Editing Luna 24

{{italic title}}
{{Short description|Final Soviet sample-return mission to the Moon, 1976}}
{{Use British English|date=February 2021}}
{{Use dmy dates|date=May 2020}}
{{Infobox spaceflight
| name               = Luna 24
| names_list         = 
| image              = Luna24 rev fig.png
| image_caption      = ''Luna 24'' landed on the northwestern rim of a 64 m diameter impact crater Lev, on the volcanic plains of Mare Crisium
| image_size         = 300px
| mission_type       = [[Luna programme|Lunar sample return]]
| operator           = Soviet space program
| COSPAR_ID          = 1976-081A
| SATCAT             = 9272
| mission_duration   = {{time interval|9 August 1976 15:04|22 August 1976 05:55|show=dhm}}
| spacecraft_type    = 
| spacecraft_bus     = Ye-8-5M
| manufacturer       = [[Lavochkin|NPO Lavochkin]]
| launch_mass        = {{cvt|5800|kg}}<ref name=beyond/>
| dimensions         = 
| power              = <!-- [[watt]]s -->
| launch_date        = 9 August 1976, 15:04:12 [[Coordinated Universal Time|UTC]]<ref name=beyond/>
| launch_rocket      = [[Proton-K]]/[[Blok D|DM]] s/n 288-02
| launch_site        = [[Baikonur Cosmodrome|Baikonur]] [[Baikonur Cosmodrome Site 81|81/23]]
| launch_contractor  = [[Khrunichev State Research and Production Space Center|Krunichev]]
| landing_date       = 22 August 1976, 05:55 UTC<ref>https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1976-081A</ref>
| landing_site       = {{coords|61|3|36|N|75|54|0|E}},<ref name=recovery_1976/><br/><small>{{cvt|200|km}} South-East of [[Surgut]], Western [[Siberia]]</small>
| orbit_reference    = [[Lunar orbit|Selenocentric]]
| orbit_regime       = 
| orbit_periapsis    = {{cvt|115|km}}
| orbit_apoapsis     = {{cvt|115|km}}
| orbit_inclination  = 120.0°
| orbit_period = 1 hour 59 minutes
| apsis = selene
| interplanetary = 
{{Infobox spaceflight/IP
 | type              = orbiter
 | object            = [[Moon|Lunar]]
 | orbits            = ~48
 | arrival_date      = 14 August 1976
}}

{{Infobox spaceflight/IP
 | type              = lander
 | object            = [[Moon|Lunar]]
 | arrival_date      = 18 August 1976, 06:36 UTC
 | departure_date    = 19 August 1976, 05:25 UTC
 | location          = {{coord|12.7145|N|62.2097|E|globe:Moon|display=inline,title|format=dec}},<ref name=Lawrence_2013/> Mare Crisium
 | sample_mass       = {{cvt|170.1|g}}
}}

| instruments        = Stereo photographic imaging system<br/>Improved drill/Remote arm for sample collection<br/>Radiation detector<br/>Radio-altimeter
| programme          = '''[[Luna programme]]'''
| previous_mission   = ''[[Luna E-8-5M No.412|Luna 1975A]]''
| next_mission       = [[Luna 25]] (''[[Roscosmos|Russian]]'')
}}
'''''Luna 24''''' was a [[Space probe|robotic probe]] of the [[Soviet Union]]'s [[Luna programme]]. The 24th mission of the Luna series of spacecraft, the mission of the ''Luna 24'' probe was the third Soviet mission to return [[lunar soil]] samples from the [[Moon]] (the first two sample return missions were ''[[Luna 16]]'' and ''[[Luna 20]]''). The probe landed in [[Mare Crisium]] (Sea of Crises). The mission returned {{cvt|170.1|g}} of lunar samples to the [[Earth]] on 22 August 1976.

