Category Soviet Robots in the Solar System

TIMELINE: 1979-1981

The pace of planetary exploration slowed considerably after 1978, particularly in the US. There were no launches to the Moon or the planets in 1979-80. ft was a striking contrast to the hectic 1960s and 1970s. Tn fact there would be no lunar or planetary launches by the IJS during the eleven years between 1978 (Pioneer Venus) and 1989 (Galileo). Continuing their assault on Venus using the successful Venera spacecraft, the Soviets had the field to themselves. At the next Venus opportunity in 1981 they launched another pair of Venera flyby/’landcrs. Both were successful, and this time produced the first color images of the surface of the planet.

Launch date

1979

No missions

1980

No missions

1981

30 Oct Venera 13 flyby/landcr Success, first color images from surface

4 Nov Venera 14 flyby/lander Success

COLOR PICTURES FROM THE SURFACE OF VENUS: 1981

Campaign objectives:

Venera 11 and 12 had not completed the goals set for them. Whilst the experiments carried out during the descent produced a prodigious amount of information on the

W. T. Huntress and M. Y. Marov, Soviet Robots in the Solar System: Mission Technologies and Discoveries, Springer Praxis Hooks 1, DOl 10.1007/978-1-4419-7898-1 16,

© Springer Science+Business Media, LLC 2011

atmosphere, the surface science was mostly a failure. The Soviets skipped a launch opportunity in order to develop new heat-resistant technologies in order to fix these problems. In 1981 they were ready to try again with better devices and instruments, principally aiming to obtain color images from the surface and to analyze a sample obtained by a drill. The landing sites were chosen in collaboration with US scientists using maps based on the radar imaging experiment perfonned by the Pioneer orbiter in 1978. ~

As flyby spacecraft, Venera 13 and 14 were essentially identical to their immediate predecessors. The major changes for 1981 concerned the lander. In particular, metal teeth were added to the periphery of the impact ring in an effort to reduce the spin and oscillation during the descent and prevent the rough landings experienced by the 1978 missions. The camera lens cover problem was fixed, and the soil sampler was redesigned to alleviate the problem that disabled it on Venera 11 and 12.

Payload

Flyby spacecraft

1. KONUS gamma-ray burst detector

2. SNEG gamma-ray burst detectors (France-USSR)

3. Magnetometer (Austria)

4. High energy particle cosmic ray detector

5. Solar wind detectors

The flyby spacecraft carried a reduced payload to facilitate an increased payload on ihc lander. Updated forms of the cosmic ray experiment and the two gamma-ray investigations were included, and an Austrian magnetometer on a 2 meter boom was attached to one of the solar panels.

Flyby payload mass: 92 kg Lander

Entry and descent

1. Accelerometers for atmospheric structure (110 down to 63 km) and then lander impact analysis

2. Temperature and pressure sensors

3. Gas chromatograph for atmospheric composition

4. Mass spectrometer for chemical and isotopic composition

5. Hydrometer for water vapor content

6. Nephclomcter for aerosol studies

7. X-ray fluorescence spectrometer for elemental composition of aerosols

8. Spectrophotometer for spectral and angular distribution of solar radiation

9. Ultraviolet photometer 320 to 390 nm

10. GROZA-2 radio for electrical activity and microphone for acoustic and seismic events

11. Doppler experiment for wind and turbulence Surface

1. Panoramic color imaging system with two cameras

2. Drill and surface sampler

3. X-ray fluorescence spectrometer for surface rock elemental composition

4. Rotating conical soil penetrometer (PrOP-V)

5. Chemical oxidation state indicator

Several of the instruments were improved from their Venera 11 and 12 versions, including the camera, drill, spectrophotometer, x-ray spectrometer for aerosols, mass spectrometer and gas chromatograph. The hydrometer humidity sensor and chemical oxidation state indicator were new; the latter being a simple chemical indicator to search for traces of oxygen in the atmosphere. The spectrophotometer measured the full spectrum from 470 to 1,200 nm using a wide-angle sky view and an array of six narrow-angle directional views. The gas chromatograph was equipped with a better detector, could sense more species, and was capable of operating in the cloud layer. l he mass spectrometer was improved to provide 2 to 40 times better mass resolution with 10 to 30 times greater sensitivity. The anomalous krypton reading of the 1978 missions was understood and corrected. The GROZA-2 instrument now; included a modified 10 kHz detector, a new7 detector in the 2 kHz band, and was better able to search for seismic events after touchdown.

The panoramic imaging system was fitted with an improved lens cover. The large increase in bandwidth for the transmission to the flyby relay spacecraft allowed each camera to have clear, red, green, and blue filters. Each camera was to cycle through its 180 degree panoramic image four times, one for each filter, taking almost an hour to complete. To ensure that a color section would be transmitted if the lander lasted only 30 minutes, one camera first scanned a full 180 degrees through the clear filter and then scanned each of three 60 degree sections in turn with red, green and blue filters.

It is a testament to the technology of the Venera landers that so many instruments were mounted outside and hence exposed to the pressure, temperature and corrosive atmosphere of Venus. These included the drill, penetrometer, mass spectrometer, gas chromatograph, hydrometer, aerosol x-ray spectrometer, oxidation state indicator, and the GROZA radio sensors and microphone. The cameras and nephelometer were mounted inside with special housings attached to the pressure vessel to enable them to observe out through windows and prisms. The platinum thermometer and aneroid pressure instrument used external sensors with wires fed through ihe pressure vessel.

The drill sampler was on the base of the lander. The machining of this device had to take account of thermal expansion at 500"C, and the process of drilling, sampling and analysis had to complete within the 30 minute guaranteed lifetime of the lander. A telescoping drill head was to bore into the surface for about 2 minutes, reaching as much as 3 cm into solid rock and coring a 2 cc sample. Information on the speed and

movement of the drilling rig. depth of drill penetration, and magnitude of the current drawn by the elec trie motor while drilling, provided information on the physical and mechanical properties of; the surface. After the few grams of material gained by the drill had been deposited on a tray, this would be moved pyrotechnically through a three-stage airlock to transfer it from the ambient 90 bar pressure to just 0.06 bar in the analysis chamber of the x-ray fluorescence spectrometer, which used plutonium, uranium-235 and iron-55 sources. The gas pumping for this transfer was enabled by a vacuum reservoir on the base of the lander.

The dynamic penetrometer was designed to determine the mechanical properties of the surface material, whether rock or soil. It consisted of a cone-shaped die that could pivot on the end of a lever and fall forward onto the ground. Л sighting device within the field of view of one of the cameras determined the depth of penetration. After penetration, a spring would cause the die to rotate in the soil and the angle of its turn would be displayed on the sighting device. A cable unit was also attached to one end of the die and an electronic unit within the lander could measure electrical resistance.

Lander payload mass: 100 kg

Mission description:

Landers

Venera 13 was launched on October 30, 1981, and made midcourse corrections on November 10 and February 21, 1982. It released its entry capsule on February 27 at a range of 33,000 km from the planet, and this entered the atmosphere on March 1. The accelerometer was turned on at about 100 km altitude and provided data on atmospheric density until parachute deployment. The parachute opened at 62 km and was jettisoned about 9 minutes later at an altitude of; 47 km. The descent instruments were activated just after the parachute opened, and the descent time from parachute opening to landing was just over an hour. The lander hit at 7.5 m/s. bounced once, and came to rest on a fiat, crumbly surface in an elevated hilly landscape at 7.55 :S 303.69 :E. It was 03:57:21 UT, 09:27 Venus solar time, and the solar zenith angle was 36 degrees. The surface transmission lasted 127 minutes.

Venera 14 was launched on November 4, 1981. and required three midcourse corrections to reach Venus. This was because the first one on November 14 w as not executed properly. After a compensating maneuver on November 23, the final trim maneuver was made on February 25. 1982. The entry system was released on March 3, and this entered the atmosphere on March 5. The parachute opened at 62 km and w as jettisoned at 47 km. The lander touched down at about 7.5 m/s on a low lying plain at 13.055 S 310.19’E, 950 km southwest of; its partner. It was 07:00:10 UT, 09:54 Venus solar time, and the solar zenith angle was 35.5 degrees. The surface transmission lasted 57 minutes.

