Category Soviet Robots in the Solar System

TIMELINE: 1977-1978

With nothing left to accomplish on the Moon, and having abandoned Mars for the immediate future, Soviet scientists and engineers focused their robotie exploration solely on Venus. In 1978 they launched a second pair of spacecraft which were near duplicates ol" Venera 9 and 10. Because the energetics for this opportunity were less favorable, it was not practicable to send an orbiter/1 under and instead the lander was to be delivered by a spacecraft that would perform a flyby and relay to Earth the data from the entry system and lander. Although both of the Venera 11 and 12 landers touched down, they suffered a number of problems and in particular were unable to provide imagery.

The US also sent spacecraft to Venus in 1978, but these were very much smaller. The Pioneer 12 Venus orbiter was an outstanding success, reporting information on the upper atmosphere for many years. Pioneer 13 adopted a collision course and deployed one large and three small entry probes, all of which successfully returned atmospheric data during their descent.

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 15,

© Springer Science+Business Media, LLC 2011

OKB-1

The founding space exploration enterprise in the Soviet Union was Experimental Design Bureau No. l (OKB-1). It had its beginnings in the Scientific Research Institute No.88 (N11-88). A new design section. Department No.3, was set up by the government in May 1946 for the dozens of engineers who had just returned from over a year of investigating the German rocket industry. Sergey Korolev headed the department as Chief Designer. It comprised almost 150 engineers and technicians, and its task, Stalin stated, was to build a Soviet version of the V-2. After succeeding with the R-l. and proceeding to design new rockets of its ow n, the department was restructured into a larger design bureau OKB-1 in the early 1950s and then separated from NII-88 in 1956. OKB-1 built the first Soviet ballistic missile to carry a nuclear warhead, the intermediate range R-5M, and the first submarine-launched ballistic missile, the R-11FM. Korolev’s proposal to build the first intercontinental ballistic missile, the R-7, was approved by the government in 1954. The first successful test of the missile wra$ carried out in August 1957 and on October 4, 1957 it was used to launch Sputnik. The R-7 has been modified, augmented and upgraded in various forms to become the most prolific and successful space launch vehicle in history.

While building for the military. Korolev’s real passion was for space exploration. OKB-1 would eventually lose the military rocket business to rivals, but it achieved great success in space exploration, along with frustrating failure, before Korolev’s death in 1966. After Sputnik. Korolev and OKB-1 pursued more ambitious goals robotic flights to the Moon and planets, and manned flights into Earth orbit. OK B-1 built the first spacecraft to impact the Moon, Luna 2, the first to photograph the far side of the Moon, Luna 3. and the first interplanetary spacecraft intended for Mars and Venus, but the failure rate was terrific. From 1958 through 1965, only four of 21 robotic flights to the Moon were successful (Luna 1, 2 and 3, and Zond 3); none of eleven attempts at Venus and none of the seven attempts at Mars w ere successful. On the other hand, OKB-1 had a singularly excellent record in manned spaceflight, launching the first man into space in 1961, the first woman into space in 1963. the first multi-person spacecraft in 1964, and the first spacewalker in 1965.

There were other design bureaus critical to the space program in the mid-1960s. Valentin Glushko’s OK B-456 w as the premier developer of rocket engines. Glushko

supplied engines for Korolev’s early rockets as well as other military rocket builders such as Chclomey. Chclomcy’s OKB-52 built the Proton rocket which became the staple heavy launcher for Soviet lunar and planetary spacecraft. In 1964 the Soviet Union made the late decision to compete with the IJS and send cosmonauts to the Moon. Korolev, Glushko and Chelomey each presented plans to the government for building the necessary rockets and spacecraft. After considerable wrangling. OKB-1 won on the basis of its head start in the manned program and long-standing work on the design of a Moon rocket. Chelomey did save his Proton rocket from the military scrapheap for the precursor manned circumlunar flights, but OKB-1 was to provide the final upper stage and the spacecraft.

During the battle for control of the manned lunar program, tvhile still conducting both manned and robotic flight programs, succeeding with one and struggling with the other. Korolev realized that OKB-1 had taken on too much. It was essentially responsible for the entire Soviet space effort including communications satellites, reconnaissance satellites, robotic and manned space exploration programs. OKB-1 had to offload something in order to relieve the pressure on his organization, so in March 1965 Korolev reluctantly transferred the robotic program to NPO – Lavochkin. Keldysh played a significant role in this decision. If any comparison to the US could be made at this point, it would be that the USSR had two NASAs one for manned missions (OKB-1) and another for robotic missions (NPO – Lavochkin). This is not a perfect comparison, however, since neither had full control of its own funding or its suppliers; that came from MOM.

After Korolev died in January 1966. OKB-1 was renamed the Central Design Bureau of Experimental Machine Building (TsKBEM) and his deputy Vasily Mishin took over. But unlike Korolev. Mishin was not a charismatic and politically savvy leader and he immediately ran into trouble. He introduced Korolev’s three-person Soyuz spacecraft into service for the first time in April 1967 with tragic results, killing the test pilot Vladimir Komarov when the parachute failed to deploy properly as he returned to Earth. He then presided over the repeated failure of the N-l rocket, which would have launched the Soviet Union’s challenge to Apollo. In 1974 he was replaced by Glushko, who merged the organization with his OKB-456, and then with Chclomcy’s OKB-52, to form the giant NPO-Encrgiya. This organization went on to produce the Energiya heavy lift rocket, the Buran space shuttle, and the Salyut and Mir space stations. Now known as the S. P. Korolev Rocket and Space Corporation Energiya (RRK Energiya) it dominates the Russian manned space flight enterprise, having operated the Mir space station for almost 15 years, supplied the Zvezda habitat module for the International Space Station, and a decade of flights of the Soyuz and Progress spacecraft to service the ISS.

There were essentially three general design series of Russian planetary spacecraft. None of them resembled their American counterparts because, unlike the latter, the Russian spacecraft required pressurized containers for most of their electronics. The Venus and Mars flights in 1960-61 used the first generation spacecraft, which were simple pressurized canisters with attached solar panels and high gain antennas. Their payloads were specific to the target planet, but in general the spacecraft were the same. Of the four launched, only Venera 1 was successfully dispatched and it failed early in its cruise through interplanetary space.

The second generation introduced the first modular spacecraft, with a pressurized carrier that had the propulsion system at one end and a module for the payload at the other. They were individually outfitted for missions to Mars or Venus, with either an entry probe or a flyby module for remote sensing. (This same modular approach was adopted for the second generation Ye-6 lunar spacecraft series.) There were two sub-types of this spacecraft, 2MV and 3MV. Six 2MV spacecraft were launched in 1962, three for Venus and three for Mars, but only one, Mars 1. survived its launch vehicle. The flight of Mars 1 was plagued with problems and it succumbed half way to its target, but the lessons learned were applied in developing the 3MV. Seventeen 3MV spacecraft were launched between 1963 and 1972, five of which. Venera 4 to 8. achieved their planetary objectives. One of the Mars types, Zond 3. did achieve significant results by imaging the far side of the Moon as it departed and subsequently testing the communications system by transmitting the pictures from deep space.

