The Soviet Union’s remote-controlled lunar rover, Lunokhod 1, was the first self-propelled craft to explore another celestial body.
The Lunokhod 1 remote-controlled lunar exploration vehicle was carried to the Moon aboard the Luna 17 spacecraft. Luna 17 was launched from the Baikonur Cosmodrome, near Tyuratam (now in Kazakhstan), by a Proton booster at thirteen hours, forty-four minutes, Greenwich mean time, on November 10, 1970. The 5,700-kilogram Luna 17 spacecraft was placed initially in a temporary 192-by-237-kilometer Earth parking orbit. Prior to completing the first orbit, the Proton’s fourth stage injected the Luna 17/Lunokhod 1 spacecraft into a translunar trajectory.
Two midcourse corrections were performed on November 12 and 14 by Luna 17’s rocket motor while en route to the Moon. Luna 17 entered an 84-kilometer circular retrograde orbit around the Moon on November 15. The next day, the spacecraft lowered its perilune (lowest point of an orbit around the moon) to 19 kilometers. The following day, Luna 17 fired its retro-rocket and began its descent to the lunar surface. A radar altimeter cut off the braking rocket at an altitude of 3,000 meters, then refired it again at 740 meters. The descent engine was cut off a final time at 20 meters altitude, and the descent was completed with the craft’s vernier engines.
The spacecraft and its Lunokhod 1 cargo made a successful soft landing at three hours, forty-seven minutes, Greenwich mean time, on November 17. Luna 17 touched down on the inner slope of a shallow 150-meter-wide crater on Mare tinbriuin at lunar coordinates 38 degrees north, 35 degrees south. The lander was banked and pitched 4 degrees as it sat on the surface.
After landing, two sets of ramps—one forward and one aft of the Lunokhod—were lowered to the surface. The first television photographs were returned at five hours, thirty-one minutes, Greenwich mean time, and showed the ramps were clear of obstacles. At six hours, twenty-eight minutes, Greenwich mean time, the rover was driven slowly down one of the ramps onto the lunar surface.
The word “Lunokhod” means “moon walker.” The 1.35-meter high, 756-kilogram rover looked like a polished titanium alloy insect and consisted of a bathtub-shaped instrument compartment 2. 15 meters long, mounted on eight electrically driven aluminum wire mesh wheels set in two rows 1.6 meters apart with a wheel base of 2.21 meters. Each of Lunokhod’s eight 51-centimeter-diameter wheels had a two-speed electric drive motor and independent suspension. If any drive motor froze up in the lunar dust, a small explosive charge would sever the driveshaft and the wheel would freewheel. The rover was capable of moving even if two wheels on each side were disabled. Various items from the Lunokhod, including the drive motors, had been tested previously in lunar orbit by the Luna 12 and 14 spacecraft.
Lunokhod was capable of traveling on a 45-degree slope. If this angle was exceeded, the rover’s brakes engaged automatically until ground control could steer the vehicle away from danger. The rover’s magnesium alloy instrument compartment contained a special polonium 210 radioisotopic heat source to keep internal equipment from freezing in the –150 degree Celsius lunar night. During the day, excess heat was radiated away and the internal temperature was sustained in the 15 to 20 degree Celsius range.
Lunokhod used two forward-looking television cameras, which returned a photograph every twenty seconds for navigation while moving on the lunar surface. These cameras had a field of view of 50 degrees and were capable of sending stereo views of closeup objects. A second photographic system consisted of four 80-by-205-millimeter, 1.3-kilogram telephotometers, which operated much like a scanning facsimile photograph transmitter. These units returned high resolution 500-by-6,000-pixel panoramas of the lunar surface.
Lunokhod used several different methods to analyze the lunar soil. The first involved photographing the rover’s tracks to see how deep the wheels sank into the lunar dust. Another passive method used a trailing ninth wheel, which acted as an odometer. The revolutions of the odometer wheel were checked against the revolutions of the drive wheels to measure the slip between the wheels and the loose Moon dust. The bearing strength of the lunar surface was tested by a penetrometer consisting of a flat metal crusiform, which was stamped into the surface and its depth photographed by a television camera. Chemical analysis of the lunar soil was accomplished with the Röntgen Isotopic Fluorescence Method of Analysis (RIFMA) instrument. This apparatus focused a beam of electrons onto the surface to be analyzed, inducing it to emit X rays whose spectrum could be measured to show the concentrations of aluminum, silicon, magnesium, potassium, calcium, iron, and titanium.