Venera 13 and 14 experienced the same electrical anomaly as had Venera 11 and 12 at 12.5 km altitude. The science sequences worked very well on descent for both

landers and also on the surface. Immediately upon landing, the lens covers popped off and imaging began. A black-and-white contingency image was transmitted first, followed by the color panoramas. The drill experiment was also started immediately after landing and the entire process of drilling, sampling, and analysis took a little over 32 minutes. Venera 13 obtained a 2 cc sample and Venera 14 obtained a 1 cc sample, each from a depth of 3 cm. The Venera 13 penetrometer worked well, but by bad luck on Venera 14 this experiment deployed on top of an ejected lens cover. The microphones picked up aerodynamic noise during the descent, the sounds of the landing, and then the deployment of the lens covers, the drilling noise and sampler pyrotechnics, winds at the site, and other sounds of the lander at work.

Flyby carrier spacecraft:

The flyby carriers each passed Venus at an approximate closest point of approach at

36,0 km and entered heliocentric orbit where they continued to return data on the Sun, including flares. As tests to assist in planning late midcourse maneuvers for the Halley’s comet encounters by the Vega missions, Venera 13 fired its engine on June 10, 1982, and Venera 14 did so on November 14, 1982.

Results:

Venera 13 lander:

Descent measuremen ts:

The microphysical properties reported by the nepheiometers indicted, three distinct layers in the main cloud system: a dense top layer from 60 km (the altitude at which the measurements began) down to 57 km, then a transparent layer from 57 to 50 km, and finally the densest layer from 50 to 48 km. Doppler measurements gave a wind profile. Interestingly, the humidity sensors on both Venera 13 and 14 indicated ten times more water in the atmosphere than was determined spectroscopically in the 46 to 50 km range. The water mixing ratio was determined from several instruments and, despite some conflicting values, it seemed to be greatest in the cloud formation

region between 40 and 60 km with less water above and below the cloud layers. The amount of water vapor at 48 km was estimated at 0.2%. The mass spectrometer was not opened until below the cloud layers to preclude it being clogged by aerosols, and it provided altitude profiles of a number of atmospheric constituents between 26 km and the surface. These findings include a neon isotope ratio slightly higher than for Earth but less than for the Sun, a small krypton mixing ratio significantly less than that measured by the gas chromatograph and by Venera 11 and 12, and an argon-40 mixing ratio about four times lower than for Earth. The gas chromatograph detected some new species including molecular hydrogen, hydrogen sulfide, and carbonyl sulfide. Other species detected included molecular oxygen, water vapor, krypton, and sulfur hexafluoride.

The coronal discharge detectors of the GROZA-2 experiment established that no vehicle discharges were responsible for the very low frequency bursts interpreted as lightning by the Venera 11 and 12 experiments. No lightning or electrical discharges were detected.

Surface measurements:

Venera 13 obtained both black-and-white and the first color panoramic images from the surface of Venus. These show the lander ring base with triangular ‘crown’ points for lander stabilization during the descent, the ejected camera covers, the color test pattern strips, the deployed PrOP-V penetrometer, and the exhaust port of the aerosol x-ray fluorescence instrument on the lander ringjusl to the left of the penetrometer. The landing site appeared to be composed of bedrock outcrops surrounded by dark, fine-grained soil. The Venera 13 and 14 panoramas both showed llat, layered stones with a dark soil between them, and scattered small grains to compose a scene reminiscent of the floor of a terrestrial ocean. The photometers noted dust raised by

the landing, but it quickly settled and the resulting sedimentation was apparent by comparison of sequential images through different filters.

The Venera 13 site showed dark, flat rocks distributed over a darker crumbled soil surfaee with some low, rolling ridges in the background. The cameras returned four panoramas each, one in each filter: clear, red. green and blue; the latter three for the color image. However, precise color balancing was difficult to achieve in processing the filter data because the deployed calibration strips were affected by heat, pressure, and the orange sky. and because the radiometric response of the camera was not well known.

The drill sample analysis indicated a potassium-rich basalt of a type that is rare on Earth. The penetrometer showed the load-bearing capacity of the soil to be similar to heavy clays or compacted dust-like sand. These are both consistent with the surface characteristics derived from stress-strain profiles measured in the mechanics of the landing, which indicated a surface covered by a weak, porous material similar to the properties of weathered basalt. The electrical resistivity of the surface was surprising low. in the semi-conductor range, perhaps due to a thin film of conducting material on insulating soil particles.

The exposed-surface chemical test on both landers for the oxidation state of the Venusian atmosphere seemed to indicate a reducing carbon dioxide-rich atmo­sphere instead of an oxidizing one, but the experiment may have been compromised by the dust disturbed upon landing. Due to the short lifetime on the surface, the GROZA-2 acoustic experiment was designed to detect the micro seismic events that commonly occur at a rate of about one every few’ seconds on Earth. No events were detected by Venera 13, but tw7o such events may have been noted by Venera 14. The Venera 13 microphone recorded the aerodynamic noise of the descent, and on the surface this data gave w ind speeds of 0.3 to 0.6 m/s. Successive pictures through different filters show ed dust being blown off the lander ring. The temperature at the landing site was 465°C and the pressure was 89.5 bar. Only 2.4% of sunlight reached the surface. Some minor changes in illumination were observed, perhaps due to clouds, but the overall impression was of a dead calm, murky atmosphere over a flat volcanic plain.

Venera 14 lander:

Deseent measurements:

The Venera 14 lander conducted the same observations as Venera 13. both during its descent and w hile on the surface, obtaining very similar results. The combined mass spectrometer results were:

the isotopic ratios were:

13/12 carbon 40/36 argon 38/36 argon 20/22 neon

and the combined gas chromatograph results were:

water vapor molecular oxygen molecular hydrogen krypton

hydrogen sulfide carbonyl sulfide sulfur hexafluoride

The x-ray fluorescence instrument measured the composition of the aerosols from 63 to 47 km. It detected both sulfur (1.10 + 0.13 mg/m3) and chlorine (0.16 + 0.04 mg/mJ) and the chlorine abundance was considerably knver than the measurement by Venera 12. This more precisely calibrated instrument measured a sulfur/’chlorine abundance ratio compatible with sulfuric acid aerosols. The aerosols in the region between 6.3 and 47 km were composed principally of sulfur compounds with some chlorine compounds. The abundance ratio of sulfur and chlorine varied with altitude. The highest density aerosols were in the range 56 to 47 km. The x-ray fluorescence instrument of Venera 13 did not operate properly.

Surface measurements:

Unlike Venera 13, the Venera 14 photometers detected no dust raised on landing. It came down on a smooth level plain with flat, layered rocks which had very little soil

between them. The composition of the drill sample indicated a low-potassium basalt similar to that of terrestrial mid-ocean ridges. A lower sulfur content than Venera 13 may well indicate that the Venera 14 site is younger. The surface properties inferred from the dynamics of touchdown indicated a surface similar to the Venera 13 site, but possibly covered with a layer of weaker, porous material. No penetrometer data was obtained from Venera 14 because the instrument swung down onto a jettisoned lens cover. The audio sensor reported two sounds that could have been distant and small seismic events. The temperature at the site was 470=,C and the pressure was 93.5 bar. Hie amount of sunlight reaching the surface was 3.5%.

X-ray fluorescence soil analysis results were:

The surface composition measurements from Venera 8, 9, 10, 13 and 14 at sites around the planet were all consistent with basalts of compositions similar to those on Earth. The great variety of igneous and metamorphic rocks widespread on Earth was not evident, most likely owing to the lack of water on Venus.

Venera 13 and 14 flyby spacecraft:

Both ilybv spacecraft collected data on the solar wind and solar x-ray Hares. They participated in an interplanetary network to triangulate on gamma-ray bursts, in this case detecting about 150 events. Later in the decade, the Vega spacecraft were to use a flyby of Venus to set up an encounter with Halley’s comet, so after leaving Venus behind Venera 13 and 14 fired their engines to rehearse the maneuvers that would be required by those later missions.

Whereas in the US the National Academy of Sciences is an advisory body to the government, the Soviet Academy of Sciences had governmental and implementation roles. It was integral to the Party, and made decisions on the worthiness of proposed space projects, approving those to be undertaken. However, the Ministry of Machine Building allocated the funding for these projects. The President of the Academy, Mstislav Keldysh, was a powerful and highly influential figure in the Soviet space program during his tenure. Before he became President of the *Acadcmy in 1961, he was head of the Institute of Applied Mathematics (TPM) and kept this position until his death in 1978, when IPM was named the Keldysh Institute. It played a major role in space navigation and mission design.

