Category Soviet Robots in the Solar System

Campaign objectives:

Korolev’s second step after demonstrating the ability to hit the Moon was to obtain photographs of its far side, which can never be observed from Earth. The Television

Scientific Research Institute developed a camera for the mission; a facsimile system using film developed on hoard and scanned by a photometer for transmission. The camera was fixed and had to be pointed at the Moon by appropriately orienting and stabilizing the spacecraft, which required a З-axis pointing and control system rather than the spin stabilization used by the Ye-1 spacecraft. The Ye-2 would be the first to accomplish this vital mode of attitude control. In addition, the spacecraft had to be placed onto a trajectory that would enable it to view the far side of the Moon from a close range and under suitable illumination, and then return to the vicinity of Earth in order to transmit its pictures.

Keldysh’s Applied Mathematics Institute designed special orbits that would allow7 the spacecraft to photograph the far side of the Moon and then return to the vicinity of Earth over the USSR to transmit the pictures back at close range. There were only two launch opportunities for these restricted types of orbits, one in October 1959 for photography on approaching the Moon, and another in April 1960 for photography on receding from it. One Ye-2A spacecraft was launched in October and two of the Ye-3 type were assigned to the follow up. The first, Luna 3, was successful, but both of the more advanced spacecraft were lost to launch vehicle failures.

The Luna 3 mission was a momentous achievement for that time, and its pictures excited the w orld. But no one outside the USSR knew7 of the failures in the program. Of nine launches, six were total losses. Luna 1 failed to achieve its prime mission, but

Luna 2 was successful. And although Luna 3 look and transmitted pictures, they were of poor quality. Nevertheless, to the outside world it appeared that the Soviets had successfully launched three lunar missions of progressively greater complexity, and could do almost anything at will. In stark contrast, at the end of 1960 America appeared to be incompetent with nine embarrassing public failures yielding just one wide miss of the Moon.

After the success of Luna 3, the Soviet lunar program experienced a З-year hiatus as the focus shifted to the more challenging planetary targets, Venus and Mars, and a new robotic spacecraft was developed for soft landing on the Moon.

Spacecraft:

Two competing telecommunication systems were started for the lunar photography, one by Bogomolov labeled Ye-2 and the other by Ryazansky labeled Ye-2A. It was decided to use the Ye-2A system. The Ye-2A spacecraft designed by Gleb Maximov was a cylindrically shaped canister 130 cm in length with hemispherical ends and a 120 cm wide flange near the top. The cylindrical section was approximately 95 cm in diameter. The canister was hermetically sealed at 0.23 bar and held the cameras and film processing apparatus, communications equipment, thermal control fans, gyroscopes, and rechargeable silver-zinc batteries. Uplink was at 102 MHz and downlink at 183.6 MHz. A backup telemetry system operated at 39.986 MHz. The spacecraft had six omnidirectional antennas, four protruding from the top and two from the bottom. The thermal control system was to prevent the internal temperature from exceeding 25 C by using passive flaps mounted along the cylinder. There were micrometeoroid detectors, cosmic ray detectors, and solar cells for recharging the batteries on the exterior. The upper hemisphere of the probe housed the camera port, and the lower hemisphere housed the cold gas З-axis attitude control jets. There was no propulsion system with which to perform midcourse maneuvers. The spacecraft was to be spin stabilized under cruise, switch to 3-axis stabilization for photography, and then resume spin stabilization. Photoelectric cells were used to maintain orientation with respect to the Sun and Moon.

The follow up spacecraft, originally designated Ye-2F, were intended to acquire more and improved images of the lunar far side. As these were being prepared, there was a parallel rush to get the new’ four-stage R-7 and the Mars and Venus spacecraft ready for launch starting in the fall of 1960. The Ye-3 project was canceled when its camera system was judged too complicated and unreliable, and the Ye-2L spacecraft was re-designated Ye-3 shortly before launch. These two spacecraft were essentially the same as the Ye-2A but with improved imaging and radio systems.

Ye-2A launch mass: 278.5 kg

Payload:

1. Yenisey-2 photo-television facsimile camera system

2. Micrometeoroid detector

3. Ion traps (3)

4. Cherenkov radiation detector

5. Scintillation and gas discharge Geiger radiation counters

6. Mass spectrometer (not flown)

Several instruments from Luna 1 and 2 were flown in addition to the new camera system. A mass spectrometer based on an instrument that was flown sueeessfully on Sputnik 3 was planned but canceled owing to mass and time constraints.

Unlike the Americans who chose to use television v id icon tube cameras for their early deep space photography missions (except the Lunar orbiter series), the Soviets used a film camera system. This was mechanically complex and heavy but provided higher resolution, greater sensitivity, better quality, and was distortion free. The Yenisey-2 facsimile imaging system on the Ye-2 and -3 spacecraft consisted of a 35 mm film camera equipped with 200 mm f/5.6 and 500 mm f/9.5 lenses, an automatic film processing unit, and a photomultiplier film scanner with a resolution of L000 pixels line. The 200 mm objective was sized to image the full disk of the Moon. The camera cycled through four exposure times from 1 /200th to 1 /800th second. It exposed adjacent frame pairs simultaneously, one through each lens, and was capable of taking 40 frames at 1.000 x 1,000 pixel resolution using temperature and radiation resistant isochromatic film. The developed film could be scanned and rewound at ground command, and could be transmitted at either 1.25 lines/second or 50 lines/second depending on the range from Earth. The video signal was sent using the 3-W 183.6 MIIz transmitter. After the Cold War, it was revealed that the Soviets did not have radiation-resistant film and used US radiation-resistant film acquired by scavenging downed American spy balloons flown over the USSR from Western Europe.

Mission description:

Only the first of these missions survived its launch vehicle. The Luna 3 spacecraft (Yc-2A No. l) was successfully launched on October 4, 1959, into an elliptical Earth orbit that took it close to the south pole of the Moon, whereupon lunar gravitation redirected the trajectory back to the vicinity of the Earth, forming a figure-of-eight loop. The spacecraft, which the Soviet press dubbed the ‘Automatic Interplanetary Station’, experienced severe overheating with consequent ragged telemetry shortly after launch. This was alleviated somewhat by reorienting the spin axis and shutting off some equipment. To prepare for photography, the spin was stopped and the gyro-controlled З-axis orientation system activated. It flew within 6.200 km of the south pole of the Moon when at closest approach at 14:16 UT on October 6, and then crossed through the plane of the Moon’s orbit out over the sunlit far side. Early on October 7 the photocell on the top end of the spaceeraft detected the sunlit Moon at a distance of 65,200 km and initiated the 40 minute photography sequence. Twenty-nine frames w’ere exposed before the mechanical shutter jammed. The final image was taken at a distance of 66,700 km.

