Arrival of a spacecraft on the surface of the Moon
Top 10 Moon landing related articles
- 1 Uncrewed landings
- 2 Crewed landings
- 3 Scientific background
- 4 Political background
- 5 Early Soviet uncrewed lunar missions (1958–1965)
- 6 Early U.S. uncrewed lunar missions (1958–1965)
- 7 Soviet uncrewed soft landings (1966–1976)
- 8 U.S. uncrewed soft landings (1966–1968)
- 9 Transition from direct ascent landings to lunar orbit operations
- 10 Soviet lunar orbit satellites (1966–1974)
- 11 U.S. lunar orbit satellites (1966–1967)
- 12 Soviet circumlunar loop flights (1967–1970)
- 13 Human Moon landings (1969–1972)
- 14 Late 20th century–Early 21st century uncrewed crash landings
- 15 21st century uncrewed soft landings and attempts
- 16 Landings on moons of other Solar System bodies
- 17 Proposed future missions
- 18 Historical empirical evidence
- 19 See also
- 20 References and notes
- 21 Further reading
- 22 External links
A Moon landing is the arrival of a spacecraft on the surface of the Moon. This includes both crewed and robotic missions. The first human-made object to touch the Moon was the Soviet Union's Luna 2, on 13 September 1959.
The United States' Apollo 11 was the first crewed mission to land on the Moon, on 20 July 1969. There were six crewed U.S. landings between 1969 and 1972, and numerous uncrewed landings, with no soft landings happening between 22 August 1976 and 14 December 2013.
The United States is the only country to have successfully conducted crewed missions to the Moon, with the last departing the lunar surface in December 1972. All soft landings took place on the near side of the Moon until 3 January 2019, when the Chinese Chang'e 4 spacecraft made the first landing on the far side of the Moon.
Moon landing Intro articles: 6
After the unsuccessful attempt by Luna 1 to land on the Moon in 1959, the Soviet Union performed the first hard Moon landing – "hard" meaning the spacecraft intentionally crashes into the Moon – later that same year with the Luna 2 spacecraft, a feat the U.S. duplicated in 1962 with Ranger 4. Since then, twelve Soviet and U.S. spacecraft have used braking rockets (retrorockets) to make soft landings and perform scientific operations on the lunar surface, between 1966 and 1976. In 1966, the USSR accomplished the first soft landings and took the first pictures from the lunar surface during the Luna 9 and Luna 13 missions. The U.S. followed with five uncrewed Surveyor soft landings.
The Soviet Union achieved the first uncrewed lunar soil sample return with the Luna 16 probe on 24 September 1970. This was followed by Luna 20 and Luna 24 in 1972 and 1976, respectively. Following the failure at launch in 1969 of the first Lunokhod, Luna E-8 No.201, the Luna 17 and Luna 21 were successful uncrewed lunar rover missions in 1970 and 1973.
Many missions were failures at launch. In addition, several uncrewed landing missions achieved the Lunar surface but were unsuccessful, including: Luna 15, Luna 18, and Luna 23 all crashed on landing; and the U.S. Surveyor 4 lost all radio contact only moments before its landing.
More recently, other nations have crashed spacecraft on the surface of the Moon at speeds of around 8,000 kilometres per hour (5,000 mph), often at precise, planned locations. These have generally been end-of-life lunar orbiters that, because of system degradations, could no longer overcome perturbations from lunar mass concentrations ("masscons") to maintain their orbit. Japan's lunar orbiter Hiten impacted the Moon's surface on 10 April 1993. The European Space Agency performed a controlled crash impact with their orbiter SMART-1 on 3 September 2006.
Indian Space Research Organisation (ISRO) performed a controlled crash impact with its Moon Impact Probe (MIP) on 14 November 2008. The MIP was an ejected probe from the Indian Chandrayaan-1 lunar orbiter and performed remote sensing experiments during its descent to the lunar surface.
The Chinese lunar orbiter Chang'e 1 executed a controlled crash onto the surface of the Moon on 1 March 2009. The rover mission Chang'e 3 soft-landed on 14 December 2013, as did its successor, Chang'e 4, on 3 January 2019. All crewed and uncrewed soft landings had taken place on the near side of the Moon, until 3 January 2019 when the Chinese Chang'e 4 spacecraft made the first landing on the far side of the Moon.
