Venera


Venera

 

(Venus), the name of the Soviet unmanned interplanetary probes launched to the planet Venus beginning in 1961.

Venera 1. Launched on Feb. 12, 1961, Venera 1 weighed 643.5 kg. On May 19-20, 1961, it passed within approximately 100,000 km of Venus and went into a solar orbit with a perihelion of 106 million km and an aphelion of 151 million km.

Venera 2. Launched on Nov. 12, 1965, with a weight of 963 kg. Venera 2 contained a compartment with a photographing-television system and a whole array of scientific equipment for the study of cosmic space. On Feb. 27, 1966, it passed within 24,000 km of the surface of Venus and went into a solar orbit with a perihelion of approximately 107 million km and an aphelion of approximately 179 million km.

Venera 3. Launched on Nov. 16, 1965, with a weight of 960 kg, Venera 3 had a descent capsule in the shape of a sphere with a 900-mm diameter, a heat-shielding cover, and a parachute. The descent capsule contained a radio system, scientific devices, power sources, and banners with representations of the state emblem of the USSR. A midcourse correction of the trajectory was made to ensure the station’s reaching the planet. On Mar. 1, 1966, the station reached the surface of Venus, thus accomplishing the first flight of an automatic cosmic flight vehicle to another planet.

Venera 4. Venera 4 was launched on June 12, 1967. Having traveled a distance of approximately 350 million km, on Oct. 18, 1967, it entered the Venusian atmosphere at cosmic speed 2, and the descent capsule separated from it. After aerodynamic braking of the vehicle, the parachute system was activated. The weight of the probe was 1,106 kg and that of the descent capsule, 383 kg. The capsule delivered a second banner with the state emblem of the USSR onto the planet’s surface. Launched from Earth, Venera 4 was the first to achieve a smooth descent into the atmosphere of another planet. Like its predecessors, the probe Venera 4 was equipped with solar batteries, vernier engines, gas cylinders, attitude sensors, low-directional and high-directional antennas, and other devices. The orbital module contained two receivers and a transmitter, telemetric commutators, decoders, and a memory unit. In the descent capsule there were two transmitters, a telemetric commutator, and a programmer.

The probe’s scientific equipment was located in the orbital module as well as the descent capsule. The orbital module contained equipment for making measurements in interplanetary space and around Venus: a three-component magnetometer with a measurement range of 50 nT (nanotesla) (50 gammas) and a sensitivity of 2 nT (2 gammas); counters of cosmic-ray particles; an indicator of the ultraviolet radiation of the sun, dispersed by neutral atoms of hydrogen and oxygen, which made it possible to record the concentrations of these gases around the planet; and collectors for charged particles. The descent capsule contained equipment for studying the planet’s atmosphere: two resistance thermometers, a barometer, an ionization meter of atmospheric density, and 11 cartridge gas-analyzers.

Results of observations carried out by Venera 4 have shown that in 1967 the intensity of bursts of the sun’s cosmic rays increased a hundredfold, compared with those in years of minimal solar activity. In the planetary trajectory leg, the flow of high-energy particles remained practically unchanged, which indicates the absence of radiation belts on the planet. This is also confirmed by magnetometric measurements. The hydrogen corona of Venus has been re corded, beginning at a distance of approximately three radii from the surface of the planet, and having a concentration three orders lower than the particle concentration in the earth’s hydrogen corona. Elemental oxygen was not found. Data from direct measurements of the parameters in the lower layer of the atmosphere show that the pressure in the terminal flight leg changed from 0.07 to 2 meganewtons/m2(from 0.7 to 20 kgf/cm2) and temperature changed from 25 ± 10° C to 270 ± 10° C. Thus, the validity of data on the high temperatures on the surface of Venus, obtained by means of radar, was confirmed.

Venera 5 and Venera 6 Venera 5 was launched on Jan. 5, 1969. The principal aim of the flight was to continue the investigations of the planet Venus begun by Venera 4. For the more complete study of Venus, Venera 6 was launched on Jan. 10, 1969. The quantity of scientific and measuring equipment on these probes was increased. On board the probes were banners depicting V. I. Lenin and with representations of the state emblem of the USSR. The weight of Venera 5 and Venera 6 without the last stage of the booster was 1,130 kg.

On May 16 and 17 both probes completed a flight of many months on the earth-Venus run. The descent capsules of the probes descended smoothly into the atmosphere of the planet on its “night” side. During the flight, the probes carried out important studies of the physical processes occurring in interplanetary space. Scientific instruments on board the vehicles measured the chemical composition, pressure, density, and atmospheric temperature of Venus during the descent. For the first time, scientific investigations of the Venusian atmosphere were actually conducted simultaneously in two of its regions.

Venera 7. Venera 7 was launched on Aug. 17, 1970, and reached Venus on Dec. 15, 1970. During the flight, 124 sessions of radio communication were conducted with the probe. After entry into the Venusian atmosphere, a specially reinforced descent capsule descended by parachute, transmitting radio signals for a period of 35 minutes.

E. F. RIAZANOV and M. G. KROSHKIN