After photography w? as complete, the spacecraft resumed spinning and the first attempt was made to retrieve images. The signal strength was low and intermittent, and only one image with almost no detail was received. A second attempt was made near apogee at 470.000 km from Earth, but again the transmission quality w as poor. The antenna patterns on the spacecraft may not have been optimal. It was decided to wait for the most ideal situation when the spacecraft returned to the vicinity of the Earth ten days later. As the spacecraft approached Earth, several attempts to retrieve the images at fast playback did not yield good results. The signals were weak, with a lot of static and radio noise. To reduce the latter, Soviet engineers enforced radio silence in the Black Sea in the vicinity of the Yevpatoria receiving antenna. Finally, on October 18 the signals improved abruptly and 17 resolvable but noisy pictures were successfully received. By design, the mission was undertaken when a portion of the near side was illuminated to provide a point of reference, so only 70% of the far side was sunlit. Contact with Luna 3 was lost on October 22 and it burned up in the Earth’s atmosphere in April 1960.

Both Ye-3 spacecraft fell victim to their launchers. The third stage of the rocket carrying Yc-3 No. l cutoff prematurely. The kerosene tank had not been completely filled! At a range of only about 200,000 km from the Earth the spacecraft fell back and burned up in the atmosphere. The Yc-3 No.2 launch failed spectacularly when at the moment of liftoff one of the strap-on boosters failed to reach full thrust, placing abnormal loads on the vehicle. Three of ihe strap-ons separated at only a few meters altitude, resulting in violent maneuvers of the four separated pieces of the rocket and powerful explosions. There was considerable damage to the pad and buildings at the launch site. This brought a fiery end to the first series of Soviet lunar spacecraft and the final use of the 8K72 R-7E Luna launcher for lunar missions.

Results:

Luna 3 was the first spacecraft to photograph the lunar far side, but the 17 pictures successfully received were very noisy and of low resolution. Only six of these were published. A tentative atlas was compiled showing the far side to be very different to the near side, being predominantly bright highland terrain, without extensive mare. Two small dark regions were named Sea of Moscow and Sea of Dreams, the latter in honor of the Mechta first flyby mission.

The Venera 7 landing on the surface of Venus was a jubilant success for the Soviets. Once the pressure and temperature at the surface were finally confirmed, the NPO – Lavochkin engineers scaled back the pressure design limit from 180 bar to 105 bar and used the saved mass for a stronger parachute and more scientific instruments. In
anticipation of their next generation of larger more complex Venus landers, a photometer was added to determine the illumination at the surface. All of the previous entry probes had been targeted at the night-time hemisphere, mainly to ensure direct-to-Earth comm uni cations. but day-side light-level measurements were required in order to design imagers for future landers. So the 1972 missions were to land in early morning daylight at sites near the terminator from which it would still be possible to transmit to Earth. A redundant deployable antenna was ineluded as a precaution against poor primary antenna pointing or obscuration of the line of sight by rough terrain.

Two launches were attempted, the first successfully dispatching Venera 8 and the second stranding its spacecraft in parking orbit. Venera 8 was the ultimate success of the 3MV series and. as events transpired, the last of its type. It achieved all that the Soviets had worked so hard for over so many years and so many attempts. It was the final reward for dogged persistence. During its construction, NPO-Lavochkin was working on the new generation of Luna spacecraft to undertake sample return, rover and orbiter missions, and the or biters and landers for Mars, both of which would use the Proton launcher, so this was the final planetary campaign to employ the 8K78M Molniya.

Venera 8 supplied the data needed to design the much more sophisticated landers that would be delivered by the next generation of advanced Venera spacecraft to be launched by the Proton rocket beginning in 1975.

Spacecraft:

The carrier spacecraft for Venera 8 was essentially the same as for all missions since Venera 4, but the entry probe was modified. The pressure design limit was reduced to accommodate additional science instruments and the parachute was strengthened, although the size of the canopy was the same as for Venera 7 in order to make the same rapid descent through the atmosphere. Since the probe was to land further from the center of the planet as viewed from Earth, the antenna transmission pattern was changed from the egg-shape that was appropriate when Earth was at the zenith to a funnel-shape for when Earth was low on the horizon. In case the capsule were to come to rest on its side, a second antenna was provided that was to be ejected onto the surface and this was a flat disk with a spiral antenna on each side to enable it to work irrespective of how it settled.

A new honeycomb composite material was used as the primary insulation of the lander. Further thermal protection was provided by using lithium nitrate trihydrate, a phase-change material that absorbs heat by melting at 30’C. In addition to forming ‘thermal accumulators’ inside the pressure vessel, this jacketed the instruments that projected outside.

Launch mass: 1,184 kg

Entry capsule mass: 495 kg

Payload:

Carrier spacecraft:

1. Solar wind charged particle detector

2. Cosmic ray gas discharge and solid state detectors

3. Ultraviolet spectrometer for Lyman-alpha measurements

Descent I landing capsule:

1. Temperature, pressure and density sensors

2. Atmospheric chemical gas analyzer

3. Broad-band visible photometers (2)

4. Gamma-ray spectrometer

5. Radio altimeter

6. Doppler experiment

An accelerometer was to measure atmospheric density during the descent prior to parachute deployment. The altimeter had been redesigned to provide an accuracy of several hundred, meters for the instruments that would operate during the parachute descent. The atmospheric composition experiment now included an ammonia litmus

test, and the atmospheric structure experiment carried four resistance thermometers, three aneroid barometers, and a capacitance barometer. A pair of single-channel broadband cadmium sulfide photometers were carried to measure the integrated downward flux with a 60 degree field of view in the wavelength range 0.52 to 0.72 microns. The optical unit was outside the capsule, mounted on top inside a separate unit scaled against high pressure and insulated against high temperature. The light reached the electronics by a 1 meter long light guide of fiber optic. The photometers were sensitive over the range 1 to 10,000 lux and encoded logarithmically.

The gamma-ray spectrometer was mounted inside the hermetically sealed probe. It was sensitive to emissions from potassium, thorium and uranium, and had been calibrated for these elements against a suite of Earth rocks.

