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Overview
Luna 1958A
Luna 1958B
Luna 1958C
Luna 1
Luna 1959A
Luna 2
Luna 3
Luna 1960A
Luna 1960B
Luna 1963B
Luna 4
Luna 1964A
Luna 1964B
Luna 5
Luna 6
Luna 7
Luna 8
Luna 9
Luna 10
Luna 1966A
Luna 11
Luna 12
Luna 13
Luna 1968A
Luna 14
Luna 1969A
Luna 1969B
Luna 1969C
Luna 15
Luna 1970A
Luna 1970B
Luna 16
Luna 17
Luna 18
Luna 19
Luna 20
Luna 21
Luna 22
Luna 23
Luna 1975A
Luna 24

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Luna Program (1958-1976)

Overview

The USSR Luna program was aimed at the exploration of Earth's closest sizeable celestial neighbor: The moon. The Luna program achieved much exploration - despite many failed missions - and set many firsts. Some of those firsts include the first probe to reach the moon, accomplished by Luna 1. Also, Luna 9 was the first craft to achieve a soft landing and to transmit pictures to Earth from the moon. Luna 16 was the first robotic probe to land on Luna and return a sample to Earth.

Luna 1958A

This craft was believed to be an attempt to reach the moon and impact on its surface. The SL-3/A-1 launcher underwent a structural failure and exploded 92 seconds after launch.

Luna 1958B

This craft was believed to be an attempt to reach the moon and impact on its surface. The SL-3/A-1 launcher exploded 100 seconds after launch. This mission was launched a few hours after the Pioneer 1 mission, an unsuccessful attempt by the U.S. to reach the moon. Because Luna was on a faster trajectory, it would have reached the moon first.

Luna 1958C

This craft was believed to be an attempt to reach the moon and impact on its surface. A first stage engine of the SL-3/A-1 launcher failed 245 seconds after launch.

Luna 1

Luna 1 was the first spacecraft to reach the moon and the first of a series of Soviet automatic interplanetary stations successfully launched in the direction of the moon. The spacecraft was sphere-shaped with five antennae extending from one hemisphere. Instrument ports also protruded from the surface of the sphere. There were no propulsion systems on the Luna 1 spacecraft itself. Because of its high velocity and its announced package of various metallic emblems with the Soviet coat of arms, it was concluded that Luna 1 was intended to impact the Moon.

After reaching escape velocity, Luna 1 separated from its 1472 kg third stage. The third stage, 5.2 m long and 2.4 m in diameter, traveled along with Luna 1. On January 3, at a distance of 113,000 km from Earth, a large (1 kg) cloud of sodium gas was released by the spacecraft. This glowing orange trail of gas, visible over the Indian Ocean with the brightness of a sixth-magnitude star, allowed astronomers to track the spacecraft. It also served as an experiment on the behavior of gas in outer space. Luna 1 passed within 5995 km of the Moon's surface on January 4 after 34 hours of flight. It went into orbit around the sun, between the orbits of Earth and Mars.

The spacecraft contained radio equipment, a tracking transmitter, and telemeter system, five different sets of scientific devices for studying interplanetary space, including a magnetometer, geiger counter, scintillation counter, and micrometeorite detector, and other equipment. The measurements obtained during this mission provided new data on the Earth's radiation belt and outer space, including the discovery that the Moon had no magnetic field and that a solar wind, a strong flow of ionized plasma emanating from the sun, streamed through interplanetary space.

Luna 1959A

This craft was believed to be an attempt to reach the moon and impact on its surface. An SL-3/A-1 launcher was used. The guidance system of the R-7 rocket failed and the spacecraft was unable to reach Earth orbit.

Luna 2

Luna 2 was the second spacecraft to reach the moon. The first spacecraft to land on the moon, it impacted the lunar surface east of Mare Serenitatis near the Aristides, Archimedes, and Autolycus craters. Luna 2 was similar in design to Luna 1 - a spherical spacecraft with protruding antennae and instrument parts. The instrumentation was also similar, including scintillation- and geiger- counters, a magnetometer, and micrometeorite detectors. The spacecraft also carried Soviet pennants. There were no propulsion systems on Luna 2 itself.