An X-ray telescope operating in the 2 to 10 angstrom range and cosmic-ray detectors also were carried by the Lunokhod. Cosmic-ray data from the Moon were used in conjunction with data returned simultaneously from Soviet Venus and Mars spacecraft. A 3.7-kilogram French laser retroreflector consisting of ten separate 14-centimeter prisms was mounted above the forward television cameras. This instrument had a reflective capacity three times that of the Apollo laser reflectors. Lunokhod was parked during the lunar night in a position that aimed the laser reflectors at Earth. The French used the 102-centimeter telescope at Pic du Midi Observatory, while the Soviets used the 262-centimeter telescope at the Crimean Astrophysical Observatory to fire bursts of red ruby laser light at the Lunokhod for lunar ranging experiments.
Lunokhod was remotely operated by a five-person team located at the Soviet Deep Space Communications Center. The team consisted of a commander, driver, navigator, systems engineer, and radio operator. Control of the Lunokhod was directed through the Soviet deep space tracking antenna at Yevpatoria in the Crimea. Because the Soviets did not have a worldwide tracking network like the National Aeronautics and Space Administration (NASA), the Lunokhod could be operated and navigated only while the Moon was visible from the Crimea. Typically, the Lunokhod was active only four hours per day. Navigating the Lunokhod on the Moon’s surface by remote control was complicated by the slow scan rate of the forward-looking television cameras and the three-second round trip time for signals between Earth and the Moon. By the time controllers received the picture, Lunokhod already would be several meters ahead of that position.
After landing, Lunokhod traveled in a southeasterly direction, then looped back toward the initial starting area. After arriving back at the lander and inspecting it, Lunokhod traveled north. Travel distance during each lunar day varied from several hundred meters to 2 kilometers. Steep slopes, boulder fields, and craters of various sizes were encountered. At one point, angles were so steep that Lunokhod’s brakes were applied while a complicated series of maneuvers were mapped to back the rover away from danger. Furthermore, roving operations on the Moon by Lunokhod had to be suspended for three days near each local lunar noon because high Sun elevations erased shadows and made navigation by television difficult.
The Lunokhod was designed for a ninety-day lifetime, but was active on the Moon for eleven months. Although the RIFMA instrument failed after seven months, Lunokhod survived for 322 Earth days until September, 1971. Attempts to revive the rover after the lunar night on October 1 failed after the radioisotope heat source exhausted its fuel and the lander froze in the night.
The Soviet Lunokhod 1 was the first roving unpiloted exploration vehicle to travel on another celestial body. In contrast to other unpiloted spacecraft, which had returned data about one small area of the Moon, Lunokhod traveled over a wide area while taking measurements.
The Lunokhod rover was not a true autonomous robot but was entirely directed by remote control from Zvedniyi Gorodok, the Soviet space center, near Moscow. The chief designers were G. N. Babakin, Valentin Glushko, A. M. Isayev, Sergei Korolev, Vasily P. Mishin, and Mikhail Ryazanski. The rover was very similar in operation to modern radio-controlled model cars and provided the Soviets with experience in teleoperations (the science of remote exploration). The fact that control of the rover was carried out from the Soviet space center showed the link between the Lunokhod program and the Soviet piloted lunar landing program. In the late 1960’s, it was obvious to the Soviets that their piloted lunar landing program was experiencing lengthy delays, while the American program was quickly approaching its goal of a piloted lunar landing by the end of the decade.
During its eleven-month lifetime, Lunokhod 1 returned twenty thousand separate photographs of the lunar surface, including two hundred panoramas. The rover traveled 10.5 kilometers over the lunar terrain and examined 80,000 square meters of surface. Over that distance, five hundred penetrometer and twenty-five RIFMA soil analyses were performed. The RIFMA soil analysis experiment confirmed that the lunar soil was made primarily of volcanic basalt. On December 12, 1970, the RIFMA apparatus detected radiation from a solar flare, which the Soviets claimed would have been lethal to an astronaut on the Moon.
The Lunokhod 1 exploration vehicle.
Sensors continuously reported Lunokhod’s internal pressure and temperature, pitch and roll attitude, and temperatures of the solar cells, wheels, and motors. The readings showed that the solar cells can reach 121 degrees Celsius. The Sun-side wheels reached 100 degrees Celsius, whereas the shadow-side wheels were only 19 degrees Celsius. Temperatures recorded by the Lunokhod during a lunar eclipse on February 10, 1971, quickly fell from 138 degrees Celsius to –100 degrees Celsius.
