Accordingly, as spaceflight became an ever more realistic possibility, the Moon took on added meaning as Earth’s nearest astronomical neighbor and a relatively easy destination for humankind to visit and explore. In the desperate rivalry between the United States and the Soviet Union during the Cold War, the Moon held enormous potential as a public relations coup for the nation reaching it first. The number of spaceflight “firsts” associated with the Moon in the 1950s and 1960s clearly demonstrated the significance assigned to lunar exploration during this first heroic era of the space age. From the first clear images of the Moon to the landings of the Apollo astronauts between 1969 and 1972, the Moon held a fascination that propelled the human efforts to explore its surface.
Robot Emissaries and International Gamesmanship
The Moon had been a target for Sergei Korolev and the Soviet space program from before the advent of the space age. Khrushchev supported space exploits because of the propaganda value they held. He, too, recognized the special place the Moon held in the public’s perception. Khrushchev approved the use of a modified R-7 rocket, as well as a new and more powerful upper stage, to launch probes to the Moon. Launched under the strictest of secrecy in 1958, the first three probes all failed. The first, named Ye-1, launched on September 23, 1958, consisted of a pressurized sphere similar to Sputnik 1 and carried five scientific instruments that could measure the gas component of interplanetary matter, meteoric particles, cosmic rays, the magnetic fields of the Moon and Earth, and heavy nuclei in primary cosmic radiation. During launch the booster became uncontrollable and disintegrated after 93 seconds. A second probe failed for the same reason on October 11, at 104 seconds into the flight. A third attempt on December 4 lasted 245 seconds before failing. The Soviet government never divulged these launch attempts.
Korolev believed that the failures occurred because he had been forced to pursue the program without adequate funding and to accelerate the launch attempts before sufficient testing was possible. He knew that infighting in Moscow had contributed to the funding problem. When called to account for these failures, Korolev quipped, “Do you think that only American rockets explode?” Unlike the secret Soviet program, failures of the Pioneer rocket were constantly reported and criticized by U.S. media and politicos.
After the Soviet Union’s success with the Luna probes, in March 1959, Pioneer 5 became the first U.S. spacecraft to fly past the Moon. Between 1958 and 1968 the Soviet Union and the United States sent a total of sixty probes around or to the Moon (Table 1), with the Soviet Union achieving all the major breakthroughs in lunar probe missions (Table 2) as well as robotic exploration (Box 1).
Figure 5. In October 1959 the Soviets sent Luna 3 to transmit pictures of the far side of the Moon—thereby giving the Soviets an important “first” in lunar exploration. The probe sent back twenty-nine photographs covering 70 percent of the far side. The photographs were degraded by radio interference and low resolution, but many lunar features could be recognized.
TABLE 1
PROBES SENT TO THE MOON, 1958–1976
USSR
USA
Number of probes launched
49
29
Successful or partially successful missions
22
15
Number of failures due to launcher malfunctions
18
8
Time from program start to 1st Moon impact
1 year
4 years
Number of attempts before 1st Moon soft landing
10
Success on 1st attempt
Source: Calculated from “Lunar Exploration Timeline,” Lunar and Planetary Institute, https://www.lpi.usra.edu/lunar/missions/, accessed 8/28/2018.
TABLE 2
KEY FIRSTS IN LUNAR EXPLORATION, 1958–1967
BOX 1: KEY FIRSTS IN ROBOTIC EXPLORATION, 1957–1960
First Earth-circling satellite launched into orbit, Sputnik 1 (USSR), October 4, 1957.
First living animal in orbit, the dog Laika launched on Sputnik 2, November 3, 1957.
First human-made object to escape Earth’s gravity and to be placed in orbit around the Sun, Luna 1 (USSR), January 2, 1959.
First clear images of the Moon’s surface, from Luna 2, September 12, 1959.
First pictures of the far side of the Moon, taken by Luna 3, October 7, 1959.
First return of living creatures from orbital flight, two dogs aboard Sputnik 5, August 6, 1960.