The third generation planetary spacecraft were a major design change, enabled by the powerful Proton launcher with the Block D upper stage. These much larger and

figure 5.5 Representative Soviet planetary spacecraft to scale: first generation Venera 1 (upper left); second generation Venera 4 to 8 (upper right); and third generation Venera 9 to 14 at lower left; and Mars 2. 3, 6 and 7 at lower right (from Space Travel Encyclopedia).

more complex spacecraft were meant to provide planetary orbiters and soft-landers, starting with Mars in 1969 and Venus in 1975. Of twenty-two launched, Venera 9 to 16 and Vega 1 and 2 ran up a string of straight successes at Venus. The other twelve experienced a more difficult challenge at Mars, where only five can be deemed even partial successes, Mars 2 and 3, Mars 5 and 6, and Phobos 2. The Phobos missions of 1988 and the Mars-96 spacecraft were derivatives of this class, but with upgrades sufficiently significant for them perhaps to be regarded as another generation.

In normal flight, Russian spacecraft were flown in uniaxial orientation in which their static solar panels were oriented constantly towards the Sun and the craft spun at 6 revolutions per hour on the axis perpendicular to the plane of the solar panels. The command uplink was at 768.6 MHz through semi-directional conically-shaped spiral antennas which were also used for low-rate data transmission. Because these antennas generate funnel-shaped radiation patterns, several were placed around the spacecraft pointing at the Sun, and at any point in the mission the one with the best funnel angle for Earth was used. For high data rate transmissions, a parabolic high – gain antenna was affixed to the spacecraft. This had to be aimed directly at Earth by disabling the uniaxial control mode, reorienting the spacecraft appropriately, and switching to the three-axis orientation control mode. Circularly polarized decimeter (~920 MHz) and centimeter (~5.8 GHz) band transmitters shared the dish antenna.

In 2MV and 3MV missions, planetary probes and landers were designed for direct transmission to Earth by small spiral antennas with pear-shaped radiation patterns.

The heavier Proton-launched Mars and Venera landers were designed to relay their transmission through flyhy or orbiter spacecraft using large meter band (186 MHz) helical antennas mounted on the rear of the solar panels. The Mars 3 class of entry vehicle carried small wire antennas on the entry stage and another set on the lander. The Venera 9 class of entry vehicle had another large helical antenna installed on top of the lander. Data from the Mars and Venus entry systems was stored for later transmission, but in the case of the Venus landers it was also relayed in real-time as a precaution. The entry system data link operated at 72,000 bits/s for Mars and at 6,144 bits/s for Venus.

Campaign objectives:

After the three Venus launches failed in late August and early September, Korolev’s team scrambled to prepare for three more launches to Mars in late October and early November. Many measures were taken to enhance the reliability of the fourth stage. There was some pressure to abandon the Mars attempts until the problems with this stage were solved, but Korolev blazed ahead.

The 1962 Mars campaign consisted of two flyby missions and one entry probe. The objectives of the entry probe were to obtain in-situ data on the composition and structure of the atmosphere, and data on surface composition. The objectives of the flyby missions were to examine the interplanetary environment between Earth and Mars, to photograph that planet in several colors, to search for a planetary magnetic field and radiation belt, to search for ozone in the atmosphere, and to search for organic compounds on the surface. A comprehensive payload was prepared for each spacecraft, but apart from the camera and a magnetometer most of the payload was deleted when it was decided instead to install instrumentation to monitor the fourth stage to find out why it was suffering so many failures. These missions then became primarily engineering test flights of the 8K78 fourth stage, with Mars as a secondary objective.

Although the fourth stage failed again on two of the launches, the second of three worked and provided the Soviets with their first spacecraft to Mars. Unfortunately, as in the case of Venera 1 it was immediately clear that Mars 1 had attitude control problems. The inability to perform a midcourse maneuver ruled out the desired close flyby of Mars. On the other hand, communications with Mars 1 were maintained for almost 5 months before it fell silent about half w ay to its target.

Spacecraft:

The 2M V Mars spacecraft were virtually identical to the versions described in detail above for the 1962 Venus missions. Although we have no description of the 300 kg entry probe of the 2M-3 No. l spacecraft we know7 it w7as not designed as a lander but as a simple spherical entry system containing a parachute, radio, and instruments intended for measurements during descent. Surviving impact must have been more a hope than a goal. In fact, since the designers had no idea just how thin the Martian atmosphere is. the entry probe would have crashed into the surface before any useful data could have been returned.

The Mars 1 spacecraft is depicted in Figure 8.4 in a stand. Above the stand is the pressurized compartment containing the scientific instruments for the flyby. Next is the ‘orbital’ compartment. The large port in the front is the star sensor, and to the right of that is the Sun sensor. The gas bottles for the attitude control system are on
the waist separating the two compartments. Topping the spacecraft is the propulsion system. The parabolic high gain antenna is fixed pointing in the opposite direction to the solar panels, and there are hemispherical radiators mounted on the ends of the panels.

Launch mass: 893.5 kg (Mars 1)

1.097 kg (probe version)

305 kg ‘

Payload:

Many of the instruments developed for the 2MV Mars spacecraft were removed in order to accommodate systems to monitor the fourth stage of the launcher. There is no information on how many were actually removed, but the magnetometer and the flyby imaging system are known to have been carried by Mars 1.

The original set of instruments is given in this list.

Carrier spacecraft:

1. Magnetometer to measure the magnetic field

2. Scintillation counters to detect radiation belts and cosmic rays

3. Gas discharge Geiger counters

4. Cherenkov detector

5. Ion traps for electrons, ions and low-energy protons.

6. Radio to detect cosmic waves in the 150 to 1,500 meter band

7. Micrometeoroid detector

Descent I landing capsule:

1. Temperature, pressure and density sensors

2. Chemical gas analyzer

3. Gamma-ray detector system to measure radiation from the surface

4. Mercury level movement detector

Flyby instrument module:

1. Facsimile imaging system to photograph the surface

2. Ultraviolet spectrometer in the camera system for ozone detection

3. Infrared spectrometer to search for organic compounds

These instruments were identical to those built for the Venus mission, except that the Mars infrared spectrometer operated in the 3 to 4 micron C-H band to search for organic compounds and vegetation on the surface of Mars.

Mission description:

Two of the three missions were lost to the new and as yet unreliable fourth stage. The 2MV-4 No.3 Mars flyby was launched on October 24, 1962, but failed to leave parking orbit when the fourth stage turbo pump failed after 17 seconds due either to a foreign particle in the assembly or to the pump overheating after a lubricant leak. The fourth stage and spacecraft broke into five large pieces that re-entered over the course of the next few’ days. The US Ballistic Missile Early Warning System radar in

Alaska, which was at a state of high alert in the midst of the Cuban missile crisis, dc tec ted the debris after launch and was initially concerned that it might represent a Soviet nuclear ICBM attack, but rapid analysis of the debris pattern put this fear to rest.