After launch and attainment of escape velocity on September 12, 1959 (September 13, Moscow time), Luna 2 separated from its third stage, which traveled along with it towards the moon. On September 13, the spacecraft released a bright orange cloud of sodium gas which aided in spacecraft tracking and acted as an experiment on the behavior of gas in space. On September 14, after 33.5 hours of flight, radio signals from Luna 2 abruptly ceased, indicating it had impacted on the moon. The impact point, in the Palus Putredinus region, is roughly estimated to have occurred at 0° longitude, 29.1° N latitude. Some 30 min after Luna 2, the third stage of its rocket also impacted the moon. The mission confirmed that the moon had no appreciable magnetic field, and found no evidence of radiation belts at the moon.

Luna 3

Luna 3, an automatic interplanetary station, was the third spacecraft successfully launched to the moon and the first to return images of the lunar far side*. The spacecraft returned very indistinct pictures, but, through computer enhancement, a tentative atlas of the lunar far side was produced. These first views of the lunar far side showed mountainous terrain, very different from the near side, and only two dark regions which were named Mare Moscovrae (Sea of Moscow) and Mare Desiderii (Sea of Dreams). (Mare Desiderii was later found to be composed of a smaller mare, Mare Ingenii (Sea of Ingenuity) and other dark craters.)

The spacecraft was a cylindrically shaped canister with hemispherical ends and a wide flange near the top end. The probe was 130 cm long and 120 cm at its maximum diameter at the flange. Most of the cylindrical section was roughly 95 cm in diameter. The canister was hermetically sealed and pressurized at 0.23 atmospheres. Solar cells were mounted along the outside of the cylinder and provided power to the chemical batteries stored inside the spacecraft. Jalousies for thermal control were also positioned along the cylinder and would open to expose a radiating surface when the interior temperature exceeded 25 °C. The upper hemisphere of the probe held the covered opening for the cameras. Four antennae protruded from the top of the probe and two from the bottom. Other scientific apparatus (micrometeoroid and cosmic ray detectors) was mounted on the outside of the probe. Gas jets for attitude control were mounted on the outside of the lower end of the spacecraft. Photoelectric cells were used to maintain orientation with respect to the sun and moon. The spacecraft had no rockets for course adjustment. The interior of the spacecraft held the cameras and film processing system, radio equipment, propulsion systems, batteries, gyroscopic units for attitude control, and circulating fans for temperature control. The spacecraft was spin stabilized and was directly radio-controlled from Earth.

The imaging system on Luna 3 was designated Yenisey-2 and consisted of a dual lens camera, an automatic film processing unit, and a scanner. The lenses on the camera were a 200 mm focal length, f/5.6 aperture objective and a 500 mm, f/9.5 objective. The camera carried 40 frames of temperature- and radiation resistant 35-mm isochrome film. The 200 mm objective could image the full disk of the moon and the 500 mm could take an image of a region on the surface. The camera was fixed in the spacecraft and pointing was achieved by rotating the craft itself. A photocell was used to detect the moon and orient the upper end of the spacecraft and cameras towards it. Detection of the moon signaled the camera cover to open and the photography sequence to start automatically.

After photography was complete, the film was moved to an on-board processor where it was developed, fixed, and dried. Commands from Earth were then given and the film was moved to a scanner where a bright spot produced by a cathode ray tube was projected through the film onto a photoelectric multiplier. The spot was scanned across the film and the photomultiplier converted the intensity of the light passing through the film into an electric signal which was transmitted to Earth. A frame could be scanned with a resolution of 1000 lines, the transmission could be done at a slow rate for large distances from Earth and a faster rate at closer range.

After launch on an 8K72 (number I1-8) on a course over the Earth's north pole the Blok-E escape stage was shut down by radio control from Earth at the proper velocity to put the Luna 3 on a trajectory to the moon. Initial radio contact showed the signal from the probe was only about half as strong as expected and the interior temperature was increasing. The spacecraft spin axis was reoriented and some equipment shut down resulting in a drop in temperature from 40 °C to about 30 °C. At a distance of 60,000 to 70,000 km from the moon, the orientation system was turned on and the spacecraft rotation was stopped. The lower end of the station was oriented towards the sun, which was shining on the far side of the moon.

