Luna 18

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Luna 18
Luna 18
Mission type Lunar sample return
COSPAR ID 1971-073A
SATCAT № 5448
Spacecraft properties
Bus Ye-8-5
Manufacturer GSMZ Lavochkin
Launch mass 5,750 kilograms (12,680 lb)
Dry mass 5,600 kilograms (12,300 lb)[citation needed]
Start of mission
Launch date 2 September 1971, 13:40:40 (1971-09-02UTC13:40:40Z) UTC
Rocket Proton-K/D
Launch site Baikonur 81/24
End of mission
Last contact 11 September 1971, 07:48 (1971-09-11UTC07:49Z) UTC
Orbital parameters
Reference system Selenocentric
Semi-major axis 6,477.8 kilometres (4,025.1 mi)
Eccentricity 0.001361
Periselene 100 kilometres (62 mi)
Aposelene 100 kilometres (62 mi)
Inclination 35 degrees
Period 119 minutes
Lunar orbiter
Orbital insertion 7 September 1971
Orbits ~48
Lunar impact (failed landing)
Impact date 11 September 1971 07:48 UTC
Impact site Lua error in Module:Coordinates at line 668: callParserFunction: function "#coordinates" was not found.
Stereo photographic imaging system
Remote arm for sample collection
Radiation detector
Radio altimeter

Luna 18, part of the Ye-8-5 series, was an unmanned space mission of the Luna program.

Luna 18 was placed in an Earth parking orbit after it was launched and was then sent towards the Moon. On 7 September 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 11 September 1971, at 3 degrees 34 minutes N, 56 degrees 30 minutes E (selenographic coordinates) in a rugged mountainous terrain. Signals ceased at the moment of impact.

This mission was the seventh Soviet attempt to recover soil samples from the surface of the Moon and the first after the success of Luna 16. After two mid-course corrections on 4 September and 6 September 1971, Luna 18 entered a circular orbit around the Moon on 7 September at 100 kilometers altitude with an inclination of 35°. After several more orbital corrections, on 11 September, the vehicle began its descent to the lunar surface. Contact with the spacecraft was lost at 07:48 UT at the previously determined point of lunar landing. Impact coordinates were 3°34' north latitude and 56°30' east longitude, near the edge of the Mare Fecunditatis ("Sea of Fertility"). Officially, the Soviets announced that "the lunar landing in the complex mountainous conditions proved to be unfavorable." Later, in 1975, the Soviets published data from Luna 18's continuous-wave radio altimeter that determined the mean density of the lunar topsoil.

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