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Vega 1 & 2
Spacecraft Vega 1 Vega 2
Country Soviet Union Soviet Union
Mission Venus Lander & Balloon,
Comet Halley Flyby
Venus Lander & Balloon,
Comet Halley Flyby
Launch Date December 15, 1984 December 21, 1984
Launch Vehicle Proton Proton
Spacecraft Mass 4920 kg 4920 kg
Key Dates Jun 11, 1985 - Venus Encounter
Mar 6, 1986 - Comet Halley Flyby
Jun 15, 1985 - Venus Encounter
Mar 9, 1986 - Comet Halley Flyby
End of Mission 1986 1986
Comments First Venus Balloon
First Comet Halley Flyby
Second Venus Balloon
Second Comet Halley Flyby

The Vega mission was a Venus mission which also took advantage of the appearance of Comet Halley in 1986. The twin spacecraft, Vega 1 and Vega 2, were named after Venera-Gallei (the Russian language does not have the letter "H"), and the spacecraft design was based on the previous Venera 9/10 missions. The two spacecraft were launched on December 15 and December 21, 1984, respectively. Arriving at Venus in June 1985, each spacecraft deployed a 1500 kg descent module towards Venus and the main spacecraft were then retargeted for a Comet Halley encounter in March 1986. The descent modules split into two parts, a lander and a balloon package, and entered into the atmosphere of Venus on June 11 and June 15, respectively. The balloon from Vega 1 lasted 56 minutes, and the Vega 2 balloon transmitted data for 46.5 hours. Both landers reached the surface of Venus and returned valuable data about the atmosphere of Venus and its soil composition.

vega_halley.jpg After the successful Venus balloon and lander mission, the mother spacecraft continued on to a rendezvous with Comet Halley. Both Vega 1 & 2 were three-axis stablized spacecraft. The spacecraft were equipped with a dual bumper shield for dust protection from the comet. Vega 1 arrived first, returning images starting on March 4, 1986, and these images were used to help pinpoint Giotto's upcoming close flyby of the comet. The early images from Vega that showed two bright areas on the comet, which were initially interpretted 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 to 400K, 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. The Vega images also 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. Vega 1 made its closest approach to the comet on March 6 at a distance of 8,890 km.

Vega 2 was just three days behind its twin for its Comet Halley encounter. Vega 2 flew in closer to the comet nucleus at a distance of 8,030 km on March 9, 1986. It returned similar data, but returned images with better clarity due to its closer approach.


Ron Baalke, STARDUST Webmaster, ron@jpl.nasa.gov
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