The spacecraft passed within 6,200 km of the moon near the south pole at its closest approach at 14:16 UT on October 6, 1959 and continued on to the far side. On October 7, the photocell on the upper end of the spacecraft detected the sunlit far side of the moon and the photography sequence started. The first image was taken at 03:30 UT at a distance of 63,500 km from the moon's surface and the last 40 minutes later from 66,700 km. A total of 29 photographs were taken, covering 70% of the far side. After the photography was complete the spacecraft resumed spinning, passed over the north pole of the moon and returned towards the Earth. Attempts to transmit the photographs to Earth began on October 8, but were believed to be unsuccessful due to the low signal strength. As Luna 3 got closer to Earth a total of 17 resolvable but noisy photographs were transmitted by October 18. Contact with the probe was lost on October 22. The probe was believed to have burned up in the Earth's atmosphere in March or April of 1960, but may have survived in orbit until after 1962.

*The camera took 29 pictures over 40 minutes on October 7, 1959, from 03:30 UT to 04:10 UT at distances ranging from 63,500 km to 66,700 km above the surface, covering 70% of the lunar far side. 17 of these frames were successfully transmitted back to Earth, humanity's first views of the far hemisphere of the moon.

Luna 1960A

This mission was an attempt to duplicate the Luna 3 achievement of photographing the far side of the moon, but it had the goal of passing closer to the lunar surface with higher resolution cameras. A premature cutoff of the stage 2 engine of the SL-3/A-1 launcher caused the spacecraft to either enter a highly elliptical orbit or fail to reach Earth orbit.

Luna 1960B

This mission was an attempt to duplicate the Luna 3 achievement of photographing the far side of the Moon, but it had the goal of passing closer to the lunar surface with higher resolution cameras. At launch, the four strap-on blocks of the SL-3/A-1 launcher failed to ignite correctly and broke loose, firing off in random directions. The accident caused considerable damage to the launch pad.

Luna 1963B

This mission is believed to have been an attempt at a soft-landing on the moon. The 1500 kg spacecraft consisted of a cylindrical section containing maneuvering and landing rockets and fuel, orientation devices and radio transmitters and a spherical top containing the 100 kg lander. The lander would be ejected onto the surface after the main body touched down, carrying a camera and devices to measure radiation. Launched an SL-6/A-2-e, the spacecraft failed to reach Earth orbit and crashed into the Pacific Ocean near Midway Island.

Luna 4

Luna 4 was the USSR's first successful spacecraft of their "second generation" lunar program. The spacecraft, rather than being sent on a straight trajectory toward the moon, was placed first in an Earth orbit and then an automatic interplanetary station was rocketed in a curving path towards the moon.

It achieved the desired trajectory but missed the moon by 8336.2 km at 13:25 UT on April 5, 1963, and entered a barycentric 90,000x700,000 km Earth orbit. The intended mission of the probe is not known, it was speculated the probe was designed to land on the moon with an instrument package based on the trajectory and on the later attempted landings of the Luna 5 and 6 spacecraft. (And the fact that a lecture program entitled "Hitting the Moon" was scheduled to be broadcast on Radio Moscow at 7:45 p.m. the evening of April 5 but was cancelled.) The spacecraft transmitted at 183.6 MHz at least until 6 April.

Luna 1964A

Luna 1964A was an attempted lunar landing mission. The spacecraft and SL-6/A-2-e launcher failed to attain Earth orbit.

Luna 1964B

Luna 1964B was an attempted lunar landing mission. The spacecraft and SL-6/A-2-e launcher failed to attain Earth orbit.

Luna 5

The Luna 5 automatic interplanetary station was designed to continue investigations of a lunar soft landing. The retrorocket system failed, and the spacecraft impacted the lunar surface at the Sea of Clouds.

Luna 6

Luna 6 was intended to travel to the moon, but, because a midcourse correction failed, it missed the Moon by 159,612.8 km.

Luna 7

The Luna 7 spacecraft was intended to achieve a soft landing on the moon. However, due to premature retrofire and cutoff of the retrorockets, the spacecraft impacted the lunar surface in the Sea of Storms.