On 22 February 2019, Israeli private space agency SpaceIL launched spacecraft Beresheet on board a Falcon 9 from Cape Canaveral, Florida with the intention of achieving a soft landing. SpaceIL lost contact with the spacecraft and it crashed into the surface on 11 April 2019.
Indian Space Research Organization launched Chandrayaan-2 on 22 July 2019 with landing scheduled on 6 September 2019. However, at an altitude of 2.1 km from the Moon a few minutes before soft landing, the lander lost contact with the control room.
Moon landing Uncrewed landings articles: 34
A total of twelve men have landed on the Moon. This was accomplished with two US pilot-astronauts flying a Lunar Module on each of six NASA missions across a 41-month period starting 20 July 1969, with Neil Armstrong and Buzz Aldrin on Apollo 11, and ending on 14 December 1972 with Gene Cernan and Jack Schmitt on Apollo 17. Cernan was the last man to step off the lunar surface.
Moon landing Crewed landings articles: 8
To get to the Moon, a spacecraft must first leave Earth's gravity well; currently, the only practical means is a rocket. Unlike airborne vehicles such as balloons and jets, a rocket can continue accelerating in the vacuum outside the atmosphere.
Upon approach of the target moon, a spacecraft will be drawn ever closer to its surface at increasing speeds due to gravity. In order to land intact it must decelerate to less than about 160 kilometres per hour (99 mph) and be ruggedized to withstand a "hard landing" impact, or it must decelerate to negligible speed at contact for a "soft landing" (the only option for humans). The first three attempts by the U.S. to perform a successful hard Moon landing with a ruggedized seismometer package in 1962 all failed. The Soviets first achieved the milestone of a hard lunar landing with a ruggedized camera in 1966, followed only months later by the first uncrewed soft lunar landing by the U.S.
The speed of a crash landing on its surface is typically between 70 and 100% of the escape velocity of the target moon, and thus this is the total velocity which must be shed from the target moon's gravitational attraction for a soft landing to occur. For Earth's Moon, the escape velocity is 2.38 kilometres per second (1.48 mi/s). The change in velocity (referred to as a delta-v) is usually provided by a landing rocket, which must be carried into space by the original launch vehicle as part of the overall spacecraft. An exception is the soft moon landing on Titan carried out by the Huygens probe in 2005. As the moon with the thickest atmosphere, landings on Titan may be accomplished by using atmospheric entry techniques that are generally lighter in weight than a rocket with equivalent capability.
The Soviets succeeded in making the first crash landing on the Moon in 1959. Crash landings may occur because of malfunctions in a spacecraft, or they can be deliberately arranged for vehicles which do not have an onboard landing rocket. There have been many such Moon crashes, often with their flight path controlled to impact at precise locations on the lunar surface. For example, during the Apollo program the S-IVB third stage of the Saturn V rocket as well as the spent ascent stage of the Lunar Module were deliberately crashed on the Moon several times to provide impacts registering as a moonquake on seismometers that had been left on the lunar surface. Such crashes were instrumental in mapping the internal structure of the Moon.
To return to Earth, the escape velocity of the Moon must be overcome for the spacecraft to escape the gravity well of the Moon. Rockets must be used to leave the Moon and return to space. Upon reaching Earth, atmospheric entry techniques are used to absorb the kinetic energy of a returning spacecraft and reduce its speed for safe landing. These functions greatly complicate a moon landing mission and lead to many additional operational considerations. Any moon departure rocket must first be carried to the Moon's surface by a moon landing rocket, increasing the latter's required size. The Moon departure rocket, larger moon landing rocket and any Earth atmosphere entry equipment such as heat shields and parachutes must in turn be lifted by the original launch vehicle, greatly increasing its size by a significant and almost prohibitive degree.
Moon landing Scientific background articles: 21
The intense efforts devoted in the 1960s to achieving first an uncrewed and then ultimately a human Moon landing become easier to understand in the political context of its historical era. World War II had introduced many new and deadly innovations including blitzkrieg-style surprise attacks used in the invasion of Poland and Finland, and in the attack on Pearl Harbor; the V-2 rocket, a ballistic missile which killed thousands in attacks on London and Antwerp; and the atom bomb, which killed hundreds of thousands in the atomic bombings of Hiroshima and Nagasaki. In the 1950s, tensions mounted between the two ideologically opposed superpowers of the United States and the Soviet Union that had emerged as victors in the conflict, particularly after the development by both countries of the hydrogen bomb.
