Editing Sputnik 2

{{short description|Second spacecraft launched into Earth orbit (1957)}}
{{Infobox spaceflight
| name                  = Sputnik 2
| image                 = Laika ac Sputnik 2 Replica (6995685051).jpg
| image_caption         = Model of Sputnik 2 at the [[Memorial Museum of Cosmonautics]] in [[Moscow]]
| mission_type          = Bioscience
| operator              = [[OKB-1]]
| Harvard_designation   = 1957 Beta 1
| COSPAR_ID             = 1957
| SATCAT                = 00003
| mission_duration      = 162 days
| orbits_completed      = 2570
| manufacturer          = [[Korolev  Bureau|OKB-1]]
| launch_mass           = {{convert|508.3|kg|lb}}
| launch_date           = {{start date text|3 November 1957, 02:30|timezone=yes}}&nbsp;UTC
| launch_rocket         = [[Sputnik (rocket)|Sputnik 8K71PS]]
| launch_site           = [[Baikonur Cosmodrome|Baikonur]] [[Baikonur Cosmodrome Site 1|1/5]]<ref name=log>{{Cite web|url=https://planet4589.org/space/gcat/data/derived/launchlog.html|title=Launch Log|last=McDowell|first=Jonathan|publisher=Jonathon's Space Report|access-date=30 September 2023}}</ref>
| crew_size             = 1
| crew_members          = [[Laika]]
| crew_photo            = 
| crew_photo_caption    = Laika
| last_contact          = 14 April 1958
| decay_date            = {{end date text|14 April 1958}}
| orbit_epoch           = 3 November 1957
| orbit_reference       = [[Geocentric orbit|Geocentric]]
| orbit_regime          = [[low Earth orbit|Low Earth]]
| orbit_apoapsis        = {{convert|1659|km|mi}}
| orbit_periapsis       = {{convert|212|km|mi}}
| orbit_inclination     = 65.33°
| orbit_semimajor       = {{convert|7306|km|mi}}
| orbit_eccentricity    = 0.0990965
| orbit_period          = 103.73&nbsp;minutes<ref name=nssdcsput2>{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTrajectory.action?id=1957-002A|title=Sputnik 2 Launch and Trajectory Information|website=NASA Space Science Data Coordinated Archive|access-date=30 September 2023}}</ref>
| apsis                 = gee
| programme             = [[Sputnik program]]
| previous_mission      = [[Sputnik 1]]
| next_mission          = [[Sputnik 3]]
}}

'''Sputnik 2''' ({{IPA|ru|ˈsputʲnʲɪk}}, {{langx|ru|Спутник-2}}, ''Satellite 2''{{--)}}, or '''Prosteyshiy Sputnik 2''' ('''PS-2''', {{langx|ru|Простейший Спутник 2|italic=no}}, ''Simplest Satellite 2''{{--)}},<ref name=challenge>{{cite book |last1=Siddiqi |first1=Asif A. |title=Challenge To Apollo: The Soviet Union and The Space Race, 1945-1974 |date=2000 |url=https://archive.org/details/nasa_techdoc_20000088626/}}</ref>{{rp|155}} launched on 3 November 1957, was the second [[spacecraft]] launched into [[Geocentric orbit|Earth orbit]], and the first to carry an animal into orbit, a [[Soviet space dogs|Soviet space dog]] named [[Laika]].

Launched by the [[Soviet Union]] via a modified [[R-7 Semyorka|R-7 intercontinental ballistic missile]], Sputnik 2 was a {{convert|4|m|ft|adj=mid|-high}} cone-shaped capsule with a base diameter of {{convert|2|m|ft}} that weighed around {{convert|500|kg|lb}}, though it was not designed to separate from the rocket core that brought it to orbit, bringing the total mass in orbit to {{convert|7.79|tonnes|lb}}. It contained several compartments for [[radio transmitter]]s, a [[telemetry]] system, a programming unit, a regeneration and [[temperature control|temperature-control]] system for the cabin, and scientific instruments. A separate sealed cabin contained the dog Laika.

Though Laika died shortly after reaching orbit, Sputnik 2 marked another huge success for the Soviet Union in [[The Space Race]], lofting huge payload for the time, sending an animal into orbit, and, for the first time, returning scientific data from above the Earth's atmosphere for an extended period. The satellite reentered Earth's atmosphere on 14 April 1958.