The rocket carrying the second spacecraft was rolled out to the pad the next day. October 25, at the peak of the missile crisis. Shortly thereafter the firing range was ordered to battle readiness, which required the preparation for launch of the two R-7 combat missiles. One of these was stationed at the launch site where the Mars rocket stood. Stored in a corner of the Assembly and Test Building, it was uncovered and the launch team switched from supporting the Mars launch to preparing the missile. Fortunately, when the order to stand down came on October 27 the Mars rocket had not yet been removed from the launch pad. The 2MV-4 No.4 flyby spacecraft was successfully launched on the optimum date of the window, November 1, and became the first spacecraft to be sent towards Mars. The mission was named Mars 1. Just as in the case of Venera 1, a serious problem was discovered immediately after launch. The pressure in one of the two nitrogen gas containers was dropping rapidly because of a leaking valve. Later analysis showed that manufacturing had allowed debris to foul one of the valves. The outgassing caused the spacecraft to tumble out of control. When the tank drained after several days, ground controllers managed to use the gas in the remaining tank to halt the tumbling, restore the spacecraft to the desired Sun pointing attitude and spin it at 6 revolutions per hour so that the batteries would be continuously recharged from the solar panels. But by then most of the dry nitrogen for the cold gas jets of the attitude control system and for pressurizing the engine was expended. The backup gyro system used for attitude control was not designed for continuous use. Stuck in the backup Sun pointing spin mode, the spacecraft was unable to point its high gain antenna at the Earth or to make a midcourse correction. The Earth link was maintained through the UHF system and the medium-gain semi­directional antennas. Contact was established every 2 days for the first 6 weeks, and then every 5 days thereafter. On March 2. 1963, the signal strength began to decline and communications were lost on March 21, probably due to a final breakdown of the attitude control system at the unprecedented range of 106,760,000 km. The silent spacecraft would have passed Mars at a distance of about 193,000 km on June 19, 1963; the intended flyby distance was between 1.000 and 10.000 km.

The third spacecraft to be launched, 2MV-3 No. l, was stranded when the fourth stage failed to reignite properly. Vibrations in the core stage caused by cavitation in its oxidizer lines had dislodged a fuse and igniter in the fourth stage. Its engine was commanded to shut down after 33 seconds. The Americans detected five pieces of debris whose origins were unclear. The spacecraft is believed to have re-entered on January 19, 1963.

Of the six 2M V spacecraft launched between August and November 1962, four were lost to failures of the fourth stage, one was lost to a failure of both the third and fourth stages. The other one was launched successfully and named Mars 1, but failed in transit. No more 2MV spacecraft were built. The design wras improved to produce the 3MV spacecraft for the next series of Mars and Venus missions in 1964 1965.

In the US, the orbital remains of the 1962 Venus and Mars spacecraft, including

Mars 1, were designated as Sputniks 19 to 24 in order of launch. All the spacecraft stranded in parking orbit re-entered within days.

Results:

No information was obtained on Mars. However, Mars 1 did acquire data during its cruise before it fell silent. The radiation zones around Earth were detected, and the distribution and flux of particles were measured. Л third zone at 80,000 km was detected. The solar wind and magnetic fields were measured in interplanetary space to a farther distance than Venera 1. Л solar wind storm was measured on November 30, 1962. ‘flic intensity of cosmic rays had almost doubled since 1959 due to a less active Sun. The micrometeoroid collision rate decreased with distance from Earth and showed intermittent increases as meteoroid showers were traversed. The Taurid meteor shower w as encountered twice at ranges from 6,000 to 40.000 km, and again at distances from 20 to 40 million km. with a strike rate of one every 2 minutes on average.

In late 1968 and early 1969 it became apparent to the Soviet Union that American astronauts might very well reach the Moon before Russian cosmonauts. Anxious to ensure that a Soviet mission was first to return lunar soil to Earth, NPO-Lavochkin hurriedly modified the Ye-8 spacecraft for a sample return mission. The lunar rover variant of this spacecraft was well advanced in design by the end of 1968. and could readily be modified simply by replacing the payload of the lander. Even although it would have scientific merit, the sample return mission had a far greater significance than being just another task for the Ye-8. The robotic sample return mission became the means to upstage Apollo by returning a sample to Earth before the Americans could do so. The fact that these complex spacecraft could be designed and built so readily, and ultimately work so well, is amazing in hindsight. It would seem to be a Russian characteristic to ”just do if to dismiss the hardship, use whatever you have at hand, and fix things up on the fly during and after build.

The modification of the Ye-8 lunar rover spacecraft to the Ye-8-5 for the sample return mission faced daunting problems, not the least of which were mass limitations on the return vehicle, lifting off from the Moon and navigating back to Earth. It was originally believed that the return vehicle would require the same complex avionics as any interplanetary spacecraft, to enable its position to be determined and to make midcourse correction maneuvers. The avionics necessary to meet these requirements far exceeded the available mass. However. D. Ye. Okhotsimskiy, a scientist at the Institute of Applied Mathematics, found a small set of flight trajectories for launches from the surface of the Moon that did not require midcourse corrections. In essence, the large gravitational influence of the Earth at lunar distance could, under certain conditions, assure an Earth return. These trajectories were limited to specific points on the Moon, varying within a general locus with the time of year, and required the lander to set dow n within 10 km of its target and the lunar liftoff for a direct ascent to occur at a precise moment. Accurate knowledge of the lunar gravitation field was also required, but this information had already been determined by the Luna 10, 11. 12 and 14 orbitcr missions.

These passive return trajectories simplified the ascent vehicle enormously. Only a single burn of the ascent vehicle was required. No active navigation was necessary, and no midcourse maneuvers were required. The only problem with a passive return was the very large error ellipse on arrival at Earth, which would make recovering the small capsule impraclically difficult. This problem was solved by using a low-mass meter wave radio beacon on the ascent vehicle so that radio tracking would be able to determine its actual trajectory, supplemented by optical observations from Earth during the latter half of its flight. In addition, the return capsule would have its own radio beacon to assist in recovery operations.

Even with these ingenious solutions, the engineers could not trim the design mass of the Ye-8-5 below 5,880 kg. At that time the most that the Proton-К could send to the Moon was 5,550 kg. However, Babakin managed to cajole the Proton maker into providing sufficient additional mass capability to launch his sample return spacecraft to the Moon. This was accomplished without major changes to the launch vehicle.

Spacecraft;

Lander stage:

The lander stage was essentially the same as designed for the rover mission and its mission profile through to lunar landing was identical. The only differences were the attachment of a surface sampling system and, for the first eight spacecraft, a pair of television cameras for stereo imaging of the sampling site and floodlights for night landings. The rover and ramps were replaced by a toroidal pressurized compartment which held the instruments and avionics for surface operations. The ascent stage was mounted on top, with the entire lander and toroidal compartment acting as its launch pad.