Willy Ley wrote in 1957 that a rocket to the Moon "could be built later this year if somebody can be found to sign some papers". On 4 October 1957, the Soviet Union launched Sputnik 1 as the first artificial satellite to orbit the Earth and so initiated the Space Race. This unexpected event was a source of pride to the Soviets and shock to the U.S., who could now potentially be surprise attacked by nuclear-tipped Soviet rockets in under 30 minutes. Also, the steady beeping of the radio beacon aboard Sputnik 1 as it passed overhead every 96 minutes was widely viewed on both sides as effective propaganda to Third World countries demonstrating the technological superiority of the Soviet political system compared to that of the U.S. This perception was reinforced by a string of subsequent rapid-fire Soviet space achievements. In 1959, the R-7 rocket was used to launch the first escape from Earth's gravity into a solar orbit, the first crash impact onto the surface of the Moon, and the first photography of the never-before-seen far side of the Moon. These were the Luna 1, Luna 2, and Luna 3 spacecraft.
The U.S. response to these Soviet achievements was to greatly accelerate previously existing military space and missile projects and to create a civilian space agency, NASA. Military efforts were initiated to develop and produce mass quantities of intercontinental ballistic missiles (ICBMs) that would bridge the so-called missile gap and enable a policy of deterrence to nuclear war with the Soviets known as mutual assured destruction or MAD. These newly developed missiles were made available to civilians of NASA for various projects (which would have the added benefit of demonstrating the payload, guidance accuracy and reliabilities of U.S. ICBMs to the Soviets).
While NASA stressed peaceful and scientific uses for these rockets, their use in various lunar exploration efforts also had secondary goal of realistic, goal-oriented testing of the missiles themselves and development of associated infrastructure, just as the Soviets were doing with their R-7.
Moon landing Political background articles: 27
Early Soviet uncrewed lunar missions (1958–1965)
After the fall of the Soviet Union in 1991, historical records were released to allow the true accounting of Soviet lunar efforts. Unlike the U.S. tradition of assigning a particular mission name in advance of a launch, the Soviets assigned a public "Luna" mission number only if a launch resulted in a spacecraft going beyond Earth orbit. The policy had the effect of hiding Soviet Moon mission failures from public view. If the attempt failed in Earth orbit before departing for the Moon, it was frequently (but not always) given a "Sputnik" or "Cosmos" Earth-orbit mission number to hide its purpose. Launch explosions were not acknowledged at all.
|Mission||Mass (kg)||Launch vehicle||Launch date||Goal||Result|
|Semyorka – 8K72||23 September 1958||Impact||Failure – booster malfunction at T+ 93 s|
|Semyorka – 8K72||12 October 1958||Impact||Failure – booster malfunction at T+ 104 s|
|Semyorka – 8K72||4 December 1958||Impact||Failure – booster malfunction at T+ 254 s|
|Luna-1||361||Semyorka – 8K72||2 January 1959||Impact||Partial success – first spacecraft to reach escape velocity, lunar flyby, solar orbit; missed the Moon|
|Semyorka – 8K72||18 June 1959||Impact||Failure – booster malfunction at T+ 153 s|
|Luna-2||390||Semyorka – 8K72||12 September 1959||Impact||Success – first lunar impact|
|Luna-3||270||Semyorka – 8K72||4 October 1959||Flyby||Success – first photos of lunar far side|
|Semyorka – 8K72||15 April 1960||Flyby||Failure – booster malfunction, failed to reach Earth orbit|
|Semyorka – 8K72||16 April 1960||Flyby||Failure – booster malfunction at T+ 1 s|
|Sputnik-25||Semyorka – 8K78||4 January 1963||Landing||Failure – stranded in low Earth orbit|
|Semyorka – 8K78||3 February 1963||Landing||Failure – booster malfunction at T+ 105 s|
|Luna-4||1422||Semyorka – 8K78||2 April 1963||Landing||Failure – lunar flyby at 8,000 kilometres (5,000 mi)|
|Semyorka – 8K78||21 March 1964||Landing||Failure – booster malfunction, failed to reach Earth orbit|
|Semyorka – 8K78||20 April 1964||Landing||Failure – booster malfunction, failed to reach Earth orbit|
|Cosmos-60||Semyorka – 8K78||12 March 1965||Landing||Failure – stranded in low Earth orbit|