Also unlike in the US, where university laboratories and NASA’s various field centers prepared scientific experiments for planetary missions, in the USSR the research institutes of the Academy of Sciences filled this role. These institutes were established by the Academy, but were funded through MOM. In the early years, the leading player was the Vernadsky Institute, more formally known as the Institute of Geochemistry and Analytical Chemistry. In 1965, at about the same time as Korolev transferred the robotic program to NPO-Lavochkin, the Soviet Academy of Sciences under Keldysh’s initiative established the Institute for Space Research (IKI; Institut Kosmicheskikh Issledovanii), which gradually built up its role in scientific missions, including providing flight instruments, and by the 1970s was a fierce competitor to Vernadsky. With Roald Sagdeev’s appointment as Director in 1973, IKI assumed scientific leadership of deep space missions. After Sagdcev quit in 1988. Vernadsky shared leadership under Valery Barsukov until the latter died in 1992. Today IKI is the leading space science institution. The institutes develop flight instruments and NPO-Lavochkin is responsible for the spacecraft and operations.

After the failures of the 1M and 1VA missions, a new multi-mission spacecraft was designed 1’or missions to Mars and Venus. The 2MV modular spacecraft had a mass of approximately 1,000 kg. The core of the spacecraft was a cylindrical pressurized ‘orbital’ module that had the propulsion module attached at one end and the payload at the other end. The payload could consist of either an entry probe or a pressurized module with instruments for flyby observations. Solar panels, antennas, thermal control devices, navigational sensors and several science instruments were attached to the side of the main module. The communications, attitude control and thermal control systems for the 2MV were greatly improved over the 1M and 1VA, and the same propulsion system was provided for midcourse trajectory corrections.

Four variants were designed. The 2MV-1 and 2MV-2 were Venus models, and the 2MV-3 and 2MV-4 were Mars models. The -1 and -3 versions were equipped with appropriate entry vehicles, and the -2 and -4 carried instruments for a flyby mission. Six spacecraft were launched, three to Venus (two probes and one flyby) in August and September 1962, and three to Mars (two flybys and one probe) in October and November 1962, Unfortunately all but one was lost to launch vehicle failures. The Mars 1 spacecraft launched on November 1, 1962, flew for almost 5 months before communications were lost on March 21, 1963, at what was then regarded as the vast range of 106 million kilometers from Earth. In view7 of this engineering success, the 2MV general design set a long-term precedent for Russian planetary spacecraft, particularly for Venus where this type of spacecraft was used until 1975.

Campaign objectives:

After having focused for several years on Mars and Venus, the Moon reasserted itself as a priority in concert with the progress of the manned space flight program. The 1959 Soviet plan to send cosmonauts on circumlunar flights had also envisaged robotic orbiters and landers. An early proposal for a Yc-5 lunar orbiter to respond to the first American attempts at small lunar orbiters was canceled along wdth its three-stage 8K73 launcher in favor of launching Ye-6 landers and Ye-7 orbiters using the four-stage 8K78 ‘Molniya* developed for planetary missions. These new spacecraft were also to exploit the design and flight experience of the second generation Mars and Venus spacecraft launched in 1962. The 2MV was a modular spacecraft with a common flight module and a mission-specific flyby or entry probe payload module. Unlike the earlier Luna spacecraft, which were launched directly towards the Moon, the Ye-6 series and all subsequent lunar missions were placed in Earth orbit for later injection onto a lunar trajectory by the restart able fourth stage.

The early Ye-6 series, built at OKB-1, was designed to accomplish the first lunar soft landing. Unfortunately, it suffered eleven straight failures between January 1963 and December 1965. Four spacecraft were lost to booster failures, two were stranded in Earth orbit by fourth-stage failures, two failed in transit and missed the Moon, and three failed at the target by crashing.

The years 1962-65 were dismal for Soviet robotic lunar and planetary exploration. The early sueecsses of Luna 1, 2, and 3. and the encouraging but ultimately fruitless flights of Venera 1 and Mars 1. had built expectations for more success. But by the end of 1962 the Molniya launcher had failed in all but one of ten launches and the truncated flight of Mars 1 had revealed the shortcomings of the 2MV series. These problems were addressed with the 3MV series, essentially the same spacecraft with advanced engines and avionics, and these advances were incorporated into the first Ye-6 series. Nevertheless by the end of 1965 three 2MV Mars missions, three 2MV Venus missions, two test and one 3MV Mars missions, one test and five 3MV Venus missions, and eleven Ye-6 lunar missions – a total of twenty-six missions had been lost without a single success at the assigned targets. Ironically, in the midst of this awful record, one of the test 3MV Mars spacecraft did achieve a measure of success at the Moon, when Zond 3 provided far-side photography of better quality than that from Luna 3. It was the only lunar accomplishment in this period. Such a long string of failures could well have shut down an American program, so vulnerable to public criticism, but in the Soviet Union it led to the determination to succeed, although not without a great deal of internal criticism by the government and outright threats of punishment.

Spacecraft:

The Ye-6 spacecraft consisted of three sections totaling 2.7 meters in height. The first section consisted of the Isayev mideourse correction and descent engine, which produced a thrust of 4.64 tons using hypergolic nitric acid/amine propellants. Four smaller 245 N thrusters mounted on outriggers were used for attitude control during the descent. The main pressurized cylindrical compartment containing avionics and communication equipment was mounted above the engine. Л pair of cruise modules were attached to the central cylinder. One held both attitude control thrusters for the translunar flight and a radar altimeter to trigger the landing sequence, and the other contained avionics sensors for attitude reference and control during the cruise. Both were discarded after the altimeter triggered the landing sequence. The lander capsule was strapped to the top of this stack. Unlike their planetary cousins, these spacecraft carried no solar panels because the flight time for the carrier module and the time on the surface for the lander were sufficiently short that the batteries would not require a recharge.

A new autonomous control system, the 1-100. was made for the Ye-6 which not only controlled the spacecraft but also the attitude and firings of both the third and fourth stages of the launcher. This approach deviated from usual practice but saved a great deal of w eight by eliminating the third and fourth stage controllers with their associated cabling and connectors. However, this had never been tried before, and w ould be the cause of further problems for a launcher that had already failed in nine out of ten attempts.

The lander capsule comprised a 105 kg hermetically sealed 58 cm sphere encased in tw’o hemispherical airbags sewn together. It carried communications equipment, a program timer, heat control systems, batteries, and scientific instruments including a television system. Once the lander was on the surface, it would deploy four petals to

expose its upper hemisphere and raise four 75 an antennas. The batteries were to supply power for a total of 5 hours over a period of 4 days, with its activities being driven either by timer or by command from Earth. The mass distribution was biased towards the bottom to assist the lander in turning upright on the surface when the petals were opened. The ideas of using air bags for impact and articulating petals to ensure a final upright stance on the surface were both quite clever, but not patented, and so the Americans adapted them for the pyramidal lander of the Mars Pathfinder mission in 1996.

After a direct approach to the target site on the Moon, the landing sequence was initiated at an altitude of 8,300 km. The attitude thrusters stabilized any roll that the spacecraft might possess and aligned the vehicle to the lunar vertical. At about 70 to 75 km altitude the radar altimeter was triggered, sending a signal to jettison the two cruise modules, inflate the airbags to 1 bar and ignite the main engine. At this time its speed relative to the Moon was about 2.630 m/s. The engine was to be shut off at an altitude of 250 to 265 meters and the four outriggers ignited for terminal descent. When a 5 meter long boom made first contact with the surface, the capsule would be ejected vertically to reduce its velocity to 15 m/s. The impact would be absorbed by the airbags. Four minutes after landing, the airbag cover would be severed along the joining seam and discarded. One minute later the lander would right itself by opening the four spring-loaded petals that formed its upper hemisphere, then raise its antennas.

The sites that could be reached by this type of mission were severely constrained, because the final approach of the translunar trajectory had to be perpendicular to the surface to direct the entire thrust of the retro-rocket straight downward. The control system of the vehicle was incapable of dealing with lateral velocity components. In practice, this limited the targets to western longitudes at latitudes that varied with the time of the year.

