View source for Venera 4

{{Short description|1967 Soviet Venus probe}}
{{Use dmy dates|date=March 2020}}
{{Infobox spaceflight
| name                  = Venera 4
| image                 = Venera 4 (MMA 2011) (1).JPG
| image_size            = 230px
| image_caption         = Venera 4 model
| insignia              = The Soviet Union 1968 CPA 3623 stamp (Venera 4 Space probe).jpg
| insignia_size         = 60px

| mission_type          = [[Venus]] lander and flyby spacecraft
| operator              = [[NPO Lavochkin|GSMZ Lavochkin]]
| COSPAR_ID             = 1967-058A
| SATCAT                = 02840
| mission_duration      = 127 days

| spacecraft            = 4V-1 <ref name=ea>{{cite web|url=http://www.astronautix.com/v/venera1vv-67.html|archive-url=https://web.archive.org/web/20161228043210/http://astronautix.com/v/venera1vv-67.html|url-status=dead|archive-date=28 December 2016|title=Venera 1V (V-67)|website=Encyclopedia Astronautica|last1=Wade|first1=Mark|access-date=9 November 2019}}</ref>
| manufacturer          = [[NPO Lavochkin|GSMZ Lavochkin]]
| launch_mass           = 1,106 kg{{sfn|Siddiqi|2018|p=68}}
| dry_mass              = 377 kg

| launch_date           = 12 June 1967, 02:39:45 UT{{sfn|Siddiqi|2018|p=68}}
| launch_rocket         = [[Molniya-M|Molniya 8K78M]]  
| launch_site           = [[Baikonur Cosmodrome|Baikonur]], [[Baikonur Cosmodrome|Site 1/5]]
| launch_contractor     = [[TsSKB-Progress]]

| last_contact          = 18 October 1967, 04:34 GMT

| orbit_reference       = [[Heliocentric orbit|Heliocentric]]  
| orbit_periapsis       = 0.71 [[Astronomical unit|AU]]
| orbit_apoapsis        = 1.02 AU
| orbit_inclination     = 4.3°
| orbit_period          = 293 days
| apsis                 = helion

| interplanetary        = 
 {{Infobox spaceflight/IP
   |type                = lander_impact
   |note                = disintegrated
   |object              = [[Venus]]
   |arrival_date        = 18 October 1967, 04:34 GMT
   |location            = {{Venus coords and quad cat|19|N|38|E}} ([[Venus|Eisila]] region)
 }}

| programme             = [[Venera program|Venera]]
| previous_mission      = [[Kosmos 96]]
| next_mission          = [[Kosmos 167]]
}}

'''Venera 4''' ({{langx|ru|Венера-4|lit=Venus-4}}), also designated '''4V-1 No.310''', was a [[Space probe|probe]] in the Soviet [[Venera program]] for the exploration of [[Venus]]. The probe comprised a [[Lander (spacecraft)|lander]], designed to enter the [[Venusian atmosphere]] and parachute to the surface, and a carrier/[[Flyby (spaceflight)|flyby]] spacecraft, which carried the lander to Venus and served as a [[Transponder (satellite communications)|communications relay]] for it.

In 1967, it was the first successful probe to perform in-place analysis of the environment of another [[planet]]. Venera&nbsp;4 provided the first chemical analysis of the Venusian atmosphere, showing it to be primarily [[carbon dioxide]] with a few percents of [[nitrogen]] and below one percent of [[oxygen]] and water vapors. While entering the atmosphere it became the first spacecraft to [[Atmospheric entry|survive entry]] into another planet's atmosphere.{{sfn|Siddiqi|2018|p=1}} The station detected a weak [[Venus#Magnetic_field_and_core|magnetic field]] and no radiation field. The outer atmospheric layer contained very little hydrogen and no atomic oxygen.<ref>{{Cite web |title=NASA - NSSDCA - Spacecraft - Details |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1967-058A#:~:text=The%20probe%20measured%20an%20atmospheric,hydrogen%20at%209900%20km%20altitude. |access-date=2024-06-12 |website=nssdc.gsfc.nasa.gov |archive-date=14 May 2019 |archive-url=https://web.archive.org/web/20190514144526/https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1967-058A#:~:text=The%20probe%20measured%20an%20atmospheric,hydrogen%20at%209900%20km%20altitude. |url-status=dead }}</ref> The probe sent the first direct measurements proving that Venus was extremely hot, that its atmosphere was far denser than expected, and that it had lost most of its water long ago.

==Spacecraft==
[[File:Venera-4 capsule in museum.JPG|thumb|left|190px|A model of the 1-meter diameter landing capsule of Venera 4 on display at the Memorial Museum of Cosmonautics in Moscow.]]