==Background==
In 1955, engineer [[Mikhail Tikhonravov]] created a proposal for "Object D", a satellite massing {{cvt|1000|kg}} to {{cvt|1400|kg}}, about a fourth of which would be devoted to scientific instruments. Upon learning that this spacecraft would outmass the announced American satellite by nearly 1,000 times, Soviet leader [[Nikita Khrushchev]] advocated for the proposal, which was approved by the government in Resolution #149-88 of 30 January 1956. Work began on the project in February with a launch date of latter 1957, in time for the [[International Geophysical Year]]. The design was finalized on 24 July.<ref name=rsp>{{cite book|title=Russian Space Probes: Scientific Discoveries and Future Missions|author1=Brian Harvey|author2=Olga Zakutnyaya|date=2011|publisher=Springer Praxis Books|location=Chichester,UK|oclc=1316077842}}</ref>{{rp|25}}

By the end of 1956, it had become clear that neither the complicated Object D nor the 8A91 satellite launch vehicle version of the R-7 ICBM under development to launch it would be finished in time for a 1957 launch. Thus, in December 1956, [[OKB-1]] head [[Sergei Korolev]] proposed the development of two simpler satellites: PS, Prosteishy Sputnik, or Primitive Satellite. The two PS satellites would be simple spheres massing {{cvt|83.4|kg}} and equipped solely with a radio antenna. The project was approved by the government on 25 January 1957.<ref name=drew>{{cite web|url=https://www.drewexmachina.com/2017/11/03/sputnik-2-the-first-animal-in-orbit/|author=Andrew LePage|title=Sputnik 2: The First Animal in Orbit|website=Drew Ex Machina|date=3 November 2017}}</ref><ref name=rsp/>{{rp|27}} The choice to launch these two instead of waiting for the more advanced Object D (which would eventually become [[Sputnik 3]]) to be finished was largely motivated by the desire to launch a satellite to orbit before the US. The first of these satellites, [[Sputnik 1]] (PS-1), was successfully launched 4 October 1957, and became the world's first artificial satellite.<ref name=challenge/>

Immediately following the launch, [[Nikita Khrushchev]] asked [[Sergei Korolev]] to prepare a Sputnik 2 in time for the 40th anniversary of the [[October Revolution|Bolshevik revolution]] in early November, just three weeks later.<ref name=":0">{{Cite book|title=Reconsidering Sputnik: Forty years since the Soviet satellite|last=Logsdon|first=Launius|publisher=Hardwood Academic|year=2000|isbn=90-5702-623-6|location=Australia|pages=86, 101}}</ref> Details of the conversation vary, but it appears likely that Korolev suggested the idea of flying a dog, while Khrushchev emphasised the importance of the date.<ref name=challenge/>{{rp|171–172}}

With only three weeks to prepare, OKB-1 had to scramble to assemble a new satellite. While PS-2 had been built, it was just a ball, identical to PS-1. Fortunately, the [[R-5 Pobeda|R-5A]] sounding rocket had recently been used to launch a series of suborbital missions carrying dogs as payloads. Korolev simply requisitioned a payload container used for these missions and had it installed in the upper stage of its [[R-7 Semyorka|R-7]] launching rocket directly beneath the PS-2 sphere.<ref name=rsp/>{{rp|30}} Upon reaching orbit, the final stage or Blok A would detach from the satellite.<ref name=drew/> No provision was made for the dog's recovery.<ref name=challenge/>{{rp|172}}

==Spacecraft==

Sputnik 2 was a {{convert|4|m|ft|adj=mid|-high}} cone-shaped capsule with a base diameter of {{convert|2|m|ft}} that weighed around {{convert|500|kg|lb}}, though it was not designed to separate from the rocket core that brought it to orbit, bringing the total mass in orbit to {{convert|7.79|tonnes|lb}}.<ref>{{Cite web|url = http://www.russianspaceweb.com/sputnik2_design.html|title = Russian Space Web}}</ref>

===Passenger===
{{main|Laika}}

''Laika'' ("Barker"), formerly ''Kudryavka'' (Little Curly), was the part-Samoyed terrier chosen to fly in Sputnik 2.<ref name=nssdcsput2/> Due to a shortness in the time frame, the candidate dog could not be trained for the mission. Again, OKB-1 borrowed from the sounding rocket program, choosing from ten candidates provided by the Air Force Institute of Aviation Medicine that were already trained for suborbital missions. Laika was chosen primarily because of her even temperament. Her backup was Albina, who had flown on two<ref name=challenge/>{{rp|173}} R-1E missions in June 1956.<ref name=rsp/>{{rp|23}} Laika weighed about {{cvt|6|kg|lb}}.<ref name=nssdcsput2/>