Lander payload:

1. Panoramic camera

2. Radiation detector

The camera weighed 3.6 kg and drew 15 W. It was a single photometer directed at the zenith inside a pressurized glass cylinder and used a nodding and rotating mirror to scan the scene both horizontally and vertically. It could expose a full 360 degree panorama in an hour with a resolution of 5.5 mm at a distance of 1.5 meters. Three small dihedral mirrors on deployable poles facilitated 3-dimensional view s of small strips of the surface. Calibration targets were dangled from the four whip antennas.

which also provided a measurement of the lander’s tilt on the surface. The radiation detector was a miniature gas discharge Geiger counter.

Mission description:

Six of the first eleven Ye-6 spacecraft were lost to launch vehicle failures, and none of those that flew to the Moon achieved a soft landing.

The first spacecraft to launch, Ye-6 No.2, was stranded in Earth orbit on January 4, 1963, when the failure of the PT-500 transformer in the power supply of the new I-100 controller prevented the fourth stage from reigniting. This was the sixth failure for the fourth stage out of eight attempts to use it. The object was designated Sputnik 25 by the Americans but was not acknowledged by the Soviets, and it re-entered the following day. The second attempt with Ye-6 No.3 on February 3. 1963, failed even to reach orbit because the 1-100 provided an improper pitch angle to the trajectory control system after the separation of the core stage. The third stage did not fire and the remaining stack fell into the Pacific near Hawaii – although this was commented upon by the American press no explanation was forthcoming from the USSR.

With the I-100 control unit fixed, Ye-6 No.4 was successfully sent towards the Moon on April 2, 1963, as Luna 4. The Soviet press announced the launch, saying that scientists were w’orking on the task of landing on the Moon, and pontificated on the possibility of human flights. But the mood soon changed. By the next day it was clear that the navigation system had malfunctioned and that it would not be possible to make the planned mideourse correction. Luna 4 missed the Moon by 8.336 km at 13:25 UT on April 5, and a miffed Soviet press claimed that a flyby was all that had been intended. The spacecraft ceased to transmit on April 6. The Soviet Academy of Sciences undertook a review7 of the program, but could not determine precisely why Luna 4’s navigation system had failed. However, some issues were identified, and it W’-as apparent that the rushed program was suffering quality control problems. It was decided to add a backup radio direction finding system, but this took time and it was a year before the next launch.

Unfortunately Ye-6 No.6 failed to reach orbit on March 21, 1964, when the third stage had an oxygen valve problem, failed to deliver full thrust, and cut off early. An upper stage failure also caused the loss of Ye-6 No.5 on April 20, 1964. when the command to fire the fourth stage failed. Suspicion fell on either the PT-500 current converter or the 1-100 controller, and extensive new testing began on these devices. It took almost a year to complete testing and modifications. The sixth attempt with Ye – 6 No.9 on March 12. 1965, was lost w7hen the fourth stage did not ignite due to a failed transformer in the power system. Unlike the ease for the first Ye-6 launch, the spacecraft was acknowledged by the Soviets and designated Cosmos 60, but it was obviously a failed lunar mission. After so many problems, the entire guidance and control system for the upper stages was reworked using a new three-phase converter, and separate guidance systems installed on the third and fourth stages. This change did not even get a test when the seventh attempt on April 10, 1965. failed because a

failed oxidizer pressurization system prevented the third stage engine from igniting, and the spacecraft. Ye-6 No.8. never reached orbit.

But Ye-6 No.10 was successfully dispatched towards the Moon on May 9. 1965. and announced as Luna 5. During the mideourse maneuver attempt on May 10. the gyroscopes in the I-100 guidance system were not given sufficient time to warm up and the spacecraft began to spin around its longitudinal axis. Engineers brought the spacecraft back under control and attempted the maneuver a second time, but sent it an incorrect command. By the time this was diagnosed it was too late to perform the maneuver. With the spacecraft on course to hit the Moon, albeit obliquely, it was decided to attempt to initiate the terminal maneuvers to exercise the system, but the guidance failed again and the engine did not fire. On May 12, the spacecraft hit the Moon at 1.6 S 25"W instead of the planned site at 31’S 8°W. becoming the second Soviet spacecraft to do so. Moscow, without portraying the mission as a failure, said a lot of information had been obtained ‘for the further development of a system for a soft landing on the Moon’s surface’’.

Ye-6 No.7 was launched on June 8. 1965, and successfully sent toward the Moon as Luna 6. The mideourse correction on June 9 began well, but a command error prevented the engine from cutting off, and it fired until the fuel was exhausted. This deflected the trajectory to such an extent that the spacecraft missed the Moon by 160,935 km on June 11, 1965. However, the engineers successfully put it through all of its landing sequence events.

An attempt to launch Ye-6 No. l 1 was canceled on September 4. 1965. when the core stage avionics failed in pre-flight testing. The vehicle was returned to the barn for major repairs to its control system. A month later, on October 4, this same rocket successfully dispatched Luna 7. This time the mideourse maneuver was performed successfully, making this the first Ye-6 in ten launches to be given the opportunity actually to attempt a lunar landing. However, in making its approach it lost attitude control, which prevented the retro-rocket from firing, and it crashed in the Ocean of Storms at 22:08:24 UT on October 7, at 9.8 N 47.8 W, west of the crater Kepler. An optical sensor had been set at the wrong angle and had lost sight of Earth during the attitude control maneuver immediately prior to starting the retro-rocket. As Moscow reported in its first admission of a failure. "Certain operations were not performed in accordance with the program and require additional optimization.”

Leonid Brezhnev, who had ousted Khrushchev the previous year, called Korolev to Moscow7 to account for the long string of failures. Korolev’s political charm stood him in good stead as he explained the difficulties and promised success with the next mission, due to launch in December. Although he did not deliver on this promise, he never had to face the new7 leadership again because he died during colon surgery on January 14. 1966. After the Moscow summons. Boris Chertok. a deputy at OKB-1. investigated the reliability and testing of spacecraft subsystems, and identified a lack of integrated testing of some subsystems during spacecraft assembly as a particular problem. Although corrective action was taken for the next launch, this was not in itself sufficient.

On December 4. 1965. Yc-6 No. l2 was launched into a lower inclination parking

orbit than its predecessors, at 51.6 degrees instead of 65 degrees. This allowed for a mass increase beyond 1.500 kg. The fourth stage then sent the spacecraft towards to Moon as Luna 8. The midcourse maneuver went well the following day, but alas the second Ye-8 to be presented with an opportunity to make a lunar landing failed. Just prior to retro-rocket ignition, the two airbags were inflated, as planned, but one was pierced by an improperly manufactured mounting bracket on a lander petal and the thrust of the escaping gas caused the spacecraft to spin. As a result, the retro-rocket cut off after just 9 of the required 42 seconds. The spacecraft crashed in the Ocean of Storms at 21:51:30 UT on December 6, at 9.ГК 63.3 W. to the west of the crater Kepler. The bracket problem was fixed, and on future missions the airbags would be inflated only after the retro-rocket had completed its burn.

Luna 8 was the eleventh straight failure in the Ye-8 program and the last before NPO-Lavochkin took over management of the Soviet lunar and planetary programs.

Results:

None.

The next sample return attempt with spacecraft Yc-8-5M No.412, the tenth in the scries, was lost when the Block D failed during its first burn and was unable to reach parking orbit. The final attempt, with No.413, was successful. Luna 24 was launched on August 9, 1976, made a midcourse correction on the 11 th, and entered a circular lunar orbit at 115 Icm with an inclination of 120 degrees on August 14. It adjusted its orbit to 120 x 12 km on the 17th and at 02:00:00 UT on the 18th it landed in darkness at 12.75°N 62.20°E in the Sea of Crises, only about 2,400 meters from the Luna 23 lander and near the Luna 15 target. The focus of the Ye-8-5M series was to obtain a deep core from the surface of the lunar mascon in Mare Crisium. The drill was able to reach the planned depth of 2.25 meters at a slightly inclined angle that equated to a vertical penetration of 2 meters. The sample was transferred to the return capsule and then at 05:25 LIT on the 19th the ascent stage lifted off. The capsule landed 200 km southeast of Surgut in Siberia at 17:53 UT on August 22. It proved to contain a sample of 170.1 grams.