The United States did not fare as well in early space-exploration efforts. It tried to match the Soviet successes as best it could, but all the early launches failed. In December 1959, after the failure of the first lunar probes, the army’s Jet Propulsion Laboratory started the Ranger project, partly in response to the public relations mess the earlier failures had created. Little improved after NASA’s creation in 1958. For example, on August 30, 1961, after JPL had been reassigned to NASA, the first Ranger reached space but the launch vehicle placed it in the wrong orbit. Two more attempts in 1961 failed, as did two in 1962. NASA then reorganized the Ranger project and did not attempt another launch until 1964. By that time President John F. Kennedy had pledged that the United States would land Americans on the Moon, and the program had been restructured to aid in learning more about the Moon itself, to ensure that the astronauts would survive. The scientists needed to know the composition and geography of the Moon, and the nature of the lunar surface. Was it solid enough to support a lander, or was it composed of dust that would swallow up the spacecraft? Would communications systems work on the Moon? Would other factors—geology, geography, radiation, and so on—affect the astronauts?
To answer these questions three distinct satellite research programs emerged. The restructured Ranger program was the first of these. NASA’s engineers eliminated all scientific instruments from Ranger crafts, leaving only a television camera. Ranger’s sole remaining objective was to go out in a blaze of glory as it crashed into the Moon while taking high-resolution pictures. On July 31, 1964, the seventh Ranger transmitted 4,316 beautiful, high-resolution pictures of the lunar Sea of Clouds. The eighth and ninth Rangers also worked well. Even so, the United States seemingly continued to lag the Soviet Union in the Cold War battlefield of technological competition in space.
The second project was Lunar Orbiter, an effort approved in 1960 to place probes in orbit around the Moon. This project, originally not intended to support Apollo, was reconfigured in 1962 and 1963 to further the Kennedy mandate more specifically by mapping the surface of the Moon and photographing about 95 percent of its surface—more than 14 million square miles—to aid in the selection of landing sites for Apollo astronauts. In addition to a powerful camera capable of sending photographs to Earth tracking stations, it carried three scientific experiments—selenodesy (the lunar equivalent of geodesy), meteoroid detection, and radiation measurement. While the returns from these instruments interested scientists in and of themselves, they were critical to Apollo. NASA launched five Lunar Orbiter satellites between August 10, 1966, and August 1, 1967, each successfully achieving its objectives. At the completion of the third mission, moreover, the Apollo planners announced that they had sufficient data to press on with an astronaut landing and could use the last two missions for other activities.
Lunar Orbiter’s bounty of images came from a unique onboard photographic system. Instead of sending television pictures back to Earth as electrical signals, Lunar Orbiter took actual photographs, developed them on board, then scanned them via a special photoelectric system. Because of this self-contained “darkroom” capacity, scientists referred to Lunar Orbiter as the “flying drugstore.” Because of concerns that radiation in space might fog photographic film, the system used a slow-speed film. To prevent blurring, the spacecraft compensated for the relatively long exposure times by constantly adjusting its optics and in some cases moving slightly. The resulting images had exceptional quality and provided resolutions of up to three feet fro
m an altitude of thirty nautical miles. For example, the Lunar Orbiter spacecraft took an iconic image of Copernicus Crater from the perspective one would get by flying over it at low altitude. After depleting the spacecraft’s film supplies, flight controllers purposely crashed all five Lunar Orbiters onto the Moon so that their radio transmitters would not interfere with future spacecraft.
Meantime, the Soviet Union also sent numerous spacecraft to the Moon. Its Luna program, sometimes called Lunik, sent fifteen successful spacecraft to the Moon between 1959 and 1976, many of which achieved firsts in the space race. While the Soviets had many failures, not publicly acknowledged at the time, the importance of this program should be acknowledged:
• Luna 2 mission made the first successful impact upon the lunar surface, the first human-made object to do so (1959)
• Luna 3 returned the first photographs of the Moon’s far side (1959)
• Luna 9 was the first probe to achieve a soft landing on another body, the Moon (1966)
• Luna 10 became the first artificial satellite of the Moon (1966)
• Luna 17 (1969) and Luna 21 (1973) deployed roving vehicles that roamed the Moon
• Luna 16 (1970), Luna 20 (1972), and Luna 24 (1976) returned samples to the Soviet Union from the lunar surface
Robotic Moon Soft-Landers
Like so many other points of intersection, soft-landing on the Moon with robotic probes also proved a venue for competition for the United States and the Soviet Union in the 1960s. The Soviets won that competition February 3, 1966, by sending Luna 9 to the Moon’s Oceanus Procellarum region, where it became the first spacecraft to soft-land on another planetary body. Equipped only with a camera and communication equipment, Luna 9 provided the first dramatic panoramic views of the surface of the Moon.