The ascent stage was powered by a silver-zinc 14 amp-hour battery, and the return capsule by a 4.8 amp-hour battery. Lander communications were provided at 922 and 768 MHz, with backups at 115 and 183 MHz. The ascent stage communicated at 101.965 and 183.537 MIIz. The return capsule had beacons at 121.5 and 114.167 MHz for radio tracking.

The sampling system for the Ye-8-5 consisted of an upright 90 cm long boom arm capable of two degrees of freedom, with a drill at its end for surface sampling. Three movements were required to place the drill on the surface through a 100 degree arc of swing, and then another three to transfer the sample to the ascent stage. From the stowed position it first swung itself vertical, then rotated in azimuth to line up on the selected sample site before swinging down onto the surface. A movement in azimuth with the head on the ground might be used to clear a small area to improve drilling. This sequence was reversed to transfer the sample to the return capsule of the ascent stage. Mounted at the end of the boom was a cylindrical container 90 mm diameter and 290 mm long for a hollow rotary/percussion drill. The drill bit had a diameter of 26 mm and was 417 mm long. Its cutter was a crown with sharp teeth. The drill was equipped with different coring mechanisms for hard coring and for loose coring. At a speed of

500 rpm, it required 30 minutes to fill the entire core length of 38 cm. The drill was both insulated and hermetically sealed, and to enable the mechanism to be lubricated using oil vapor it was not opened until just before use. Some parts used a lubricant designed to reduce friction in a vacuum. A standby motor was provided as a contingency to overcome obstacles encountered during drilling. The whole device weighed 13.6 kg.

An improved drill system tvas provided for the Ye-8-5M version, which had a rail mounted deployment mechanism. This drill was capable of penetrating to a depth of

2.5 meters and preserving the stratigraphy, but it could not be articulated to select a sampling site. It used an elevator mechanism rather than the articulated boom arm to transfer the sample to the return capsule.

Ascent stage:

The ascent stage was a smaller, vertically mounted open structure composed of a pressurized cylindrical avionics compartment above three spherical propellant tanks and the rocket engine. This was the same engine as used on the lander, but was not throttled. Four vernier engines were attached outboard of the propellant tanks. There were perpendicular antennas mounted radially at 90 degree intervals near the top of the avionics compartment. The spherical return capsule was held in place on top by deployable straps. Including the return capsule, the ascent stage was 2 meters tall. It weighed 245 kg dry and 520 kg with propellant. The KRD-61 Isayev engine burned nitric acid and UDMH and produced a thrust of 18.8 kN for 53 seconds to impart a velocity of 2.6 to 2.7 km/s, which was enough to escape from the Moon on a direct ascent trajectory.

Return capsule:

The return capsule was a 50 cm sphere covered with ablative material for entry at a speed of about 11 km/s and a peak deceleration load of 315 G. It had three internal sections. The upper section contained the parachutes (a 1.5 square meter drogue and a 10 square meter main) and beacon antennas, the middle section contained the lunar sample, and the base had the heavy equipment including batteries and transmitters.

on entry.

Luna 15 launch mass: 5,667 kg

Luna 16 launch mass: 5,727 kg

Luna 18 launch mass: 5,750 kg

Luna 20 launch mass: 5,750 kg

Lima 23 launch mass: 5,795 kg

Luna 24 launch mass: 5,795 kg

4,800 kg (Luna 24)

1,880 kg

520 kg (515 kg for Luna 23 and 24) 35 kg (34 kg for Luna 23 and 24)

Payload:

1. Stereo panoramic imaging system with lamps (deleted on Luna 23 and 24)

2. Remote arm for sample collection (improved drill on Luna 23 and 24)

3. Radiation detectors

4. Temperature sensor inside capsule

The stereo imaging system had two 300 x 6,000 panoramic scan cameras of the type used on the earlier Yc-6 landers and Lunokhod rovers. Mounted on the lander just below the level of the ascent stage on the same side as the sampling system, they were spaced 50 cm apart, angled at 50 degrees to the vertical, and gave a field of view of 30 degrees. The orientation of the lander was determined by measuring the position of Earth in a panoramic image. Stereo images were taken of the surface between the
two landing legs to select the position to be sampled. They also imaged sampling and drilling operations, For the Luna 23 and 24 sample ret urn missions the earner as and lamps were deleted.

Mission description:

Only six of the eleven spacecraft in this series were launched successfully. Of these, three succeeded in returning lunar samples to Earth.

The first attempt

The first launch (Ye-8-5 No.402) was attempted on June 14, 1969. one month prior to the Apollo 11 launch date, but the Block D failed to ignite for its first burn and the payload re-entered over the Pacific Ocean.

Luna 15

The second spacecraft in this series was successfully launched on July 13, 1969, just 3 days before Apollo 11, and the Soviets announced that Luna 15 was to land on the Moon on July 19, one day ahead of the Americans, with the objective of returning something to Earth. At 10:00 UT on July 17 it entered a 240 x 870 km lunar orbit inclined at 126 degrees. ‘This orbit was much higher than intended, so the next day it was trimmed to 94 x 220 km. Another trim a day later yielded an orbit 85 x 221 km. Ideally the orbit should have been near-circular at about 100 km, but the Soviets had underestimated the effect of the lunar in a scons and they were also suffering attitude control problems. Meanwhile. Apollo 11 had arrived and entered an equatorial orbit The drama was palpable. In Russia its nature was clear, but in America the ultimate purpose of Luna 15 was mysterious and opinions ranged from the suspicious to the sublime to the ridiculous. Apollo 8 astronaut Frank Borman, just back from a visit to the Soviet Union, appealed for information and the Academy of Sciences supplied orbit data, operational frequencies, and assurances that Luna 15 would not endanger the Apollo 11 mission.

On July 20. after several more orbit changes, Luna 15 began its descent sequence during its 39th orbit by lowering its perilune to 16 km above the landing site in the Sea of Crises. The intention was to land just 2 hours before Apollo 11 landed further west in the Sea of Tranquility. But when controllers saw the radar data from the first perilune pass they became concerned. The one and only target appeared uneven and potentially dangerous. It must have been with the utmost reluctance and dismay that the decision was taken to postpone the landing to test the radar and perform further observations. As a result of this delay, not only was there now’ no chance of landing ahead of the Americans, the nature of the return trajectory would make it impossible to get a sample back first. All of this w as unknown to an anxious world, wondering wrhat stunt Luna 15 was going to pull in order to upstage Apollo 11. Eighteen hours later, on its 52nd orbit, Luna 15 w*as commanded to land at 15:46:43 UT on July 21. after Armstrong and Aidrin had already walked on the Moon. The descent maneuver failed and. for reasons still to be explained, the transmission ceased 4 minutes after the de-orbit burn started. It erashed at 17 N 60 H, about 800 km east of Tranquility Base. Jodrell Bank flashed notification to the Americans that Luna 15 had impacted at a velocity of 480 m/s just as Apollo 11 ‘s lunar module was preparing to leave the Moon. The Soviets reported that Luna 15 had ’"reached the lunar surface in a preset area" but remained silent on its true mission and there was no propaganda victory.

