View source for Vega 2

{{Short description|Soviet mission to Venus and Halley's Comet (1984–1987)}}
{{Infobox spaceflight
| name                  = Vega 2
| names_list            = Venera–Halley 2

<!--image of the spacecraft/mission-->
| image                 = Vega model - Udvar-Hazy Center.JPG
| image_caption         = A replica of the ''[[Vega program|Vega]]'' spacecraft displayed at the [[Steven F. Udvar-Hazy Center|Udvar-Hazy Center]], Virginia, US
| image_size            = 300px

<!--Basic details-->
| mission_type          = [[Venus]]/[[Halley's Comet|Halley]] exploration
| operator              = Soviet space program
| COSPAR_ID             = {{cospar|1984-128A}}<br>{{cospar|1984-128E}}<br>{{cospar|1984-128F}}
| SATCAT                = 15449<br>15856<br>15857
| mission_duration      = Lander: 56 minutes<br>Balloon: {{time interval|15 Jun 1985|17 Jun 1985}}<br/> Flyby: {{time interval|21 Dec 1984|24 Mar 1987}}

<!--Spacecraft properties-->
| spacecraft            = 5VK No. 902
| spacecraft_type       = [[5VK]]
| manufacturer          = [[NPO Lavochkin]]
| launch_mass           = {{convert|4840|kg|abbr=on}}<ref name=beyond/>
| landing_mass          = {{convert|1520|kg|lb|abbr=on}}
| dimensions            = {{convert|2.7|x|2.3|x|5.7|m|ft|abbr=on}} (lander)

<!--Launch details-->
| launch_date           = {{start date|1984|12|21}}, 09:13:52 UTC<ref name=beyond/>
| launch_rocket         = [[Proton-K]]/[[Blok D|D]]
| launch_site           = [[Baikonur Cosmodrome|Baikonur]] [[Baikonur Cosmodrome Site 200|200/40]]
| launch_contractor     = [[Khrunichev State Research and Production Space Center|Khrunichev]]

<!--end of mission-->
| last_contact          = March 24, 1987<ref name=beyond/>

<!--orbit parameters-->
<!--as science-related articles, SI units should be the principal units of measurement, however we usually use {{convert}} to display imperial units in parentheses after the initial values-->
| orbit_reference       = [[Heliocentric orbit|Heliocentric]]
| orbit_eccentricity    = 0.17
| orbit_periapsis       = 0.70 AU
| orbit_apoapsis        = 0.98 AU
| orbit_inclination     = 51.5°
| orbit_period          = 281 days
| apsis                 = helion

|interplanetary         = <!--Infobox spaceflight/IP can be called multiple times for missions with multiple targets or combined orbiter/lander missions, etc-->
 {{Infobox spaceflight/IP
   |type                = flyby
   |object              = [[Venus]]
   |arrival_date        = June 15, 1985
   |distance            = {{convert|24,500|km|mi|abbr=on}}
 }}

 {{Infobox spaceflight/IP
   |type                = atmospheric
   |object              = [[Venus]]
   |component           = Vega 2 ''Balloon''
   |arrival_date        = 02:06:04, June 15, 1985
 }}

 {{Infobox spaceflight/IP
   |type                = lander
   |object              = [[Venus]]
   |component           = Vega 2 ''Lander''
   |arrival_date        = 03:00:50, June 15, 1985
   |location            = {{coord|8.5|S|164.5|E|globe:Venus|name=Vega 2}}
 }}

 {{Infobox spaceflight/IP
   |type                = flyby
   |object              = [[Halley's Comet|1P/Halley]]
   |arrival_date        = March 9, 1986
   |distance            = ~{{convert|8,030|km|mi|abbr=on}}
 }}

<!--Only use where a spacecraft/mission is part of a clear programme of sequential missions.
If in doubt, leave it out-->
| programme2            = '''[[Vega program]]'''
| programme             = '''[[Halley Armada]]'''
| previous_mission      = [[Vega 1]]
| next_mission          = [[Sakigake]]

<!--mission insignia or patch-->
| insignia              = 1986 venera galley nh.jpg
| insignia_size         = 100px
}}

'''Vega 2''' (along with [[Vega 1]]) was a [[Soviet Union|Soviet]] [[space probe]] part of the [[Vega program]] to explore [[Halley's Comet]] and [[Venus]]. The spacecraft was a development of the earlier ''[[Venera]]'' craft. The name VeGa (ВеГа) combines the first two letters of the Russian words for Venus (Венера: "Venera") and Halley (Галлея: "Galleya"). They were designed by [[Babakin Space Centre]] and constructed as '''[[5VK]]''' by [[Lavochkin]] at [[Khimki]]. The craft was powered by large twin [[Photovoltaic module|solar panel]]s. Instruments included an [[radio telescope|antenna]] dish, [[camera]]s, [[spectrometer]], [[infrared]] sounder, [[magnetometer]]s (MISCHA) and [[Plasma (physics)|plasma]] probes. The {{convert|4,840|kg|lb}} craft was launched on top of a [[Proton-K]] from [[Baikonur Cosmodrome]], [[Tyuratam]], [[Kazakh SSR]]. Both Vega 1 and 2 were [[three-axis stabilized]] spacecraft. The spacecraft were equipped with a dual bumper shield for dust protection from Halley's Comet.

