Third Generation Veneras
1975 VENUS FLIGHTS—VENERA 9 AND 10
In 1975, the Soviets upgraded their Venus exploration program by initiating use of the larger D class launch vehicle for Venus missions instead of the A-2-e.
Venera 9 was launched on June 8, 1975, and was described as a new type of Venus spacecraft. On June 14, Venera 10 was launched, and the Soviets announced that it was similar in design and mission to Venera 9. Both spacecraft were orbiter/lander combinations. Soviet sources noted that while earlier Venera probes had required many commands from Earth to control their course, this time there were onboard digital computers which made many of the necessary calculations, adding flexibility to the operations.
THE LANDERS
On October 20, the Venera 9 lander and orbiter separated, and on October 22, the lander entered the atmosphere of Venus at a speed of 10.7 km/sec. Following aerodynamic braking and parachute deployment, the Venera 9 lander touched down at 0813 Moscow time, and operated for 53 minutes on the surface.
The Venera 10 spacecraft separated into its two parts on October 23, and the lander reached the surface on October 25 at 0817 Moscow time. It landed 2,200 kilometers from Venera 9, and operated for 65 minutes on the surface.
The lander stood about 2 meters high, and the experiments were protected within a two-hemisphere shell able to withstand temperatures up to 2,000° C and 300 tons pressure. Lander instrumentation was precooled to —10° C and its exterior equipment to —100° C before entry, to lengthen the amount of time it could function on the surface. A special system of circulating fluids distributed the heat load.
Results from the experiments produced many surprises. First, it was discovered that the lighting was as bright as Moscow on a cloudy June day, so that the floodlights which had been carried on the spacecraft were not required.
Fifteen minutes after Venera 9 landed, a television panoramic picture began to emerge on Earth. There was no noticeable dust, and the picture was quite clear even without further processing. Details were good to a distance of 50-100 meters. A scattering of rocks 30-40 centimeters across, and a large stone on the apparent horizon, were observed. The panorama extended out to 160 meters, and the horizon may have been 200-300 meters away, but this is unclear. There was a defined curvature between surface and air at this horizon. The fact that rocks cast shadows suggested that direct sunlight was reaching the surface, in contrast to the expected solid cloud cover. Surprisingly, also, the rocks were not eroded, but showed sharp cleavages as if relatively young. Until this time, scientists had assumed that Venus was an old, geologically "dead" planet, but the existence of rocks with sharp edges strongly suggested that instead it is young and geologically active. These observations have been supported by subsequent United States and Soviet missions to Venus.
Pictures returned from Venera 10 showed that it had landed in an area with large pancake rocks, possibly with cooled lava or other weathered rocks in between.
Four Soviet scientists provided more details on the equipment carried on the Venera 9 and Venera 10 landers in a February 21, 1976, Pravda article.49 The descent module carried the following instruments: a panoramic telephotometer; a photometer to measure light fluxes in the green, yellow, red, and two near-infrared spectra; a photometer to measure atmospheric brightness in three wavelength bands near 8 microns and to determine the chemical composition of the atmosphere; optical entry instrumentation to measure the radiation intensity of the atmosphere and clouds in two phases from 63 to 34 kilometers and from 63 to 18 kilometers; temperature and pressure sensors used from 63 kilometers to the surface; accelerometers to measure G forces during the deceleration phase; a mass spectrometer to determine the chemical composition of the atmosphere between 63 and 34 kilometers altitude; an anemometer to measure surface wind velocity; a gamma ray spectometer to detect any radioactive elements in surface rocks; and a radiation densitometer.
The article also outlines some of the data received from the landers. The temperature at the Venera 9 landing site was 460° C, and the pressure was 90 atmospheres. The surface illumination was about 10,000 lux. Local wind velocity was 0.4 to 0.7 meters per second. At 35-40 kilometers altitude, the ratio of carbon dioxide to water vapor was 1000 to 1. At the Venera 10 landing site, wind velocity was 0.8 to 1.3 meters per second.
