Editing Luna 18

{{Short description|Space probe}}
{{italic title}}
{{Infobox spaceflight
| name                   = ''Luna 18''
| image                  = Luna 16.jpg
| image_caption          = A Ye-8-5 model in the Museum of Cosmonautics, Moscow.

| mission_type           = [[Planetary Science|Lunar sample return]]
| operator               = Soviet space program
| COSPAR_ID              = 1971-073A
| SATCAT                 = 5448
| mission_duration       = 9 days (launch day to day of last contact)

| spacecraft_bus         = [[Ye-8-5]]
| manufacturer           = [[Lavochkin|GSMZ Lavochkin]]
| dry_mass               = {{convert|5600|kg}}{{citation needed|date=July 2014}}
| launch_mass            = {{Convert|5725|kg}}<ref name=beyond>{{cite book|url=https://www.nasa.gov/sites/default/files/atoms/files/beyond-earth-tagged.pdf|title=Beyond Earth: A Chronicle of Deep Space Exploration, 1958–2016|last1=Siddiqi|first1=Asif|publisher=NASA History Program Office|edition=second|year=2018|isbn=9781626830431}}</ref>

| launch_date            = {{start-date|2 September 1971, 13:40:40|timezone=yes}}&nbsp;UTC<ref name=beyond/>
| launch_rocket          = [[Proton-K]]/[[Blok D|D]]
| launch_site            = [[Baikonur Cosmodrome|Baikonur]] [[Baikonur Cosmodrome Site 81|81/24]]
| launch_contractor      = 
| last_contact           = {{end-date|11 September 1971, 07:48|timezone=yes}}&nbsp;UTC

| orbit_epoch            = 6 September 1971, 20:00:00&nbsp;UTC<ref name="nasa">{{Cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1971-073A|title=NASA - NSSDCA - Spacecraft - Trajectory Details|website=nssdc.gsfc.nasa.gov|access-date=2018-05-02}}</ref>
| orbit_reference        = [[Selenocentric orbit|Selenocentric]]
| orbit_regime           = 
| orbit_periapsis        = {{Convert|1824.9|km|mi}}
| orbit_apoapsis         = {{Convert|1842.3|km|mi}}
| orbit_inclination      = 35&nbsp;degrees
| orbit_eccentricity     = 0.001361
| orbit_period           = 119&nbsp;minutes
| apsis                  = selene

| interplanetary         = {{Infobox spaceflight/IP
 | type             = orbiter
 | object           = [[Moon|Lunar]]
 | orbits           = 54<ref name="nasa" />
 | arrival_date     = 7 September 1971
}} {{Infobox spaceflight/IP
 | type             = lander_impact
 | object           = Lunar
 | arrival_date     = 11 September 1971 07:48 UTC
 | location         = {{coord|3|34|N|56|30|E|globe:moon}}
}}

| instruments            = Stereo photographic imaging system<br/>Remote arm for sample collection<br/>Radiation detector<br/>Radio altimeter

| programme          = '''[[Luna programme]]'''
| previous_mission   = [[Luna 17]]
| next_mission       = [[Luna 19]]
}}
'''''Luna 18''''', part of the Ye-8-5 series, was an [[uncrewed spacecraft|uncrewed space mission]] of the [[Luna program]].

==Overview==
''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 rocket]]s. It impacted the Moon on 11 September 1971, at 3 degrees 34 minutes N, 56 degrees 30 minutes E (selenographic coordinates) in rugged mountainous terrain. Signals ceased at the moment of impact.

This mission was the seventh Soviet attempt to [[Sample return mission|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 soil|lunar topsoil]].

==See also==
* [[List of artificial objects on the Moon]]
* [[List of missions to the Moon]]

==References==
{{Reflist}}

==External links==
{{Portal|Spaceflight}}
* [http://www.zarya.info/Diaries/Luna/Luna.php Zarya - Luna programme chronology]
* [https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1971-073A NASA NSSDC Master Catalog]

{{Moon spacecraft}}
{{Lunar landers}}
{{Luna programme}}
{{Orbital launches in 1971}}

[[Category:Luna programme]]
[[Category:Sample return missions]]
[[Category:Missions to the Moon]]
[[Category:1971 in spaceflight]]
[[Category:1971 in the Soviet Union]]
[[Category:Spacecraft that impacted the Moon]]
[[Category:Spacecraft that orbited the Moon]]
[[Category:Spacecraft launched in 1971]]
[[Category:1971 on the Moon]]