Both Laika and Albina had telemetry wires surgically attached to them before the flight to monitor respiration frequency, pulse, and blood pressure.<ref name=challenge/>{{rp|173}}

The pressurized cabin on Sputnik 2 was padded and allowed enough room for Laika to lie down or stand. An air regeneration system provided oxygen; food and water were dispensed in a gelatinized form. Laika was chained in place and fitted with a [[safety harness|harness]], a bag to collect waste, and [[electrode]]s to monitor vital signs. A television camera was mounted in the passenger compartment to observe Laika. The camera could transmit 100-line video frames at 10 frames/second.<ref name=nssdcsput2/>

===Experiments===

[[File:Atmospheric_electromagnetic_opacity.svg|thumb|300px|Wavelengths of light blocked by Earth's atmosphere.]]

Sputnik 2 was the first platform capable of making scientific measurements in orbit. This was potentially as significant as the biological payload. The [[Atmosphere of Earth|Earth's atmosphere]] blocks the Sun's X-ray and ultraviolet output from ground observation. Moreover, solar output is unpredictable and fluctuates rapidly, making sub-orbital [[sounding rocket]]s inadequate for the observation task. Thus a satellite is required for long-term, continuous study of the complete solar spectrum.<ref name="SP100">{{cite book |date=1966 |title=Significant Achievements in Solar Physics 1958–1964|publisher=NASA|oclc=860060668}} {{PD-notice}}</ref>{{Rp|5–6, 63–65}}<ref name=NAP>{{cite book|chapter-url=https://www.nap.edu/read/11299/chapter/8#157 |author=Committee on the Navy's Needs in Space for Providing Future Capabilities, Naval Studies Board, Division on Engineering and Physical Sciences, National Research Council of the National Academies|title=The Navy's Needs in Space for Providing Future Capabilities |chapter=Appendix A: Department of the Navy History in Space|page=157|date=2005|access-date=January 6, 2019|publisher=The National Academies Press|archive-url=https://web.archive.org/web/20190107015833/https://www.nap.edu/read/11299/chapter/8#157|archive-date=January 7, 2019|url-status=live|isbn=978-0-309-18120-4|doi=10.17226/11299}} {{PD-notice}}</ref>

Accordingly, Sputnik 2 carried two spectrophotometers, one for measuring solar ultraviolet rays and one for measuring X-rays. These instruments were provided by Professor Sergei Mandelstam of the Lebedev Institute of Physics and installed in the nose cone above the spherical PS. In addition, Sergei Vernov, who had completed a cosmic ray detector (using [[Geiger counter]]s) for Object D, demanded that the instrument his Moscow University team (including Naum Grigoriev, Alexander Chudakov, and Yuri Logachev) had built also be carried on the flight. Korolev agreed, but as there was no more room on the satellite proper, the instrument was mounted on the Blok A and given its own battery and telemetry frequency.<ref name=rsp/>{{rp|30,32}}

Engineering and biological data were transmitted using the Tral_D telemetry system, which would transmit data to Earth for 15 minutes of each orbit.<ref name=nssdcsput2/>

==Launch preparations==
Sputnik 2's launch vehicle, the R-7 ICBM (also known by the system's GRAU index 8K71)<ref>Zaloga, Stephen J.. ''The Kremlin's Nuclear Sword'', Washington.  The Smithsonian Institution Press, 2002, p. 232. {{ISBN|1-58834-007-4}}</ref> was modified for the PS-2 satellite launch and designated 8K71PS.<ref name=challenge/>{{rp|163}} 8K71PS serial number M1-2PS arrived at the NIIP-5 Test Range, the precursor to the [[Baikonur Cosmodrome]], on 18 October 1957 for final integration of the rocket stages and satellite payload.<ref name=drew/> Laika was put in the payload container mid-day 31 October, and that night, the payload was attached to the rocket. The container was heated via an external tube against the cold temperatures at the launch site.<ref name=challenge/>{{rp|173}}

==Mission==
[[Image:Ussrsputnik2-20kop1957scott2032.jpg|thumb|150px|left|[[USSR]] [[postage stamp]] "Спутник-2"]]