Examination of surface rock for radioactive elements found 0.3 percent potassium, 0.0002 percent thorium, and 0.0001 percent uranium. Rock density was 2.7 to 2.9 grams per cubic centimeter.
THE ORBITERS
Both orbiters were put into their respective orbits the same day as their landers went to the surface of Venus. In addition to carrying experiments for orbital research, each served as a relay station between Earth and each lander.
The Venera 9 orbiter was placed in an orbit 112,000 by 1,300 kilometers, with a period of 48 hours, 18 minutes. Venera 10's orbit was 114,000 by 1,400 kilometers, with a period of 49 hours, 23 minutes.
The orbiters studied the structure, temperature, and radiation of the planet's cloud layers using spectrometers, radiometers, and photopolarimeters. By using radio sounding, they also measured the density of ions and electrons, and at high altitudes, the energy spectra directly with ion traps. Weak magnetic fields and particles in the solar wind stream were also measured.
The Pravda article cited earlier described the orbiter research in three categories: studies of the Venus cloud layer, studies of the upper atmosphere by radiophysical and optical means, and studies of solar wind interaction. Instruments used in cloud layer research included: a panoramic camera; an infrared spectrometer to measure the absorption band intensity of atmospheric gases and the reflecting capability in the 1.5 to 3.0 micron range; an infrared radiometer in the 8-30 micron range to measure cloud layer temperature; a photometer supplied by France to measure brightness of the ultraviolet light at 0.35 microns; a photopolarimeter to measure brightness and polarization of solar radiation reflected by the cloud layer in the 0.4 to 7.0 micron range; and a spectrometer in the 0.24 to 0.70 micron range to study the above-cloud layer. The upper atmosphere experiments included a photometer to measure solar radiation scattered by hydrogen atoms in the outer layers of the atmosphere and a spectrometer to measure the Venusian atmospheric glow in the 0.3 to 0.8 micron range. Solar wind studies used a magnetometer, a plasma electrostatic spectrometer and charged particle traps.
The orbiters measured the temperature of Venus' clouds at the upper boundary at —35° C and found that the cloud temperature on the nocturnal side was about 10° C higher. The brightness in ultraviolet rays varied within 20 percent. Other data indicated that the atmospheric temperature decreases with altitude, but at the 66-55 kilometer level, local temperature elevations are observed. The electron concentration on the daytime side of Venus was found to be significantly higher than on the nocturnal side, but was 10 times higher than in the terrestrial ionosphere.
1978 VENUS FLIGHTS—VENERA 11 AND 12
Venera 11 was launched on September 9, 1978, and Venera 12 5 days later. As with Venera 9 and 10, these were combination spacecraft, but instead of an orbiter and a lander, these were a flyby bus and a lander. Each had a mass of 3,940 kilograms, less than Venera 9 and Venera 10, because the 1978 launch window had much greater energy requirements to reach Venus. The flyby bus also permitted longer contact time with the lander.
On September 25, the Soviet Union reported that corrections had been made to the Venera 11 and Venera 12 flight trajectories. There had been 37 radio communications to measure the trajectory, check onboard systems operations, and transmit scientific and
telemetric data. (50) TASS announced on October 18 that Venera 11 and Venera 12 were continuing on their paths as planned, and studies were being conducted on physical processes in space.
RESEARCH CONDUCTED EN ROUTE TO VENUS
The Venera flights continued joint Soviet-French research on cosmic gamma ray flares which had begun on Prognoz 6, Prognoz 7 and Sneg 3, (51) and the Sneg-2MZ instrument, an omnidirectional gamma radiation detector, was used to locate the source and characteristics of gamma ray bursts.