Mission description:

Venera 8 was launched on March 27, 1972, made its midcourse correction maneuver on April 6, and arrived at Venus on July 22. The solar panels charged the batteries of the capsule and a system in the cruise module pre-cooled the capsule by circulating air through it at -15C’C. After being released 53 minutes prior to entry, the capsule hit the atmosphere at 11.6 km/s at 08:37 UT at an angle of 77 degrees on the sunlit side.

approximately 500 km from the morning terminator. Eighteen seconds later it had slowed to 250 m/s and deployed its pilot parachute. The reefed main parachute opened at 60 km altitude and the canopy was fully opened at 30 km. The instruments were activated at 50 km and transmitted data during the 55 minute descent. There was a clear line of sight to Yevpatoria. The capsule thumped onto the surface at 10.70°S 335.25°E. It was 6:24 Venus solar time and the solar zenith angle was 84.5 degrees. The parachute was jettisoned on impact and the secondary antenna was

deployed onto the surface. The capsule transmitted for another 63 minutes reporting measurements on the surface, starting with a 13 minute stream from the primary antenna, then a 20 minute stream from the secondary antenna, and finally a 30 minute stream from the primary.

The Venera 8 carrier spacecraft returned measurements on the upper atmosphere and ionosphere prior to breaking up in the atmosphere.

The second spacecraft to be launched failed to depart from low Harth orbit due to a fourth-stage misfire when the failure of a timer caused the engine to stop after only 125 seconds. It was stranded in a highly elliptical orbit and designated Cosmos 482. At the end of June a fragment separated. This was probably the entry capsule, and it remained in orbit when the main spacecraft re-entered on May 5, 1981.

Results:

The Venera 8 capsule returned a wealth of data about the atmosphere and surface. It determined atmospheric density from accelerometer data in the altitude range 100 to 65 km and directly measured atmospheric temperature, pressure, composition and down-welling light flux from 55 km down to the surface. Although imprecise, these first profiles of the solar flux versus altitude were sufficient to confirm that the high temperatures were caused by the greenhouse effect. The illumination at the surface was measured and the pattern of change in attenuation attributed to clouds. Profiles of the speed and direction of horizontal winds from 55 km down to the surface were obtained from Doppler data. The wind speed was 100 m/s above 50 km, 40 to 70 m/s in the haze layer near 45 km, surprisingly rapid at 20 to 40 m/s below this down to 20 km, and only about 1 m s from 10 km to the surface. The wind was super-rotating coincident with the motion of the high ultraviolet clouds.

The first report from the radio altimeter was at an altitude of 45.5 km and it gave a total of 35 readings, the last at 900 meters. The capsule drifted 60 km horizontally as it descended. The altimeter produced a ground profile with two mountains 1,000 and 2,000 meters tall, a hollow 2.000 meters deep, and a gentle upward slope toward the landing site. Two echo intensity profiles were obtained from which it w as possible to compute the dielectric constant and a surface density of 1.4 g/ec. The photometers made 27 measurements, and the light level declined steadily from 50 to 35 km as the probe descended through the clouds. Venera 8 was the first to distinguish three main optical regions in the atmosphere: two cloud layers w’ith a thicker upper layer of fog from 65 to 49 km and a lower haze layer from 49 to 32 km. Then the light level was essentially constant to the surface, indicating a relatively clear atmosphere below the clouds. The illumination in this part of the atmosphere was comparable to a cloudy day on Harth at tw ilight. The w eak surface brightness indicated that only 1 % of the incident sunlight reached the surface. On the other hand, the Sun was only 5 degrees above the horizon. The important finding was that the illumination wras sufficient for the next lander to operate a camera.

The gas analyzer returned a composition of 97% carbon dioxide, 2% nitrogen.

0. 9% water vapor, and 0.15% oxygen. Although the ammonia test gave a positive detection at altitudes between 44 and 32 km with readings of 0.1 to 0.01 %. this was compromised by sulfuric acid which also reacts positively. A significant point is that the gas analyzer eon firmed the presence of sulfuric acid in the clouds. This had been offered as an explanation of why the clouds were so arid and yet were able to form cloud droplets. And the fact that such droplets would reflect sunlight so efficiently explained why the planet had such a high albedo.

On the surface, Venera 8 reported a pressure of 93 + 1.5 bar and a temperature of 470 ± 8’C. confirming the measurements by Venera 7 and in good agreement with an extrapolation of the data from the Venera 4, 5 and 6 probes down to the surface using models of the adiabatic temperature lapse rate.

The gamma-ray spectrometer made measurements in the descent, and tw o on the surface. It reported 4% potassium. 6.5 ppm thorium, and 2.2 ppm uranium indicative of a more granitic than basaltic composition. However. this result was contested and all later Venera landers found more common basaltic compositions. Radar mapping many years later showed that Venera 8 landed in an upland volcanic region that was probably older than the lava plains that constitute most of the planet. Alternatively, a potassium-rich basalt that is relatively rare on Earth could account for this particular data.

EARLY SOVIET ROCKET DEVELOPMENT

The enabling technological step towards lunar and planetary space flight was the development of the military intercontinental ballistic missile (ICBM). From this, it is only a small incremental step to the development of a rocket capable of launching Earth-orbiting satellites, and then only another small step to one capable of sending spacecraft on trajectories to the Moon and beyond. The developers of ICBMs in both the US and USSR dreamed about space flight from the very beginning, and always in the back of their minds knew that the weapons on which they were working could ultimately be used for space exploration. This was as true for Sergey Korolev in the Soviet Union as for Wernher von Braun both in wartime Germany and later in the US. Each rapidly adapted their large rockets for flights to Earth orbit and beyond. The launch of Sputnik and the first Soviet launches to the Moon were made during the initial months of testing the R-7, the Soviet Union’s first ICBM. Subsequently, various versions of the R-7 became standard launchers for both military and civilian Soviet space missions. The ‘space race’ in the 1960s between these two nations was essentially defined by the development of ever more powerful rockets on both sides. The first intercontinental rockets developed in the US were the Atlas and Titan, and both were used in the civilian program for manned and robotic missions. However, the giant Soviet N-l and American Saturn V rockets were developed to land men on the Moon, and hence were far larger than required for military applications. Military rockets were modified by both nations to send spacecraft to the Moon and planets by adding upper stages for the extra boost required to achieve interplanetary velocities. Without these military rockets and the development of their associated upper stages, there would have been no access to space for interplanetary missions.