Campaign objectives:

The 1978 Venus campaign objectives were to repeat the resounding successes of the Venera 9 and 10 landers with new instruments to analyze both the atmosphere and surface. The 1976-77 opportunity was skipped in order to build the new7 apparatus, and a launch in 1978 dictated a much higher arrival velocity at Venus than in 1975. The larger propellant load required for the longer orbit insertion burn was unable to be accommodated together with the mass of the new instruments, so the carrier was downgraded to a flyby role. A positive outcome wras that a flyby spacecraft would remain in view7 of the lander for longer in order to relay data from the surface. Both of the previous landers had still been operating when their orbiters flew7 below their horizons. The new7 lander investigations featured a high resolution color camera and an experiment to drill into the surface. The descent investigations included new7 experiments to study the chemical composition of the atmosphere, the nature of the clouds, and any electrical activity in the atmosphere. The flyby instrumentation was reduced in order to maximize the mass available for the descent and surface science.

Spacecraft:

Although assigned only to a flyby role the Venera 11 and 12 spacecraft were almost identical to their or biter predecessors, but the lander relay was increased to 3 к bits/s per channel. After releasing the entry system 2 days prior to arriving at the planet, Venera 11 (and all later flyby spacecraft) made a deflection maneuver to establish a flyby w7hich would enable it to relay to Earth for longer than w^as possible using an
orbitcr. The spacecraft were identical and the landers had the same configuration as their recent predecessors but the floodlights were deleted and the camera lens cap was redesigned. The complexity and mass of the parachute system was reduced to accommodate more instruments. Only a single supersonic braking parachute was used instead of a sequence of two, and only one main parachute was used instead of a system of three. Some of the instruments were modified and new ones were added, in some cases being installed on the shock absorbing impact ring. All landers from now through to Vega 2 carried a technology experiment consisting of a set of small solar cells arranged around the lander ring.

4,450 kg (Venera 11) 4,461 kg (Venera 12) 2,127 kg 1,600 kg

731 kg

Payload:

Flyby spacecraft:

1. Extreme-ultraviolet (30 to 166 nm) spectrometer (France)

2. Magnetometer

3. Plasma spectrometer

4. Solar wind detectors

5. High energy particle detectors

6. KONUS gamma-ray burst detector

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

KONUS was an interplanetary cruise experiment to try and identify the source of mysterious astronomical gamma-ray bursts by having the two spacecraft coordinate with the Prognoz satellite in Earth orbit to triangulate on individual bursts. SNEG was an instrument complementary to KONUS, built in cooperation with the French. And a new French-built extreme-ultraviolet spectrometer covered the spectral lines of atomic hydrogen, helium, oxygen and other elements that it was thought might be present in the exosphere of Venus. The solar wind detector was a hemispherical proton telescope, and the high energy particle experiments used four semiconductor counters, two gas-discharge counters and four scintilla­tion counters.

Lander:

Entry and descent:

1. Scanning spectrophotometer (0.43 to 1.17 microns)

2. Mass spectrometer Гог atmospheric composition

3. Gas chromatograph for atmospheric composition

4. Nephelometer for aerosols of about 1 micron in size

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

6. Accelerometers for atmospheric structure from 105 to 70 km

7. Temperature and pressure sensors for 50 km to the surface

8. GROZA radio sensor at 8 to 95 kHz for electrical and acoustic activity

9. Doppler experiment for wind and turbulence

The experiments for determining the light scattering properties of the atmosphere were modified for a higher spectral resolution. The angular scattering nephelometers were deleted because they had satisfactorily measured the particle size and refractive index when carried on the Venera 9 and 10 landers. Instead, only the back scattering nephelometers w ere retained to examine the spatial uniformity of the cloud layers in different regions of the planet. The scanning spectrophotometer was improved for a higher spectral resolution. Every 10 seconds it measured radiation coming from the zenith using a ramp interference filter at a resolution of about 20 nm continuously over the range 430 to IT70 nm, and the angular distribution of radiation (a full 360 degrees) in the vertical plane in the bands 0.4 to 0.6, 0.6 to 0.8, 0.8 to 1.3. and 1.1 to

1.6 microns using a rotating prism mounted on the aerobrake. The temperatures and pressures were measured by a suite of four thermometers and three barometers, flic monopole radio-frequency mass spectrometer of Venera 9 and 10 w as replaced by a Bennett radio-frequency design and the inlet system modified to prevent it becoming clogged by cloud particles which might then contaminate the atmospheric readings. The microscopic leak admitting the atmosphere to the instrument w7as replaced by a piezoelectric valve that would open a relatively large hole for a very short time in order to admit a pulse of atmosphere into a long sample tube which w? ould trap cloud particles. In addition the instrument was not to be operated until the lander wras at about 25 km. well below the aerosols. The apparatus w^as pumped down between atmospheric readings to purge the sample. Two other new atmospheric composition experiments were included. The gas chromatograph used neon to carry atmospheric samples through columns of porous materials and a Penning ionization detector. It had one column 2 meters long that was optimized for water, carbon dioxide and the compounds hydrogen sulfide, carbonyl sulfide, and sulfur dioxide; a second column 2.5 meters long for the volatile gases helium, molecular hydrogen, argon, molecular oxygen, molecular nitrogen, krypton, methane and carbon monoxide; and a third column just 1 meter long specifically for argon. An x-ray fluorescence spectrometer used gamma rays to excite the emission of x-rays from cloud particles collected on a cellulose acetate filter by drawing atmospheric gas through the instrument, thereby measuring the elemental composition of the aerosols.

The GROZA experiment comprised an acoustic detector and an electromagnetic wave detector using loop antennas with four narrow-band receivers at 10, 18, 36 and 80 kHz and a wide-band receiver over the range 8 to 95 kHz. This was to start at an altitude of 60 km and operate down to and on the surfaec. The electromagnetic wave detector was to register radio bursts from lightning and the acoustic signals could be interpreted in terms of thunder, wind speed past the lander during the descent and, while on the ground, perhaps even seismic quakes.

Surface:

1. Panoramic two-camera color imaging system

2. Soil drill with x-ray fluorescence spectrometer analysis system

3. Rotating conical soil penetrometer (PrOP-V)

The panoramic camera system had been improved by adding clear, red, green and blue filters for three-color imaging, and by increasing the image quality from 128 x 512 pixels at 6 bit encoding to 252 x 1,024 pixels at 9 bit encoding and 1 bit parity. It was capable of resolving detail as fine as 4 or 5 mm at a range of 1.5 meters. The transmission bandwidth had been increased by a factor of twelve, one reason for this being the Kvant-D upgrade to the Soviet communications facilities; in particular the introduction of 70 meter antennas at Yevpatoria and Ussuriisk. The increase in the transmission rate from the surface of Venus from 256 bits, s to 3,000 bits/s enabled a color panorama to be sent in 14 minutes, as against 30 minutes for a lower resolution black-and-white panorama previously.