Another experiment, called "Konus," was used for cosmic gamma ray studies while the spacecraft were en route to Venus. Konus took periodic measurements of the intensity and spectrum of the cosmic background with six scintillation counters forming the detector system. The source of the gamma ray burst was located by means of a triaxial stabilization of the space vehicle. From September to December 1978, Konus registered 27 gamma bursts and 120 solar flares. An experiment designated "KV-77" measured high-energy particles while Venera 11 and 12 were en route to Venus. A powerful flareup on the Sun occurred on September 23 and a stream of charged particles was observed for more than 2 days. At the same time, a dramatic increase in the intensity of protons and alpha particles of solar origin were recorded in all measured energy ranges in interplanetary space. (52)
Venera 11 and Venera 12 also conducted studies on interplanetary plasmas, and both vehicles carried identical plasma spectrometers. A Soviet scientific journal described the scientific objectives of the solar wind and geomagnetospheric research as: obtaining information on the heating and acceleration of solar wind ion components by measuring the parameters of proton and alpha components; investigation of the velocity of propagation of interplanetary shockwaves; study of the structure of the interactive region between the solar wind and the Earth's magnetosphere; analysis of the dissipation of ion energy in circumterrestrial and interplanetary shockwaves by measuring the proton and alpha components of the solar wind; and measurement of the solar wind as the American Pioneer-Venus passed through. Some Venera 11 and Venera 12 instruments, including the plasma spectrometers, were used to make observations on December 4 and 9 in cooperation with the U.S. Pioneer-Venus spacecraft. (53)
By October 13, Venera 11 was 11.5 million kilometers from Earth and Venera 12 was 10.6 million kilometers from Earth. By November 4, Venera 11 and Venera 12 were more than 20 million kilometers from Earth. The French-Soviet gamma ray experiment had registered new outbursts of gamma rays of different energies and more than 20 weak x ray eruptions on the Sun. (54)
On November 24, 1978, TASS announced that more than 72 radio communications has been held with Venera 11 and Venera 12 during which some preliminary data processing had been conducted.
SURFACE EXPERIMENTS
Venera 12 was first to reach Venus after a 98-day flight, and the descent module entered the atmosphere at 11.2 kilometers per second on December 21, 1978. The flyby bus continued its flight about 35,000 km past Venus. The temperature on the Venusian surface was 460° C and the pressure was 88 atmospheres. The module transmitted data for 110 minutes; communications ceased at 0800 when the Venera 12 module was in the shadow of Venus. (55)
Venera 11 reached Venus on December 25, 1978, and the descent module made a soft landing at 0624 Moscow time approximately 800 kilometers from Venera 12. The temperature on the surface was 446° C and the pressure was 88 atmospheres. The Venera 11 lander transmitted data for 95 minutes. The Venera 11 station was put in a flyby trajectory 35,000 km from Venus. (56)
No pictures were transmitted from the landers this time, and Soviet scientists have unofficially acknowledged that the imaging systems on both spacecraft failed.
RESEARCH DURING DESCENT
During the descent, the Venera 12 lander conducted experiments to determine the chemical composition of the clouds and atmosphere, and a study of electric charges in the planet's atmosphere from an altitude of 62 km to the surface. (57)
The entire September-October 1979 issue of Kosmicheskiye Issledovaniya (Cosmic Research) was devoted to technical discussions of the Venera 11 and Venera 12 flights. The majority of these articles were written on those experiments which were conducted during descent of the landers to the Venusian surface.