|Semyorka – 8K78||10 April 1965||Landing||Failure – booster malfunction, failed to reach Earth orbit|
|Luna-5||1475||Semyorka – 8K78||9 May 1965||Landing||Failure – lunar impact|
|Luna-6||1440||Semyorka – 8K78||8 June 1965||Landing||Failure – lunar flyby at 160,000 kilometres (99,000 mi)|
|Luna-7||1504||Semyorka – 8K78||4 October 1965||Landing||Failure – lunar impact|
|Luna-8||1550||Semyorka – 8K78||3 December 1965||Landing||Failure – lunar impact during landing attempt|
Moon landing Early Soviet uncrewed lunar missions (1958–1965) articles: 10
Early U.S. uncrewed lunar missions (1958–1965)
In contrast to Soviet lunar exploration triumphs in 1959, success eluded initial U.S. efforts to reach the Moon with the Pioneer and Ranger programs. Fifteen consecutive U.S. uncrewed lunar missions over a six-year period from 1958 to 1964 all failed their primary photographic missions; however, Rangers 4 and 6 successfully repeated the Soviet lunar impacts as part of their secondary missions.
Failures included three U.S. attempts in 1962 to hard land small seismometer packages released by the main Ranger spacecraft. These surface packages were to use retrorockets to survive landing, unlike the parent vehicle, which was designed to deliberately crash onto the surface. The final three Ranger probes performed successful high altitude lunar reconnaissance photography missions during intentional crash impacts between 2.62 and 2.68 kilometres per second (9,400 and 9,600 km/h).
|Mission||Mass (kg)||Launch vehicle||Launch date||Goal||Result|
|Pioneer 0||38||Thor-Able||17 August 1958||Lunar orbit||Failure – first stage explosion; destroyed|
|Pioneer 1||34||Thor-Able||11 October 1958||Lunar orbit||Failure – software error; reentry|
|Pioneer 2||39||Thor-Able||8 November 1958||Lunar orbit||Failure – third stage misfire; reentry|
|Pioneer 3||6||Juno||6 December 1958||Flyby||Failure – first stage misfire, reentry|
|Pioneer 4||6||Juno||3 March 1959||Flyby||Partial success – first US craft to reach escape velocity, lunar flyby too far to shoot photos due to targeting error; solar orbit|
|Pioneer P-1||168||Atlas-Able||24 September 1959||Lunar orbit||Failure – pad explosion; destroyed|
|Pioneer P-3||168||Atlas-Able||29 November 1959||Lunar orbit||Failure – payload shroud; destroyed|
|Pioneer P-30||175||Atlas-Able||25 September 1960||Lunar orbit||Failure – second stage anomaly; reentry|
|Pioneer P-31||175||Atlas-Able||15 December 1960||Lunar orbit||Failure – first stage explosion; destroyed|
|Ranger 1||306||Atlas – Agena||23 August 1961||Prototype test||Failure – upper stage anomaly; reentry|
|Ranger 2||304||Atlas – Agena||18 November 1961||Prototype test||Failure – upper stage anomaly; reentry|
|Ranger 3||330||Atlas – Agena||26 January 1962||Landing||Failure – booster guidance; solar orbit|
|Ranger 4||331||Atlas – Agena||23 April 1962||Landing||Partial success – first U.S. spacecraft to reach another celestial body; crash impact – no photos returned|
|Ranger 5||342||Atlas – Agena||18 October 1962||Landing||Failure – spacecraft power; solar orbit|
|Ranger 6||367||Atlas – Agena||30 January 1964||Impact||Failure – spacecraft camera; crash impact|
|Ranger 7||367||Atlas – Agena||28 July 1964||Impact||Success – returned 4308 photos, crash impact|
|Ranger 8||367||Atlas – Agena||17 February 1965||Impact||Success – returned 7137 photos, crash impact|
|Ranger 9||367||Atlas – Agena||21 March 1965||Impact||Success – returned 5814 photos, crash impact|
Three different designs of Pioneer lunar probes were flown on three different modified ICBMs. Those flown on the Thor booster modified with an Able upper stage carried an infrared image scanning television system with a resolution of 1 milliradian to study the Moon's surface, an ionization chamber to measure radiation in space, a diaphragm/microphone assembly to detect micrometeorites, a magnetometer, and temperature-variable resistors to monitor spacecraft internal thermal conditions. The first, a mission managed by the United States Air Force, exploded during launch; all subsequent Pioneer lunar flights had NASA as the lead management organization. The next two returned to Earth and burned up upon reentry into the atmosphere after achieved maximum altitudes of around 110,000 kilometres (68,000 mi) and 1,450 kilometres (900 mi), far short of the roughly 400,000 kilometres (250,000 mi) required to reach the vicinity of the Moon.