The gamma-rav soil analysis instrument inside the Venera 8, 9 and 10 landers was replaced by a superior instrument. A drill mounted on the shock-absorbing impact ring w as to core a sample of the surface and then pass it through a series of pressure – reduction stages to the x-ray fluorescence spectrometer carried inside the lander. The penetrometer was on a deployable arm and reported its results on a dial that was to be read by the cameras.

1ission description:

Venera 11 lander:

Venera 11 was launched on September 9, 1978, and made midcourse corrections on September 16 and December 17. After the entry capsule was released on December 23 the spacecraft made the deflection burn in order to perform a flyby of the planet at the desired relay communications altitude, and on December 25 the entry system hit the atmosphere at 11.2 km/s. After a 1 hour descent the lander touched down at a speed of 7 to 8 m/s on the day-side at 14 S 299 E. It w as 03:24 UT, 11:10 Venus solar time, and the solar zenith angle was 17 degrees. The lander transmitted from the surface for 95 minutes before the relay spacecraft flew over the horizon after 110 minutes, so none of the transmission was lost.

figure 15.3 Venera 11 and Venera 12 encounter design, showing entry capsule targeting followed by flyby vehicle deflection and lander relay communications.

Venera 12 lander:

Venera 12 was launched on September 14, 1978, pursued a faster trajectory with midcourse corrections on September 21 and December 14, and arrived ahead of its partner. It released its entry system on December 19. This entered the atmosphere on December 21 at a velocity of 11.2 km/s. The parachute was jettisoned at 49 km and after a 1 hour descent the lander touched down at about 8 m/s on the day-side at 7°S 294°E. It was 03:30 UT, 11:16 Venus solar lime, and the solar zenith angle was 20 degrees. Unlike Venera 11, it kicked up a cloud of dust that took about 25 seconds to settle. Both landers encountered an unexplained anomaly at an altitude of 25 km, where instrument readings went off-scale and there was an electrical discharge from the vehicle. This lander transmitted from the surface for 110 minutes until the flyby spacecraft passed below the horizon. It is therefore not known when it finally ceased to function.

Venera 11 and 12 flyby spacecraft:

After the deflection maneuver, each spacecraft Hew by Venus at a range of about

35,0 km and relayed the data from its lander to Earth throughout the descent and then during the period of surface activity. The last reports from the flyby spacecraft were in January 1980 for Venera 11 and March 1980 for Venera 12.

Results:

Venera 11 and 12 decent measurements:

The landers inferred atmospheric density from accelerometer data over the altitude range 100 to 65 km and then directly measured atmospheric temperature and pressure from 61 km down to the surface. Opacity was measured from 64 km to the surface, the chemical composition of aerosols from 64 km to 49 km, aerosol scattering from 51 km down to the surface, and thunderstorm activity from 60 km down to the surface. The gas chromatograph analyzed nine atmospheric samples from 42 km to the surface. The new mass spectrometer measured atmospheric composition from 23 km to 1 km. Wind velocities were measured from about 23 km down to the surface, and altitude profiles of horizontal wind speed and direction were obtained from Doppler data.

The spectrophotometer produced the first realistic water vapor profile, identifying water vapor as the second most important greenhouse gas in the atmosphere (after carbon dioxide). The contemporary analysis indicated a profile that decreased from 200 ppm at the cloud base to 20 ppm at the surface, but a re-analysis many years later obtained a better fit for the Venera 11,12 and 14 spectrophotometer data using a constant mixing ratio for water vapor of about 30 ppm from 50 km to the surface. The mass spectrometers on these missions reported values as high as 0.5% at 44 km and 0.1% at 24 km; these are much larger mixing ratios for water vapor than were obtained from the spectrophotometer and other remote spectral measurements from Hanh, and are considered suspect.

The mass spectrometer results from Venera 11 and 12 obtained by the analysis of 176 complete spectra of 22 samples were reported as:

carbon dioxide

molecular nitrogen

argon

neon

krypton with isotopic ratios as follows:

0. 0112 ± 0.0002 1.19 ± 0.07 0.197 ± 0.002

The gas chromatograph made eight measurements betw een 42 km and the surface with the following results:

2.5 + 0.3 %

25 to 100 ppm

40+10 ppm

130 + 35 ppm

28 + 7 ppm (low altitudes)

less than 20 ppm

krypton

hydrogen sulfide carbonyl sulfide

The x-ray fluorescence spectrometer on Venera 12 measured cloud particles from 64 km to 49 km and was then overcome by the high temporal tires. It missed sulfur (< 0.1 mg/m3). but found chlorine (0.43 + 0.06 mg/nri) in cloud particulates. The chlorine was suspected to be a non-volatile compound such as aluminum chloride at the time, but it was not specifically identified. The large amount of chlorine relative to sulfur was incompatible with the theory that the clouds were composed of sulfuric acid droplets, but these anomalous data were corrected by the Venera 14 mission.

Both Venera 11 and 12 detected a large number of electromagnetic pulses in the descent from 32 to 2 km similar to those produced by distant lightning Hashes on Harth. The activity was more intense on Venera 11 than Venera 12, and diminished in intensity towards the surface. No such pulses were detected by Venera 11 after it touched down, but one large burst was noted by Venera 12 while on the surface. The microphones were saturated by aerodynamic noise during the descent and detected no thunder on the surface, but they did pick up sounds issued by the instruments and surface activities.

As with Venera 9 and 10. the light scattering data indicated clouds with a base at an altitude of 47 km, and a much lower loading of aerosols below that. Venera 11 and 12 found the atmosphere to be generally free of aerosols below ^30 km. The nephelometer on Venera 11 measured cloud particles throughout the descent and its results confirmed the uniformity of the cloud layers as reported by Venera 9 and 10. The base cloud layer was located between 51 and 48 km, with a mist below that. The nephelomeler on Venera 12 did nol function correctly. It was confirmed that only about 3 to 6% of the sunlight reaches the surface. Intense Rayleigh scattering in the dense atmosphere gives poor visibility. Above several kilometers altitude the surface must be invisible. At ground level the horizon will be visible, but the detail of the landscape must fade quickly into an orange haze. The Sun is not visible as a disk, merely a uniformly lit hazy sky.

Venera 11 and 12 surface measurements:

The temperature at the Venera 11 landing site was 458 + 5 C and the pressure was 91 + 2 bar. There was no surface imaging because the lens covers would not open. These had been redesigned after the problems w ith one camera on each of Venera 9 and 10, but with disastrous results. The transmit ted pictures were uniformly black. The soil drill collected a sample, but it was not properly delivered to the instrument container and no soil analysis was accomplished.

