The Vega program was a series of Venus

Venus

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

 missions which also took advantage of the appearance of Comet Halley

Comet Halley

Halley's Comet or Comet Halley is the best-known of the short-period comets, and is visible from Earth every 75 to 76 years. Halley is the only short-period comet that is clearly visible to the naked eye from Earth, and thus the only naked-eye comet that might appear twice in a human lifetime...

 in 1986. Vega 1

Vega 1

Vega 1 is a Soviet space probe part of the Vega program. The spacecraft was a development of the earlier Venera craft...

 and Vega 2

Vega 2

Vega 2 is a Soviet space probe part of the Vega program. The spacecraft was a development of the earlier Venera craft. They were designed by Babakin Space Center and constructed as 5VK by Lavochkin at Khimki...

 were unmanned spacecraft

Spacecraft

A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....

 launched in a cooperative effort among the Soviet Union

Soviet Union

The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

 (who provided the spacecraft and launch vehicle) and Austria

Austria

Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...

, Bulgaria

Bulgaria

Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...

, Hungary

Hungary

Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...

, the German Democratic Republic

German Democratic Republic

The German Democratic Republic , informally called East Germany by West Germany and other countries, was a socialist state established in 1949 in the Soviet zone of occupied Germany, including East Berlin of the Allied-occupied capital city...

, Poland

Poland

Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

, Czechoslovakia

Czechoslovakia

Czechoslovakia or Czecho-Slovakia was a sovereign state in Central Europe which existed from October 1918, when it declared its independence from the Austro-Hungarian Empire, until 1992...

, France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, and the Federal Republic of Germany

West Germany

West Germany is the common English, but not official, name for the Federal Republic of Germany or FRG in the period between its creation in May 1949 to German reunification on 3 October 1990....

 in December 1984. They had a two-part mission to investigate Venus

Venus

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

 and also flyby Halley's Comet.

The flyby of Halley's Comet had been a late mission change in the Venera

Venera

The Venera series probes were developed by the Soviet Union between 1961 and 1984 to gather data from Venus, Venera being the Russian name for Venus...

 program following on from the cancellation of the US Halley mission in 1981. A later Venera mission was cancelled and the Venus part of the Vega 1 mission was reduced. Because of this, the craft was designated Vega, a contraction of "Venera" and "Gallei" (Russian words for "Venus" and "Halley", respectively). The spacecraft design was based on the previous Venera 9

Venera 9

Venera 9 was a USSR unmanned space mission to Venus. It consisted of an orbiter and a lander. It was launched on June 8, 1975 02:38:00 UTC and weighed 4,936 kg...

 and Venera 10

Venera 10

Venera 10 was a USSR unmanned space mission to Venus. It consisted of an orbiter and a lander. It launched on June 14, 1975 03:00:31 UTC.-Orbiter:The orbiter entered Venus orbit on October 23, 1975...

 missions.

The two spacecraft were launched on December 15 and December 21, 1984, respectively. With their redesignated dual missions, the Vega probes became part of the Halley Armada

Halley Armada

The Halley Armada is the generally accepted and popularly used name of five space probes sent to examine Halley's Comet during its 1986 sojourn through the inner solar system, connected with apparition "1P/1982 U1"...

, a group of space probes that studied Halley's Comet during its 1985/86 perihelion.

The Vega spacecraft

Vega 1 and 2 were identical sister ships. The spacecraft was a development of the earlier Venera

Venera

The Venera series probes were developed by the Soviet Union between 1961 and 1984 to gather data from Venus, Venera being the Russian name for Venus...

craft. They were designed by Babakin Space Center and constructed as 5VK by Lavochkin

Lavochkin

NPO Lavochkin is a Russian aerospace company. It is a major player in the Russian space program, being the developer and manufacturer of the Fregat upper stage, as well as interplanetary probes such as Phobos Grunt...

 at Khimki

Khimki

Khimki is a city in Moscow Oblast, Russia, situated just northwest of Moscow, at the west bank of the Moscow Canal. Population: 207,125 ; 141,000 ; 106,000 ; 23,000 .-History:...