Sputnik 2 was launched at 02:30:42 [[Coordinated Universal Time|UTC]] on 3 November 1957 from LC-1 of the NIIP-5 Test Range via Sputnik 8K71PS rocket (the same pad and rocket that launched Sputnik 1)<ref name=log/> The satellite's orbit was {{cvt|212|×|1660|km|mi}} with a period of 103.7 minutes.<ref name=nssdcsput2/> After reaching orbit Sputnik 2's nose cone was jettisoned successfully, but the satellite did not separate from the Blok A. This, along with the loss of some thermal insulation, caused temperatures in the spacecraft to soar.<ref name=nssdcsput2/>

At peak acceleration, Laika's respiration increased to between three and four times the pre-launch rate.<ref name="SPUT1">{{cite web |url=http://www.svengrahn.pp.se/histind/Sputnik2/sputnik2more.html |title=Sputnik-2, more news from distant history |first=Sven |last=Grahn |access-date=2 February 2004 |archive-url=https://web.archive.org/web/20150924112150/http://www.svengrahn.pp.se/histind/Sputnik2/sputnik2more.html |archive-date=24 September 2015 |url-status=live |mode=cs2 }}</ref> The sensors showed her heart rate was 103 beats/min before launch and increased to 240 beats/min during the early acceleration.  After three hours of [[weightlessness]], Laika's pulse rate had settled back to 102 beats/min,<ref name="JAP">{{citation |journal= Journal of Applied Physiology|title=Historical aspects of the early Soviet/Russian manned space program |volume=91 |issue=4 |pages=1501–1511 |first=John B. |last=West |date=1 October 2001 |pmid=11568130 |doi=10.1152/jappl.2001.91.4.1501 |s2cid=24284107 }}</ref> three times longer than it had taken during earlier ground tests, an indication of the stress she was under. The early [[telemetry]] indicated that Laika was agitated but eating her food.<ref name=nssdcsput2/> After approximately five to seven hours into the flight, no further signs of life were received from the spacecraft.<ref name="SPUT1"/>

The Soviet scientists had planned to euthanise Laika with a serving of poisoned food. For many years, the [[Soviet Union]] gave several conflicting statements that she had died either from [[asphyxia]],<ref name="Beischer1962">{{citation |last1=Beischer |first1=DE |last2=Fregly |first2=AR |title=Animals and man in space. A chronology and annotated bibliography through the year 1960 |journal=US Naval School of Aviation Medicine |volume=ONR TR ACR-64 |issue=AD0272581 |date=1962 |url=http://archive.rubicon-foundation.org/9288 |access-date=14 June 2011 |archive-url=https://web.archive.org/web/20150811085105/http://archive.rubicon-foundation.org/xmlui/handle/123456789/9288 |archive-date=11 August 2015 |url-status=usurped }}</ref> when the batteries failed, or that she had been euthanised. Many rumours circulated about the exact manner of her death. In 1999, several Russian sources reported that Laika had died when the cabin overheated on the fourth day.<ref name="AZ">{{cite web |url=http://www.space.com/news/laika_anniversary_991103.html |archive-url=https://web.archive.org/web/20060220234602/http://www.space.com/news/laika_anniversary_991103.html |archive-date=20 February 2006 |title=The True Story of Laika the Dog |first=Anatoly |last=Zak |website=[[Space.com]] |date=3 November 1999 |access-date=14 May 2023 |url-status=dead |mode=cs2 |quote=Recently, several Russian sources revealed that Laika survived in orbit for four days and then died when the cabin overheated.}}</ref> In October 2002, Dimitri Malashenkov, one of the scientists behind the Sputnik{{spaces}}2 mission, revealed that Laika had died by the fourth circuit of flight from overheating. According to a paper he presented to the [[World Space Congress]] in [[Houston|Houston, Texas]], "It turned out that it was practically impossible to create a reliable temperature control system in such limited time constraints."<ref name="DM">{{citation |title=Abstract:Some Unknown Pages of the Living Organisms' First Orbital Flight |last=Malashenkov |first=D. C. |date=2002 |bibcode=2002iaf..confE.288M |page=288 |journal=IAF Abstracts}}</ref>

Because of the size of Sputnik 2 and its attached Blok A, the spacecraft was easy to track optically. In its last orbits, the combined body tumbled end over end, flashing brightly before it was incinerated over the north Atlantic after circling the Earth 2,370 times over the course of 162 days.<ref name=rsp/>{{rp|32}} The spacecraft reentered the Earth's atmosphere on 14 April 1958, at approximately 0200 hrs, on a line that stretched from New York to the Amazon. Its track was plotted by British ships and three "Moon Watch Observations", from New York. It was said to be glowing and did not develop a tail until it was at latitudes south of 20° North. Estimates put the average length of the tail at about {{convert|50|nmi}}.<ref>{{Cite journal|author1=King-Heele, D.G. |author2=Walker, D.M.C. |date=1958-08-16|title=The Last Minutes of Satellite 1957β (Sputnik 2)|journal=Nature|volume=182 |issue=4633 |page=426 |doi=10.1038/182426a0 |bibcode=1958Natur.182..426K |s2cid=4153514 }}</ref>