NASA then collaborated with the United States Army's Ballistic Missile Agency to fly two extremely small cone-shaped probes on the Juno ICBM, carrying only photocells which would be triggered by the light of the Moon and a lunar radiation environment experiment using a Geiger-Müller tube detector. The first of these reached an altitude of only around 100,000 kilometres (62,000 mi), serendipitously gathering data that established the presence of the Van Allen radiation belts before reentering Earth's atmosphere. The second passed by the Moon at a distance of more than 60,000 kilometres (37,000 mi), twice as far as planned and too far away to trigger either of the on-board scientific instruments, yet still becoming the first U.S. spacecraft to reach a solar orbit.
The final Pioneer lunar probe design consisted of four "paddlewheel" solar panels extending from a one-meter diameter spherical spin-stabilized spacecraft body equipped to take images of the lunar surface with a television-like system, estimate the Moon's mass and topography of the poles, record the distribution and velocity of micrometeorites, study radiation, measure magnetic fields, detect low frequency electromagnetic waves in space and use a sophisticated integrated propulsion system for maneuvering and orbit insertion as well. None of the four spacecraft built in this series of probes survived launch on its Atlas ICBM outfitted with an Able upper stage.
Following the unsuccessful Atlas-Able Pioneer probes, NASA's Jet Propulsion Laboratory embarked upon an uncrewed spacecraft development program whose modular design could be used to support both lunar and interplanetary exploration missions. The interplanetary versions were known as Mariners; lunar versions were Rangers. JPL envisioned three versions of the Ranger lunar probes: Block I prototypes, which would carry various radiation detectors in test flights to a very high Earth orbit that came nowhere near the Moon; Block II, which would try to accomplish the first Moon landing by hard landing a seismometer package; and Block III, which would crash onto the lunar surface without any braking rockets while taking very high resolution wide-area photographs of the Moon during their descent.
The Ranger 1 and 2 Block I missions were virtually identical. Spacecraft experiments included a Lyman-alpha telescope, a rubidium-vapor magnetometer, electrostatic analyzers, medium-energy-range particle detectors, two triple coincidence telescopes, a cosmic-ray integrating ionization chamber, cosmic dust detectors, and scintillation counters. The goal was to place these Block I spacecraft in a very high Earth orbit with an apogee of 110,000 kilometres (68,000 mi) and a perigee of 60,000 kilometres (37,000 mi).
From that vantage point, scientists could make direct measurements of the magnetosphere over a period of many months while engineers perfected new methods to routinely track and communicate with spacecraft over such large distances. Such practice was deemed vital to be assured of capturing high-bandwidth television transmissions from the Moon during a one-shot fifteen-minute time window in subsequent Block II and Block III lunar descents. Both Block I missions suffered failures of the new Agena upper stage and never left low Earth parking orbit after launch; both burned up upon reentry after only a few days.
The first attempts to perform a Moon landing took place in 1962 during the Rangers 3, 4 and 5 missions flown by the United States. All three Block II missions basic vehicles were 3.1 m high and consisted of a lunar capsule covered with a balsa wood impact-limiter, 650 mm in diameter, a mono-propellant mid-course motor, a retrorocket with a thrust of 5,050 pounds-force (22.5 kN), and a gold- and chrome-plated hexagonal base 1.5 m in diameter. This lander (code-named Tonto) was designed to provide impact cushioning using an exterior blanket of crushable balsa wood and an interior filled with incompressible liquid freon. A 42 kg (56 pounds) 30-centimetre-diameter (0.98 ft) metal payload sphere floated and was free to rotate in a liquid freon reservoir contained in the landing sphere.