. The craft was powered by twin large solar panels and instruments included an antenna dish, cameras, spectrometer, infrared sounder, magnetometer

Magnetometer

A magnetometer is a measuring instrument used to measure the strength or direction of a magnetic field either produced in the laboratory or existing in nature...

s (MISCHA), and plasma probes. The 4,920 kg craft was launched by a Proton 8K82K rocket

Proton rocket

Proton is an expendable launch system used for both commercial and Russian government space launches. The first Proton rocket was launched in 1965 and the launch system is still in use as of 2011, which makes it one of the most successful heavy boosters in the history of spaceflight...

 from Baikonur Cosmodrome

Baikonur Cosmodrome

The Baikonur Cosmodrome , also called Tyuratam, is the world's first and largest operational space launch facility. It is located in the desert steppe of Kazakhstan, about east of the Aral Sea, north of the Syr Darya river, near Tyuratam railway station, at 90 meters above sea level...

, Tyuratam

Tyuratam

Tyuratam is a station on the main Moscow to Tashkent railway, located in Kazakhstan. The name is a word in the Kazakh language and means "Töre's grave"; Töre, or more formally, Töre-Baba, was a noble, a descendant of Genghis Khan...

, Kazakh SSR

Kazakh SSR

The Kazakh Soviet Socialist Republic , also known as the Kazakh SSR for short, was one of republics that made up the Soviet Union.At in area, it was the second largest constituent republic in the USSR, after the Russian SFSR. Its capital was Alma-Ata . Today it is the independent state of...

. 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.

Bus Instruments

1. imaging system
2. infrared spectrometer
3. ultraviolet, visible, infrared imaging spectrometer
4. shield penetration detector
5. dust detectors
6. dust mass spectrometer
7. neutral gas mass spectrometer
8. APV-V plasma energy analyzer
9. energetic-particle analyzer
10. magnetometer
11. wave and plasma analyzers

The Venus mission

Vega 1 arrived at Venus on June 11, 1985 and Vega 2 on June 15, 1985, and each delivered a 1,500 kg, 240 cm diameter spherical descent unit. The units were released some days before each arrived at Venus and entered the atmosphere without active inclination changes. Each contained a lander and a balloon explorer.

Descent craft

The landers were identical to that of the previous five Venera

Venera

The Venera series probes were developed by the Soviet Union between 1961 and 1984 to gather data from Venus, Venera being the Russian name for Venus...

missions and were to study the atmosphere and surface, each had instruments to study temperature, pressure, a UV spectrometer, a water concentration meter, a gas-phase chromatograph

Gas-liquid chromatography

Gas chromatography , is a common type of chromatography used in analytical chemistry for separating and analysing compounds that can be vaporized without decomposition. Typical uses of GC include testing the purity of a particular substance, or separating the different components of a mixture...

, an X-ray

X-ray

X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

 spectrometer

Spectrometer

A spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization...

, a mass spectrometer and a surface sampling device.

The Vega 1 lander's surface experiments were inadvertently activated at 20 km from the surface by an especially hard wind jolt, and so failed to provide results. It landed at 7.5°N, 177.7°E.

The Vega 2 lander touched down at 03:00:50 UT on 15 June 1985 at 8.5° S, 164.5° E, in eastern Aphrodite Terra

Aphrodite Terra

Aphrodite Terra is a highland region on Venus, near the equator. It is about the same size as Africa, and much rougher than Ishtar Terra.The surface appears buckled and fractured which suggests large compressive forces. There are also numerous extensive lava flows. Channels cross this terrain and...