The main carrier spacecraft 4 stood {{convert|3.5|m}} high, its solar panels spanned {{convert|4|m}} and had an area of {{convert|2.5|m2}}. The carrier spacecraft included a {{convert|2|m}} long [[magnetometer]], an ion detector, a cosmic ray detector and an [[Lyman-alpha forest|ultraviolet spectrometer]] capable of detecting hydrogen and oxygen gases. The devices were intended to operate until entry into the Venusian atmosphere. At that juncture, the station was designed to release the probe capsule and disintegrate. The rear part of the carrier spacecraft contained a liquid-fuel thruster capable of correcting the flight course. The flight program was planned to include two significant course corrections, for which purpose the station could receive and execute up to 127 different commands sent from the Earth.<ref name=harvey/>

The front part of the carrier spacecraft contained a nearly spherical landing capsule {{convert|1|m}} in diameter and weighing {{convert|383|kg}}. Compared to previous (failed) [[Venera program|Venera]] probes, the capsule contained an improved heat shield that could withstand temperatures up to {{convert|11000|C}}. Instead of the previous liquid-based cooling design, a simpler and more reliable gas system was installed.<ref name=v3>{{cite web|url=http://www.laspace.ru/rus/venera4.php|archive-url=https://web.archive.org/web/20140222000836/http://www.laspace.ru/rus/venera4.php|url-status=dead|archive-date=22 February 2014|access-date=19 October 2020|title=Venera 4|language=ru|website=NPO Lavochkina}}</ref> The durability of the capsule was checked by exposing it to high temperatures, pressures, and accelerations using three unique testing installations. The heat resistance was checked in a high-temperature vacuum system emulating the upper layers of the atmosphere.{{sfn|Ulivi|Harland|2007|pp=55–56}} The capsule was pressurized up to 25 atmospheres. (The surface pressure on Venus was unknown at the time. Estimates ranged from a few to hundreds of atmospheres).<ref>{{cite journal|author=Vakhnin, V. M. |year=1968|title=A Review of the Venera 4 Flight and Its Scientific Program|journal=J. Atmos. Sci.|volume=25|issue=4|pages=533–534|doi=10.1175/1520-0469(1968)025<0533:AROTVF>2.0.CO;2|bibcode=1968JAtS...25..533V|doi-access=free}}</ref> Finally, it was subjected to accelerations of up to 450 [[g-force|g]] in a centrifuge. The centrifuge test caused cracking of electronic components and cable brackets, which were replaced shortly before launch. The timing for the launch was rather tight, so as not to miss the [[launch window]] — the days of the year when the path to the destination planet from Earth is energetically least demanding.<ref>{{Cite web |title=What is a 'launch window'? |url=https://www.esa.int/Science_Exploration/Space_Science/What_is_a_launch_window |access-date=2024-06-12 |website=www.esa.int |language=en}}</ref><ref>{{Cite web |title=Projects |url=https://www.laspace.ru/en/activities/projects/venera-4/ |access-date=2024-06-12 |website=www.laspace.ru}}</ref>

The capsule could float in case of a water landing. Considering the possibility of such a landing, its designers made the lock of the capsule using sugar;<ref name=harvey/>{{sfn|Ulivi|Harland |2007|pp=55–56}}<ref>[https://web.archive.org/web/20090807234459/http://www.novosti-kosmonavtiki.ru/phpBB2/viewtopic.php?t=1424&highlight=&sid=5900d3fa070e9b19160a25cbcde8d6a4 Photo of the lock]. novosti-kosmonavtiki.ru, 18 February 2005.</ref> it was meant to dissolve in liquid water, releasing the transmitter antennas. The capsule contained a newly developed vibration-damping system, and its parachute could resist temperatures up to {{convert|450|C|K}}.{{sfn|Ulivi|Harland|2007|pp=55–56}}

The capsule contained an [[altimeter]], thermal control, a parachute and equipment for making atmospheric measurements. The latter included a [[thermometer]], [[barometer]], [[hydrometer]], altimeter and a set of gas analysis instruments. The data were sent by two transmitters at a frequency of 922 MHz and a rate of 1 bit/s; the measurements were sent every 48 seconds. The transmitters were activated by the parachute deployment as soon as the outside pressure reached {{convert|0.6|atm}}, which was thought to occur at the altitude about {{convert|26|km}} above the surface of the planet. The signals were received by several stations, including the [[Jodrell Bank Observatory]].<ref name=v3/><ref name=harvey/>

The capsule was equipped with a rechargeable battery with a capacity sufficient for 100 minutes of powering the measurement and transmitter systems. To avoid becoming discharged during the flight to Venus, the battery was kept charged using the solar panels of the carrier spacecraft. Before the launch, the entire Venera 4 station was sterilized to prevent possible biological contamination of Venus.<ref name=v3/>