This payload sphere contained six silver-cadmium batteries to power a fifty-milliwatt radio transmitter, a temperature sensitive voltage controlled oscillator to measure lunar surface temperatures, and a seismometer designed with sensitivity high enough to detect the impact of a 5 lb (2.3 kg) meteorite on the opposite side of the Moon. Weight was distributed in the payload sphere so it would rotate in its liquid blanket to place the seismometer into an upright and operational position no matter what the final resting orientation of the external landing sphere. After landing, plugs were to be opened allowing the freon to evaporate and the payload sphere to settle into upright contact with the landing sphere. The batteries were sized to allow up to three months of operation for the payload sphere. Various mission constraints limited the landing site to Oceanus Procellarum on the lunar equator, which the lander ideally would reach 66 hours after launch.
No cameras were carried by the Ranger landers, and no pictures were to be captured from the lunar surface during the mission. Instead, the 3.1 metres (10 ft) Ranger Block II mother ship carried a 200-scan-line television camera which was to capture images during the free-fall descent to the lunar surface. The camera was designed to transmit a picture every 10 seconds. Seconds before impact, at 5 and 0.6 kilometres (3.11 and 0.37 mi) above the lunar surface, the Ranger mother ships took picture (which may be viewed here).
Other instruments gathering data before the mother ship crashed onto the Moon were a gamma ray spectrometer to measure overall lunar chemical composition and a radar altimeter. The radar altimeter was to give a signal ejecting the landing capsule and its solid-fueled braking rocket overboard from the Block II mother ship. The braking rocket was to slow and the landing sphere to a dead stop at 330 metres (1,080 ft) above the surface and separate, allowing the landing sphere to free fall once more and hit the surface.
On Ranger 3, failure of the Atlas guidance system and a software error aboard the Agena upper stage combined to put the spacecraft on a course that would miss the Moon. Attempts to salvage lunar photography during a flyby of the Moon were thwarted by in-flight failure of the onboard flight computer. This was probably because of prior heat sterilization of the spacecraft by keeping it above the boiling point of water for 24 hours on the ground, to protect the Moon from being contaminated by Earth organisms. Heat sterilization was also blamed for subsequent in-flight failures of the spacecraft computer on Ranger 4 and the power subsystem on Ranger 5. Only Ranger 4 reached the Moon in an uncontrolled crash impact on the far side of the Moon.
Heat sterilization was discontinued for the final four Block III Ranger probes. These replaced the Block II landing capsule and its retrorocket with a heavier, more capable television system to support landing site selection for upcoming Apollo crewed Moon landing missions. Six cameras were designed to take thousands of high-altitude photographs in the final twenty-minute period before crashing on the lunar surface. Camera resolution was 1,132 scan lines, far higher than the 525 lines found in a typical U.S. 1964 home television. While Ranger 6 suffered a failure of this camera system and returned no photographs despite an otherwise successful flight, the subsequent Ranger 7 mission to Mare Cognitum was a complete success.
Breaking the six-year string of failures in U.S. attempts to photograph the Moon at close range, the Ranger 7 mission was viewed as a national turning point and instrumental in allowing the key 1965 NASA budget appropriation to pass through the United States Congress intact without a reduction in funds for the Apollo crewed Moon landing program. Subsequent successes with Ranger 8 and Ranger 9 further buoyed U.S. hopes.
Moon landing Early U.S. uncrewed lunar missions (1958–1965) articles: 60
Soviet uncrewed soft landings (1966–1976)
The Luna 9 spacecraft, launched by the Soviet Union, performed the first successful soft Moon landing on 3 February 1966. Airbags protected its 99 kilograms (218 lb) ejectable capsule which survived an impact speed of over 15 metres per second (54 km/h; 34 mph). Luna 13 duplicated this feat with a similar Moon landing on 24 December 1966. Both returned panoramic photographs that were the first views from the lunar surface.
Luna 16 was the first robotic probe to land on the Moon and safely return a sample of lunar soil back to Earth. It represented the first lunar sample return mission by the Soviet Union, and was the third lunar sample return mission overall, following the Apollo 11 and Apollo 12 missions. This mission was later successfully repeated by Luna 20 (1972) and Luna 24 (1976).