The Venera 11 descent module carried a backscattering nepelometer which was designed to measure the aerosol component of the atmosphere. Measurements were taken from an altitude of 51 kilometers to the surface. The greatest signal intensity was registered at 51 to 48 kilometers altitude. Increased levels were also measured in the 17-13 and 12-8 kilometer altitude ranges. In the remaining regions, the signal registered below the instruments response capability. (58)
Venera 11 and Venera 12 studied low-frequency electromagnetic radiation in the Venusian atmosphere. The discharges of energy resembled terrestrial lightning. The study of electric charges was begun at 62 kilometers and continued to the surface. One thunderstorm region was observed to occupy an area 150 kilometers horizontally and 2 kilometers vertically. The mean frequency of occurrence of discharges was far greater than during terrestrial thunderstorms. (59)
The two spacecraft carried spectrophotometnc experiments, called IOAV scanning spectrophotometers. This equipment was used to study the spectral composition and spatial distribution of scattered solar radiation from 65 kilometers to the surface of Venus. The IOAV scanned continuously in the visible and near-infrared spectrum and also made circular scans in space. The objectives of the experiment were: to examine the spectral composition of scattered solar radiation in order to estimate the atmospheric content of substances with large absorption bands; to study the vertical structure of the atmosphere and horizontal homogeneity of the cloud layer; and to determine the energy balance of the atmosphere of Venus. (60) The experiment registered the spectra of the Venus daytime sky in the range of 4,500 to 12,000 angstroms and an angular distribution of brightness of scattered radiation in four filters. Absorption bands of carbon dioxide, water and gaseous sulfur were found in the spectra. It was found that about 6 percent of the total solar flux reached the planetary surface. (61)
Venera 11 and Venera 12 carried the Sigma gas chromatograph to investigate the chemical composition of the atmosphere. It weighed 10 kilograms and used a highly sensitive ionization detector. Nine samples were collected during descent between 42 kilometers and the surface. Mass spectrometers on the two spacecraft took 11 gas samples of the Venusian atmosphere from 23 kilometers altitude to the surface, 176 mass spectra were transmitted to Earth. The mass spectrometers revealed that the ratio of argon 36 to argon 40 on Venus was 200 to 300 times higher than on Earth.
VENERA 13 AND 14
Venera 13 was launched on October 30, 1981, and was followed 5 days later, November 4, by the launch of Venera 14. Both were launched with the D-l-e booster into Earth orbit, and then sent into a planetary trajectory using an orbital platform.
Enroute to the planet, both spacecraft conducted studies of gamma-ray bursts, and more than 20 bursts were registered using equipment developed by France and the Soviet Union, including more than 10 associated with solar flares. An Austrian magnetometer was used to study the interplanetary magnetic field as well.
The Venera 13 lander arrived at Venus on March 1, 1982, and proceeded to the surface, landing at 7°30' south latitude, 303° longitude, on the plains east of the Phoebus area. Scientific data were returned for 127 minutes, four times longer than planned. (1) Venera 14 landed on March 5 at 13°15' south latitude, 310°9' longitude, and transmitted data for 57 minutes. The landing sites were chosen based on radar images from the U.S. Pioneer-Venus probe, (2) and were assumed by Soviet and American scientists to be enters of volcanic activity on Venus. The buses did not enter orbit around Venus, but continued on a fly-by trajectory and entered heliocentric orbit. Experiments on the bus continued to operate after the landers had separated, and by June 1982 a total of 89 cosmicgamma bursts and more than 300 solar flares had been recorded. (3) The experiments were expected to continue operating to the end of 1983. (4)
The landers were different from previous Soviet Venera spacecraft in that they could transmit color, rather than black and white, pictures and were equipped with soil sampling equipment. (5) The eight panoramic views sent back to Earth by Venera 13 showed the Venusian surface to be covered with sharp rocks, partially covered with fine dust, and sand. Large grey boulders were also observed. The Venera 14 spacecraft landed in a plain area, covered with sandstone. Initially, the Soviets stated that the surface was brown, but later concluded that it was yellowish orange, with some green. The Venusian sky reflects the colors of the surface, and is primarily orange.
Soil analysis was accomplished using a drill to obtain a sample which was then sucked inside the spacecraft by a vacuum cleaner type device. Analysis was accomplished using an x ray fluorescent spectrometer contained in a special chamber which maintained a pressure of 50 mm Hg (I/2000th of that outside) and a temperature of 30" C (compared to 457° C outside).