The history of rocketry in Russia can be traced back to their use by the military in the 13th Century – the same time that rockets made their appearance as a weapon in western Europe. A Rocket Enterprise was founded in Moscow’ in the 1780s. and in 1817 the Russian engineer Alexander Zasyadko wrote a manual on the production of

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_4,

© Springer Science 4-Business Media, LLC 2011

rockets and their use for artillery bombardment. By the beginning of WW-I, Russia had developed the artillery rocket into a significant weapon with a range of almost 10 km. This development gained momentum after the Russian revolution in 1917, as the newly established Soviet Union became an industrial state with a large military force. The establishment of the Gas Dynamics Laboratory in Leningrad in 1928 for development of military missiles marked the beginning of the later powerful Soviet military rocket design bureaus.

The first consideration of the rocket for use other than as a military weapon was by the Russian visionary Konstantin Tsiolkovskiy, whose book ‘The Exploration of the World’s Space with Jet-Propulsion Instrument’ wfas published in 1903; the same year as the Wright brothers’ first powered flight. Tsiolkovskiy, a schoolteacher, laid the theoretical foundation for space flight and interplanetary space travel using the rocket. In the 1930s, his work led a number of enthusiasts to found an organization called the Group of Research in Jet Propulsion (GIRD) whose first project was to construct a rocket-powered airplane. Sergey Korolev, the famed ‘Chief Designer’ of the Soviet space program in the 1960s, was a founding member. The government

The Cold War race to build an I CBM 33

began to sponsor the organization in 1932. and the group launched both a hybrid engine rocket and a liquid-fueled rocket in 1933. They were merged with the Gas Dynamics Laboratory in September 1933 as the Jet Propulsion Scientific Research Institute (RMI).

Progress was slow and resources very limited for these amateur rocketry pioneers in the 1930s. At that time, no government was interested in supporting a program to develop peaceful exploration of space. Military applications were the only hope for obtaining state budgetary support, and this happened first and most successfully in Germany during WW-II.

Campaign objectives:

Nineteen months after their frustrating third campaign to Venus, the Soviets were ready with three more spacecraft for the late 1965 launch window. They had tried to reach this planet at every opportunity since February 1961, but after one test launch and seven launches they had nothing to show for it. Only two of the seven spacecraft survived their launch vehicles, and both of these failed in flight rather quickly. But the engineers reckoned they had fixed the problems that crippled Zond 1 and were encouraged by the success of Zond 3 at the Moon and its long interplanetary flight, so they prepared for the second 3MV Venus campaign with confident expectation.

Several 3MV spacecraft were left over from the November 1964 Mars campaign when only one had been launched during the window, flying as Zond 2. Another had been launched in July 1965 as Zond 3 for a test to Mars distance. Three 3MV Mars spacecraft, one configured with an entry probe (3MV-3 No. l) and the other two for flyby observations (3MV-4 No.4 and No.6), were modified for the Venus window in 1965. Their original target. Mars, accounts for their anomalous ‘tail numbers’. Only

two were successfully dispatched. Venera 2 and 3 flew to the vicinity of their target and became the first truly successful interplanetary cruises since Korolev had begun launching planetary spacecraft in 1960. The long interplanetary cruise provided new confidence in the spacecraft, but the fact that they failed at or near their target made them agonizing disappointments. There was a fourth spacecraft, probably with an entry probe, but this was unable to be launched before the window closed.

Venera 2 and 3 were also the last planetary spacecraft to be built and launched by OKB-1 because in late 1965 Korolev had transferred responsibility for robotic lunar and planetary missions to NPO-Lavochkm. The next Venera spacecraft for the 1967 window would be built and launched under the leadership of Gcorgi Babakin.

Spacecraft:

The Venera 2 and 3 spacecraft were basically the same as Zond 2 and 3 but modified for the new target. The Venera 3 entry probe was essentially the same as that carried by Zond 1. By the time the mission was launched, there was strong evidence that the surface of Venus was hot, possibly 400°C. Although the surface pressure was not yet well determined, it was apparent that conditions were beyond the limits to which the 3MV probe was designed (77aC and 5 bar). As it was too late to make changes, Venera 3 was launched in full knowledge that its probe would provide only data on the atmosphere and would not survive the full descent to the surface.

963 kg (Venera 2)

958 kg (Venera 3)

~ 950 kg (Cosmos 96) 337 kg

Payload:

Venera 2 carrier spacecraft:

1. Lyman-alpha and oxygen spectrometer

2. Triaxial fluxgatc magnetometer

3. Micrometeoroid detector

4. Charged particle detectors

5. Cosmic ray gas discharge and solid state detectors

6. Cosmic radio emission receivers for 20 to 2,200 kl-Iz

7. Decimeter band, radio solar plasma detector

The cosmic ray detectors now consisted of the gas discharge counters and silicon solid-state detectors. The decimeter band radiometer dish antenna was mounted on the ring between the avionics and instrument compartments.

Venera 2 flyby instrument module:

1. Facsimile imaging system

2. Ultraviolet spectrometer at 285 to 355 nm in the imaging system

3. Ultraviolet spectrometer for ozone at 190 to 275 nm

4. Infrared spectrometer at 7 to 20 and 14 to 38 microns

The camera system and ultraviolet spectrometers were identical to those carried by Zond 2 and 3. The camera was provided with a 200 mm lens. The Venus infrared spectrometer was similar to that of Mars 1 but designed to measure thermal radiation from the atmosphere and clouds. It covered two ranges in 150 increments each, the first using an InAn window7 and the second a LiF mirror. The instrument had a mass of 13 to 15 kg, was 50 cm in size, and was mounted outside the instrument module, coaxial with the imaging system, and included a visible photometer for reference. It could also make a spatial scan of the planet at the two fixed wavelengths of 9.5 and 18.5 microns.

Venera.? carrier spacecraft:

1. Lyman-alpha and atomic oxygen photometers

2. Triaxial fluxgate magnetometer

3. Charged particle detectors

4. Cosmic ray gas discharge and solid state detectors

5. Decimeter band radio solar plasma detector

The cosmic ray instrument had an additional gas discharge counter on Venera 3. and both the micrometeoroid detector and the radio emission receivers were deleted.

Venera.? descent I landing capsule:

1. Temperature, pressure and density sensors

2. Atmospheric composition, acidity and electrical conductivity experiments

3. Gamma-ray surface composition detector and cosmic ray detector

4. Visible airglow photometer

5. Mercury level motion experiment

The probe instruments were spares from the 1964 campaign. The photometer was included again since Venera 3 was to be a night-time landing. As with all of the ЗМ V missions, the probe also carried pennants of the Soviet Union.