In 1970 and 1973 two Lunokhod ("Moonwalker") robotic lunar rovers were delivered to the Moon, where they successfully operated for 10 and 4 months respectively, covering 10.5 km (Lunokhod 1) and 37 km (Lunokhod 2). These rover missions were in operation concurrently with the Zond and Luna series of Moon flyby, orbiter and landing missions.
|Mission||Mass (kg)||Booster||Launch date||Goal||Result||Landing zone||Lat/Lon|
|Luna-9||1580||Semyorka – 8K78||31 January 1966||Landing||Success – first lunar soft landing, numerous photos||Oceanus Procellarum||7.13°N 64.37°W|
|Luna-13||1580||Semyorka – 8K78||21 December 1966||Landing||Success – second lunar soft landing, numerous photos||Oceanus Procellarum||18°52'N 62°3'W|
|Proton||19 February 1969||Lunar rover||Failure – booster malfunction, failed to reach Earth orbit|
|Proton||14 June 1969||Sample return||Failure – booster malfunction, failed to reach Earth orbit|
|Luna-15||5,700||Proton||13 July 1969||Sample return||Failure – lunar crash impact||Mare Crisium||unknown|
|Cosmos-300||Proton||23 September 1969||Sample return||Failure – stranded in low Earth orbit|
|Cosmos-305||Proton||22 October 1969||Sample return||Failure – stranded in low Earth orbit|
|Proton||6 February 1970||Sample return||Failure – booster malfunction, failed to reach Earth orbit|
|Luna-16||5,600||Proton||12 September 1970||Sample return||Success – returned 0.10 kg of Moon soil back to Earth||Mare Fecunditatis||000.68S 056.30E|
|Luna-17||5,700||Proton||10 November 1970||Lunar rover||Success – Lunokhod-1 rover traveled 10.5 km across lunar surface||Mare Imbrium||038.28N 325.00E|
|Luna-18||5,750||Proton||2 September 1971||Sample return||Failure – lunar crash impact||Mare Fecunditatis||003.57N 056.50E|
|Luna-20||5,727||Proton||14 February 1972||Sample return||Success – returned 0.05 kg of Moon soil back to Earth||Mare Fecunditatis||003.57N 056.50E|
|Luna-21||5,950||Proton||8 January 1973||Lunar rover||Success – Lunokhod-2 rover traveled 37.0 km across lunar surface||LeMonnier Crater||025.85N 030.45E|
|Luna-23||5,800||Proton||28 October 1974||Sample return||Failure – Moon landing achieved, but malfunction prevented sample return||Mare Crisium||012.00N 062.00E|
|Proton||16 October 1975||Sample return||Failure – booster malfunction, failed to reach Earth orbit|
|Luna-24||5,800||Proton||9 August 1976||Sample return||Success – returned 0.17 kg of Moon soil back to Earth||Mare Crisium||012.25N 062.20E|
Moon landing Soviet uncrewed soft landings (1966–1976) articles: 13
U.S. uncrewed soft landings (1966–1968)
The U.S. robotic Surveyor program was part of an effort to locate a safe site on the Moon for a human landing and test under lunar conditions the radar and landing systems required to make a true controlled touchdown. Five of Surveyor's seven missions made successful uncrewed Moon landings. Surveyor 3 was visited two years after its Moon landing by the crew of Apollo 12. They removed parts of it for examination back on Earth to determine the effects of long-term exposure to the lunar environment.
