The Vega 1 lander’s surface experiments were inadvertently activated at 20 km
(12 mi) from the surface by an especially hard wind jolt and so failed to provide
results. It reached the surface at 7.5°N, 177.7°E.
The Vega 2 lander touched down safely at 03:01 UT on June 15, 1985 at
8.5°S, 164.5°E in eastern Aphrodite Terra, some 0.1 km (0.062 mi) above the
planetary mean radius. The measured pressure at the landing site was 91 atmospheres and the temperature was 736 K (463°C; 865°F). The surface sample was
found to be an anorthosite-troctolite, an igneous form of rock. The lander transmitted data from the surface for 56 minutes before succumbing to the hostile
environment.
The two balloon “aerobots” were designed to float at 54 km (34 mi) above the
surface, in the most active layer of the Venusian cloud system. The instrument
package had enough battery power for sixty hours of operation, and measured
temperature, pressure, wind speed, and aerosol density. The balloon envelopes
were surfaced with polytetrafluoroethylene to resist the corrosive atmosphere.
Both balloons operated for over 46 hours from injection into the atmosphere to
their final transmissions.
They were spherical super-pressure types with a diameter of 3.54 m (11.6 ft)
and were filled with helium. A 6.9 kg (15 lb) gondola assembly was 1.3 m (4 ft 3
in) long and connected to the balloon envelope by a 13 m (43 ft) tether. The mass
of the entire assembly was 21 kg (46 lb).
The top section of the gondola assembly was capped by a conical antenna 37 cm
(15 in) tall and 13 cm (5.1 in) 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, which consisted of:
• An arm carrying thin-film resistance thermometers and a velocity anemometer. The anemometer consisted of a free-spinning plastic propeller whose
spin was measured by LED-photodetector opto-interrupters.
• A module containing a PIN diode photodetector to measure light levels and
a vibrating quartz beam pressure sensor.
• A package at the bottom carrying the batteries and a nephelometer to measure cloud density through light reflection.
The small low-power transmitter only allowed a data rate of 2,048 bit/s, but the
system performed data compression in order to squeeze more 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 Soviet
Academy of Sciences and the international network, coordinated by the Centre
National d’Études Spatiales (CNES) of France.
Appendix 5: Planetary Balloons 315
(12 mi) from the surface by an especially hard wind jolt and so failed to provide
results. It reached the surface at 7.5°N, 177.7°E.
The Vega 2 lander touched down safely at 03:01 UT on June 15, 1985 at
8.5°S, 164.5°E in eastern Aphrodite Terra, some 0.1 km (0.062 mi) above the
planetary mean radius. The measured pressure at the landing site was 91 atmospheres and the temperature was 736 K (463°C; 865°F). The surface sample was
found to be an anorthosite-troctolite, an igneous form of rock. The lander transmitted data from the surface for 56 minutes before succumbing to the hostile
environment.
The two balloon “aerobots” were designed to float at 54 km (34 mi) above the
surface, in the most active layer of the Venusian cloud system. The instrument
package had enough battery power for sixty hours of operation, and measured
temperature, pressure, wind speed, and aerosol density. The balloon envelopes
were surfaced with polytetrafluoroethylene to resist the corrosive atmosphere.
Both balloons operated for over 46 hours from injection into the atmosphere to
their final transmissions.
They were spherical super-pressure types with a diameter of 3.54 m (11.6 ft)
and were filled with helium. A 6.9 kg (15 lb) gondola assembly was 1.3 m (4 ft 3
in) long and connected to the balloon envelope by a 13 m (43 ft) tether. The mass
of the entire assembly was 21 kg (46 lb).
The top section of the gondola assembly was capped by a conical antenna 37 cm
(15 in) tall and 13 cm (5.1 in) 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, which consisted of:
• An arm carrying thin-film resistance thermometers and a velocity anemometer. The anemometer consisted of a free-spinning plastic propeller whose
spin was measured by LED-photodetector opto-interrupters.
• A module containing a PIN diode photodetector to measure light levels and
a vibrating quartz beam pressure sensor.
• A package at the bottom carrying the batteries and a nephelometer to measure cloud density through light reflection.
The small low-power transmitter only allowed a data rate of 2,048 bit/s, but the
system performed data compression in order to squeeze more 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 Soviet
Academy of Sciences and the international network, coordinated by the Centre
National d’Études Spatiales (CNES) of France.
Appendix 5: Planetary Balloons 315