Luna 8

Luna 8 was launched with the probable mission of achieving a soft landing on the moon. However, the retrofire was late, and the spacecraft impacted the lunar surface in the Sea of Storms. The mission did complete the experimental development of the star-orientation system and ground control of radio equipment, flight trajectory, and other instrumentation.

Luna 9

Luna 9 was the first spacecraft to achieve a lunar soft landing and to transmit photographic data to Earth. The landing probe was a hermetically sealed container with radio equipment, a program timing device, heat control systems, scientific apparatus, power sources, and a television system.

The Luna 9 payload was carried to Earth orbit by an A-2-E vehicle and then conveyed toward the moon by a fourth stage rocket that separated itself from the payload. Flight apparatus separated from the payload shortly before Luna 9 landed. After landing in the Ocean of Storms on February 3, 1966, the four petals, which formed the spacecraft, opened outward and stabilized the spacecraft on the lunar surface. Spring-controlled antennas assumed operating positions, and the television camera retractable mirror system, which operated by revolving and tilting, began a photographic survey of the lunar environment. Seven radio sessions, totaling 8 hours and 5 minutes, were transmitted as were three series of TV pictures. When assembled, the photographs provided a panoramic view of the nearby lunar surface. The pictures included views of nearby rocks and of the horizon 1.4 km away from the spacecraft.

Luna 10

Luna 10 spacecraft was launched towards the moon from an Earth orbiting platform. The spacecraft entered lunar orbit on April 3, 1966 and completed its first orbit 3 hours later (on April 4, Moscow time). Scientific instruments included a gamma-ray spectrometer for energies between 0.3-3.0 MeV, a triaxial magnetometer, a meteorite detector, instruments for solar-plasma studies, and devices for measuring infrared emissions from the moon and radiation conditions of the lunar environment. Gravitational studies were also conducted.

The spacecraft played back to Earth the "International" during the Twenty-third Congress of the Communist Party of the Soviet Union. Luna 10 was battery powered and operated for 460 lunar orbits and 219 active data transmissions before radio signals were discontinued on May 30, 1966.

Luna 1966A

Luna 1966A is tentatively identified as a lunar orbiter mission. It is believed the SL-6/A-2-e launcher failed to bring the spacecraft to Earth orbit.

Luna 11

Luna 11 was launched towards the moon from an Earth-orbiting platform and entered lunar orbit on August 28, 1966. The objectives of the mission included the study of:

  1. lunar gamma- and X-ray emissions in order to determine the moon's chemical composition
  2. lunar gravitational anomalies
  3. the concentration of meteorite streams near the moon
  4. the intensity of hard corpuscular radiation near the moon

A total of 137 radio transmissions and 277 orbits of the moon were completed before the batteries failed on October 1, 1966.

Luna 12

Luna 12 was launched towards the moon from an Earth-orbiting platform and achieved lunar orbit on October 25, 1966. The spacecraft was equipped with a television system that obtained and transmitted photographs of the lunar surface. The photographs contained 1100 scan lines with a maximum resolution of 14.9-19.8 m. Pictures of the lunar surface were returned on October 27, 1966. The number of photographs is not known. Radio transmissions from Luna 12 ceased on January 19, 1967, after 602 lunar orbits and 302 radio transmissions.

Luna 13

The Luna 13 spacecraft was launched toward the moon from an Earth-orbiting platform and accomplished a soft landing on December 24, 1966, in the region of Oceanus Procellarum. The petal encasement of the spacecraft was opened, antennas were erected, and radio transmissions to Earth began four minutes after the landing. On December 25 and 26, 1966, the spacecraft television system transmitted panoramas of the nearby lunar landscape at different sun angles. Each panorama required approximately 100 minutes to transmit. The spacecraft was equipped with a mechanical soil-measuring penetrometer, a dynamograph, and a radiation densitometer for obtaining data on the mechanical and physical properties and the cosmic-ray reflectivity of the lunar surface. It is believed that transmissions from the spacecraft ceased before the end of December 1966.

Luna 1968A

Luna 1968A is tentatively identified as an attempted launch to reach lunar orbit. The spacecraft and SL-6/A-2-e launcher failed to reach Earth orbit. Presumably the Luna probe itself was equipped similarly to the later Luna 14 probe.