The temperature at the Venera 12 site was 468 + 5 C and the pressure was 92 + 2 bar. The fact that this suffered exactly the same camera and soil analysis experiment failures as its partner implied a systematic design flaw. Vibrations while descending broke the sample transfer system on the drill and no soil analysis was possible. The soil penetrometers also failed on both landers.

The surface experiments were an almost total failure on both landers. It is possible
that they suffered rough landings which damaged the instruments that were mounted on the impact ring. The lack of results was very disappointing, hut in typical Soviet fashion this spurred the engineers on to succeed at the next flight opportunity.

Venera 11 and 12 flyby spacecraft:

The ultraviolet spectrometer detected Lyman-alpha emissions from hydrogen atoms and 584 angstrom (He-I) emissions from helium atoms. These provided exospheric temperatures and number densities. Time profiles for 143 gamma-ray bursts were obtained by Venera 11 and 12 and the results triangulated with an identical detector on Prognoz 7 in harth orbit. On Kebruary 13 and March 17, 1980, Venera 12 used its extreme-ultraviolet spectrometer to observe Comet Bradfield.

The Scientific Production Organization NPO-Lavochkin was originally founded in 1937 as the Lavochkin Aircraft Design Bureau, OKB-301, named for its Chief Designer. Lavochkin produced a number distinguished fighter aircraft during WW-11

and then surface-to-air missile designs after the war, producing the first operational system for the defense of Moscow. In 1953 the SAM business was transferred to a new design bureau and OKB-301 pursued ramjet intercontinental cruise missiles as a hedge against problems with ICBM development. But the successful introduction of ICBMs in the late 1950s left OKB-301 without work. Semyon Lavochkin died in 1960 and the organization transferred in 1962 to Chelonrey’s OKB-52. The factory was closed, but reopened in 1965 as NPO-Lavochkin under the steady and capable leadership of Georgi Nikolayevich Babakin specifically to take responsibility for the robotic lunar and planetary spacecraft programs transferred from OKB-1.

The new NPO-Lavochkin realized immediate success using its inheritance from OKB-1 augmented by a history of great skill and experience in aviation technology. Luna 9 soft landed on the Moon’s surface in January 1966, and before the year was over there were three successful lunar orbiters and a second soft lander. The first successful Venus entry probe, Venera 4, followed in 1967. NPO-Lavochkin went on to continue this highly successful series of spacecraft at Venus, a successful series of lunar orbiters, rovers and sample return missions, and the singularly complex and successful Vega missions which delivered landers and balloons to Venus enroute to a flyby of Halley’s comet. LTnfortunately, NPO-Lavochkin had no success at Mars: their campaigns in 1969, 1971, and 1973 were riddled with failures, and worse was to come in 1988 and 1996. Their astronomy missions have met with better success, in particular the Granat and Astron space observatories. Today NPO-Lavochkin is the single engineering center for the production of robotic scientific spacecraft.

Russia built the first interplanetary spacecraft for launch attempts at Mars in 1960 and Venus in 1961. These two sets of spacecraft were similar, but the 1M pair built for Mars and the 1VA pair built for Venus had differences relating to the different thermal conditions expected and the communication differences involved. Each pair was identical. Only one of these spacecraft, Venera 1, survived the launch vehicle and was dispatched towards its target, but contact was lost 7 days later.

TIMELINE: JAN 1963-DEC 1965

Between their success with Luna 3 in October 1959 and the opening of 1963, the Soviets suffered two failed lunar missions, five failed Mars missions, and five failed Venus missions. During those long 39 months, Sergey Korolev’s engineers had been working on a new lunar soft-lander to take advantage of the four-stage version of the R-7. Unfortunately, this new Luna would suffer an even longer and more frustrating series of failures than the Ranger crash-lander being developed by the Americans. In fact, there would be eleven failures over the three years 1963-65 before managing a soft landing, with four of the six launch failures being caused by malfunctions of the fourth stage. Of those that were successfully deployed, Luna 4 to 8, two missed the Moon and the other three crashed onto it. The real objectives of these missions were not revealed at the time. Meanwhile, in 1964-65 the LTS finally had a string of successes with Ranger 7 to 9.

fn parallel, the Soviets were applying the lessons from Venera 1 and Mars 1 in the development of the 3MV planetary spacecraft, basically an improved version of the 2MV, for the planetary launch windows of 1964 and 1965. To gain some experience with the new spacecraft, it was decided in late 1963 to make two interim flight tests, but these spacecraft were lost to launch vehicle failures on November 11, 1963 and February 19, 1964. Undeterred, wrhen the Venus launch window opened the Soviets proceeded to launch spacecraft to Venus on March 27 and April 2, 1964. Only the second spacecraft w? as launched successfully, but because it was immediately clear that on board failures would prevent it from reaching its target it was named Zond 1 instead of being given a Venera designation. A launch to Mars – was accomplished successfully on November 30, but once again the spacecraft was sufficiently crippled that it would not make its target and so it was named Zond 2.

The loss of so much hard work must have been doubly galling with the success of the Mariner 4 flyby of Mars on July 15, 1965. As with Venus, the LTS had somehow reached Mars first! Troubled by the significant problems suffered by Zond 1 and 2, the Soviets decided to conduct another 3MV test flight. Launched on July 18, 1965,

W. T. Huntress and M. Y. Marov, Soviet Robots in the Solar System: Mission Technologies І Іл

and Discoveries, Springer Praxis Books 1, DOl 10.1007/978-1-4419-7898-1 9,

© Springer Science 4-Business Media, LLC 2011

outside a launch window, Zond. 3 was unable to reach Mars but it could fly the kind of trajectory that would be used by a real mission. The timing of the departure was arranged so that it could test its camera system by photographing the far side of the Moon. It exercised its navigation systems, propulsion system, flight and instrument operations, and returned its pictures. Unfortunately communications were lost before it reached the equivalent of Mars distance, preventing it from demonstrating its deep space capabilities.

The Zond 3 experience paid off on the flights of Venera 2 and Venera 3, both of which were launched later in November 1965, the first equipped to make a flyby and the second with an entry probe. They flew without serious problems and became the first Soviet planetary spacecraft to reach their target. But they added to rheir maker’s woes by both losing communication, Venera 2 just as it arrived and Venera 3 when
seventeen days from its target on a collision trajectory. Neither mission returned any data from Venus.

The years 1964-65 were crucial turning points in the Soviet space program. Since 1959 OKB-1 had been working on a plan to send eosmonauts on circumlunar flights, and had designed the Soyuz system for this objective. It had no plans to land people on the Moon. The Soviets initially saw the US stated intention to land a man on the Moon as mere hyperbole, but by 1964 it had become clear that major resources had been assigned to the program and that the development of the necessary rockets and spacecraft was progressing. Confident that their Soyuz could beat the Americans to a circumlunar mission but reluctant to be upstaged by a lunar landing, the Politburo directed Korolev in August 1964 to proceed with landing cosmonauts on the Moon in addition to performing the circumlunar program. However, in what would prove to be a huge management mistake, the government divided the development work for these programs amongst competing design bureaus without central leadership or responsibility. The space program was reorganized and additional resources applied. To manage all the work, new design bureaus were established and responsibilities distributed. At this point Soviet space policy underwent a fundamental change, and instead of pursuing long standing plans for the conquest of space it began to directly compete with the American program.