Mission description:

The Venera 2 flyby spacecraft was successfully launched on November 12, 1965 .It was intended to fly in front of the sunlit hemisphere of Venus and photograph it at a range of less than 40,000 km. The initial trajectory w as so precise that no midcourse maneuver was required. The thermal system did not function well and the spacecraft began to overheat as it neared its target, causing problems with the communications system. An improper coating of the radiation domes was suggested as the cause. By February 10. which proved to be the final interrogation session, the temperature was considerably increased, the quality of communications was seriously degraded, and the command from Harth to initiate flyby observations was not acknowledged. After the flyby Venera 2 failed to respond to commands to download the flyby data, and on March 4 it was declared lost. It may very well have achieved its mission and been unable to transmit its results to Harth. The closest point of approach to the planet was at 02:52 UT on February 27, 1966, at a distance of 23.950 km.

Venera 3 was dispatched towards Venus on November 16, 1965. It performed satisfactorily during cruise and a midcourse correction on December 26 put it on an impact trajectory 800 km from the bull’s-eye. How7ever. the communications system failed on February 16, just seventeen days prior to arrival. The spacecraft may have released its entry probe automatically at 06:56 UT on March 1. 1966, but there was no telemetry from the capsule. Even so. the probe became the first human artefact to reach another planet, near the terminator on the night side somewhere between 20°S and 20 N and between 60 E and 80 E.

The post-mission investigation into the loss of Venera 2 and 3 revealed problems with the thermal control system in both spacecraft which had caused components in the communications system to overheat and fail.

The third spacecraft, 3MV-4 No.6, was launched on November 23. A broken fuel line caused one of the engine chambers in the third stage to explode shortly prior to stage shutdown, with the result that the fourth stage inherited an unstable attitude. It managed to achieve orbit, but the tumbling prevented it from restarting its engine for the escape maneuver. Written off as Cosmos 96, it re-entered on December 9.

A fourth spacecraft (probably 3MV-3 No.2) w as to be launched at the very end of the w indow on November 26, 1965. but was scrubbed w7hen a problem was found in the launch vehicle during pre-flight checks. The launch was abandoned because the vehicle could not be recycled before the window closed.

These were the last robotic interplanetary spacecraft launched by OKB-1. Out of a total of 39 launch attempts in a period of a little more than seven years, only Luna 2, Luna 3, and Zond 3 fulfilled their missions. Twenty lunar launch attempts gave eight successful launches, with only three spacecraft being fully successful. Hlevcn Venus launch attempts gave four successful launches, but unfortunately no spacecraft were successful. Out of six Mars launch attempts only two succeeded, but both spacecraft failed. Two ЗМ V test launches also failed.

Results:

The 1965 campaign produced no data from Venus. Some results were published on micrometeoroids, the interplanetary magnetic field, cosmic rays, low energy charged particles, solar wind plasma fluxes and their energy spectra.

TIMELINE: 1986-1988

Bolstered with confidence as a result of the extremely successful Vega missions and leading the internationalization of robotic planetary exploration after the Americans had sidelined themselves, the Soviets decided to make another attempt at the Red Planet in 1988. As approved in 1976 by Mstislav Keldysh after the demise of the very ambitious rover and sample return proposals, this Lime the focus would be on the moon Phobos. The spacecraft would enter Martian orbit and after several weeks of orbital phasing during which it would study the planet, it would make a very slow – pass just 50 meters over the surface of Phobos to deposit two landers and undertake not only passive remote sensing by imagers and spectrometers but also active remote sensing with radar, ion beams and laser beams. In addition to the new power hungry active remote sensing instruments, the massive spacecraft would be equipped with a variety of other scientific instruments. Once again the Soviets invited the world’s scientific community to provide investigations for the mission, and this time even American instruments were accommodated.

The Phobos project was a model for international cooperation, but in the end also turned out to be a lesson in the international dissonance caused when such a mission fails. Phobos 1 and Phobos 2 were successfully launched in July 1988, but Phobos 1 was lost early in its interplanetary cruise owing to an elementary operational error. Phobos 2 reached Martian orbit and in just a few weeks conducted enough first-class observations of the planet to make up for all the flawed Soviet missions in the past, but then, just days prior to the close encounter with Phobos, the spacecraft failed to respond to a scheduled communications session and was lost.

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 19,

© Springer Science+Business Media, LLC 2011

Launch date

1986

No missions

1987

No missions

1988

7 JuJ Phobos 1 Mars orbitcr Lost enroute

12 Jul Phobos 2 Mars orbitcr Failed in orbit before Phobos encounter

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.

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.

Afanasyev, Sergey Aleksandrovich 1918-2001 ‘

First Minister of General Machine Building 1965-1983

Sergey Afanasyev’s organization managed the institutions and workforce that built ballistic missiles and satellites vital to the defense of the Soviet Union, as well as the spacecraft and launch vehicles for their politically important space ex­ploration program. Leonid Brezhnev once told him,

“We believe in you, but if you fail w;e will put you against a brick wall and shoot you.” Known as “the big hammer”, he could be a very rude and intimidating man but he had a talent for orches­trating immense projects. He was among the most powerful people involved in the USSR’s space program, which included Korolev and his rival Glushko. His criticism of Korolev’s management of the manned space program resulted in the separation of the robotic program from Korolev’s bailiwick to that of Georgi Babakin in 1965. He oversaw the Soviet Union’s response to the Apollo project and was ultimately responsible for canceling it after many setbacks.

TIMELINE: OCT 1960-FEB 1961

The Moon had been the principal target for the USSR in 1958 and 1959, and for the US as well through 1960, hut both had ambitions to send spacecraft to the planets. Venus was the closest and most accessible, but Mars, slightly farther away, was the most fascinating. Having been successful at the Moon, the Soviet Union was ready to start launching planetary missions in 1960. The US, struggling to achieve success at the Moon, decided to put off attempting planetary missions.

Korolev developed a four-stage version of the R-7 rocket to launch missions to the planets, and a spacecraft quite different from the initial Luna series to meet the challenges of interplanetary flight. The new rocket and spacecraft were ready for the launch opportunities for Mars in late 1960 and for Venus in early 1961. The first attempts to send a spacecraft to Mars were on October 10 and 14, 1960. and in both cases the third stage failed, giving the new fourth stage and spacecraft no chance to perform. Later on February 4, 1961, the first attempt to send a spacecraft to Venus was foiled when the engine of the new fourth stage failed to ignite. Finally, on its fourth launch on February 12, 1961, the new rocket succeeded in sending its payload on a trajectory towards the planet Venus. Unfortunately, the Venera 1 spacecraft had a number of problems and failed early in its flight.