Luna 14

The Luna 14 spacecraft entered lunar orbit on April 10, 1968. The spacecraft instrumentation was similar to that of Luna 10 and provided data for studies of the interaction of the Earth and lunar masses, the lunar gravitational field, the propagation and stability of radio communications to the spacecraft at different orbital positions, solar charged particles and cosmic rays, and the motion of the Moon. This flight was the final flight of the second generation of the Luna series.

Luna 1969A

This mission was an attempted lunar rover (Lunakhod). The SL-12/D-1-e launcher exploded 40 seconds after launch.

Luna 1969B

This mission is tentatively identified as an attempted lunar sample return. The sample return apparatus, or Moonscooper, consisted of a descent stage at the 3.96 m diameter base containing retro-rockets, instrumentation and fuel tanks for landing as well as a robot arm. On top of this was a cylindrically-shaped instrumentation unit. An ascent stage was on top of this, consisting of ascent rockets and a sphere-shaped sample return compartment. The compartment had a hatch into which the robot arm could place lunar samples. The entire assembly was 3.96 m high and weighed 1880 kg. The launch, on a Proton booster, failed for unknown reasons.

Luna 1969C

This mission was an attempted lunar sample return. The sample return apparatus, or Moonscooper, consisted of a descent stage at the 3.96 m diameter base containing retro-rockets, instrumentation and fuel tanks for landing as well as a robot arm. On top of this was a cylindrically-shaped instrumentation unit. An ascent stage was on top of this, consisting of ascent rockets and a sphere-shaped sample return compartment. The compartment had a hatch into which the robot arm could place lunar samples. The entire assembly was 3.96 m high and weighed 1880 kg. The launch, on a Proton booster, failed for unknown reasons.

Luna 15

Luna 15 was placed in an intermediate Earth orbit after launch and was then sent toward the moon. The spacecraft was capable of studying circumlunar space, the lunar gravitational field, and the chemical composition of lunar rocks. It was also capable of providing lunar surface photography. After completing 86 communications sessions and 52 orbits of the moon at various inclinations and altitudes, the spacecraft impacted the lunar surface on July 21, 1969.

Luna 1970A

This mission has been tentatively identified as an attempted lunar sample return, similar to the later Luna 16 mission. The SL-12/D-1-e launcher failed and the spacecraft did not reach Earth orbit.

Luna 1970B

This mission has been tentatively identified as an attempted lunar orbiter equipped with automatic cameras to search for potential landing sites. The SL-12/D-1-e launcher failed and the spacecraft did not reach Earth orbit, crashing into the Pacific Ocean.

Luna 16

Luna 16 was the first robotic probe to land on the moon and return a sample to Earth and represented the first lunar sample return mission by the Soviet Union and the third overall, following the Apollo 11 and 12 missions. The spacecraft consisted of two attached stages, an ascent stage mounted on top of a descent stage. The descent stage was a cylindrical body with four protruding landing legs, fuel tanks, a landing radar, and a dual descent engine complex. A main descent engine was used to slow the craft until it reached a cutoff point which was determined by the onboard computer based on altitude and velocity. After cutoff a bank of lower thrust jets was used for the final landing. The descent stage also acted as a launch pad for the ascent stage. The ascent stage was a smaller cylinder with a rounded top. It carried a cylindrical hermetically sealed soil sample container inside a re-entry capsule. The spacecraft descent stage was equipped with a television camera, radiation and temperature monitors, telecommunications equipment, and an extendable arm with a drilling rig for the collection of a lunar soil sample.

The Luna 16 automatic station was launched toward the moon from a preliminary Earth orbit and after one mid-course correction on September 13 it entered a circular 111 km lunar orbit on September 17, 1970. The lunar gravity was studied from this orbit, and then the spacecraft was fired into an elliptical orbit with a perilune of 15.1 km. The main braking engine was fired on September 20, initiating the descent to the lunar surface. The main descent engine cut off at an altitude of 20 m and the landing jets cut off at 2 m height at a velocity less than 2.4 m/s, followed by vertical free-fall. At 05:18 UT, the spacecraft soft landed on the lunar surface in Mare Foecunditatis (the Sea of Fertility) as planned, approximately 100 km west of Webb crater.