== Spacecraft ==
[[File:Луна-24 3 (24432633921) cropped.jpg|left|thumb|Model of <nowiki>''Luna 24''</nowiki> Moon lander]]
Luna 24 was based on the Ye-8-5 spacecraft body, consisting of two attached stages, an ascent stage mounted on top of a descent stage. The lander stood 3.96 meters tall and had an unfueled landed mass of 1880 kg. With a full load of fuel its launch mass was between 5600 and 5750 kg.<ref name="Display">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1976-081A|title=Display: Luna 24 1976-081A|publisher=NASA|date=10 February 2021|access-date=17 February 2021}} {{PD-notice}}</ref>

The descent stage was the same as the Ye-8 lower stage for the Lunokhod rovers, a cylindrical body with four protruding landing legs, fuel tanks, a landing radar altimeter, and a dual descent engine complex. The main descent rocket, the KTDU-417, was a throttleable 1920 kg thrust engine used for mid-course corrections, orbit insertion, braking for descent to the surface, and 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 (210 and 350 kg) vernier jets was used for the final landing. The descent stage also acted as a launch pad for the ascent stage. The spacecraft descent stage was equipped with a television camera, radiation and temperature monitors, telecommunications equipment, and a 90 cm extendable arm with a drilling rig for the collection of a lunar soil sample. Communications were via a conical antenna at the end of a boom at 768 and 922 [[Hertz|MHz]] (downlink) and 115 MHz (uplink).<ref name=Display/>

The ascent stage was a smaller cylinder with a spherical top which replaced the Lunokhod rover and housing from the Ye-8 bus. It carried a cylindrical hermetically sealed soil sample container inside a spherical re-entry capsule, mounted on a 1920 kg thrust KRD-61 rocket. Total mass of the ascent stage was 520 kg, of which 245 kg was the [[nitric acid]] and [[Unsymmetrical dimethylhydrazine|UDMH]] propellant. It was 2 meters tall. The sample return cabin was 50 cm in diameter and had a mass of 39 kg. The KRD-61 could only fire once, for 53 seconds, to put it on a free return trajectory to Earth. Specific impulse of the engine was 313 seconds, it could impart a velocity of 2600–2700 m/s to the return craft.<ref name=Display/>

== Mission ==
{| class="wikitable" align="left" style="font-size:smaller; margin-right: 20px"
!Lunar<br/>mission
!Sample<br/>returned
!Year
|-
| ''[[Luna 16]]''
|align="right"| 101 g <ref name=nssdc-16/>
|align="right"| 1970
|-
| ''[[Luna 20]]''
|align="right"| 30 g <ref name=nssdc-20/>
|align="right"| 1972
|-
| ''Luna 24''
|align="right"| 170.1 g <ref name=nssdc-24/>
|align="right"| 1976
|-
|}

''Luna 24'' was the third attempt to recover a sample from the unexplored [[Mare Crisium]], the location of a large lunar [[Mass concentration (astronomy)|mascon]] (after ''[[Luna 23]]'' and a launch failure in October 1975). After a [[trajectory]] correction on 11 August 1976, ''Luna 24'' entered [[lunar orbit]] three days later. Initial [[Orbital elements|orbital parameters]] were {{cvt|115|by|115|km}} at 120° [[Orbital inclination |inclination]]. After further changes to its orbit, ''Luna 24'' set down safely on the lunar surface at 06:36 [[Coordinated Universal Time|UTC]] on 18 August 1976 at 12°45' North [[latitude]] and 62°12' East [[longitude]], not far from where ''Luna 23'' had landed.<ref name=solarsystem.nasa/> Exact landing location (12.7145° N, 62.2097° E) was determined by the [[Lunar Reconnaissance Orbiter]] probe orbital cameras in 2012.<ref name=lro-2012/>  The crater adjacent to the lander was subsequently named ''Lev'' by the [[IAU]].<ref>{{cite web |url = https://planetarynames.wr.usgs.gov/Feature/14952 |title = Lev |publisher = [[IAU]]/[[USGS]]/[[NASA]] |work = Gazetteer of Planetary Nomenclature |access-date = 23 December 2024}}</ref>