Analysis showed that at the Venera 13 site, the rock was leucitic basalt with a high potassium and magnesium content, which is rare on Earth, but found in the Mediterranean volcanic area. At the Venera 14 site, the rock corresponded to oceanic tholeitic basalts which are widespread on Earth. Scientists concluded from the absence of secondary changes in the soil that it was relatively young.
The mechanical strength of the rocks was measured using a spring-powered rod, and it was found to be in the range 2.6-10 daN/square centimeter at the Venera 13 site, and 65-250 daN/square centimeter for the Venera 14 location (although the Soviets stated that there was a partial equipment failure on Venera 14). (6)
The spacecraft also studied seismic activity using unilaxial seismometers which could measure only the vertical component of ground displacement. Venera 13 recorded no seismic events, while two were recorded with Venera 14, but Soviet scientists felt that they could not preclude the possibility that they resulted from instrument effects or wind, so stated only that the data were inadequate to draw unambiguous conclusions about seismic activity at the sites. (7)
The two landers also analyzed the Venusian atmosphere on their way to the surface using a mass spectrometer, gas chromatograph, optical spectrophotometer, a hydrometer, a nephelometer, and an x ray fluorescent spectrometer. Data showed the most ultraviolet radiation is absorbed at an altitude of 60 km, and Venus' clouds are mostly sulfur. Soviet scientists also detected xenon and a new isotope of neon in the atmosphere.
VENERA 15 AND 16
In 1983, the Soviets launched another pair of Venus spacecraft, but these were significantly different from previous Venus probes—both are orbiters which carry side-looking radars for mapping the surface of the planet. Venera 15 was launched on June 2, 1983, and Venera 16 on June 6 by D-l-e launch vehicles. As with previous Venera spacecraft, studies of cosmic rays and charged particles were made enroute to the planet. Venera 15 entered Venusian orbit on October 10, 1983, followed by Venera 16 on October 14. Orbital periods are approximately 24 hours, and the orbits are highly inclined at 87 °, (8) providing coverage of the polar regions of the planet. Apogees are on the order of 65,000 km, and perigees about 1,000 km. (9) The side-looking radars point 10° off nadir, (10) and although their resolution is only 1-2 kilometers at best, (11) about the same as is achievable using Earth-based radars, the probes do provide data on regions of the planet not seen from Earth.
The spacecraft are based on the same design used since Venera 9, but the radar is positioned in place of the landing probe. More fuel was required to put each spacecraft into polar orbit around Venus, so the fuel tanks were lengthened by more than 1 meter, and the solar panel array size was almost doubled to provide power for the radar. The radar, called Polyus-V, has an antenna 6 meters long and 1.4 meters across, and the cone of the launch vehicle had to be lengthened to accommodate the radar in its folded state. Improvements in both the spacecraft transmitter and the receiving antennas on Earth are said to have increased the capacity of the Venus-Earth link 30 times, with a transmission rate of 100,000 units of information per second. (12) The radar was designed by the Moscow Power Engineering Institute. Initial data reception is made at the Long-Range Space-Communications Center, and then transmitted to the Institute of Radio Engineering and Electronics of the Soviet Academy of Sciences for processing and analysis. A special high speed processor was developed for these missions, and processing of one image takes 8 hours. (13)
The first radar images were received from Venera 15 on October 16, and from Venera 16 on October 20, although orbital adjustments were made to each throughout their first month in orbit.
An onboard radio altimeter can measure the height of the area with an accuracy of up to 50 meters. (14) The radar has a 20-minute scanning period and views through three slits simultaneously, with an area about 150 kilometers wide viewed through each slit; (15) one slit faces directly ahead, and the others slightly to the left and right. (16) Each image displays an area of 1 million square kilometers. (17)
An infrared spectrometer-interferometer is also carried on each spacecraft for obtaining atmospheric temperature profiles. The instrument was developed by the East German Academy of Sciences. (18)
Images from Venera 15 showed the region of the north pole of Venus to be similar to Tibet and the Himalayas. Photographs published in Aviation Week and Space Technology showed large volcanic features, rolling terrain and band-link structures that could be canyons or ridges. (19) The Soviets plan to produce four maps of Venus based on the Venera 15 and 16 data.