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 7,

© Springer Science+Business Media, LLC 2011

THE FIRST LAUNCH TO MARS: 1960

Campaign objectives:

In planning of their 1973 campaign for Mars the Soviets were aware of the IJS plan to send orbiter/landers to the planet in 1975. They also knew that these Vikings were considerably more capable than their own 1971 lander. Adding to this problem, the 1973 opportunity required more energy than that of 1971 and they could not repeat the M-71 orbiter /lander strategy. If they were to send landers to Mars in 1973. then the carrier spacecraft would have to fly past the planet. Their spacecraft were too massive and the Proton-K launcher did not have enough capability to combine an orbiter and a lander in 1973. Chagrined by the poor performance of their spacecraft in 1971 in comparison to the success of the Mariner 9 orbiter, yet encouraged by the near-success of the Mars 3 lander, the Soviets w ere determined to score a success at Mars ahead of the Viking missions. In fact the US had hoped to launch these in 1973 but financial problems forced a postponement to 1975. Knowing there would be no American competition in 1973, the Soviets decided upon four launches to send an armada consisting of two or biters and two flyby landers. The or biters would be sent first so that they could act as communications relays for the landers on the surface. After releasing its lander, a carrier spacecraft would relay telemetry from the entry system to Earth in real-time during the entry and descent, and then perform its own remote-sensing observations of the planet in making its flyby.

By 1973 the US and USSR were in a period of detente, and cooperation between the two space programs had increased with a number of joint working groups and a joint Apollo-Sovuz mission scheduled for 1975. The Soviets gave the US the data from Mars 2 and 3 and from Venera 8 in return for an accurate ephemeris for Mars, models of its atmosphere, and Mariner 9 orbital imagery of the zones chosen for the Mars 6 and 7 landers.

In order to save cost and reduce risk, Soviet engineers used the same spacecraft as in 1971 with minimum changes. But they were plagued with electronics problems in test and in flight. One crucial difference between the 1971 electronics packages and those built for 1973 were that gold leads had been replaced with aluminum on a key transistor used throughout the spacecraft. This difference was discovered very late in the integration and test program, wiien some of the new 2T-312 transistors suffered failures. The difficulties with the 2T-312 transistor were to be the Achilles’ heel of the 1973 campaign. They were in almost every engineering subsystem and science instrument on the spacecraft. Tests showed that these transistors generally failed 1.5 to 2 years after production. This would correspond to Mars arrival, and they could not all be replaced in time to meet the launch window. An analysis estimated a 50% likelihood of a complete mission failure owing to these transistors. In a US program this would have mandated postponing the mission, but the Soviet decision makers, in their rush to beat the Amerieans to the surface of Mars, dismissed the concerns of the engineers and opted to take the risk and launch with the suspect transistors.

The problem of the transistors became manifest almost immediately after launch, and plagued the entire campaign. All four spacecraft reached Mars but with three in a seriously crippled state. One orbiter flew past the planet, one lander missed and the other lander was lost just before touchdown after returning a degraded set of descent data. Mars 5 was able to achieve orbit, but then failed after less than a month.

The paucity of data from this flotilla compared to the mass of data returned from the single long-lived Mariner 9 orbiter, considered together with the lack of a viable competitor to the forthcoming Viking missions, led the Soviets to abandon Mars in favor of Venus for the foreseeable future – and it would be 15 years before they tried again.

Spacecraft:

The overall design and subsystems of the spacecraft for the 1973 Mars campaign were the same as before, although the scientific instruments were slightly different. The most signifieam engineering difference was the installation of a new telemetry system solely to enable the flyby carrier to relay data from its entry system to Earth in real-time; this would prove crucial in the ease of Mars 6. The landers telemetry system remained the same and communications from the surface would be through the or biters.

The M-73 orbiters were almost identical to the M-71S spacecraft. Their function was to enter into orbit around Mars, communicate with the landers, and obtain their own information on the composition, structure, and properties of the atmosphere and surface of the planet. The science payload was mounted on top of the spacecraft, in the same place as the entry systems of the flyby spacecraft. The principal function of the flyby carrier was to release the entry system on a proper entry trajectory and provide a real-time telemetry relay during the descent. It had science instruments for cruise and Mars flyby observations. Because the Mars 3 lander had made it to the surface, the entry systems were the same. However, the science payload of the landers was upgraded.

Mars 4 and 5 launch mass: 3,440 kg (orbiter; dry mass 2,270 kg)

Mars 6 and 7 launch mass: 3,260 kg (flyby vehicle)

1,210 kg (entry vehicle)

635 kg (lander system on descent)

358 kg (lander)

4,470 kg (total)

Payloads:

Some of the M-73 scientific instruments were redesigned forms of those carried by Mars 2 and 3, but others were new. The Mars 4 and 5 orbiters and the Mars 6 and 7 flyby spacecraft were equipped as follows:

1. FTU facsimile imaging system

2. Optical-mechanical panoramic imaging system

3. Infrared radiometer (8 to 40 microns) for measurement of surface temperature (Mars 5 only)

4. Infrared photometer in five carbon dioxide bands around 2 microns to obtain surface altitude profiles

5. Microwave polarimeter (3.5 cm) for measurement of dielectric constant and subsurface temperatures

6. Two polarimeters in ten bands from 0.32 to 0.70 microns to characterize surface texture (French-Soviet)

7. Four band visible photometer in range 0.37 to 0.6 microns for measurement of color and albedo of the surface and atmosphere (Mars 5 only)

8. Infrared narrow-band 1.38 micron photometer for measurement of water vapor content in the atmosphere

9. Ultraviolet photometer (0.260 and 0.280 microns) for measurement of ozone

10. Scanning photometer (0.3 to 0.9 microns) to study emissions in the upper atmosphere (Mars 5 only)

11. Gamma-ray spectrometer for surface elemental composition

12. Micrometeoroid sensors (Mars 6 and 7 only)

13. Lyman-alpha photometer for measurement of upper atmosphere hydrogen (French-Soviet)

14. Solar wind plasma sensors (8) for measurement of speed, temperature and composition in the 30 eV to 10 keV energy range (Mars 4 and 7 only)

15. Boom mounted three-axis lluxgate magnetometer (Mars 4 and 7 only)

16. STHRHO-2 to study solar radio emissions (French-Soviet. Mars 7 only)

17. ZIIEMO to study solar protons and electrons (French-Soviet, Mars 6 and 7 only)

18. Multichannel electrostatic analy/cr (Mars 4 and 5 only)

19. Dual-frequency radio occultation experiment to profile ionospheric electrons and tropospheric density.

Two types of imaging system were employed. The first was a version of the M-71 FTU camera with various technical improvements and more film and faster scanning rates. The second was a single line push-broom panoramic imager that was to scan a 30 degree field of view from horizon to horizon and was sensitive in both the visible and near-infra red. It stored its data on a 90 minute analog tape recorder for replay to Earth.