Under command from ground control, the lander deployed its sample arm and pushed its drilling head about two metres into the nearby soil. The sample was safely stowed in the small return capsule, and after nearly a day on the Moon, ''Luna 24'' lifted off successfully at 05:25 UTC on 19 August 1976. After an uneventful return trip, ''Luna 24''{{'}}s capsule entered [[Atmosphere of Earth|Earth's atmosphere]] and parachuted safely to land at 05:55 UTC on 22 August 1976, about {{cvt|200|km}} southeast of [[Surgut]] in western [[Siberia]]. Study of the recovered {{cvt|170.1|g}} of soil indicated a laminated type structure, as if laid down in successive deposits. The Soviet Union swapped a gram of the mission sample for a lunar sample from [[NASA]] in December 1976.<ref name=solarsystem.nasa/> ''Luna 24'' was the final lunar spacecraft to be launched by the Soviet Union. It was also the last spacecraft to make a soft landing on the Moon until the landing of China's ''[[Chang'e 3]]'' on 14 December 2013, 37 years later. For over 40 years, it was also the last Lunar sample return mission until China's [[Chang'e 5]] in December 2020.

== Detection of water in returned samples ==
{{see also|Lunar water}}

In February 1978, Soviet scientists M. Akhmanova, B. Dement'ev, and M. Markov of the Vernadsky Institute of Geochemistry and Analytic Chemistry published a paper claiming a detection of water fairly definitively.<ref name=Geokhimiya_rus/><ref name=Geochemistry_eng/> Their study showed that the samples returned to [[Earth]] by the probe contained about 0.1% water by mass, as seen in infrared absorption spectroscopy (at about 3 [[Micrometre|μm]] wavelength), at a detection level about 10 times above the threshold,<ref name=Crotts_hist1/> although Crotts points out that "The authors... were not willing to stake their reputations on an absolute statement that terrestrial contamination was completely avoided."<ref name=Crotts_hist2/>  This would represent the first detection of water content on the surface of the moon, although that result has not been confirmed by other researchers.<ref name=Spudis/>

== See also ==
{{Portal|Spaceflight}}
* [[Timeline of artificial satellites and space probes]]
* [[List of artificial objects on the Moon]] (descent stage)
* [[List of missions to the Moon]]

== References ==
{{Reflist|refs=

<ref name="Lawrence_2013">
{{ cite web
| url= http://lroc.sese.asu.edu/posts/650
| title= LROC Coordinates of Robotic Spacecraft – 2013 Update|author=Samuel Lawrence
| publisher=lroc.sese.asu.edu
| date= 24 September 2013 
| access-date= 9 June 2015
| archive-url= https://web.archive.org/web/20150509061816/http://lroc.sese.asu.edu/posts/650| archive-date= 9 May 2015
| url-status= live }}
</ref>

<ref name="recovery_1976">
{{ cite web
| url= http://epizodsspace.airbase.ru/bibl/inostr-yazyki/sov-luna/sovets-luna.pdf
| title= Soviet and Russian Lunar Exploration
| page= 314
| archive-date= 29 July 2019
| archive-url= https://web.archive.org/web/20190729155018/http://epizodsspace.airbase.ru/bibl/inostr-yazyki/sov-luna/sovets-luna.pdf
| url-status=live }}
</ref>

<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
| author1= Asif Siddiqi
| publisher= NASA History Program Office
| edition= second
| year= 2018
| isbn= 9781626830431 }}
</ref>

<ref name="nssdc-16">
{{ cite web
| url= https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1970-072A
| title= Luna 16
| website= nssdc.gsfc.nasa.gov
| publisher= [[NASA]]
| date= 10 February 2021
| access-date= 17 February 2021 }} {{PD-notice}}
</ref>

<ref name="nssdc-20">
{{ cite web
| url= https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1972-007A
| title= Luna 20
| website= nssdc.gsfc.nasa.gov
| publisher= [[NASA]]
| date= 10 February 2021
| access-date= 17 February 2021 }} {{PD-notice}}
</ref>

<ref name="nssdc-24">
{{ cite web
| url= https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1976-081A
| title= Luna 24
| website= nssdc.gsfc.nasa.gov
| publisher= [[NASA]]
| date= 10 February 2021
| access-date= 17 February 2021 }} {{PD-notice}}
</ref>