== Venus mission ==
The descent module arrived at Venus on 15 June 1985, two days after being released from the Vega 2 flyby probe. The module, a {{convert|1500|kg|lb}}, {{convert|240|cm|ft}} diameter sphere, contained a surface lander and a [[balloon]] explorer. The flyby probe performed a [[gravity assist|gravitational assist]] maneuver using Venus, and continued its mission to intercept the comet.<ref name=nssdc1/>

===Lander===
The surface lander was identical to that of Vega 1 as well as the previous six ''[[Venera]]'' missions. The objective of the probe was the study of the atmosphere and the exposed surface of the planet. The scientific payload included a UV spectrometer, temperature and pressure sensors, a water concentration meter, a [[Gas-liquid chromatography|gas-phase chromatograph]], an [[X-ray]] [[spectrometer]], a [[mass spectrometer]], and a surface sampling device. Several of these scientific tools (the UV spectrometer, the mass spectrograph, and the devices to measure pressure and temperature) were developed in collaboration with French scientists.<ref name=nssdc1/>  Since the probe made a nighttime landing, no images were taken.

The Vega 2 lander touched down at 03:00:50 UT on 15 June 1985 at around {{Venus coords and quad cat|7.14|S|177.67|E}}, in the northern region of  [[Aphrodite Terra]]. The altitude of the touchdown site was {{convert|0.1|km|ft}} above the planetary mean radius. The measured pressure at the landing site was 91 [[atmosphere (unit)|atm]] and the temperature was {{convert|736|K}}. The surface sample was found to be an [[anorthosite]]–[[troctolite]] rock, rarely found on Earth, but present in the [[lunar highlands]], leading to the conclusion that the area was probably the oldest explored by any Venera vehicle. It transmitted data from the surface for 56 minutes.<ref name=nasa1/>

===Balloon===
[[File:Russian "Vega" balloon mission to Venus on display at the Udvar-Hazy museum.jpg|thumb|Vega balloon probe on display at the [[Steven F. Udvar-Hazy Center|Udvar-Hazy Center]] of the Smithsonian Institution.]]

The Vega 2 Lander/Balloon capsule entered the Venusian atmosphere ({{convert|125|km|disp=sqbr}} altitude) at 02:06:04 UT (Earth received time; Moscow time 05:06:04) on 15 June 1985 at roughly {{convert|11|km/s}}. At approximately 2:06:19 UT the parachute attached to the landing craft cap opened at an altitude of {{convert|64|km}}. The cap and parachute were released 15 seconds later at {{convert|63|km}} altitude. The balloon package was pulled out of its compartment by parachute 40 seconds later at {{convert|61|km}} altitude, at 7.45 degrees S, 179.8 degrees east. A second parachute opened at an altitude of {{convert|55|km}}, 200 seconds after entry, extracting the furled balloon.

The balloon was inflated 100 seconds later at {{convert|54|km}} and the parachute and inflation system were jettisoned. The ballast was jettisoned when the balloon reached roughly {{convert|50|km}} and the balloon floated back to a stable height between {{convert|53|and|54|km}} some 15 to 25 minutes after entry. The mean stable height was {{convert|53.6|km}}, with a pressure of {{convert|535|mbar}} and a temperature of {{convert|308-316|K}} in the middle, most active layer of the Venus three-tiered cloud system. The balloon drifted westward in the zonal wind flow with an average speed of about {{convert|66|m/s}} at nearly constant latitude. The probe crossed the terminator from night to day at 9:10 UT on 16 June after traversing {{convert|7400|km}}. The probe continued to operate in the daytime until the final transmission was received at 00:38 UT on 17 June from 7.5 S, 76.3 E after a total traverse distance of {{convert|11100|km}}, about 29% of the planet's circumference. It is not known how much further the balloon traveled after the final communication.<ref name=nasa1/>

== Halley mission ==
After their encounters, the Vegas' motherships were redirected by Venus's gravity to intercept [[Halley's Comet]].