This was the first landing made in the dark on the moon, as the sun had set about 60 hours earlier. According to the Bochum Radio Space Observatory in the Federal Republic of Germany, strong and good quality television pictures were returned by the spacecraft. However, such pictures were not made available to the U.S. by any sources so there is question as to the reliability of the Bochum report.

The drill was deployed and penetrated to a depth of 35 cm before encountering hard rock or large fragments of rock. The column of regolith in the drill tube was then transferred to the soil sample container. After 26 hours and 25 minutes on the lunar surface, the ascent stage, with the hermetically sealed soil sample container, lifted off from the Moon carrying 101 grams of collected material at 07:43 UT on September 21. The lower stage of Luna 16 remained on the lunar surface and continued transmission of lunar temperature and radiation data. The Luna 16 re-entry capsule returned directly to Earth without any mid-course corrections, made a ballistic entry into the Earth's atmosphere on September 24 and deployed parachutes. The capsule landed approximately 80 km SE of the city of Dzhezkazgan in Kazakhstan at 03:26 UT.

Luna 17

Luna 17 was launched from an Earth parking orbit towards the moon and entered lunar orbit on November 15, 1970. The spacecraft soft landed on the moon in the Sea of Rains. The spacecraft had dual ramps by which the payload, Lunokhod 1, descended to the lunar surface. Lunokhod 1 was a lunar vehicle formed of a tub-like compartment with a large convex lid on eight independently powered wheels.

Lunokhod was equipped with a cone-shaped antenna, a highly directional helical antenna, four television cameras, and special extendable devices to impact the lunar soil for soil density and mechanical property tests. An x-ray spectrometer, an x-ray telescope, cosmic-ray detectors, and a laser device were also included. The vehicle was powered by a solar cell array mounted on the underside of the lid.

Lunokhod was intended to operate through three lunar days but actually operated for eleven lunar days. The operations of Lunokhod officially ceased on October 4, 1971, the anniversary of Sputnik 1. Lunokhod had traveled 10,540 m and had transmitted more than 20,000 TV pictures and more than 200 TV panoramas. It had also conducted more than 500 lunar soil tests.

Luna 18

Luna 18 was placed in an Earth parking orbit after it was launched and was then sent towards the moon. On September 7, 1971, it entered lunar orbit. The spacecraft completed 85 communications sessions and 54 lunar orbits before it was sent towards the lunar surface by use of braking rockets. It impacted the moon on September 11, 1971, at 3° 34 minutes N, 56° 30 minutes E (selenographic coordinates) in a rugged mountainous terrain. Signals ceased at the moment of impact.

Luna 19

Luna 19 was placed in an intermediate Earth parking orbit and, from this orbit, was sent toward the moon. It was placed in a lunar orbit on October 3, 1971. Luna 19 extended the systematic study of lunar gravitational fields and location of mascons (mass concentrations). It also studied the lunar radiation environment, the gamma-active lunar surface, and the solar wind. Photographic coverage via a television system was also obtained.

Luna 20

Luna 20 was placed in an intermediate Earth parking orbit and from this orbit was sent towards the moon. It entered lunar orbit on February 18, 1972. On February 21, 1972, Luna 20 soft landed on the moon in a mountainous area known as the Apollonius highlands near Mare Foecunditatis (Sea of Fertility), 120 km from where Luna 16 had impacted. While on the lunar surface, the panoramic television system was operated. Lunar samples were obtained by means of an extendable drilling apparatus. The ascent stage of Luna 20 was launched from the lunar surface on February 22, 1972 carrying 30 grams of collected lunar samples in a sealed capsule. It landed in the Soviet Union on February 25, 1972. The lunar samples were recovered the following day.

Luna 21

The Luna 21 spacecraft landed on the moon and deployed the second Soviet lunar rover (Lunokhod 2). The primary objectives of the mission were to collect images of the lunar surface, examine ambient light levels to determine the feasibility of astronomical observations from the moon, perform laser ranging experiments from Earth, observe solar X-rays, measure local magnetic fields, and study mechanical properties of the lunar surface material.

