 360° coverage of all the viewable lunar surface and of the spacecraft structure as well. During the sequence of picture taking, pictures were televised from the Moon to Earth at the rate of one about every 5 seconds. Each picture required approximately five commands to be radioed from Earth to the spacecraft in order to position the camera and snap its shutter."
"The photograph on the opposite page was taken by Surveyor Vl on November 17, 1967, after the first liftoff-and-translation maneuver on the Moon," explained BENJAMIN MILWlTZKY, Surveyor Program Manager, NASA. [That is true as well of the right-hand panel of the illustration at the bottom of this page.] "In this historic operation, the spacecraft was moved to a new location, approximately 8 feet from its original landing point.
"The picture shows the effects of the vernier-rocket engine blast on the double imprint previously made in the lunar surface by one of the spacecraft's crushable blocks during the initial touchdown. Material has been excavated from the imprints and deposited over a broad area on the lunar surface in a thin, dark coating forming a sheet-and-ray pattern. As has been observed in all Surveyor missions, the underlying lunar material is appreciably darker than the surface material. The latter appears to be a very thin layer whose higher reflectivity may result from the effects of solar and cosmic radiation.
"From this and other Surveyor Vl photos, it appears that rocket exhaust gases can strongly erode and excavate an area that has been previously disturbed, but have relatively little effect on the undisturbed lunar surface. These observations further reinforce the concept that the lunar surface is composed of very fine particles lightly held together by vacuum cohesion resulting from long exposure to the near-perfect void of outer space."
The pictures at left were taken before and after the vernier-engine firing. "Prior to the hop, the photometric chart on the end of omni antenna B was clean," wrote RAOUL CHOATE, Lunar and Planetary Sciences, Jet Propulsion Laboratory. "After the hop, the chart was covered with a coating of lunar soil up to 0.9 millimeter thick. Because the rest of the spacecraft remained relatively clean after the firing, it is surmised that the chart was hit by an individual soil clump. The clump was probably 2 to 3 inches in diameter.
"This photograph, better than any other Surveyor picture, illustrates the ability of lunar soil to adhere to vertical and near-vertical faces."
For scientists seeking insight into the Moon's structure and history, Surveyor Vll obtained the panoramic picture on the next page in the area that is shown below it in an Orbiter V photograph.
The Surveyor Program, ROBERT C. SEAMANS, JR., then NASA's Deputy Administrator, wrote at its conclusion, "was initiated in 1960 before a national commitment was made to land astronauts on the Moon and return them safely. Hence the objective was initially to land spacecraft on the Moon in order to obtain maximum scientific information after touchdown. The Surveyor operation differed from Ranger, which obtained data prior to impact, and Orbiter, which photographed the lunar surface while orbiting the Moon. The Surveyor program objectives gradually shifted emphasis as the Apollo manned lunar landing program became more firm. The designers of the Apollo lunar lander had to know the bearing strength of the Moon's surface in order to establish requirements for impact velocity and footpad area. Many other questions arose that could only be answered by landing Surveyor on possible Apollo landing sites. At the time these missions were planned, it was anticipated that the entire seven Surveyor spacecraft would be needed to investigate several Apollo sites. Actually four successful landings of Surveyor were achieved with the first six spacecraft and all Apollo requirements were then satisfied. It should be recognized that an enormous amount of valuable scientific information was obtained from each of these four missions, but the landing locations were restricted to the nearly equatorial sites achievable with Apollo. The success of these missions permitted the seventh spacecraft to be sent to a location where the maximum additional scientific data could be obtained. The highlands about 18 miles north of the large crater Tycho were selected. Many thousands of useful photographs of the Moon were obtained by Surveyor Vll television cameras from this site. A selection of these pictures was used to form the panoramic view of the Iunar terrain northeast of the spacecraft (on the top of the facing page).