. The altitude of the touchdown site was 0.1 km above the planetary mean radius. The measured pressure at the landing site was 91 atm and the temperature was 736 K. The surface sample was found to be an anorthosite

Anorthosite

Anorthosite is a phaneritic, intrusive igneous rock characterized by a predominance of plagioclase feldspar , and a minimal mafic component...

-troctolite

Troctolite

Troctolite is a mafic intrusive rock type. It consists essentially of major but variable amounts of olivine and calcic plagioclase along with variable minor pyroxene. It is an olivine-rich, pyroxene-depleted relative of gabbro. However, unlike gabbro, no troctolite corresponds in composition to a...

. It transmitted data from the surface for 56 minutes.

Payload

• Meteocomplex T,P sensors
• Sigma-3 gas chromatograph
• LSA particle size spectrometer
• IFP aerosol analyser
• VM-4 hygrometer
• ISAV-A nephelometer / scatterometer
• Malakhit-V mass spectrometer
• ISAV-S UV spectrometer
• GZU VB-02 drill + BDRP-AM25 soil X-ray fluorescence spectrometer
• GS-15-STsV gamma ray spectrometer
• PrOP-V penetrometer
• MSB small solar batteries

Balloon

The two balloon aerobot

Aerobot

An aerobot is an aerial robot, usually used in the context of an unmanned space probe or unmanned aerial vehicle.While work has been done since the 1960s on robot "rovers" to explore the Moon and other worlds in the Solar system, such machines have limitations...

s were designed to float at 54 km from the surface, in the most active layer of the Venusian cloud system. The instrument pack had enough battery power for sixty hours of operation and measured temperature, pressure, wind speed and aerosol density. Both Vega-1 and Vega-2 balloons operated for more than 46 hrs from injection to the final transmission.

The balloons were spherical superpressure types with a diameter of 3.54 metres (11.6 ft) and filled with helium

Helium

Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...

. A gondola assembly weighing 6.9 kilograms (15.2 pounds) and 1.3 meters (4.26 ft) long was connected to the balloon envelope by a tether 13 metres (42.6 ft) long. Total mass of the entire assembly was 21 kilograms (46 pounds).

The top section of the gondola assembly was capped by a conical antenna 37 centimetres (14.6 inches) tall and 13 centimetres (5 ¹⁄₈ inches) wide at the base. Beneath the antenna was a module containing the radio transmitter and system control electronics. The lower section of the gondola assembly carried the instrument payload and batteries.

The instruments consisted of:

• An arm carrying thin-film resistance thermometers and a velocity anemometer
  Anemometer
  An anemometer is a device for measuring wind speed, and is a common weather station instrument. The term is derived from the Greek word anemos, meaning wind, and is used to describe any airspeed measurement instrument used in meteorology or aerodynamics...
  
  . The anemometer consisted of a free-spinning plastic propeller whose spin was measured by LED
  LEd
  LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....
  
  -photodetector optointerrupters.
• A module containing a PIN diode
  PIN diode
  A PIN diode is a diode with a wide, lightly doped 'near' intrinsic semiconductor region between a p-type semiconductor and an n-type semiconductor region. The p-type and n-type regions are typically heavily doped because they are used for ohmic contacts....
  
   photodetector
  Photodetector
  Photosensors or photodetectors are sensors of light or other electromagnetic energy. There are several varieties:*Active pixel sensors are image sensors consisting of an integrated circuit that contains an array of pixel sensors, each pixel containing a both a light sensor and an active amplifier...
  
   to measure light levels and a vibrating quartz
  Quartz
  Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
  
   beam pressure sensor
  Pressure sensor
  A pressure sensor measures pressure, typically of gases or liquids. Pressure is an expression of the force required to stop a fluid from expanding, and is usually stated in terms of force per unit area. A pressure sensor usually acts as a transducer; it generates a signal as a function of the...
  
  .
• A package at the bottom carrying the batteries and a nephelometer
  Nephelometer
  A nephelometer is a stationary or portable instrument for measuring suspended particulates in a liquid or gas colloid. A nephelometer measures suspended particulates by employing a light beam and a light detector set to one side of the source beam. Particle density is then a function of the...
  
   to measure cloud density through light reflection.