==Mission==
Two nominally identical 4V-1 probes were launched in June 1967. The first probe, Venera 4, was launched on 12 June by a [[Molniya-M]] carrier rocket flying from the [[Baikonur Cosmodrome]].<ref name="LL">{{cite web|url=http://planet4589.org/space/log/launchlog.txt|title=Launch Log|first=Jonathan|last=McDowell|website=Jonathan's Space Page |access-date=11 April 2013}}</ref> A course correction was performed on 29 July when it was {{convert|12,000,000|km}} away from Earth; otherwise, the probe would have missed Venus. Although two such corrections had been planned, the first one was accurate enough and therefore the second correction was canceled. On 18 October 1967, the spacecraft entered the Venusian atmosphere with an estimated landing place near {{Venus coords and quad cat|19|N|38|E}}.<ref name=harvey/> The second probe, [[Kosmos 167]], was launched on 17 June but failed to depart low Earth orbit.<ref>{{Cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1967-063A|title=Cosmos 167|website=NASA Space Science Data Coordinated Archive}}</ref>

During entry into the Venusian atmosphere, the heat shield temperature rose to {{convert|11000|C}} and at one point the cabin deceleration reached 300 G.{{sfn|Ulivi|Harland|2007|p=63}} The descent lasted 93 minutes. The capsule deployed its parachute at an altitude of about {{convert|52|km}}, and started sending data on pressure, temperature and gas composition back to Earth. The temperature control kept the inside of the capsule at {{convert|−8|C}}. The temperature at {{convert|52|km}} was recorded as {{convert|33|C}}, and the pressure as less than {{convert|1|atm}}. At the end of the {{convert|26|km}} descent<!--after 26 km of descent?-->, the temperature reached {{convert|262|C}} and pressure increased to {{convert|22|atm}}, and the signal transmission terminated. The atmospheric composition was measured as 90–93% [[carbon dioxide]], 0.4–0.8% oxygen, 7% nitrogen and 0.1–1.6% water vapor.<ref name=harvey/> This data was crucial to the [[Venera 7]] design later on.

===Radar altimeter===
The altitude of the Venera probe relative to the surface was measured using a [[radar altimeter]] operating at 770 MHz. The altimeter had an integer ambiguity of {{convert|30|km}}: that is, the same radar signal would be given at an altitude of X, X plus {{convert|30|km}}, X plus {{convert|60|km}}, etc.<ref>{{cite web|last1=Mitchell|first1=Don P.|publisher=Mentallandscape|url=http://mentallandscape.com/V_Lavochkin1.htm|title=Plumbing the Atmosphere of Venus |year=2003|access-date=8 December 2017}}</ref> (an effect known as "[[aliasing]]"). At the time the distance of the cloud tops above the surface was not known, and due to this ambiguity, the first radar return, now believed to be at an actual altitude of about {{convert|55|km}}, was initially misinterpreted as {{convert|26|km}}. Therefore, based on the misinterpreted radar results, the Soviet team initially announced the probe descended to the surface.<ref>
{{cite journal|jstor=1723876 |pmid=17814841|year=1968|last1=Reese|first1=D. E.|last2=Swan|first2=P. R.|s2cid=32723831|title=Venera 4 probes atmosphere of venus|journal=Science|volume=159|issue=3820|pages=1228–30|doi=10.1126/science.159.3820.1228|bibcode=1968Sci...159.1228R}}</ref><ref>{{Cite journal|doi=10.1175/1520-0469(1968)025<0533:AROTVF>2.0.CO;2|year=1968|volume=25|pages=533–534|title=A Review of the Venera 4 Flight and Its Scientific Program|last1=Vakhnin|first1=V. M.|journal=Journal of the Atmospheric Sciences|issue=4|bibcode=1968JAtS...25..533V|doi-access=free}}</ref> This result was quickly dismissed as inconsistent with the planetary diameter measured by radar,<ref>{{cite journal|pmid=17768889|year=1968|last1=Ash|first1=M. E.|last2=Campbell|first2=D. B.|last3=Dyce|first3=R. B.|last4=Ingalls|first4=R. P.|last5=Jurgens|first5=R.|last6=Pettengill|first6=G. H.|last7=Shapiro|first7=I. I.|last8=Slade|first8=M. A.|last9=Thompson|first9=T. W.|s2cid=128460735|title=The case for the radar radius of venus|journal=Science|volume=160|issue=3831|pages=985–7|doi=10.1126/science.160.3831.985|bibcode=1968Sci...160..985A}}</ref><ref>{{cite journal|pmid=17736042 |year=1968 |last1=Eshleman |first1=V. R. |last2=Fjeldbo |first2=G. |last3=Anderson |first3=J. D. |last4=Kliore |first4=A. |last5=Dyce |first5=R. B. |s2cid=24923659 |title=Venus: Lower atmosphere not measured |journal=Science |volume=162 |issue=3854 |pages=661–5 |doi=10.1126/science.162.3854.661 |bibcode=1968Sci...162..661E }}</ref> and the pressure readings by the capsule were much lower than predicted by the recently developed models of the Venus atmosphere.<ref name=v3/>{{sfn|Ulivi|Harland|2007|pp=55–56}}