Arriving on the lunar surface, Luna 9 landed west of craters Reiner and Marius. Luna 9 was designed to release a landing pod immediately before striking the surface. A hinged arm reaching forward from the retrorocket was used to detect the surface. The egg-shaped pressurized pod, weighing 250 pounds on Earth, detached and rolled across the surface. After four minutes four spring-loaded “petals” unfolded, and a thirty-inch radio antenna extended. This design ensured that the pod would operate “right side up.” Images showed rocks ranging from four to eight inches distributed on the surface. The television camera on Luna 9 was able to rotate 360 degrees, although imagery was not returned of the entire view because the spacecraft landed at an angle. Between the second and third transmissions from the Moon, Luna 9’s inclination changed from 16.5 degrees to 27.5, perhaps because thermal expansion and contraction caused rocks beneath the lander to shift.
Months after the Soviet Union’s success with Luna 9, the United States succeeded in soft-landing Surveyor 1 on the Moon, on June 2, 1966. Carrying two cameras, Surveyor 1 provided multiple images of the surrounding lunar terrain and nearby surface materials. Surveyor 1 was placed into a direct trajectory to the Moon’s surface. During its final descent, it was slowed by a solid-propellant retrorocket. This element was then jettisoned, removing about 60 percent of Surveyor’s mass. Three small engines slowed the lander’s velocity to about three miles per hour. At that point the rockets were shut off and Surveyor coasted to a gentle landing.
Surveyor 1 photographed and studied the soil of a flat area inside a sixty-mile crater north of Flamsteed Crater in southwest Oceanus Procellarum. The television system transmitted 10,338 photos before nightfall on June 14. The spacecraft also acquired data on the radar reflectivity and bearing strength of the lunar surface, as well as spacecraft temperatures for use in the analysis of the lunar surface temperatures. Surveyor 1’s mission was terminated by a dramatic drop in battery voltage.
The Soviet Union remained committed to robotic lunar exploration as well. It landed a second soft-lander on the surface with Luna 13 on December 24, 1966, in the region of Oceanus Procellarum. The same petal encasement as used on Luna 9 was opened, antennas were erected, and radio transmissions to Earth began four minutes after the landing. Unlike the earlier probe, Luna 13 carried new instruments mounted at the end of folding five-foot arms. The first experiment tested density of the lunar soil. One end of the arm was slammed into the soil using a small explosive charge, and the seismic waves reflecting back to the surface were measured. The other arms carried radiation density meters, which exposed the lunar soil to gamma rays and measured the reflected energy. On December 25 and 26, the spacecraft television system transmitted panoramas of the nearby lunar landscape at different Sun angles. Each panorama required approximately one hundred minutes to transmit.
After the failure of Surveyor 2 on September 22, 1966, NASA’s Surveyor 3 successfully soft-landed on the lunar surface on April 17, 1967, and provided imagery and soil analysis. The lander “bounced” more than once on the surface before coming to rest. Footprints from the initial impact were visible from the final landing site. Besides a camera similar to that on Surveyor 1, this lander also carried a mechanical scoop that dug several small trenches in the lunar soil. Over the next three weeks the camera returned more than sixty-three hundred images showing the surrounding rocks and the movements of the scoop. Two years after landing, Surveyor 3 was visited by the Apollo 12 astronauts. The television camera and other sections were removed and returned to Earth. The camera was later put on display in the Smithsonian Institution’s National Air and Space Museum.