The small low-power transmitter only allowed a data transmission rate of 2,048 bits per second, though the system performed data compression to squeeze more information through the narrow bandwidth. Nonetheless, the sampling rate for most of the instruments was only once every 75 seconds. The balloons were tracked by two networks of 20 radio telescopes in total back on Earth: the Soviet network, coordinated by the USSR Academy of Sciences and the international network, coordinated by CNES

CNES

The is the French government space agency . Established under President Charles de Gaulle in 1961, its headquarters are located in central Paris and it is under the supervision of the French Ministries of Defence and Research...

.

The balloons were dropped onto the planet's darkside and deployed at an altitude of about 50 kilometres (31.1 mi). They then floated upward a few kilometres to their equilibrium altitude. At this altitude, pressure and temperature conditions of Venus are similar to those of Earth, though the planet's winds moved at hurricane velocity and the carbon dioxide

Carbon dioxide

Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 atmosphere is laced with sulfuric acid

Sulfuric acid

Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

, along with smaller concentrations of hydrochloric

Hydrochloric acid

Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....

 and hydrofluoric acid

Hydrofluoric acid

Hydrofluoric acid is a solution of hydrogen fluoride in water. It is a valued source of fluorine and is the precursor to numerous pharmaceuticals such as fluoxetine and diverse materials such as PTFE ....

.

The balloons moved swiftly across the night side of the planet into the light side, where their batteries finally ran down and contact was lost. Tracking indicated that the motion of the balloons included a surprising vertical component, revealing vertical motions of air masses that had not been detected by earlier probe missions.

The Halley mission

After their encounters, the Vegas' motherships were redirected by Venus' gravity to intercept Comet Halley.

Vega 1 made its closest approach on March 6, around 8,890 km from the nucleus, and Vega 2 made its closest approach on March 9 at 8,030 km. 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

Coma (cometary)

frame|right|The [[153P/Ikeya-Zhang|comet Ikeya-Zhang]] exhibiting a bright, condensed coma In astronomy, a coma is the nebulous envelope around the nucleus of a comet. It is formed when the comet passes close to the Sun on its highly elliptical orbit; as the comet warms, parts of it sublimate...

, 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

Solar wind

The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...

 interaction.

In total Vega 1 and Vega 2 returned about 1,500 images of Comet Halley. Spacecraft operations were discontinued a few weeks after the Halley encounters.

The on-board TV system was created in international cooperation of the scientific and industrial facilities from the USSR, Hungary

Hungary

Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...

, France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 and Czechoslovakia

Czechoslovakia

Czechoslovakia or Czecho-Slovakia was a sovereign state in Central Europe which existed from October 1918, when it declared its independence from the Austro-Hungarian Empire, until 1992...

. TV data were processed by international team, including the USSR, Hungary, France, GDR and USA scientists. The basic steps of data acquisition and preprocessing were performed in IKI

Russian Space Research Institute

The Russian Space Research Institute is the leading organization of the Russian Academy of Sciences on space exploration to benefit fundamental science....

 using the image processing computer system, based on PDP11/40 compatible host.

Vega 1 and 2 are currently in heliocentric orbit

Heliocentric orbit

A heliocentric orbit is an orbit around the Sun. All planets, comets, and asteroids in our Solar System are in such orbits, as are many artificial probes and pieces of debris. The moons of planets in the Solar System, by contrast, are not in heliocentric orbits as they orbit their respective planet...

s.

External links

• RSSI.ru, Vega mission images from the Space Research Institute (IKI)
• NASAN.gov, Raw data from Vega 1 and Vega 2 on board instruments
• MentalLandscape.com, Soviet Exploration of Venus
• Harvard.edu, The Vega balloons - A tool for studying atmosphere dynamics on Venus