===Analysis===
The ''Venera 4'' data was analyzed together with the data of the ''[[Mariner 5]]'' probe, under a combined Soviet–American working group of [[COSPAR]] in 1969,<ref>{{cite journal|doi=10.1016/0019-1035(69)90052-9|author=[[Carl Sagan]]|date=September 1969|title=The COSPAR Meetings in Prague|journal=[[Icarus (journal)|Icarus]]|volume=11|issue=2|pages=268–272|bibcode=1969Icar...11..268S }}</ref><ref>{{cite conference |title=Report on the Activities of the COSPAR Working Group VII |page=94 |date=11–24 May 1969 |location=Prague, Czechoslovakia |book-title=Preliminary Report, COSPAR Twelfth Plenary Meeting and Tenth International Space Science Symposium |publisher=[[National Academy of Sciences]]}}</ref> an organization of early space cooperation,<ref>{{cite web |author=Sagdeev, Roald |author2=Eisenhower, Susan |date=28 May 2008 |title=United States-Soviet Space Cooperation during the Cold War |url=http://www.nasa.gov/50th/50th_magazine/coldWarCoOp.html |access-date=19 July 2009 |archive-date=25 December 2018 |archive-url=https://web.archive.org/web/20181225032051/https://www.nasa.gov/50th/50th_magazine/coldWarCoOp.html |url-status=dead }}</ref> allowing a more complete drawing of the profile of the [[atmosphere of Venus]].

==Achievements==
For the first time, ''[[in situ]]'' analysis of the atmosphere of another planet was performed and the data sent back to Earth; the analysis included chemical composition, temperature, and pressure. The measured ratio of [[carbon dioxide]] to [[nitrogen]] of about 13 corrected the previous estimates so much (an inverse ratio was expected in some quarters) that some scientists contested the observations. The main station detected no radiation belts; relative to Earth, the measured magnetic field was 3000 times weaker, and the hydrogen [[Stellar corona|corona]] was 1000 times less dense. No atomic oxygen was detected. All the data suggested that water, if it had been present, had leaked from the planet long before. This conclusion was unexpected considering the thick Venusian clouds. Because of the negligible humidity, the sugar lock system, employed on Venera 4 in case of a water landing, was abandoned in subsequent Venus probes.<ref name=v3/><ref name=harvey/>

The mission was considered a complete success, especially given several previous failures of Venera probes.<ref name=v3/> Although the Venera 4 design did allow for data transmission after landing, the Venera 3–6 probes were not built to withstand the pressures at the Venusian surface. The first successful soft landing on Venus was achieved by [[Venera 7]] in 1970.{{sfn|Siddiqi|2018|p=3}} 

The people at program had realized that instead of a smoother, faster descent through the atmosphere like on Earth, the probe hit the atmosphere at incredible speeds yet quickly slowed to about 18kph (11.2mph) in mere seconds. This combined with knowledge learned on Venera 4 (22 bar atmosphere) meant that they had no time to waste once descent into Venus began. This realization paved the way for Venera 5,6,etc.

==See also==
* [[List of missions to Venus]]

==References==
<references>

<ref name=harvey>{{cite book|title=Russian planetary exploration|first1=Brian|last1=Harvey|url=https://books.google.com/books?id=jKmIclMIwPAC&pg=PA101|publisher=Springer|year=2007|isbn=978-0-387-46343-8|pages=98–101}}</ref>

</references>

==Cited sources==
{{Commons category|Venera 4}}
* {{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 A. |lccn=2017059404|isbn=9781626830424|publisher=NASA|edition=second|year=2018|id=SP2018-4041|series=The NASA history series|location=Washington, D.C.}}
* {{cite book|url=https://books.google.com/books?id=Fi1mCYJWBwAC&pg=PA63|title=Robotic Exploration of the Solar System: The golden age 1957–1982|first1=Paolo|last1=Ulivi|first2=David Michael |last2=Harland|publisher=Springer|year= 2007|isbn=978-0-387-49326-8}}

{{Venera}}
{{Orbital launches in 1967}}
{{Venus spacecraft}}
{{DEFAULTSORT:Venera 04}}

[[Category:Venera program]]
[[Category:Derelict landers (spacecraft)]]
[[Category:Spacecraft launched in 1967]]
[[Category:1967 in the Soviet Union]]
[[Category:4V-1]]