Vega 2

The Vega 2 lander touched down at 03:00:50 UT on 15 June 1985 at around 7°08′S 177°40′E / 7.14°S 177.67°E / -7.14; 177.67, in the northern region of

The Vega 2 Lander/Balloon capsule entered the Venusian atmosphere (125 kilometres [78 mi] altitude) at 02:06:04 UT (Earth received time; Moscow time 05:06:04) on 15 June 1985 at roughly 11 kilometres per second (6.8 mi/s). At approximately 2:06:19 UT the parachute attached to the landing craft cap opened at an altitude of 64 kilometres (40 mi). The cap and parachute were released 15 seconds later at 63 kilometres (39 mi) altitude. The balloon package was pulled out of its compartment by parachute 40 seconds later at 61 kilometres (38 mi) altitude, at 7.45 degrees S, 179.8 degrees east. A second parachute opened at an altitude of 55 kilometres (34 mi), 200 seconds after entry, extracting the furled balloon.

The balloon was inflated 100 seconds later at 54 kilometres (34 mi) and the parachute and inflation system were jettisoned. The ballast was jettisoned when the balloon reached roughly 50 kilometres (31 mi) and the balloon floated back to a stable height between 53 and 54 kilometres (33 and 34 mi) some 15 to 25 minutes after entry. The mean stable height was 53.6 kilometres (33.3 mi), with a pressure of 535 millibars (535 hPa) and a temperature of 308–316 K (35–43 °C; 95–109 °F) 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 66 metres per second (220 ft/s) at nearly constant latitude. The probe crossed the terminator from night to day at 9:10 UT on 16 June after traversing 7,400 kilometres (4,600 mi). 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 11,100 kilometres (6,900 mi). It is not known how much further the balloon traveled after the final communication.^[4]

Halley mission

After their encounters, the Vegas' motherships were redirected by Venus' 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 14,000,000 kilometres (8,700,000 mi).

Vega 2 made its closest approach at 07:20 UT on March 9, 1986, at 8,030 kilometres (4,990 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

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.^[5] 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.^[5]

Contact with Vega 2 was lost on 24 March 1987.^[5] Vega 1 had previously exhausted its attitude control propellant on 30 January 1987.^[5]

Vega 2 is currently in

• List of missions to Venus

References

• Vega 2 Measuring Mission Profile by NASA's Solar System Exploration
• Vega mission images from the Space Research Institute (IKI)
• Raw data from Vega 1 and Vega 2 on board instruments
• Soviet Exploration of Venus
• Vega 2 Mission Comet Halley Data Archive at the NASA Planetary Data System, Small Bodies Node