== Results==

===Geopolitical impact===
Massing {{cvt|508.3|kg}}, Sputnik 2 marked a dramatic leap in orbital mass over Sputnik 1<ref name=challenge/>{{rp|173}} as well as the American [[Vanguard 1|Vanguard]], which had yet to fly.<ref name=rsp/>{{rp|25}} The day after Sputnik 2 went into orbit the [[Gaither Report|Gaither committee]] met with [[Dwight D. Eisenhower|President Eisenhower]] to brief him on the current situation, demanding an urgent and more dramatic response than to the smaller Sputnik 1.<ref name="race">{{cite book |last=Cox |first=Donald W. |year=1962 |title=The space race; from Sputnik to Apollo, and beyond |url=https://archive.org/details/spaceracefromspu00coxd |url-access=registration |location=Philadelphia |publisher=Chilton Books |lccn=62018224}}</ref>{{rp|26}} It was clear now that the Soviets had missiles far superior to any in the American arsenal,<ref name=drew/> a fact whose demonstration by Sputnik 2 was eagerly propounded by Soviet Premier Khrushchev at every opportunity. In the U.S.S.R., just six days after the launch of Sputnik 2, on the 40th anniversary of the October revolution, Khrushchev boasted in a speech “Now our first Sputnik is not lonely in its space travels.” Nevertheless, unlike most of the U.S., President Eisenhower kept calm through the time afterward just as he did after Sputnik 1 was launched. According to one of the president's aides, “The president's burning concern was to keep the country from going hog-wild and from embarking on foolish, costly schemes.”<ref name="race"/>{{rp|26, 31–32}}

[[File:Photograph of Sputnik 2 taken from Patrick AFB in March 1958.jpg|thumb|Photograph of Sputnik 2 and its rocket taken by Air Force personnel at Air Force Missile Test Center, Patrick AFB, Florida, in March 1958.]]

The mission sparked a debate across the globe on the [[mistreatment of animals]] and [[animal testing]] in general to advance science.<ref name="NLM">{{cite web |url=https://www.nlm.nih.gov/exhibition/animals/laika.html |title=Animals as Cold Warriors: Missiles, Medicine and Man's Best Friend |publisher=National Library of Medicine |date=19 June 2006 |access-date=28 September 2006 |archive-url=https://web.archive.org/web/20151006132551/https://www.nlm.nih.gov/exhibition/animals/laika.html |archive-date=6 October 2015 |url-status=live |mode=cs2 }}</ref> In the United Kingdom, the [[Dogs Trust|National Canine Defence League]] called on all dog owners to observe a minute's silence on each day Laika remained in space, while the [[Royal Society for the Prevention of Cruelty to Animals]] (RSPCA) received protests even before [[Radio Moscow]] had finished announcing the launch. [[Animal rights]] groups at the time called on members of the public to protest at Soviet embassies.<ref name="BBCold">{{citation |url=http://news.bbc.co.uk/onthisday/hi/dates/stories/november/3/newsid_3191000/3191083.stm |title=On this day |publisher=BBC |date=3 November 1957 |access-date=26 September 2006 |archive-url=https://web.archive.org/web/20151008161445/http://news.bbc.co.uk/onthisday/hi/dates/stories/november/3/newsid_3191000/3191083.stm |archive-date=8 October 2015 |url-status=live }}</ref> Others demonstrated outside the United Nations in New York.{{r|NLM}} Laboratory researchers in the [[United States|U.S]]. offered some support for the Soviets, at least before the news of Laika's death.<ref name="NLM"/><ref name="NSMR">{{cite web |url=https://www.nlm.nih.gov/exhibition/animals/images/laika7Big.jpg |title=Human Guinea Pigs and Sputnik 2 |publisher=National Society for Medical Research |date=November 1957 |access-date=28 September 2006 |archive-url=https://web.archive.org/web/20150520210547/http://www.nlm.nih.gov/exhibition/animals/images/laika7Big.jpg |archive-date=20 May 2015 |url-status=live |mode=cs2 }}
</ref>