The spacecraft initiated its encounter on March 7, 1986, by taking 100 photos of the comet from a distance of {{convert|14,000,000|km|mi}}.

Vega 2 made its closest approach at 07:20 UT on March 9, 1986, at {{convert|8,030|km|mi}}. The data intensive examination of the comet covered only the three hours around closest approach. They were intended to measure the physical parameters of the nucleus, such as dimensions, shape, temperature and surface properties, as well as to study the structure and dynamics of the [[Coma (cometary)|coma]], the gas composition close to the nucleus, the dust particles' composition and mass distribution as functions of distance to the nucleus and the cometary-[[solar wind]] interaction.

During the encounter, Vega 2 took 700 images of the comet, with better resolution than those from the twin [[Vega 1]], partly due to the presence of less dust outside the coma at the time. Yet Vega 2 recorded an 80% power loss during the encounter as compared to Vega 1's 40%.

After further imaging sessions on 10 and 11 March 1986, Vega 2 finished its primary mission.

== Post Halley==

A 6 million kilometer distant flyby of [[2101 Adonis]] was considered, however, Vega 2 didn't have enough fuel left to make the necessary orbital changes for the flyby.<ref name=Ulivi90 /> Instead the Vega probes took the opportunity to measure the dust as they passed through the orbits of [[72P/Denning–Fujikawa]], [[Biela's Comet]] and [[289P/Blanpain]].<ref name=Ulivi90/>

Contact with Vega 2 was lost on 24 March 1987.<ref name=Ulivi90 /> Vega 1 had previously exhausted its [[Spacecraft attitude control|attitude control]] propellant on 30 January 1987.<ref name=Ulivi90/>

Vega 2 is currently in [[heliocentric orbit]], with [[Periapsis|perihelion]] of 0.70 [[Astronomical unit|AU]], [[Apoapsis|aphelion]] of 0.98 AU, [[Orbital eccentricity|eccentricity]] of 0.17, [[Orbital inclination|inclination]] of 2.3 degrees and [[orbital period]] of 281 days. {{citation needed|date=October 2024}}

==See also==
{{Portal|Spaceflight}}
*[[List of missions to Venus]]

== References ==
<references>
<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= 978-1-626-83043-1 }}
</ref>

<ref name="nasa1">{{Cite web
| url= https://solarsystem.nasa.gov/missions/vega-2/in-depth/
| title= In Depth: Vega 2
| website= solarsystem.nasa.gov
| publisher= [[NASA]]
| access-date= 14 April 2015 }}
</ref>

<ref name="nssdc1">{{cite web
| url= https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1984-128A
| title= Vega 2
| website= nssdc.gsfc.nasa.gov
| publisher= [[NASA]]
| access-date= 22 July 2024
| archive-date= 15 November 2017
| archive-url= https://web.archive.org/web/20171115160634/https://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1984-128A
| url-status= dead
}}</ref>

<ref name=Ulivi90>{{cite book
| author1= Paolo Ulivi
| author2= David M. Harland
| date= 2009
| title= Robotic Exploration of the Solar System Part II: Hiatus and Renewal 
| publisher= Springer
| pages= 90–92
| isbn= 978-0-387-78904-0 }}
</ref>
</references>

==External links==
*[https://web.archive.org/web/20061004051358/http://solarsystem.nasa.gov/missions/profile.cfm?MCode=Vega_02 Vega 2 Measuring Mission Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
*[http://arc.iki.rssi.ru/IPL/vega.html Vega mission images from the Space Research Institute (IKI)]
*[https://web.archive.org/web/20070311040927/http://starbase.jpl.nasa.gov/archive/vega2-c-tvs-5-rdr-halley-transform-v1.0/hal_0026/ Raw data from Vega 1 and Vega 2 on board instruments]
*[http://www.mentallandscape.com/V_Vega.htm Soviet Exploration of Venus]
* [https://pdssbn.astro.umd.edu/data_sb/missions/vega2/index.shtml ''Vega 2'' Mission Comet Halley Data Archive] at the NASA Planetary Data System, Small Bodies Node

{{Venus spacecraft}}
{{Comet spacecraft}}
{{Orbital launches in 1984}}

[[Category:Missions to Halley's Comet]]
[[Category:Vega program]]
[[Category:Derelict satellites in heliocentric orbit]]
[[Category:1984 in spaceflight]]
[[Category:1984 in the Soviet Union]]
[[Category:Derelict space probes]]
[[Category:France–Soviet Union relations]]
[[Category:Extraterrestrial aircraft]]
[[Category:Spacecraft launched in 1984]]
[[Category:Extraterrestrial atmosphere entry]]