The other issue forcing a shake up in the Soviet space program was the long string of robotic lunar and planetary program failures between 1960 and 1965. Thus far. Korolev had been responsible for virtually all types of Soviet spacecraft and now he had been given the further task of overtaking the Americans in the race to the Moon. By his own admission. OKB-1 was overburdened and unable to devote enough time and resources to the robotic missions. In March 1965, on the advice of Keldysh, he asked his friend Georgi Babakin. who headed NPO-Lavochkin, to take over after the current production run of lunar and planetary spacecraft at OKB-1 ran its course. In April, Korolev handed over OKB-l’s plans and knowledge base to Lavochkin. The remaining robotic spacecraft were launched during the rest of the year, ending w ith Luna 8 and Venera 3, while Lavochkin designed modifications and set up to produce new’ spacecraft.

The next three sample return attempts were lost to launcher failures. In September Ye-8-5 No.403 was stranded in parking orbit when the Block D failed to restart. An oxygen fuel valve had stuck open after the first firing and allowed all the oxidizer to escape. It was designated Cosmos 300 by the Soviets, and re-entered after 4 days. In October a programming error caused the Block D to misfire and spacecraft No.404. designated Cosmos 305, re-entered during its first orbit. In February 1970 spacecraft No.405 was lost wdien a pressure sensor command error shut down the second stage after 127 seconds of flight and the vehicle was destroyed. This precipitated a review7 of the Proton launch vehicle, w hich had a miserable record with many more failures than successes in the Ye-8 and lunar Zond series at that time. Changes w ere made as a result of this review, and in August 1970 a successful suborbital diagnostic flight was flown. The following month another sample return attempt was made and, after five successive failures in a period of 15 months, success w’as finally achieved.

Luna 16

Luna 16 was launched at 13:25:53 UT on September 12, 1970. Seventy minutes after entering parking orbit, the Block D reignited and performed the translunar injection burn. After a course correction on September 13. the spacecraft entered a nearly circular 110 x 119 km orbit at 70 degrees inclination on September 17. After gravity data had been acquired in this orbit, two orbital adjustments were made on September 18 and 19, the first into an elliptical orbit wdth its perilune 15.1 km above the landing site and an apolune of 106 km, and the second to adjust the orbit plane to 71 degrees inclination. As the spacecraft approached perilune on September 20. the extra tanks were jettisoned. The engine was ignited at perilune. 05:12 UT, and fired for 270 seconds to cancel the orbital velocity and initiate the free fall. Triggered by the radar altimeter, the engine was restarted at an altitude of 600 meters and velocity of 700 km hr. It was shut down at an altitude of 20 meters and a velocity of 2 m/s. The primary verniers were ignited for the tenninal phase, and cut off at a height of 2 meters, then the spacecraft dropped to impact at about 4.8 m/s. Touchdown occurred at 05:18 UT in the Sea of Fertility at 0.68 S 56.30 H. only 1.5 km from the planned point.

Because Luna 16 touched down 60 hours after local sunset and was not fitted w ith floodlights it did not provide any images. The drill was deployed after an hour, and in 7 minutes of operations it penetrated to a depth of 35 cm before encountering an obstacle. 1 he boom then lifted the core sample from the surface and swung it up to

the return capsule atop the ascent stage, inserting it through an open hatch that then closed. Some soil was lost from the sampler during this operation. At 07:4.1 UT on September 21, after 26 hours and 25 minutes on the Moon, the ascent stage lifted off and escaped at 2.7 krn/s. The lower stage remained on the surface and continued to transmit lunar temperature and radiation data. The ascent stage returned directly to Earth. On September 24, at a distance of 48,000 km, the straps released the return capsule. Four hours later it hit the atmosphere traveling at 11 km/s on a trajectory at 30 degrees to the vertical on a ballistic entry with a peak deceleration of 350 G. At an altitude of 14.5 km the top of the capsule was ejected and the drogue parachute deployed. At 11 km the main chute was unfurled and the beacon antennas deployed. The capsule landed at 03:26 UT on September 24, approximately 80 km southeast of the city of Dzhezkazgan in Kazakhstan.

Luna 16 proved, to contain 101 grams of lunar material. It was a triumph, and the Soviet press made the best of it, hyping the use of robots over manned missions. For the Americans, Luna 16 confirmed what they suspected about Luna 15, that it was a sample return attempt intended to upstage Apollo 11.

Luna 18

The next attempt at sample return was made one year later. Luna 18 was launched on September 2, 1971, made midcourse corrections on the 4th and 6th, and entered a 101 km circular lunar orbit inclined at 35 degrees the following day. After lowering its perilune to 18 km it was commanded to land on September 11, but the signals cut off abruptly at 07:48 UT at an altitude of about 100 meters. The main engine had run out of fuel due to excessive consumption in earlier operations, and the wreckage lies at 3.57°N 56.50°E in rugged highland terrain.

Luna 20

Luna 20 was the second attempt after Luna 18 to obtain a sample from in the lunar highlands. Launched on February 14, 1972, it was tracked by telescopes to compute an accurate trajectory, made a midcourse correction the following day and entered a 100 km circular lunar orbit at 65 degrees on February 18. It lowered its perilune to 21 km the following day. And finally, at 19:19 UT on February 21, it touched down in the Apollonius highlands near the Sea of Fertility at 3.53°N 56.55,:>E, only 1.8 km from where Luna 18 crashed. The Sun was 60 degrees above the horizon. Images of the surface were transmitted prior to the sampling operations. The drill encountered resistance, and had to be paused three times to prevent overheating. It was ultimately able to achieve a depth of only 25 cm. The recovered sample core was transferred to the return capsule.

The ascent stage lifted off at 22:58 UT on February 22, and then upon its return to Earth fell into a strong snow storm. .Although it came down over the Karkingir river 40 km north of Dzhczkazgan, when it landed at 19:19 UT on February 25 it touched down on an island. The ice, wind, and snow presented the recovery team with severe difficulties. It was recovered the following day, and when opened proved to contain only 55 grams of lunar soil.

Luna 23

The first improved Ye-8-5M sample return vehicle, No.410, became Luna 23 with a successful launch on October 28, 1974. After a midcourse correction on October 31, it entered an almost circular 94 x 104 km orbit at 138 degrees on November 2. Upon lowering its perilune to 17 km it was commanded to land on November 6. Although Luna 23 landed on target in the southern part of Sea of Crises at 12.68’N 62.28°E, it did so at 11 m/s and the impact shock wrecked the sample collection apparatus and caused other damage. No samples wjere obtained and the ascent stage was not lired. The lander continued to transmit until contact was lost on November 9.