===Experimental data===
The cosmic ray detector transmitted for one week, going silent on 9 November when its battery was exhausted. The experiment reported unexpected results the day after launch, noting an increase in high-energy charged particles from a normal 18 pulses/sec to 72 pulses/sec at the highest latitudes of its orbit. Per two articles in the Soviet newspaper [[Pravda]], the particle flux increased with altitude as well. It is likely that Sputnik 2 was detecting the lower levels of the [[Van Allen Belt]] when it reached the [[apogee]] of its orbit. However, because Sputnik 2 telemetry could only be received when it was flying over the Soviet Union, the data set was insufficient to draw conclusions, particularly as, most of the time, Sputnik 2 traveled below the Belt.<ref name="race"/>{{rp|32}} Additional observational data had been received by Australian observers when the satellite was overhead, and Soviet scientists asked them for it. The secrecy-minded Soviets were not willing to give the Australians the code that would give them the ability to descramble and use the data themselves. As a result, the Australians declined to turn over their data.<ref name=physicstoday>{{cite journal|url=https://pubs.aip.org/physicstoday/article/70/12/46/904087/Discovering-Earth-s-radiation-beltsSix-decades|title=Discovering Earth's radiation belts|author1=Daniel N. Baker|author2=Mikhail I. Panasyuk|journal=Physics Today |date=1 December 2017|volume=70 |issue=12 |pages=46–51 |doi=10.1063/PT.3.3791 |bibcode=2017PhT....70l..46B |accessdate=1 October 2023}}</ref> Thus, the Soviet Union missed out on its chance to get credit for the scientific discovery, which ultimately went to James Van Allen of the State University of Iowa, whose experiments on [[Explorer 1]] and [[Explorer 3]] first mapped the radiation belts that now bear his name.<ref name=VanAllen>{{cite book|title=The Exploration of Space|chapter=The Geomagnetically Trapped Corpuscular Particles|author=James Van Allen|editor=Robert Jastrow|date=1960|publisher=The MacMillan Company|location=New York|oclc=853599}}</ref>

As for the ultraviolet and X-ray photometers, they  were calibrated such that they were oversaturated by orbital radiation, returning no usable data.<ref name="race"/>{{rp|32}}

==Surviving examples==
A USSR-built engineering model of the R-7 Sputnik 8K71PS (Sputnik II) is located at the [[Cosmosphere]] space museum in [[Hutchinson, Kansas]], [[United States]].  The museum also has a flight-ready backup of the [[Sputnik 1]], as well as replicas of the first two American satellites, [[Explorer 1]] and [[Vanguard 1]].<ref>{{cite web |title=Hall of Space Museum |url=https://cosmo.org/explore/attractions/hall-of-space-museum/ |website=[[Cosmosphere]] |date=2 September 2022 |archive-url=https://web.archive.org/web/20231022023055/https://cosmo.org/explore/attractions/hall-of-space-museum/ |archive-date=October 22, 2023 |url-status=live}}</ref>

A replica of Sputnik 2 is located at the [[Memorial Museum of Cosmonautics]] in [[Moscow]].

==See also==
{{Portal|Spaceflight|Soviet Union}}
* [[Animals in space]]
* [[Timeline of artificial satellites and space probes]]

==Footnotes==
{{Reflist}}

==External links==
{{Commons category|Sputnik-2}}
*[http://www.mentallandscape.com/S_Sputnik.htm Sputnik: 50 Years Ago]
*[http://www.russianspaceweb.com/sputnik2.html Anatoly Zak on Sputnik-2]
*[http://www.zarya.info/Diaries/Sputnik/Sputnik2.php Sputnik 2 Diary]
*[https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1957-002A NSSDC Master Catalog: Spacecraft Sputnik 2]
*[https://web.archive.org/web/20060831060945/http://astronautix.com/craft/sputnik2.htm Sputnik 2 at Astronautix]

{{Orbital launches in 1957}}

[[Category: 1957 in the Soviet Union]]
[[Category: 1958 in the Soviet Union]]
[[Category: Animal testing in the Soviet Union]]
[[Category: Biosatellites]]
[[Category: Dogs in the Soviet Union]]
[[Category: Earth observation satellites of the Soviet Union]]
[[Category: Soviet inventions]]
[[Category: Spacecraft launched in 1957]]
[[Category: Spacecraft which reentered in 1958]]
[[Category: Sputnik|2]]
[[Category: Successful space missions]]