Although NASA lost contact with Surveyor 4 on July 17, 1967, it followed with Surveyors 5, 6, and 7 over the next few months. While on its trajectory to the Moon, Surveyor 5 experienced serious problems with a helium pressurization system that was necessary for the retrorockets to work. Flight engineers were able to work around the problem, and Surveyor 5 successfully landed on September 10, 1967. Thousands of images were returned by the television camera. Surveyor 5 also carried an alpha ray scatterer that measured composition of the lunar soil. Surveyor 6 landed on November 9, 1967. It carried instruments similar to Surveyor 5’s. On November 17, after controllers noted that enough fuel remained for a brief firing of the retrorockets, Surveyor 6 became the first spacecraft to take off from the lunar surface. When the retrorockets were fired, it performed a “hop,” reaching a height of about ten feet and coming to rest about eight feet from its previous position. Both sets of footprints in the lunar soil were plainly visible in images from the television camera. Surveyor 7 landed on January 10, 1968, north of the crater Tycho. Surveyor 7 carried both a mechanical arm and an alpha scattering instrument. The arm was needed to move the latter device when it was found to be stuck. Over three weeks, the alpha scattering sensor was lowered and then moved to test composition of soil from the surface and within trenches.
Figure 6. Charles Conrad, Jr., Apollo 12 commander, examines the Surveyor 3 spacecraft during the second extravehicular activity (EVA-2) in 1969. The lunar module (LM) Intrepid is in the right background. This picture was taken by astronaut Alan L. Bean, lunar module pilot. Apollo 12 landed on the Moon’s Ocean of Storms, only six hundred feet from Surveyor 3. The television camera and several other components were taken from Surveyor 3 and brought back to Earth for scientific analysis. Surveyor 3 soft-landed on the Moon on April 20, 1967.
Five of the seven Surveyor spacecraft completed their missions, although the vernier rockets on Surveyor 3 did not shut down at the proper point, causing the 650-pound robot to skip twice across the lunar surface before stopping beneath a small crater rim.
Making the Most of Robotic Lunar Exploration
The Soviet Union continued its effort to explore the Moon well into the 1970s, although the American robotic effort ended with the Surveyor program. During the space race of the 1960s the United States and the Soviet Union competed for space firsts across a broad front of human and robotic missions targeted on the Moon, Venus, and Mars. The United States won the most significant prize by landing a human on the Moon first, demonstrating its capability so thoroughly that the Soviet Union withdrew from the race, disingenuo
usly claiming that it had not been racing the United States at all. Instead, it succeeded in landing the first robotic rovers on the Moon, Lunokhods 1 and 2.
The first rover, Lunokhod 1, was soft-landed on the lunar surface by Luna 17 on November 17, 1970. Weighing just under one ton, this rover was intended to operate for ninety days while guided from the Soviet mission control center outside Moscow. It had been launched on November 10, and flight controllers undertook two course corrections to bring it into lunar orbit on November 15. After landing, this eight-wheeled rover departed Luna 17 by means of ramps extending from both sides of the lander. It was the first roving remote-controlled robot to land on another world. Lunokhod 1 far exceeded its design life, and traveled around the lunar Mare Imbrium (Sea of Rains) for eleven months after landing. It ran only during the two-week-long lunar day, stopping occasionally to recharge its batteries via its solar panels. The rover’s operations officially ceased on October 4, 1971, on the fourteenth anniversary of the launch of Sputnik 1.
Viewed initially as a scout for a landing site for Soviet cosmonauts, this rover had originated in 1963 and was to carry a beacon that would be used to guide the cosmonauts to the surface. By the time that it flew, however, this mission had been preempted by events. Lunokhod 1 therefore explored the lunar surface and returned scientific information about the geology and landscape of the Moon, imaging its surface, undertaking laser-ranging experiments from Earth, and measuring magnetic fields. It carried a cone-shaped antenna, a highly directional helical antenna, four television cameras, and an extendable arm to test the lunar soil for soil density. Soviet scientists also included an X-ray spectrometer, an X-ray telescope, cosmic-ray detectors, and a laser-ranging device.
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