"In this illustration the distance from Surveyor to the horizon varies from hill to hill, but the horizon in the center of the picture is about 8 miles away. Near the horizon a series of ridges and hills can be seen somewhat similar in form to many rounded hills found in parts of the eastern United States. Just below the horizon are small ravines and gullies probably formed during the flow of debris at the time or shortly after it was deposited. In the foreground is a rocky crater which lies about 18 feet from Surveyor's camera. The crater, about 5 feet in diameter, is filled with rocks. The rock on the near rim of the crater is 2 feet across and casts a 4-foot-long shadow to its left. The photo interpretation was made by Dr. Eugene Shoemaker of the U.S. Geological Survey, who was the principal investigator for the Surveyor television experiment.
"The Surveyor VII mission also permitted other than photographic data to be obtained. For example, as in previous missions, an alpha backscatter experimental package developed by Dr. Anthony Turkevich of the University of Chicago was lowered to the Iunar surface. This experiment provided data on the chemical composition of the Iunar surface."
The Orbiter V high-resolution photo (below on the facing page) shows where Surveyor Vll landed.
"This region was chosen," explained ABE SILVERSTEIN, Director. Lewis Research Center, NASA, "because it is believed to be covered by material ejected from beneath the lunar highlands when Tycho was formed. Because of the roughness of the ejecta blanket, Surveyor Vll's target area was a circle only 12.4 miles in diameter, one-third the normal size, in order to provide a reasonable probability for a survivable landing. Both the launch vehicle and the spacecraft performed so precisely that, after a single midcourse maneuver, Surveyor Vll landed less than 1 1/2 miles from the center of the small target circle.
"The landing point on the photo was determined by Dr. Ewen Whitaker of the University of Arizona by correlating more than 25 lunar-surface features visible in both Orbiter V and Surveyor Vll pictures.
"This is another good illustration of the manner in which the Surveyor and Orbiter spacecraft were used in combination for effective Iunar exploration ."
Surveyor VII, launched on January 7, 1968, at 06:30 GMT, successfully landed on the Moon on the Tycho ejecta blanket on January 10, 1968, at 01:05 GMT. The coordinates of the landing site were 40.89° S latitude and 11.44° W longitude. From that position, it transmitted 21274 television pictures during the first lunar-day operations. Its camera system also spotted laser beams aimed toward it from two observatories on Earth.
The Surveyor photograph of the partially sunlit Earth [top left], is described by C. O. ALLEY, of the University of Maryland: "Surveyor VII's TV camera detected as starlike images two narrow laser beams sent to the Moon from, respectively, the Kitt Peak National Observatory, near Tucson, Ariz., and the Table Mountain Observatory, near Los Angeles.
"The blue-green argon-ion laser beams seen within the white circle on the photograph each contained only about I watt of power," Alley explained, "but appeared somewhat brighter than the brightest star, Sirius.
"This engineering test of the aiming of the beams, a few miles wide at the Surveyor site, was conceived and coordinated by me and my fellow-professor D. G. Currie, of the University of Maryland's Department of Physics and Astronomy, to gain experience for the Apollo laser-ranging retroreflector experiment, for which I am principal investigator "
"The photograph at bottom left shows the detail of the center part of a rocky crater at the Surveyor Vll landing site, reported R. H. STEINBACHER, of Jet Propulsion Laboratory. "The narrow-angle picture of rocks 18 to 20 feet from the spacecraft has a field of view of about 3 feet diagonally across the picture. Some of the rocks are as much as 1 foot in size. The blocky, angular appearance of the rocks is characteristic of what is believed to be a relatively new crater. Close examination of these rocks and of the many others at this highland landing site was a main scientific objective of this mission."
The attention-commanding photograph at the right was among those that Surveyor Vll took of lunar rocks of special geological interest.
"This remarkably detailed, narrow-angle photograph of a cracked lunar rock gave us our first glimpse of fissure cracks in the blocky material of the Moon's surface," declared GLENN A. REIFF, Manager, Mariner IV and V programs, NASA. "The cracks in view here are about one-fourth inch wide, and were doubtless caused in place by expansion and contraction in the very severe temperature extremes of the airless Moon.
"These rocks, approximately 6 inches in size, are dense and fine-grained. Differences in light reflectivity on their surfaces suggest that the rocks contain at least two types of minerals. That curious image in the lower left-hand corner is a reflection from part of the spacecraft structure.
