Vega 1 (along with its twin Vega 2) was 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 Centre The Babakin Science and Research Space Centre (russian: Научно-испытательный центр имени Г.Н. Бабакина) is a division of the Lavochkin Design Bureau based in Khimki, Russia. It is managed by them on behalf of ...

and constructed as

5VK The 5VK planetary probe (short for 5th-generation Venus-Comet probe) is a designation for a common design used for Soviet unmanned probes to comet 1P/Halley and Venus. It was an incremental improvement of earlier 4MV probes used for Mars and Venu ...

by Lavochkin at

Khimki Khimki ( rus, Химки, p=ˈxʲimkʲɪ) is a city in Moscow Oblast, Russia, 18.25 kilometres northwest of central Moscow, and immediately beyond the Moscow city boundary. History Origins and formation Khimki was initially a railway station tha ...

. The name VeGa (ВеГа) combines the first two letters from the Russian words for Venus (Венера: "Venera") and Halley (Галлея: "Galleya"). The craft was powered by twin large solar panels and instruments included an antenna dish, cameras,

spectrometer A spectrometer () is a scientific instrument used to separate and measure spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where the ...

, infrared sounder,

magnetometer A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, o ...

s (MISCHA), and plasma probes. The 4,840 kg craft was launched by a Proton 8K82K rocket from

Baikonur Cosmodrome The Baikonur Cosmodrome ( kk, Байқоңыр ғарыш айлағы, translit=Baiqoñyr ğaryş ailağy, ; russian: Космодром Байконур, translit=Kosmodrom Baykonur, ) is a spaceport in an area of southern Kazakhstan leased to R ...

, Tyuratam, Kazakh SSR. Both Vega 1 and 2 were

three-axis stabilized Spacecraft attitude control is the process of controlling the orientation of a spacecraft (vehicle/satellite) with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, et ...

spacecraft. The spacecraft were equipped with a dual bumper shieldV. A. Agureikin, S. I. Anisimov, A. V. Bushman, G. I. Kanel', V. P. Karyagin, A. B. Konstantinov, B. P. Kryukov, V. F. Minin, S. V. Razorenov, R. Z. Sagdeev, S. G. Sugak, V. E. Fortov, (1984). "Thermo-physical and gas-dynamic studies of the meteorite shield for the Vega spacecraft". ''High Temperature'' 761-778 22(5). Wo
A1984ALC5000020
Scopu
2-s2.0-0021489019
/ref> for dust protection from Halley's comet.

Venus mission

The descent module arrived at Venus on 11 June 1985, two days after being released from the Vega 1 flyby probe. The module, a 1500-kg sphere with a diameter of 240 cm, contained a surface lander and a balloon explorer. The flyby probe performed a

gravitational assist In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver, or swing-by is the use of the relative movement (e.g. orbit around the Sun) and gravity of a planet or other astronomical object to alter the p ...

maneuver using Venus, and continued its mission to intercept the comet.NASA—NSSDC—Spacecraft—Details
/ref>

Descent craft

The surface lander was identical to that of Vega 2 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 an ultraviolet

, temperature and pressure sensors, a water concentration meter, a gas-phase chromatograph, an X-ray

, a mass spectrometer, and a surface sampling device. Since the probe made a nighttime landing, no images were taken. 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. The lander successfully touched down at in the Mermaid Plain north of

Aphrodite Terra Aphrodite Terra is one of the three continental regions on the planet Venus, the others being Ishtar Terra and Lada Terra. It is named for Aphrodite, the Greek equivalent of the goddess Venus, and is found near the equator of the planet. Aphrod ...

. Due to excessive turbulence, some surface experiments were inadvertently activated 20 km above the surface. Only the mass spectrometer was able to return data. Tools on the lander include: * Thermometers * Barometers * UV absorption

—ISAV-S * Optical aerosol analyzer, Nephelometer—ISAV-A * Aerosol particle-size counter—LSA * Aerosol mass spectrometer—MALAKHIT-M * Aerosol gas chromatograph—SIGMA-3 * Aerosol X-ray fluorescence spectrometer—IFP * Hygrometer—VM-4 * Soil X-ray fluorescence spectrometer—BDRP-AM25 * Gamma-ray spectrometer—GS-15STsV *

Penetrometer A penetrometer is a device to test the strength of a material. Soil There are many types of penetrometer designed to be used on soil. They are usually round or cone shaped. The penetrometer is dropped on the test subject or pressed against it and t ...

/ Soil ohmmeter—Prop-V * Stabilized oscillator / Doppler radio

Balloon

The Vega 1 Lander/Balloon capsule entered the Venus atmosphere (125 km altitude) at 2:06:10 UT (Earth received time; Moscow time 5:06:10 a.m.) on 11 June 1985 at roughly 11 km/s. At approximately 2:06:25 UT the parachute attached to the landing craft cap opened at an altitude of 64 km. The cap and parachute were released 15 seconds later at 63 km altitude. The balloon package was pulled out of its compartment by parachute 40 seconds later at 61 km altitude, at 8.1 degrees N, 176.9 degrees east. A second parachute opened at an altitude of 55 km, 200 seconds after entry, extracting the furled balloon. The balloon was inflated 100 seconds later at 54 km and the parachute and inflation system were jettisoned. The ballast was jettisoned when the balloon reached roughly 50 km and the balloon floated back to a stable height between 53 and 54 km some 15 to 25 minutes after entry. The mean stable height was 53.6 km, with a pressure of 535 mbar and a temperature of 300–310 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 69 m/s (248 km/hr) at nearly constant latitude. The probe crossed the terminator from night to day at 12:20 UT on 12 June after traversing 8500 km. The probe continued to operate in the daytime until the final transmission was received at 00:38 UT on 13 June from 8.1 N, 68.8 E after a total traverse distance of 11,600 km or about 30% of the circumference of the planet. It is not known how much farther the balloon traveled after the final communication.

Halley mission

After their encounters, the Vegas' motherships used the gravity of Venus, also known as a gravity assist, to intercept Halley's Comet. Images started to be returned on 4 March 1986, and were used to help pinpoint Giotto's close flyby of the comet. The early images from Vega showed two bright areas on the comet, which were initially interpreted as a double nucleus. The bright areas would later turn out to be two jets emitting from the comet. The images also showed the nucleus to be dark, and the infrared spectrometer readings measured a nucleus temperature of 300 K to 400 K, much warmer than expected for an ice body. The conclusion was that the comet had a thin layer on its surface covering an icy body. Vega 1 made its closest approach on 6 March at around 8,889 kilometers (at 07:20:06 UT) of the nucleus. It took more than 500 pictures via different filters as it flew through the gas cloud around the coma. Although the spacecraft was battered by dust, none of the instruments were disabled during the encounter. 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 A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...

, 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. The Vega images showed the nucleus to be about 14 km long with a rotation period of about 53 hours. The dust mass spectrometer detected material similar to the composition of carbonaceous chondrites meteorites and also detected clathrate ice. After subsequent imaging sessions on 7 and 8 March 1986, Vega 1 headed out to deep space. In total Vega 1 and Vega 2 returned about 1500 images of Comet Halley. Vega 1 ran out of attitude control propellant on 30 January 1987, and contact with Vega 2 continued until 24 March 1987. Vega 1 is currently in

heliocentric orbit A heliocentric orbit (also called circumsolar orbit) is an orbit around the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. All planets, comets, and asteroids in the Solar System, and the Sun i ...

, with perihelion of 0.70 AU, aphelion of 0.98 AU, eccentricity of 0.17, inclination of 2.3 degrees and orbital period of 281 days.

References

External links