End of the Moon, but the beginning for a propulsion stage

Luna 24 was the last of the Luna series and the final Soviet lunar mission. A third rover was built and another sample return spacecraft tvas prepared, but in 1977 the

Figure 11.30 Luna 16 recovery and soil sample (below). The balloons were inflated post­landing to right the capsule for antenna exposure.

launcher for the rover was requisitioned for a communications satellite and attention swung towards the ill-fated 5M Mars sample return project. Later all lunar and Mars plans were canceled in favor of continuing the successful Venus missions.

However, the reliable Ye-S cruise stage was modified to produce the autonomous propulsion stage for the 1988 Plrobos spacecraft, and went on to become the Fregat upper stage that is currently used by Proton-K and Soyuz launchers.

Results:

The altimeter on Luna 15 returned data during the descent until loss of signal, and this provided useful in forma lion on the mean density of the lunar soil. The sample that Luna 16 got from the Sea of Fertility was a dark, powdery mare basalt similar to that obtained by Apollo 12 in the Ocean of Storms. In 1971 three grams of Luna 16 soil were exchanged with NASA for three grams of Apollo 11 samples and three grams of Apollo 12 samples. The Vernadsky Institute of Geochemistry in Moscow* conducted analyses of the soils returned from these missions. Some samples were donated to other countries including France. Austria and Czechoslovakia. Although small, the Luna 20 soil from the highlands differed significantly from the Luna 16 mare sample. It was clearly lighter in color, with larger panicles. More than half of the rock particles were ancient anorthosite compared to less than 2% in the Luna 16 sample. Tw o grams were exchanged for one gram of highlands material obtained by Apollo 15, and US scientists were able to date the Luna 20 sample at 3 billion years. The 2 meter core from Luna 24 exhibited layering that clearly indicated successive deposition. Small portions of this core were exchanged with US scientists.

TIMELINE: 1982-1983

The final missions in the Soviet Venera series were launched in June 1983. Having achieved most of their objectives with the Venera landers, these two spacecraft were outfitted with large radar antennas replacing the entry system and sent to Venus as orbital radar mappers. Both were successful, with their radars discerning the surface through the ubiquitous clouds to map from 30"N to the north pole with a resolution of about 2 km.

Launch date

1982

No missions

1983

2 Jun Venera 15 orbiter Successful radar mapper

7 Jun Venera 16 orbiter Successful radar mapper

PIERCING TIIE CLOUDY VEIL OF VENUS: 1983

Campaign objectives:

After six consecutive successes of their heavy Venus landers starting with Venera 9, the Soviets decided to send radar imaging orbiters in the 1983 opportunity instead of more landers. In 1978 the US Pioneer 12 orbiter had obtained radio altimetry data of the entire planet at the very low resolution of 150 km. and operated the altimeter in a side-looking mode to obtain a narrow equatorial strip of topography at a resolution

W. T. Huntress and M. Y. Marov, Soviet Robots in the Solar System: Mission Technologies and Discoveries, Springer Praxis Hooks 1, DOl 10.1007/978-1-4419-7898-1 17,

© Springer Science+Business Media, LLC 2011 of 30 km. This data was used to target the Venera 13 and 14 landers in 1981. The 1983 Venera radar or hi tors were intended to use hi sialic radar techniques ю improve the resolution to 2 km or better, albeit only over about 25% of the planet.

Venus had become more or less a ”Red ‘ planet, left almost exclusively to Soviet exploration. After the Mariner 5 flyby in 1967 it was over a decade before the US revisited the planet, and the two small Pioneers in 1978 were primarily focused on the ionosphere and atmosphere. But at that same time the US was also developing a proposal for a Venus Orbiting Imaging Radar (VOIR) mission. NPO-Lavochkin had been working on a Venus radar mapper since 1976 and, after having pioneered local surface imaging, the Soviets wanted to conduct their radar mapping mission before the Americans. As events transpired, they did not have to compete, since VOIR was canceled in 1981 and replaced by a simpler, less costly mission named Magellan that was noi launched until 1989. In essence all that NPO-Lavochkin had to do was to replace the entry system of its spacecraft with a side-looking radar to obtain imagery and electrical properties of the surface of the planet, and to add a radio altimeter to measure the topography on the ground track. But modifying the spacecraft to carry the radar was not without challenge.

Rumors of a Soviet Venus radar mapping mission began to circulate in the US in 1979, as NASA was trying to obtain funding for its VOIR mission. Familiar with the heavy nuclear-powered RORSAT orbiting radars the Soviets used to track Western navies, most observers in the IJS did not believe they had the technology to build a lightweight low-power synthetic aperture radar. It was indeed a struggle, particularly the data storage and computing requirements, and the launch had to be slipped from 1981 to 1983, but ultimately it performed rather well.

Spacecraft:

Venera 15 and 16 were the first in this series of carrier vehicles to be modified in a significant way since Venera 9. The bus was lengthened by 1 meter to accommodate the 1,300 kg of propellant needed to put such a heavy craft into orbit around Venus. The load of nitrogen for the attitude control system was increased from 36 to 114 kg to permit the large number of attitude changes that the orbital mission would entail. Two more solar panels were added outboard of the standard pair to provide the extra power to operate the radar system. The parabolic antenna was enlarged by 1 meter to a diameter of 2.6 meters to increase the bandwidth from 6 to 108 kbits/s and a new 5 cm band telemetry system was introduced to communicate with the 64 and 70 meter ground stations. The spacecraft were identical, and consisted of a cylinder 5 meters long and 1.1 meters in diameter. A 1.4 x 6.0 meter parabolic panel antenna for the synthetic aperture radar (SAR) was installed at the top, in place of the entry system. The entire SAR system weighed 300 kg. A 1 meter diameter parabolic dish antenna was mounted nearby for the radio altimeter. The electrical axis ol’the radio altimeter antenna was aligned with the long axis of the spacecraft, and the SAR was angled 10 degrees off this axis. During imaging, the radio altimeter would be lined up with the local vertical and the SAR would look off’ to the side by 10 degrees.

Launch mass: 5,250 kg (Venera 15) 5,300 kg (Venera 16)

Fuel mass: 2,443 kg (Venera 15) 2,520 kg (Venera 16)

Payload:

1. Polyus-V synthetic aperture radar (SAR) operating at a wavelength of 8 an

2. Omega radiometric altimeter

3. Thermal infrared (6 to 35 microns) Fourier emission spectrometer (IFSE, DDR-USSR)

4. Cosmic ray detectors (6)

5. Solar plasma detectors

6. Magnetometer (Austria)

7. Radio occultation experiment

All of the components of the SAR and radio altimeter were shared except for the antennas. The electronics cycled the 80 W traveling wave tube oscillator between the antennas every 0.3 seconds. An onboard computer controlled their sequencing and operation. The SAR antenna would illuminate the surface over 3.9 milliseconds with 20 cycles of 127 phase shifts for cross-track encoding. Spacecraft motion over that same interval swept out a 70 meter virtual antenna. After each transmission, the antenna was switched to the receiver, which digitized the magnitude and phase of the reflected radar pulses and stored the data as 2,540 complex numbers in a solid-state memory buffer. To keep up with the radar illumination cycle of 0.3 seconds, the data were read out alternately onto two tape recorders to complete a period of 16 minutes

ol mapping during a periapsis pass. Each such pass produced about 3,200 return images to compose a data strip approximately 120 x 7,500 km. Once the data were received on Earth, each individual 3.9 millisecond return was divided by time delay mto 127 ranges across-track and 31 ranges along-track and then processed to correct for atmospheric, geometric, and orbital effects. The individual return images for a pass were then assembled to yield, an image strip representing the slope, roughness, and emissivity of the surface of Venus.

During altimetry, the antenna would transmit a code sequence of 31 pulses, each of 1.54 microseconds duration. After transmission, the antenna was switched to the receiver, which recorded the reflection of the pulses from the surface over a period of 0.67 millisecond. The oval footprint of the altimeter radio beam was 40 km cross-track and 70 km along-track. After onboard processing of the return waveform, the data were stored on the tape recorder for later transmission to Earth, which further processed the data to correct for atmospheric, geometric, and orbital effects to yield altitudes. A low resolution mode was used until the orbital elements were precisely determined, and then it was switched to a high resolution mode. In combination with Doppler analysis, the high resolution mode reduced the footprint to 10 x 40 km with an error of about 1 km. The vertical accuracy was about 50 meters.