<ref name="solarsystem.nasa">
{{ cite web
| url= http://solarsystem.nasa.gov/missions/profile.cfm?Print=0&Sort=Nation&MCode=Luna_24&Nation=USSR&Display=ReadMore&FIELDNAMES= 
| title= Solar System Exploration: USSR: Luna 24
| website= solarsystem.nasa.gov 
| publisher= [[NASA]]
| access-date= 16 November 2016 
| archive-date= 30 April 2015
| archive-url= https://web.archive.org/web/20150430002507/http://solarsystem.nasa.gov/missions/profile.cfm?Print=0&Sort=Nation&MCode=Luna_24&Nation=USSR&Display=ReadMore&FIELDNAMES=
| url-status=dead }} {{PD-notice}}
</ref>

<ref name="lro-2012">
{{ cite news
| url=http://lroc.sese.asu.edu/news/index.php?/archives/539--Mare-Crisium-Failure-then-Success.html
| title= Mare Crisium: Failure then Success
| date= 16 March 2012
| publisher= LROC News System
| author1= Jeff Plescia
| access-date= 2 December 2020
| archive-date= 8 December 2013
| archive-url= https://web.archive.org/web/20131208045758/http://lroc.sese.asu.edu/news/index.php?%2Farchives%2F539--Mare-Crisium-Failure-then-Success.html
| url-status=live }} {{PD-notice}}
</ref>

<ref name="Geokhimiya_rus">
{{ cite journal
| author1= M. Akhmanova
| author2= B. Dement'ev
| author3= M. Markov
| date= February 1978
| language= ru
| title= Water in the regolith of Mare Crisium (Luna-24)?
| journal= Geokhimiya
| issue= 285 }}
</ref>

<ref name="Geochemistry_eng">
{{ cite journal
| author1= M. Akhmanova
| author2= B. Dement'ev
| author3= M. Markov
| year= 1978
| title= Possible Water in Luna 24 Regolith from the Sea of Crises
| journal= Geochemistry International
| volume= 15
| issue= 166 }}
</ref>

<ref name="Crotts_hist1">
{{ cite arXiv
| author1= Arlin Crotts
| eprint= 1205.5597v1
| title= Water on The Moon, I. Historical Overview
| class= astro-ph.EP
| year= 2012 }}
</ref>

<ref name="Crotts_hist2">
{{ cite web
| url= https://www.thespacereview.com/article/1485/1
| title= Water on the Moon
| author1= Arlin Crotts
| date= 12 October 2009
| publisher= The Space Review
| access-date= 13 November 2023 }}
</ref>

<ref name="Spudis">
{{ cite web
| url= https://www.smithsonianmag.com/air-space-magazine/who-discovered-water-on-the-moon-110774900/
| title= Who discovered water on the Moon?
| author1= Paul D. Spudis (June 1, 2012)
| publisher= [[Smithsonian Magazine]]
| date= 1 June 2012
| access-date= 13 November 2023 }}
</ref>
}}

== External links ==
* {{Commonscatinline}}
* [http://www.zarya.info/Diaries/Luna/Luna24.php Zarya – ''Luna 24'' chronology]
* [https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1976-081A NASA NSSDC Master Catalog]
* {{cite web|url=http://www.technologyreview.com/view/428030/soviet-moon-lander-discovered-water-on-the-moon/ <!-- old URL: http://www.technologyreview.com/blog/arxiv/27883/ --> |title=Soviet Moon Lander Discovered Water on The Moon in 1976|work=The Physics arXiv Blog|publisher=Technology Review|date=30 May 2012}}
* [http://lroc.sese.asu.edu/posts/461 Mare Crisium: Failure then Success], article showing [[Lunar Reconnaissance Orbiter|LROC]] images of ''Luna 23'' and ''Luna 24'' on the lunar surface
* [http://mentallandscape.com/C_CatalogMoon.htm Catalog of Soviet Luna Probe images]

{{Luna programme}}
{{Moon spacecraft}}
{{Orbital launches in 1976}}

[[Category:Luna programme]]
[[Category:Sample return missions]]
[[Category:Missions to the Moon]]
[[Category:Soft landings on the Moon]]
[[Category:1976 in the Soviet Union]]
[[Category:Spacecraft launched in 1976]]
[[Category:1976 on the Moon]]