In addition to lunar science, the Lunokhod 1 mission provided the Soviets with valuable engineering data on lubricating moving parts in a vacuum. An unusual problem to overcome was the tendency of metallic parts to freeze together, a process called vacuum welding. The thermal stresses induced by the lunar day and night cycles were also studied for data needed to improve future space machinery. Initial fears that Lunokhod’s wire mesh wheels would clog with lunar dust attracted by static electricity were proved to be unfounded. During operation, moondust fell off the wheels like dry sand.
Joint laser ranging experiments were also carried out in collaboration with the French. Precise measurement of the travel time of the laser light reflected from Lunokhod helped fix the Earth-Moon distance to within 30 centimeters. Lunokhod 1 also became the target of international politics and propaganda. During Lunokhod’s first lunar night, the Soviets and the French both attempted laser shots at the rover’s laser reflector. The Soviets were successful, while the French were not. Open speculation accused the Soviets of supplying the French the wrong lunar coordinates, which would assure the Soviets the honor of being first to locate the Lunokhod.
The Soviets argued that remote exploration of the Moon by Lunokhod-type rovers was much cheaper and safer than human exploration. The Lunokhod mission came only seven months after the aborted Apollo 13 mission. The Soviets cited the Apollo 13 problems as part of the justification for unpiloted exploration of the Moon.
-
Cadbury, Deborah. Space Race: The Epic Battle Between America and the Soviet Union for Dominion of Space. New York: HarperCollins, 2006. A 384-page account of American and Soviet efforts to launch the first satellite and to send humans to the Moon. -
Gatland, Kenneth. Robot Explorers. London: Blandford Press, 1972. A chronology of Soviet and American lunar and planetary space exploration programs. Contains numerous color illustrations providing insights into the design and functions of American and Soviet lunar and planetary spacecraft. -
Hartmann, William K. Moons and Planets. 5th ed. Belmont, Calif.: Brooks/Cole, 2005. Provides detailed information about all objects in the solar system. Suitable on three separate levels: high school students, general readers, and college undergraduates studying planetary geology. -
Long, Kim. The Moon Book: Fascinating Facts About the Magnificent, Mysterious Moon. Boulder, Colo.: Johnson Books, 1998. A “manual” of sorts that provides easy reading on Moon facts. -
McDougall, Walter A. The Heavens and the Earth: A Political History of the Space Age. 2d ed. Baltimore: Johns Hopkins University Press, 1997. A political history of the space age. Well researched. Describes and analyzes the decisions by the leaders of both the United States and the Soviet Union and their effects on the respective space programs. -
Scott, David, and Alexei Leonov. Two Sides of the Moon: Our Story of the Cold War Space Race. New York: Simon & Schuster, 2004. A personal account of the space race between the Soviet Union and the United States by two major players in the programs of their respective countries. -
Short, Nicholas M. Planetary Geology. Englewood Cliffs, N.J.: Prentice Hall, 1975. Summarizes the accomplishments and scientific results of both American and Soviet lunar and planetary space programs. Stresses the chemical nature of the Moon and inner planets, their geological similarities and differences, and their origins. College-level reading, and illustrated with many diagrams and photographs taken by the space missions. -
Siddiqi, Asif A. Sputnik and the Soviet Space Challenge. Gainesville: University Press of Florida, 2003. An award-winning book that offers a comprehensive and detailed history of the Soviet space program from its earliest days. An essential resource. -
Smolders, Peter L. Soviets in Space: The Story of the Salyut and the Soviet Approach to Present and Future Space Travel. Translated by Marian Powell. New York: Taplinger, 1974. A well-illustrated narrative on all aspects of the Soviet space program. Concentrates on the successful portions of the Soviet space program. Contains numerous diagrams and photographs. Suitable for general readers. -
Turnill, Reginald. Spaceflight Directory. London: Frederick Warne, 1978. A lavishly illustrated summary of spaceflight activities by all nations. Lists chronologies of major piloted and unpiloted space missions. Suitable for readers at the high school and college level. -
Wilson, Andrew. Solar System Log. London: Jane’s, 1987. A compilation of all piloted and unpiloted lunar and planetary spaceflights up to mid-1985 by all space-faring nations. A well-illustrated chronology of the history, spacecraft, mission, and discoveries of all deep space exploration missions. Suitable for all readers.
Luna 2 Becomes the First Human-Made Object to Impact on the Moon
Luna 3 Provides the First Views of the Far Side of the Moon
Ranger Program
Venera 3 Is the First Spacecraft to Impact Another Planet
Luna 9 Makes the First Successful Lunar Soft Landing
Lunar Orbiter 1 Sends Photographs of the Moon’s Surface
First Humans Land on the Moon
Apollo 12 Mission Marks Second Moon Landing