It was also decided to include an infrared Fourier-transform spectrometer supplied by East Germany. This weighed 35 kg and was intended to provide a higher spectral resolution than the infrared radiometer operated by the Pioneer 12 orbiter. ft divided the spectrum into a continuous set of 256 channels over the range 6 to 35 microns. It had a field of view of 100 x 100 km, and provided 60 complete spectra along each periapsis pass. The objectives were to obtain atmospheric temperature profiles from the 15 micron carbon dioxide band in the 90 to 65 km altitude range, the temperature of the upper cloud deck, the abundances of aerosols, sulfur dioxide and water vapor in the atmosphere, and data on the thermal structure and dynamics of the clouds and atmosphere.

The cosmic ray and solar wind experiments were similar to those flown on every Venus mission since Venera 1.

Mission description:

Venera 15 was launched on June 2. 1983, and conducted midcourse corrections on June 10 and October 1 before entering orbit around Venus on October 10. Venera 16 was launched on June 7, conducted midcourse corrections on June 15 and October 5. and entered orbit on October 14. Their orbital planes were inclined about 4 degrees relative to one another, so that any area that was missed by one spacecraft should be able to be imaged by the other. Venera 15 made an orbital trim on October 17, and Venera 16 did so on October 22. Each operating orbit was inclined at 87.5 degrees to the equator, with the periapsis at 1,000 km and the apoapsis at — 65,000 km and a period of 24 hours. The periapsis was positioned at about at 62 N and each periapsis passage would image the surface on a 70-degree arc. Both spacecraft began science operations on November 11. Small burns w’ere made from time to time to preserve the periapsis. accommodate high gain antenna position changes as the Sun-vehicle – Earth angle decreased, and maintain the 3 hour interval between the periapses of the two spacecraft.

Mapping and altimetry would typically begin at 80"N on the inbound side of the pole and continue over the pole down to 30 N on the retreating side. Radar imaging w as conducted continuously w ith a best resolution of about 1 km. The data collected on each 16 minute periapsis pass was stored on the tape recorders, then replayed to Earth during a daily 100 minute communications window prior to the next periapsis. During each 24 hour interval Venus would rotate on its axis by 1.48 degrees, and so successive mapping passes partially overlapped one another. At that rate. 8 months was required to cover all longitudes. The 24 hour orbit was necessary to enable the spacecraft downloads to be synchronized with the receiving stations in the USSR. Several orbital corrections w ere made during the mission to maintain the period and shape of each orbit. In June 1984. Venus went through superior conjunction and no transmissions were possible while it passed behind the Sun as seen from Earth. This provided an opportunity to conduct radio occultation experiments to study the solar and interplanetary plasma. After conjunction. Venera 16 rotated its orbit backwards 20 degrees relative to its partner to map areas missed prior to superior conjunction, and mapping was concluded shortly thereafter, on July 10.

Between them, the two spacecraft were able to image all of the planet from 30: N to the north pole, or about 25% overall. The resolution of 1 to 2 km w;as similar to w hat could be achieved by the 300 meter Arccibo radio telescope dish operating as a radar, but it w? as limited to equatorial latitudes and could not get the accompanying altimetry.

Venera 15 reportedly exhausted its supply of attitude control gas in March 1985. but Venera 16 continued to transmit data from its other instruments until May 28 of that year. No attempts w ere made to change orbits for higher resolution or increased coverage.

Results:

Together, the two spacecraft imaged from 30°N to the north pole at a resolution of 1 to 2 km. The primary product consisted of 27 radar mosaics at a scale of 1:5,000,000 of the northern 25% of the planet. The results confirmed that the highest elevations, meaning those which stand more than 4 km above the plains, have greatly enhanced radar reflectivity.

The radar experiments produced major discoveries about the surface of the planet, imaging new types of terrain that included:

Coronae large circular or oval features with deep concentric rings

Domes flat, nearly circular raised features some with central calderas

Arachnoids – collapsed domes with radial cracks

Tessera – large regions of linear ridges and valleys

Prior to Venera 15 and 16, the coronae glimpsed by Arecibo had been thought to be impact features filled with lava. About 30 coronae and 80 arachnoids were in the area mapped. As no evidence of plate lectonics was evident, the coronae, domes and arachnoids were all postulated lo be surface expressions of mantle plumes heating an immobile crust. There wjere no direct terrestrial analogs. The tessera appeared to be the oldest crustal regions on the planet, and were often overlapped by lava flows.

Even if large ohjects that penetrate the thick atmosphere are destroyed before they can reach the ground, they can create a shock wave that leaves an impression on the surface. There were about 150 craters in the area surveyed. Analysis of the cratering data led to a very young age of 750 + 250 million years, consistent with the idea of catastrophic resurfacing making the tessera, and large scale ‘blistering’ over mantle plumes between resurfacing events.

The altimeter produced extensive data on topography in the northern hemisphere. In combination with the radar data, scientists w’ere able to produce detailed maps of the surface.

The infrared spectrometer on Venera 16 malfunctioned, but the one on Venera 15 worked in orbit for 2 months before it too failed. The spectra clearly resolved carbon dioxide, water vapor, sulfur dioxide, and sulfuric acid aerosol. This data was strong confirmation that the particles in the upper cloud layer were a 75 to 85% solution of sulfuric acid. The aerosol distribution and mixing ratios for sulfur dioxide and water vapor were determined in the altitude range 105 to 60 km. The thermal structure and optical properties of the atmosphere were also determined in this altitude range. The clouds ranged from 70 to 47 km, but in the polar region the clouds were 5 to 8 km lower and the air above 60 km was warmer than in equatorial regions. The average surface temperature was measured at 500°C. but some warmer spots were detected along with some cooler regions. There were no features in Ihe spectrum to suggest the presence of organic compounds.

The two orbiters produced 176 radio occultation profiles between October 1983 and September 1984.

The USSR’s first missile test range was established after WW-II at Kapustin Yar near Volgograd, formerly Stalingrad. Throughout the 1950s this was used to test the early short and intermediate range Soviet rockets, and later for launching the smaller Cosmos satellites. As Korolev worked on his first ICBM design, the R-7, it became clear that a new launch site would be required to accommodate radio guidance and tracking stations along a much longer range within Soviet territory, and to move the work beyond range of US tracking stations in Turkey. Tyuratam in Kazakhstan was selected for the R-7 launch complex. The site was called Baikonur, after a railhead some 270 km to the northeast, in an attempt to deceive the Americans in targeting their missiles. Construction started in 1955, and over the years the site has become an immense facility some 85 km by 125 km in extent including dozens of assembly and launch complexes, numerous control centers and tracking stations, work areas for tens of thousands of workers, the town of Lcninsk to house them, and a 1,500 km test range.

The first launch complex to be built was the one for the R-7, and it is still in use today. It is part of the ‘Center’ or ‘Korolev’ area that includes the N-l assembly and launch complex that was later converted for Energiya and Buran. The ‘Left Flank’ or ‘Chelomey Arm’ to the northwest has assembly and launch complexes for the Proton, Tsiklon and Rokot. The ‘Right Flank’ or ‘Yangel Arm’ to the northeast has a backup R-7 pad and facilities for Zenit and Cosmos.

As with the first campaign to Mars and Venus in 1960-61, the second campaign to both planets in 1962 failed. Of the ten spacecraft launched, only two survived launch and neither of those completed its cruise in a functioning state. But the long Highi of Mars 1 was very encouraging, and the 2M V design was upgraded with new avionics to make the 3MV spacecraft for the 1964 launch opportunities to Venus and Mars.

Six 3MV launches were planned for the 1964 campaign, three each for Mars and Venus, but only five came off. In view of the high rate of previous failures, the first launch in each set of three was to test the 3MV/launeh vehicle system. However, both the Mars vehicle test flight in November 1963 and the Venus vehicle test flight in February 1964 were lost to launch vehicle failures. Although there was little time left before the launch window to Venus opened in March 1964, it proved possible to launch the two spacecraft in late March and early April. The first mission was lost to a launch vehicle failure, and the second, designated Zond 1, failed 2 months into the cruise when pressurization was lost. A single 3MV was successfully launched to Mars in November 1964. Designated Zond 2, it failed in transit after 1 month, in this case because of avionics problems. Both of these missions were given the designation wZond’ because it was realized shortly after launch that neither would be able reach its target in a functioning state.