"I'm looking forward to the day," Reiff continued, "when we can obtain photographs of such exceptional detail as this from the surface of Mars or one of the other planets. However, we can't anticipate obtaining Martian surface detail comparable to that of Surveyor Vll's pictures of the Moon until such time as spacecraft actually land on the surface of the Red Planet.
"What we can look forward to, though, is that a number of the principles pioneered by Surveyor, such as guidance and landing techniques, can be used in future Mariners for exploring Mars."
"The narrow-angle picture at bottom right, taken by Surveyor Vll's television camera, shows the rolling lunar terrain northeast of the landing site," wrote F. N. SCHMIDT, of Bellcomm, Inc. "Surveyor Vll landed about 18 miles north of the large crater Tycho, the most prominent of all lunar craters at full Moon. The undulating surface is part of a series of ridges and hills that are a characteristic feature on the flanks of most large lunar crater rims. They were probably formed by the flow of debris ejected by the meteor impact that excavated the crater."
"The alpha-scattering instrument's sensor head is shown on the left-hand side of this Surveyor VII picture [top left]," explained C. E. CHANDLER, Surveyor Project engineer, Jet Propulsion Laboratory. "Because of a problem in the mechanical deployment mechanism, the sensor head did not drop to the surface on command but remained, as shown, in its background-count position. The scoop of the surface sampler, shown in the middle of the photograph, was then manipulated by command in an attempt to nudge the head and free the deployment mechanism. This initial effort did not succeed, but later the head was successfully deployed by a similar attempt, and the alpha-scattering instrument obtained lunar-composition data from a total of three sites close to the spacecraft." The instrument, in fact, spent a total of 43 hours 5 minutes in surface analysis; 12 hours 7 minutes in background count.
One of the several objectives of the Surveyor VII mission was to manipulate the lunar material with the surface sampler in view of the television camera. Six bearing-strength tests were conducted by pressing the bucket of the surface sampler against the lunar surface while recording drive-motor currents. Also, the sampler dug several trenches, one of which (bottom left) was approximately 16 inches long and a little more than 6 inches deep.
In commenting on that photograph, RONALD F. SCOTT, of the California institute of Technology, wrote: "This picture shows the second trench dug by Surveyor VlI's surface sampler. The scoop of the sampler, with its serial number, can be seen at the bottom of the picture, after completing a pass through the trench. The .cohesive nature of the lunar soil is clearly indicated by the very smooth vertical wall left by the sampler scoop.
"The sampling device was designed to perform tests such as this on the lunar surface to determine the mechanical properties of the surface material," Scott continued. "However, Floyd Roberson, my JPL colleague, and 1, who operated the sampler, also used it on Surveyor Vll to move the sensor head of the alpha-scattering experiment down to the lunar surface. Later, we used it to move the head [see facing page] to different positions on the surface."
Still another use was found for the versatile sampler. When temperatures in the sensor head rose too high, the sampler scoop was used like a parasol, shading the instrument from the Sun.
"The 3-inch rock at left center in the picture at top right was the second of three samples analyzed by means of the alpha-scattering experiment on Surveyor VII," said ERNEST J. FRANZGROTE, of Jet Propulsion Laboratory. "The picture was taken as the surface-sampler mechanism [upper right] was moving the alpha-scattering instrument to its third location, a plowed-up area at the right-hand edge of the picture. The circular impression on the lunar surface surrounding the rock shows the resting place of the bottom of the instrument during the analysis."
Surveyor data have shown the lunar maria to be remarkably uniform in their physical and chemical properties. Chemical analysis in the lunar highlands, by the crater Tycho, differed in that the concentration of iron and neighboring heavy elements was only half or less than that found in the maria. This deficit may explain the higher albedo (greater brightness) of the highlands. It also suggests that the highland material may be of somewhat lower density.
"This picture at bottom right, taken by Surveyor Vll's 600-line TV camera, consists of two views of the lunar surface," explained D. H. LE CROISSETTE, Manager, Surveyor instrument Development, Jet Propulsion Laboratory. "The central part of the picture shows the surface sampler poised above the lunar surface, as viewed through an auxiliary mirror placed on the mast of the spacecraft. The mirror was 3 1/2 by 9 1/2 inches in size, and was positioned so that a stereo view of a portion of the surface could be obtained where the surface sampler could reach.