|Mission||Mass (kg)||Booster||Launch date||Goal||Result||Landing zone||Lat/Lon|
|Surveyor 1||292||Atlas – Centaur||30 May 1966||Landing||Success – 11,000 pictures returned, first U.S. Moon landing||Oceanus Procellarum||002.45S 043.22W|
|Surveyor 2||292||Atlas – Centaur||20 September 1966||Landing||Failure – midcourse engine malfunction, placing vehicle in unrecoverable tumble; crashed southeast of Copernicus Crater||Sinus Medii||004.00S 011.00W|
|Surveyor 3||302||Atlas – Centaur||20 April 1967||Landing||Success – 6,000 pictures returned; trench dug to 17.5 cm depth after 18 hr of robot arm use||Oceanus Procellarum||002.94S 336.66E|
|Surveyor 4||282||Atlas – Centaur||14 July 1967||Landing||Failure – radio contact lost 2.5 minutes before touchdown; perfect automated Moon landing possible but outcome unknown||Sinus Medii||unknown|
|Surveyor 5||303||Atlas – Centaur||8 September 1967||Landing||Success – 19,000 photos returned, first use of alpha scatter soil composition monitor||Mare Tranquillitatis||001.41N 023.18E|
|Surveyor 6||300||Atlas – Centaur||7 November 1967||Landing||Success – 30,000 photos returned, robot arm and alpha scatter science, engine restart, second landing 2.5 m away from first||Sinus Medii||000.46N 358.63E|
|Surveyor 7||306||Atlas – Centaur||7 January 1968||Landing||Success – 21,000 photos returned; robot arm and alpha scatter science; laser beams from Earth detected||Tycho Crater||041.01S 348.59E|
Moon landing U.S. uncrewed soft landings (1966–1968) articles: 13
Transition from direct ascent landings to lunar orbit operations
Within four months of each other in early 1966 the Soviet Union and the United States had accomplished successful Moon landings with uncrewed spacecraft. To the general public both countries had demonstrated roughly equal technical capabilities by returning photographic images from the surface of the Moon. These pictures provided a key affirmative answer to the crucial question of whether or not lunar soil would support upcoming crewed landers with their much greater weight.
However, the Luna 9 hard landing of a ruggedized sphere using airbags at a 50-kilometre-per-hour (31 mph) ballistic impact speed had much more in common with the failed 1962 Ranger landing attempts and their planned 160-kilometre-per-hour (99 mph) impacts than with the Surveyor 1 soft landing on three footpads using its radar-controlled, adjustable-thrust retrorocket. While Luna 9 and Surveyor 1 were both major national accomplishments, only Surveyor 1 had reached its landing site employing key technologies that would be needed for a crewed flight. Thus as of mid-1966, the United States had begun to pull ahead of the Soviet Union in the so-called Space Race to land a man on the Moon.
Advances in other areas were necessary before crewed spacecraft could follow uncrewed ones to the surface of the Moon. Of particular importance was developing the expertise to perform flight operations in lunar orbit. Ranger, Surveyor and initial Luna Moon landing attempts all flew directly to the surface without a lunar orbit. Such direct ascents use a minimum amount of fuel for uncrewed spacecraft on a one-way trip.
In contrast, crewed vehicles need additional fuel after a lunar landing to enable a return trip back to Earth for the crew. Leaving this massive amount of required Earth-return fuel in lunar orbit until it is used later in the mission is far more efficient than taking such fuel down to the lunar surface in a Moon landing and then hauling it all back into space yet again, working against lunar gravity both ways. Such considerations lead logically to a lunar orbit rendezvous mission profile for a crewed Moon landing.
Accordingly, beginning in mid-1966 both the U.S. and U.S.S.R. naturally progressed into missions featuring lunar orbit as a prerequisite to a crewed Moon landing. The primary goals of these initial uncrewed orbiters were extensive photographic mapping of the entire lunar surface for the selection of crewed landing sites and, for the Soviets, the checkout of radio communications gear that would be used in future soft landings.
An unexpected major discovery from initial lunar orbiters were vast volumes of dense materials beneath the surface of the Moon's maria. Such mass concentrations ("mascons") can send a crewed mission dangerously off course in the final minutes of a Moon landing when aiming for a relatively small landing zone that is smooth and safe. Mascons were also found over a longer period of time to greatly disturb the orbits of low-altitude satellites around the Moon, making their orbits unstable and forcing an inevitable crash on the lunar surface in the relatively short period of months to a few years.
Controlling the location of impact for spent lunar orbiters can have scientific value. For example, in 1999 the NASA Lunar Prospector orbiter was deliberately targeted to impact a permanently shadowed area of Shoemaker Crater near the lunar south pole. It was hoped that energy from the impact would vaporize suspected shadowed ice deposits in the crater and liberate a water vapor plume detectable from Earth. No such plume was observed. However, a small vial of ashes from the body of pioneer lunar scientist Eugene Shoemaker was delivered by the Lunar Prospector to the crater named in his honor – currently the only human remains on the Moon.