The FTLT optics were as before: two bore-sighted cameras, one an f/2.8 lens with a focal length of 52 mm and a 35.7 degree field of view, and the other an 174.5 lens with a 350 mm focal length and a 5.67 degree field of view. They each weighed about 9 kg. The wide angle camera was equipped with red. green, blue and orange filters, and the narrow angle one used an orange long-pass filter. Twenty meters of 25.4 mm film was contained in a radiation-shielded magazine. This was sufficient for at most 480 frames. Exposure times alternated between 1 50th and 1/150th of a second. Each camera produced a 23 x 22.5 mm frame and the film could be scanned at up to ten resolutions, only three of which were used actually: 235 x 220,940 x 800, and 1.880 x 1,760 pixels. The scanned images were transmitted at either 512 or 1.024 pixels per second by the dedicated impulse transmitter. At the intended operating altitude these cameras would provide resolutions of between 100 and 1,000 meters.

The push-broom panoramic camera system was first used by Luna 19 in 1971. It comprised two optical-mechanical cameras, each with a single photomultiplier tube and a rotating prism to scan a 30 degree field of view aeross the spacecraft’s track. One camera had red and orange filters and was sensitive across the visible spectrum and the other used a red long-pass filter with a photomultiplier that was sensitive in the infrared. They scanned at 4 lines/seeond and produced 250 cycles line for video recording on magnetic tape at 1,000 IIz. The readout rate was 1 line/second and the transmission was commanded at 256 or 512 pixels line resolution.

The payload of the entry system and lander w as essentially the same as flown on Mars 2 and 3, but with upgraded imagers, mass spectrometer, and temperature and pressure sensors. The Doppler experimeni to measure winds during the descent was new. Most significantly, it was nowr possible to transmit the descent data in real-time rather than storing it for transmission after landing. They were equipped as follow s:

1. Accelerometer for atmospheric density during entry

2. Doppler experiment for winds and turbulence on descent

3. Temperature and pressure sensors on descent and landing

4. Radio altimeter for providing altitudes on descent

5. Mass spectrometer for atmospheric composition on descent and landing

6. Atmospheric density and wind velocity on the surface

7. Two panoramic television cameras for stereo viewing of the surface

8. Gamma-ray spectrometer for soil composition mounted in a petal

9. X-ray spectrometer for soil composition deployed to the surface from a petal

10. PrOP-M walking robot deployed to the surface from this same petal with

onboard gamma-ray densitometer and conical penetrometer.

Doppler measurements and the radio altimeter, accelerometer, temperature, and pressure sensors operated from the beginning of parachute deployment right down to the surface.

Mission descriptions:

All four spacecraft were dispatched successfully but predictably and inevitably first Mars 6, then Mars 7, then Mars 4 suffered system-wide failures within a matter of weeks owing to the faulty transistor. Only Mars 5 arrived relatively trouble free and was able to enter orbit around Mars, but it suffered a pressure leak and shortly thereafter fell silent.

Mars 4:

Mars 4 was launched on July 21, 1973. It made a midcourse correction on July 30, but the computer developed problems that prevented a second midcourse correction. It reached the planet on February 10, 1974, but the engine failed to ignite for the orbit insertion maneuver and the spacecraft flew? past the planet at a range of 1,844 km.

Mars 5:

Mars 5 was launched on July 25, 1973. It made midcoursc corrections on August 3 and on February 2, 1974, and followed through with the orbit insertion maneuver at 15:44:25 UT on February 12 to achieve a 1,760 km x 32,585 km orbit with a period of 24.88 hours inclined at 35.3 degrees to the equator. Some unknown event during orbit insertion triggered a slow leak in the instrument compartment. An accelerated plan of observations w as prepared that focused on obtaining high resolution imagery of the surface. But when the pressure fell below operating levels in the transmitter housing on February 28 after only 22 orbits, this prematurely ended the mission and ruled out the use of this spacecraft as a relay for the landers that were scheduled to arrive in early March.

Mars 6:

Mars 6 was launched on August 4, 1973, and conducted a midcourse correction on August 13. At the end of September the science and operations dow nlink was lost, almost certainly due to the failure of a 21-312 transistor. Only two channels in the telemetry system remained operational, neither of which provided any information on spacecraft status. Refusing to give up, the engineers continued to send commands to the spacecraft in the hope that the receivers might still be functioning. As it turned out the command uplink was unaffected, and Mars 6 dutifully obeyed the commands and executed its autonomous functions. Unable to report to Earth, in February 1974 it autonomously determined its position, calculated the second midcourse correction and carried this out. Upon approaching the planet on March 12, it properly executed the optical navigation and targeting, and then released its entry system at a range of

48,0 km from the planet with just 3 hours remaining to atmospheric entry.

Ground controllers first realized that Mars 6 had done its job shortly thereafter, at 08:39.07 UT, when data began to arrive through the dedicated relay channel. At that time the entry system was 4.800 km from its target. The spacecraft was able to relay data throughout entry and descent, and then continued past the planet, passing within 1,600 km of the surface. This performance was a monumental achievement in spacecraft autonomy for the Soviet program so early in the history of planetary exploration.

The entry system penetrated the atmosphere at 09:05:53 UT at a speed of 5.6 km/s and an 11.7 degree angle of attack. Loss of signal due to plasma effects occurred at 09:06:20 at an altitude of 75 km. The signal was regained at 09:07:20 at 29 km. with the start of the data transmission. The main parachute was deployed at 09:08:32 after the entry system had slowed to 600 m/s at an altitude of 20 km. The canopy opened fully at 09:08:44. and the capsule started to transmit data on altitudes, temperatures and pressures. The mass spectrometry was stored for transmission after the landing. The Doppler shifts on the signal were noted. The capsule appeared to be swaying under the parachute more than expected, impairing the transmission quality. Ignition of the rocket engines was confirmed but the transmission cut off at 09:11:05 when the lander was "in direct proximity to the surface’*, probably when it hit the surface. The velocity at the time of signal loss was 61 m/s, which was excessive for a safe touchdown. The transmitter was programmed to turn off after the lander had been released in order to switch over to a different set of VHF antennas on the lander. No further signals were received. The fate of the lander is unknown. It lies at 23.90 S 19.42 W in the Margaritifer Sinus region, in the vicinity of Samara Valley, where the landscape is characterized by steep slopes.