The 3MV spacecraft that missed its Mars launch window in November 1964 was launched as a test spacecraft in July 1965. It conducted a successful flyby of the Moon as Zond 3, but failed its planetary test objectives when communications were lost before reaching Mars distance. It was the last 3MV launched to Mars. Later in November 1965 three more were launched to Venus. The first, Venera 2, was lost only 17 days before Venus encounter and the second, Venera 3, was lost just as the spacecraft approached the planet. However, they w7ere both the first Soviet planetary missions to reach the vicinity of their targets. The third spacecraft was lost to a launch vehicle failure.

By March 1966 the Soviet planetary program had no success to show for nineteen launch attempts, eleven to Venus and eight to Mars, since the start of the program in October 1960. Meanwhile, the US had achieved successful flyby missions of Venus in 1962 and Mars in 1965. Also, the builder of all Soviet robotic spacecraft to date, OKB-1, was overloaded with work on the manned space program and so the robotic program was transferred to NPO-Lavochkin. Throughout 1966 Lavochkin modified Korolev’s designs to deal with the problems revealed by previous flights, and began to produce their own versions of the Ye-6 and Ye-8 lunar spacecraft and the 3MV planetary spacecraft for Venus. It was decided not to attempt further ЗМ V missions to Mars, and instead to design a new’ heavier spacecraft w’hich would enter into orbit around the planet and deliver a soft lander. This strategy was intended to upstage the US flyby missions of Venus and Mars scheduled for the 1967-1969 launch window’s with entry probe and lander missions to Venus and with orbiter and lander missions to Mars.

Lavochkin prepared two new’ 3MV spacecraft with entry probes for the Venus 1967 opportunity. The entry probe was designed to make atmospheric measurements while descending by parachute and to survive impact on the surface for an assumed marginal atmospheric pressure. Both were launched in June 1967. The second w as lost to a launch vehicle failure, but on October 18, 1967 the first. Venera 4, became

the first successful planetary entry probe. The Soviets initially believed that it had survived all the way to the surface, but it transpired that it had been overwhelmed by conditions while still high in the atmosphere.

This strategy of two Venus probe launches at each opportunity was repeated for the next three Venus launch opportunities in 1969, 1970 and 1972. There were four successes in six launches, Venera 5 and 6 in 1969, Venera 7 in 1970, and Venera 8 in 1972. The probes were strengthened for each opportunity until they were finally able to survive the high pressures and temperatures at the surface of Venus. The first spacecraft to land and survive on the surface of another planet was Venera 7. Venera 8 duplicated the feat in 1972 near the morning terminator on the illuminated side of Venus and with a more versatile set of measurements.

Campaign objectives:

Korolev’s team had failed in their first two campaigns at both Mars and Venus. In 1960-61 only one mission of four. Venera 1, succeeded in reaching interplanetary space but it failed soon thereafter. In 1962 they had a new7 multipurpose spacecraft ready, the 2MV series, and launched three each to Mars and Venus. This time, only one of six. Mars 1, was successfully dispatched and it fell silent before reaching its target. Meanwhile, the Americans had frustrations of their own, suffering fourteen failed lunar missions through 1962. Their only success. Mariner 2 at Venus in 1962. served to further frustrate the Soviets who had worked hard to beat the Americans to our neighboring planets.

By now it was evident that there w ere serious problems w ith the reliability of the 8K78 launcher, in particular its fourth stage, and with the spacecraft. The troubled but lengthy flight of Mars 1 revealed problems serious enough to merit a redesign of the 2MV, and Korolev directed that these lessons be applied to building a new 3MV series for the Venus and Mars windows in 1964. and that test flights be conducted in between planetary opportunities. And, of course, he continued to instrument the fourth stage to diagnose its problems. The test flights were intended to validate the whole system from launcher to spacecraft.

The 3MV spacecraft was similar to the 2MV but with improved avionics. Special versions, designated 3MV-1A and 3MV-4A, were built for test missions simulating flights to Venus and Mars. These were lighter test models and did not carry a full set of science instruments. The first 3MV was launched in November 1963. The intent was to test planetary Hyby operations and the camera system at the Moon, and then perform operations to Mars distance before the Mars launch window opened a year later. The launch failed. It was followed in February 1964 with a launch of a test flight to Venus distance just prior to the opening of the Venus window in late March. This launch also failed. Despite these two losses, the Soviets had little option but to proceed with the 1964 program. Two of 3M V spacecraft were launched in the Venus window in March and April, the first succumbing to its launch vehicle and the second. Zond 1. failing in transit.

Undaunted, the Soviets continued with preparations for Mars. Although two flyby spacecraft and at least one entry probe were built, there were technical problems and only one spacecraft made it to the launch pad. The 3MV-4 No.2 flyby spacecraft was successfully dispatched on November 30, 1964. When it became clear that the spacecraft would not be able to meet its objectives, it was named Zond 2. The other Mars spacecraft prepared for this launch window were scrubbed and stored w hile the problems with the ЗМV were investigated. They w’ould subsequently be used for the Zond 3 mission and for the Venus campaign in 1965.

Following the string of five 3MV mission failures in 1963 1964, it was decided to conduct another test. The 3M V-4 No.3 Mars flyby spacecraft that missed its window in 1964 was launched 8 months later. Its task was the same as the spacecraft lost in November 1963, to test the spacecraft and science instruments in a lunar flyby and then test the deep space capabilities of the spacecraft by flying to Mars distance even though the planet would not be present upon arrival. After a successful launch, the spacecraft was designated Zond 3. (The Zond designation had initially been assigned to spacecraft that were clearly not going to be able to meet their objectives, as in the cases of Zond 1 and 2, and would henceforth be used for spacecraft launched either for deliberate testing purposes or to conduct science.) The lunar flyby was timed to photograph the far side of the Moon using the Mars camera, and Zond 3 successfully achieved its test objectives at the Moon. It failed to reach Mars distance but was able to maintain communications for almost 8 months, finally falling silent at a range of over 150 million km.

The Zond 3 spacecraft was the last of the 3MV Mars series to be launched before the robotic lunar and planetary programs were transferred to NPO-Lavochkin, where it w’as decided to abandon the troublesome 3MV design for Mars and instead design a new, heavier and much more capable spacecraft for launch by the Proton. None of the tw o 1M, three 2MV and three 3MV spacecraft launched to Mars, a total of eight including the two 3MV tests, had reached their targets, although Zond 3 did succeed at the Moon.

Spacecraft:

The ЗМ V spacecraft was similar in appearance and general function to the 2MV. It w? as slightly longer at 3.6 meters and had the same inline modular design consisting of a pressurized avionics or "orbital’ module, a propulsion system, and a pressurized flyby instrument module or entry probe. Minor changes were made to the shape in order to modify the moment of inertia and to account for solar wind torques, but the other dimensions were the same as the 2MV. A black shield was added in order to prevent scattered light from interfering with the optical sensors.

A thermal protection cowl was added to the Isayev KDU-414 propulsion system. This system was used for the 1M, 1VA, and all 2MV and ЗМ V spacecraft through to Venera 8. with variously sized tanks for its unsymmetrical dimethylhydrazine and nitric acid propellants. It w as capable of multiple firings, and on the 2MV and 3MV was gimbaled for thrust vectoring under gyroscopic control. The propulsion system assembly, including its tanks, was about 1 meter in length. For 3MV Venus missions the eompressed nitrogen gas bottles used to pressurize the engine propellants and for cold gas attitude control jets were mounted on the engine cowling. For 3MV Mars missions these bottles were on the collar bctw’een the avionics module and the flyby or entry module. Major improvements were made to the avionics, and redundancy w as added to the attitude control system jets. The high gain antenna w as increased to a diameter of 2.3 meters. Low gain omnidirectional antennas were installed on the

hemispherical radiators that circulated liquid. In addition to the attitude, navigation, thermal and operational control systems, the avionics module held 32 cm and meter band transmitters, 39 cm and meter band receivers, and two tape recorders. The solar panels charged a 112 amp-hour NiCd battery array that supplied the spacecraft with DC power at 14 volts.

In addition to the science instruments and the 5 cm impulse image transmitter, the flyby module contained an 8 cm continuous wave transmitter for backup image or spacecraft data transmission, and backup fonns of the command receiver and other avionics capable of operating the spacecraft in the event of a failure in the avionics module.