The rover stood 135 cm high and had a mass of 840 kg. It was about 170 cm long and 160 cm wide and had 8 wheels each with an independent suspension, motor and brake. The rover had two speeds, ~1 km/hr and ~2 km/hr. Lunokhod 2 was equipped with three TV cameras, one mounted high on the rover for navigation, which could return high resolution images at different rates (3.2, 5.7, 10.9 or 21.1 seconds per frame). These images were used by a five-man team of controllers on Earth who sent driving commands to the rover in real time. Power was supplied by a solar panel on the inside of a round hinged lid which covered the instrument bay, which would charge the batteries when opened. A polonium-210 isotopic heat source was used to keep the rover warm during the lunar nights. There were 4 panoramic cameras mounted on the rover. Scientific instruments included a soil mechanics tester, solar X-ray experiment, an astrophotometer to measure visible and UV light levels, a magnetometer deployed in front of the rover on the end of a 2.5 m boom, a radiometer, a photodetector (Rubin-1) for laser detection experiments, and a French-supplied laser corner-reflector. The lander and rover together weighed 1814 kg.

The SL-12/D-1-e launcher put the spacecraft into Earth parking orbit followed by translunar injection. On January 12, 1973, Luna 21 was braked into a 90x100 km orbit about the moon. On January 13 and 14, the perilune was lowered to 16 km altitude. On January 15 after 40 orbits, the braking rocket was fired at 16 km altitude, and the craft went into free fall. At an altitude of 750 m the main thrusters began firing, slowing the fall until a height of 22 m was reached. At this point the main thrusters shut down and the secondary thrusters ignited, slowing the fall until the lander was 1.5 m above the surface, where the engine was cut off. Landing occurred at 23:35 UT in LeMonnier crater at 25.85° N, 30.45° E. The lander carried a bas relief of Lenin and the Soviet coat-of-arms.

After landing, the Lunokhod 2 took TV images of the surrounding area, then rolled down a ramp to the surface at 01:14 UT on January 16 and took pictures of the Luna 21 lander and landing site. It stopped and charged batteries until January 18, took more images of the lander and landing site, and then set out over the moon. The rover would run during the lunar day, stopping occasionally to recharge its batteries via the solar panels. At night the rover would hibernate until the next sunrise, heated by the radioactive source. Lunokhod 2 operated for about 4 months, covered 37 km of terrain including hilly upland areas and rilles, and sent back 86 panoramic images and over 80,000 TV pictures. Many mechanical tests of the surface, laser ranging measurements, and other experiments were completed during this time. On June 4 it was announced that the program was completed, leading to speculation that the vehicle probably failed in mid-May or could not be revived after the lunar night of May-June. The Lunokhod was not left in a position such that the laser retroreflector could be used indicating that the failure may have happened suddenly.

Luna 22

Luna 22 was a lunar orbiter mission. The spacecraft carried imaging cameras and also had the objectives of studying the moon's magnetic field, surface gamma ray emissions and composition of lunar surface rocks, and the gravitational field, as well as micrometeorites and cosmic rays. Luna 22 was launched into Earth parking orbit and then to the moon. It was inserted into a circular lunar orbit on June 2, 1974. The spacecraft made many orbit adjustments over its 18 month lifetime in order to optimize the operation of various experiments, lowering the perilune to as little as 25 km. Maneuvering fuel was exhausted on September 2 and the mission was ended in early November.

Luna 23

Luna 23 was a Moon lander mission which was intended to return a lunar sample to Earth. Launched to the moon by a Proton SL-12/D-1-e booster, the spacecraft was damaged during landing in Mare Crisium (Sea of Crises). The sample collecting apparatus could not operate and no samples were returned. The lander continued transmissions for 3 days after landing. In 1976, Luna 24 landed several hundred meters away and successfully returned samples.

Luna 1975A

This mission has been identified as an attempted lunar sample return, possibly similar to the later Luna 24 mission. As with Luna 24, the mission was targeted for Mare Crisium (Sea of Crises). The SL-12/D-1-e launcher failed due to a problem with a rocket booster and the spacecraft did not reach Earth orbit.

Luna 24

The last of the Luna series of spacecraft, the mission of the Luna 24 probe was the third Soviet mission to retrieve lunar ground samples (the first two were returned by Luna 16 and 20). The probe landed in the area known as Mare Crisium (Sea of Crisis). The mission successfully returned 170 grams of lunar samples to the Earth on August 22, 1976.


References

NASA's National Space Science Data Center.