"In this picture, the sampler had already conducted a bearing test in the soil and had started to dig a trench. The rest of the photograph is a direct view of another part of the lunar surface, looking between the mirror and some structural members of the spacecraft. The rocks shown in this view are about 1 foot across."
The hard work of Surveyor Vll's long lunar day, on which the Sun set on January 22, 1968, also included collecting data on touchdown dynamics, temperatures, and radar reflectivity. The spacecraft obtained data on touchdown dynamics by means of telemetry from strain gages mounted on its landing legs; radar-reflectivity data in the course of its terminal descent; and thermal data from onboard sensors.
Describing the spectacular, historic view above, FLOYD L. THOMPSON, then Director, Langley Research Center, wrote: "At 16:35 GMT on August 23, 1966, the versatile manmade Lunar Orbiter spacecraft responded to a series of commands sent to it from Earth, across a quarter-million miles of space, and made this over-the-shoulder view of its home planet from a vantage point 730 miles above the far side of the Moon.
"At that moment," Thompson continued, "the Sun was setting along an arc extending from England [on the right] to Antarctica [on the left]. Above that line, the world, with the east coast of the United States at the top, was still bathed in afternoon sunlight. Below, the major portion of the African Continent and the Indian Ocean were shrouded in the darkness of evening.
"By this reversal of viewpoint, we here on the...
....Earth have been provided a sobering glimpse of the spectacle of our own planet as it will be seen by a few of our generation in their pursuit of the manned exploration of space. We have achieved the ability to contemplate ourselves from afar and thus, in a measure, accomplish the wish expressed by Robert Burns: 'To see oursels as ithers see us! "
Also visible in dramatic new perspective in this photograph is the singularly bleak Iunar landscape, its tortured features evidently hammered out by a cosmic bombardment that may have extended over billions of years.
Because the airless, weatherless Moon appears to preserve its surface materials so well, it may serve science as an illuminating record of past events in the solar system. ROBERT JASTROW, Director Goddard Institute for Space Studies, has called the Moon "the Rosetta Stone of the planets."
Orbiter missions have been critically important in selecting lunar sites most suitable for astronaut landings, They have also provided what some scientists have called a "truly staggering" amount of new information about the Moon's surface.
JOHN F. McCAULEY, U.S. Geological Survey, wrote of the photo at the right: "This fascinating crater on the far side of the Moon has a gently domed floor, crisscrossed with linear depressions [about 1 kilometer wide] that give it the appearance of a turtle's back. Similar, crudely polygonal fracture patterns occur on Earth in domes formed by upward movement of plastic or liquid material.
"The doming of the floor of this crater could be the product of local magmatic activity or of slow isostatic rebound. Both alternatives point to probable activity of internal origin in the lunar crust."
Regarding the photo below, DONALD E. GAULT, Ames Research Center, declared: "Here is a graphic example on a colossal scale of one of the basic processes active on the lunar surface. Of these two unnamed craters on the far side of the Moon, the smaller, 45 kilometers in diameter, is the older,....
....since its northwest rim has collapsed and been displaced violently inward by the formation of the larger crater [55 kilometers in diameter]. This inward avalanche of rocky debris from the collapsed rim, together with ejecta spewed out along ballistic trajectories from the larger crater, has partially filled and obliterated the smaller structure. Thus, the mechanism by which impact craters are produced is an equally efficient agent for destroying craters, and impact scars do not necessarily provide a complete record of cratering events."
"From the best Earth-based telescopic photographs of the Moon, we selected eight areas across the Equator that appeared to be sufficiently free of craters to permit the astronauts to land safely," explained URNER LIDDEL, of NASA. When Lunar Orbiter I began photographing these areas, with between 100 and 1000 times the clarity of telescopic pictures from Earth, its high-resolution camera did not work dependably. Most of its pictures, therefore, were of medium resolution, like the one on the opposite page. Even these, however, revealed that lunar-mare areas that looked smooth from Earth were actually covered with small craters."