Mars 7:

Mars 7 was launched 4 days after Mars 6 but flew a faster trajectory which arrived at the planet 3 days earlier. It made only one course correction on August 16, 1973. An early failure in the communications system cost it one transmitter, but it was able to remain in contact. At Mars the targeting maneuvers to set up the entry system were executed properly and the entry system was released on March 9. 1974. However, most likely owing to a failed 2T-312 transistor, the entry system computer did not issue the command to fire the retro-rocket, with the result that it missed the planet by 1,300 km. The intended target was in the crater Galle at 51.2 S 30.9 W. The carrier spacecraft provided some data during its flyby.

Results:

Orbiters:

Imagery

After Mars 4 failed to execute its orbit insertion maneuver it flew past the planet and continued to return interplanetary data from solar orbit. During the flyby it returned one swath of twelve pictures and two panoramas in a 6 minute imaging cycle from a range of 1,900 to 2Л 00 km. Two dual-frequency radio occultation profiles were also obtained, one on passing behind the planet as viewed from Earth and the other upon exiting and these supplied the first indication of a night-side ionosphere.

The Mars 5 orbiter operated for only 25 days after orbit insertion, and returned atmospheric data and images of a small portion of the southern hemisphere of Mars. In all it returned 108 pictures, but the narrow angle ones were motion blurred. The useful data included 43 wide angle images and five panoramas which were returned in five imaging sessions over a 9 day period, all of roughly the same area, which was near the imaging track of Mariner 6 and showed swaths of the area south of Valles Marineris from 5 N 330 W to 20 S 130"W. Measurements by other remote sensing instruments were also made near periapsis along seven adjacent arcs in this region. High cirrus clouds and yellow clouds of fine dust w ere identified.

Surface properties

Data returned from orbit by the infrared radiometer on Mars 5 showed a maximum surface temperature of-Г C, -43 C near the terminator, and -73°C at night. It gave a thermal inertia for the soil that was consistent with grains 0.1 to 0.5 mm in size, and polarization data in the visible spectrum implied grain sizes smaller than 0.04 mm in aeolian deposits of variable cover. The polarization at 3.5 cm suggested a dielectric constant of 2.5 to 4 at depths of several tens of cm. The oxygen, silicon, aluminum, iron, uranium, thorium, and potassium sensed by the gamma-ray spectrometer from orbit suggested a surface similar to terrestrial mafic rocks.

Lo wer atmosphere

Six altitude profiles were measured by the carbon dioxide photometer along a path between 20 and 120 :W in longitude and spanning 20 to 40r’S in latitude, and these were in general agreement with the Mariner 9 ultraviolet spectrometer data. Surface pressures as high as 6.7 millibars were determined. Mars 3 had found only 10 to 20 precipitable microns of water vapor while the dust storm was raging in 1971. Two years later. M ars 5 found abundances as high as 100 precipitable microns south of the Tharsis region. The water vapor content was variable by a factor of 4 to 5 across the planet. An ozone layer about 7 km thick was detected at 40 km altitude in the equatorial region, not near the surface as anticipated, with a concentration of about 1/1,000th that of Earth’s ozone layer. The Mariners were able to detect ozone only at the poles where it is more abundant. The existence of argon in the atmosphere was confirmed.

Upper atmosphere and ionosphere

The Lyman-alpha instrument found the exosphere temperature to be 295 to 355K. with the temperatures in the altitude range 87 to 200 km being 10 degrees lower. No upper atmosphere emissions were noted by the visible spectrometer in the range 0.3 to 0.8 microns. Mars 5 also performed a radio occulta lion experiment on one orbit and its results, with those from the flyby occupation measurements for Mars 4 and 6. showed the existence of a night-side ionosphere with a maximum electron density of 4,600/cc at an altitude of 110 km, and an atmospheric pressure near the surface of 6.7 millibars.

The fields and particles instruments returned a significant data set to complement the M-71 orbiter data. Two distinct plasma zones were found inside the bow shock between the undisturbed solar wind and the planetary magnetosphere: a thermalized plasma behind the bow shock, and a small electrical current carried by protons in the magnetotail. The bow shock was held at an altitude of 350 km. The plasma results and magnetometer measurements were consistent with the planet having an intrinsic magnetic field of about 0.0003 times the strength of Earth’s field, and inclined 15 or 20 degrees from the rotational axis which, as in the case of Earth, is tilted 23 degrees from the perpendicular to the plane of its orbit.

Flyby spacecraft:

The radio occupation made by the Mars 6 carrier spacecraft verified the detection by Mars 4 and 5 of a night-side ionosphere. The French STEREO instrument on Mars 7 w orked satisfactorily throughout the cruise to Mars but the spacecraft did not return any useful science during the flyby. It was the last of the armada to fall silent, wiiieh it did in September 1974.

Entry systems:

The Mars 6 entry system transmitted for 224 seconds during its descent before it fell silent, providing the first in-situ measurements of this atmosphere. Although a lot of it was unreadable due to the degradation of another 2T-312 transistor, enough data w’as obtained to profile the temperature and pressure from an altitude of about 29 km down to the surface. The density of the atmosphere from 82 km down to this level was inferred from accelerometer data. Winds of 12 to 15 m s were measured from an altitude of 7 km dowm to near the surface. A surface pressure of 6.1 millibars and a temperature of -28 C were derived from temperature, pressure, accelerometer and Doppler data. The surface winds were 8 to 12m/s. Other parameters included a lapse rate of 2.5K/km, the presence of the tropopause at an altitude of 25 to 30 km. and an almost isothermal stratosphere at a temperature of 150 to 160K. These values were consistent with measurements by the Mars 5 orbiter, and were later confirmed by the Viking missions. Instruments also indicated "several times" more atmospheric water vapor than previously reported. The mass spectrometer data were stored during the descent for transmission after landing, and so were lost. However, the current to the vacuum pump was transmitted during the descent as an engineering parameter, and a sleep increase in current was interpreted as an indication of argon at an abundance of 25 to 45%. which was implausibly large; the actual value was found by the Vikings to be a more reasonable 1.6%.

Landers:

Ко transmissions were ever received from the Mars 6 lander and no results w’ere obtained from the surface. The Mars 7 entry system missed the planet entirely.