Each of these spacecraft, both Mars and Venus versions, had experimental plasma pulse engines on the engine cowl for attitude control in addition to the standard cold gas jets. They were tested successfully on Zond 2. and were later perfected and used regularly on Soviet spacecraft.

Launch mass: 800 kg (Cosmos 21)

950 kg (Zond 2)

960 kg (Zond 3)

Payload:

3MV-1A ISo.2:

1. Facsimile imaging system

2. Radiation detector

3. Charged particle detector

4. Magnetometer

5. Micrometeoroid detector

6. Lyman-alpha atomic hydrogen detector

7. Radio telescope

8. Ultraviolet and x-ray solar radiation experiment Zond 2 and 3:

1. Facsimile imaging system

2. Ultraviolet 285 to 355 nm spectrograph in the camera system

3. Ultraviolet 190 to 275 nm spectrograph for ozone

4. Infrared 3 to 4 micron spectrometer to search for organic compounds

5. Gas discharge and scintillation counters to detect Martian radiation belts

6. Charged particle detector

7. Magnetometer

8. Micrometeoroid detector

After the 1962 campaign, a major improvement was made to the facsimile film imaging system for the flyby missions. The imager mass w7as reduced from 32 to 6.5 kg while using 25.4 mm film capable of storing 40 images. Zond 2 carried two of these cameras equipped with 35 and 750 mm lenses. Zond 3 carried one camera with a 106.4 mm lens. Alternative exposures at 1 100th and 1/300th of a second were used, and an image could be taken and developed every 2.25 minutes. The 25 mm film could be repeatedly rewound for scanning at 550 or 1Л00 lines per frame. Imaging data were stored on the tape recorder that was included in the infrared spectrometer electronics. The 5 cm impulse transmitter and modulation scheme were improved for a factor of four decrease in image transmission times. In the high quality mode, camera images were transmitted at 550 pixels/second. which was 2 seconds per scan line, requiring a total of 34 minutes to send a 1,100 x 1,100 image. If necessary, the images could be sent at much slower rate by the 8 cm continuous wave transmitter. An ultraviolet spectrometer operating in the 285 to 355 nm range was built into the camera and reeorded its data on three frames of the film. These instruments were carried inside the flyby module and observed through three portholes – one for each lens and the spectrometer. Л second ultraviolet spectrometer operating in the 190 to 275 nm range was carried externally and produced digital data. The optical system for the infrared spectrometer was also mounted externally, and w as equipped with a small visible wavelength photometer to provide a reference signal. All of the optical instruments were bore-sighted.

Mission description:

The 3MV-1A No.2 mission ended in failure when the spacecraft was stranded in low Earth orbit. The third and fourth stages apparently separated abnormally. The fourth stage diverged in attitude during coast, and was incorrectly aligned when the engine ignited. Telemetry w’as lost at 1,330 seconds into the flight and the fourth stage with its payload remained in Earth orbit. With this mission, the Soviets initiated a policy of designating lunar and planetary missions stranded in parking orbit as ‘Kosmos a designation that was previously used for scientific satellites, in an effort to obscure their intended purpose. Today. Cosmos is used to designate military missions. 4 he failed 3MV-1A became Cosmos 21 and it re-entered 3 days later.

One year later, after another failed test launch of a 3MV Venus spacecraft and two launches to Venus, including Zond 1. the 3MV-4 No.2 spacecraft was launched on November 30. 1964, for what was intended to be a flyby of Mars at a distance of 1.500 km. However, one of the solar panels did not open due to a broken pull cord. The second panel was finally deployed on December 15 after several engine firings shook it loose, but by then it was too late to perform the first trajectory correction. It suffered other problems, including a timer that failed to activate the thermal control system properly. Unlike Zond 1 earlier in the year, the Soviets revealed Mars as an objective but. knowing that the flyby would not occur in the planned manner, they named the spacecraft Zond 2 and said its objectives were to carry out experiments ‘"in the vicinity of Mars”.

During the last authenticated communications session on December 18, 1964, the plasma engines were successfully tested. After that, communications became erratic. Jodrell Bank monitored transmissions from Zond 2 in Ianuarу and on February 3. 10 and 17. but it is unclear if any further operations were conducted. The Soviets finally announced on May 5 that contact had been lost. The USSR lost the opportunity to be the first to fly past Mars. This honor went to Mariner 4 on July 15. 1965, which the US had launched 2 days before Zond 2. On August 6 the silent Zond 2 flew by Mars at a range of 650.000 km.

Zond 3 was launched successfully on July 18, 1965. Approximately 33 hours later the imaging sequence began at a range of 11,570 km from the lunar near side, and continued through the lunar far side passage over a period of 68 minutes as the range closed to 9.960 km. The closest point of approach had been 9,219 km on the far side. A total of 28 linages were developed on board and transmitted on July 29, by which time the spacecraft was 1.25 million km from Earth. The spacecraft continued on its deep space test flight. A midcourse correction of 50 m/s was made on September 16 at a range of 12.5 million km. The images were rebroadcast from 2.2 million km and again at 31.5 million km to test the capabilities of the communications system. The last communication was on March 3, 1966, at a range of 153.5 million km, well on the way to the orbital distance of Mars.

Results:

There were no results for Mars. Zond 2 made a successful technology demonstration that was important for later deep space missions by operating its six plasma engines prior to the loss of communications, but they were found insufficient to control the attitude of the spacecraft. Zond 3 photographed 19 million square kilometers of the lunar surface including the.30% of the lunar far side that had been in darkness for Tuna 3. The twenty-five visible-band images and three ultraviolet-band images were of much better quality than the Luna 3 pictures. The Soviets achieved an engineering success with their first course correction to be performed using both solar and stellar references.

TIMELINE: AUG 1970-FEB 1972

The Soviets reached the zenith of their success at the Moon with robotic missions in 1970 and 1971. In September 1970 the Luna 16 mission successfully returned a sample of the Moon to Earth; an impressive achievement still unmatched by the US. In November the Luna 17 mission successfully deployed the first robotic rover on the Moon, Lunokhod 1; another achievement unmatched by the US. An attempt at sample return in September 1971 failed when communications were lost as Luna 18 was landing. It was followed immediately by Luna 19, a successful orbiter version of the spacecraft. Luna 20 became the second successful sample return mission in February 1972.

The Soviets also finally achieved a landing on Venus after eleven attempts since February 1961. Venera 7 was launched on August 17, 1970. with a descent capsule modified to withstand the massive surface pressure on Venus, and this succeeded in descending through the entire atmosphere and gently impacting the surface where it continued to operate for 23 minutes before succumbing to the high temperature. The Soviets finally had some success at Mars in 1971 after eight attempts since October 1960. The 1971 opportunity was not as energetically favorable as in 1969. requiring the landers to be released in the approach rather than after entering orbit around the planet. This and several engineering problems with the Mars-69 spacecraft forced a complete redesign. The 1971 Mars spacecraft became the basic design reference for all Soviet Proton-launched planetary spacecraft thereafter.

The Soviet plan in 1971 was to start with an orbiter to Mars which would provide precise information on the position of the planet to the spacecraft that followed, to enable these to deploy their landers on the necessarily very precise entry trajectories before themselves entering into orbit. This plan tvas foiled when the launch of the leading orbiter failed on May 10. Fortunately, the Soviets had a backup plan in which the approaching carrier spacecraft would use on board optical navigation to determine the position of Mars and autonomously update their navigation system so that they could properly deploy their landers. This complex and sophisticated system was far in advance of its lime, but very risky. The Mars 2 syslem rvorked, but due to a software error it dispatched its lander on an entry angle which was too steep and

W. T. Huntress and M. Y. Marov, Soviet Robots in the Solar System: Mission Technologies and Discoveries, Springer Praxis Books 1, DOl 10.1007/978-1-4419-7898-1 12,

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Launch date

1971

1972

14 Feb Luna 20 sample return

resulted in a crash. It worked perfectly for Mars 3 whose entry system placed the first successful lander on Mars, but after sending 20 seconds of uninterpretable data it fell silent. Both spacecraft entered orbit around the planet and transmitted images of its surface and data on its atmosphere, surface and plasma environment.

The US also had a major success at Mars in 1971. Mariner 9 was the lirst mission from this launch opportunity to arrive and became the first spacecraft to enter orbit. With more sophisticated cameras and systems, and an excellent instrument suite, its accomplishments completely eclipsed those of the much heavier Soviet orbiters.