References:
A. SOVIET SPACE PROGRAMS: 1976-80 (WITH SUPPLEMENTARY DATA THROUGH 1983), UNMANNED SPACE ACTIVITIES, PREPARED AT THE REQUEST OF Hon. JOHN C. DANFORTH, Chairman, COMMITTEE ON COMMERCE, SCIENCE, AND TRANSPORTATION, UNITED STATES SENATE, Part 3, MAY 1985, Printed for the use of the Committee on Commerce, Science, and Transportation, 99th Congress, 1 st. session, COMMITTEE PRINT, S. Prt. 98-235, U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 1985
49. Avduyevskiy, V. (Corresponding member. Academy of Sciences, U.S.S.R.), V. Ishevskiy (Doctor of Technical Sciences), M. Marov and V. Moroz (Doctors of Physics-Mathematical Sciences), Pravda, Feb.21, 1976, pp. 3-4.
50. Tass, 1700 GMT, Sept. 25, 1978.
51. Moscow World Service in English, 1630 GMT, Oct. 13, 1978.
52. Kosmicheskiye Issledovaniya, vol. 17, No. 5, September-October 1979. Pp. 820-829.
53. Kosmicheskiye Issledovaniya, vol. 17, No. 5, 1979. Pp. 780-792.
54. Tass in Russian, 1528 GMT, Dec. 21, 1978.
55. Tass in English, 1242 GMT, Nov. 4, 1978.
56. Tass in Russian, 1446 GMT, Dec. 25, 1978.
57. Moscow World Service in English, 0930 GMT, Dec. 21, 1978.
58. Kosmichesldye Issledovaniya, vol. 17, No. 5, 1979, pp. 743-747
59. Pis'ma v. Astronomicheskiy Zhurnal, vol. 5, No. 5, 1979, pp. 229-236.
60. Kosmicheskiye Issledovaniya, vol. 17, No. 5, 1979, pp. 714-726.
61. Pis'ma, op. cit., pp. 229-236
1. Tass, 0740 GMT, Mar. 2, 1982.
2. Aviation Week and Space Technology, Nov. 9, 1981, p. 23.
3. Kosmicheskiye Isseldovaniya, vol. 21, No. 3. May-June 1983, pp. 480-488.
4. Vienna, Volksstimme, July 19, 1983, p. 3.
5.There have been hints that the Venera 11 and 12 imaging systems would have sent back color photographs if they had worked.
6. Kosmicheskiye Issledovaniya, vol. 21, No. 3, May-June 1983, pp. 323-330.
7. Ibid., pp. 355-360.
8. Paiz, B.J. Summary of Venera 15/16. Pasadena, CA, Vista Laboratory, 1984, p. 4.
9. Ibid.
10. Sotsialisticheskaya industriya, Oct. 21, 1983, p. 3.
11. Moscow Domestic Television Service, 1800 GMT, Oct. 19, 1983.
12. Izvestiya, Oct. 21, 1983, p. 3.
13. Pravda, Nov. 17, 1983, p. 3. Another report in Pravda on Feb. 26, 1984, stated that it takes 12 hours to sift through the output of the two Veneras each day, with another 4 hours required for collating the radar data with the altimeter data.
14. Izvestiya, Oct. 21, 1983, p. 3.
15. Trud,0ct.20,1983,p.4.
16. Izvestiya, Oct. 21, 1983, p. 3.
17. Moscow Domestic Television Service, 1800 GMT, Oct. 19, 1983.
18. Izvestiya, Oct. 22, 1983, p. 3.
19. Soviet Venus Probe Reveals Volcanoes, Aviation Week and Space Technology, Nov. 28, 1983, p. 23.
