VeGa AZ balloons

The two VeGa (Venera-Halley) spacecraft released balloons ('Aerostatic Zonds') into the atmosphere of Venus, as part of their deployment of the latest Venera-class landers to investigate the planet's atmosphere and surface. At the time of writing these remain the only balloons to have been sent to the atmosphere of another world. During the planning stage for this mission, larger French-led balloons had been considered but the inclusion of comet Halley in the mission plan for the flyby spacecraft forced the use of the smaller, Soviet balloons eventually flown. Both were successful, surviving for nearly two days in the nightside atmosphere while being tracked by radio telescopes on Earth (Figure 16.8).

Venus

Measure winds, vertical heat flux and cloud particle density.

First planetary balloon NPO Lavochkin (formerly OKB-301) Baikonour, Proton 8K82K/11S824M (within VeGa 1 &

2 probes)

VeGa 1 AZ VeGa 2 AZ

15/12/1984 21/12/1984

11/06/1985 15/06/1985

Floating altitude Floating altitude

46.5 h later 46.5 h later

6.9 kg gondola, 2 kg helium, total 20.5 kg

• VLBI measurements of position & velocity (Sagdeev, Blamont, Preston)

• Doppler expt (Kerzhanovich)

• Meteocomplex (T, P sensors, vertical-wind anemometer, light level/lightning detectors) (Linkin, Blamont)

• Nephelometer (Ragent, Blamont, Linkin) The Project Scientist was Roald Z. Sagdeev

Release from lander back cover during descent. Float at benign altitude with temperatures ^30-40 °C 250 W-hr lithium battery (1kg) One-way DTE: 4.5 W at 1.667 GHz at 4 bit s^1 (initially for 270 s every 30 minutes); DVLBI measurements of position

Table (Cont.) EDI architecture

Landing speed(s) Active operations (deployments, etc.)

Key references

Released from VeGa lander at 61 km; parachute deployed at 55 km. Rise from 50 km to 54 km operating altitude. 3.54m Teflon fabric balloon, filled with helium

Jettison of parachute and inflation system. Ballast released at 50 km. Deployment of boom carrying temperature sensors and anemometer

Kremnev et al., 1986; Sagdeev et al., 1986; Aleksashkin et al., 1988a,b; Vorontsov et al, 1988; Hunten et al, 1983; Marov and Grinspoon, 1998; Blamont et al., 1993; Sagdeev et al., 1986; TsUP, 1985; MNTK, 1985

Figure 16.8 VeGa AZ balloons.
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