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Second Generation Mars

By Charles S. Sheldon II[1917-1981], was Chief of the Science Policy Research Division of the Library of Congress, Congressional Research Service



Although the rumors of the summer of 1968 were that there would be new major Mars attempts late in 1969, there were no successful launches announced and no Kosmos hidden failures in Earth orbit at appropriate, windows. (18) However, there were multiple rumors of two launch failures at the appropriate window. The 1971 opportunity was taken by both the Soviet Union and the United States .

Launch Failures

The United States was unsuccessful on May 8, 1971 in sending Mariner 8 on its way to Mars. The Centaur stage went out of control and the payload fell in the Atlantic near Puerto Rico .

Less publicized was the Soviet launch of Kosmos 419 on May 10, two days later. Although the Russians named the launch, they did not add the usual statements about everything going well. It 'attained Earth orbit, but did not fire its Zond rocket which would have launched it toward Mars and given it a Mars name. By inference, it almost certainly was like the flights which followed shortly in being launched by a D-l-e. Within two days it had decayed from orbit.

Launch of Mars 2, Mars 3, and Mariner 9

Moscow announced the successful launch of Mars 2 on May 19 as soon as it was clear that its Zond rocket had launched it on a trajectory toward Mars from its orbital launch platform. It was announced as weighing 4,650 kilograms, not including the weight of the accompanying rocket stage. This was a D-l-e launch. Telemetry was being received on 928.4 MHz.

The same kind of announcement came on May 28 that Mars 3 was also on the way to Mars in a virtually identical pattern, and with the same weight, except that Mars 3 also carried a French Stereo experiment designed to supply readings of solar radio emissions and cosmic rays in the interplanetary medium as part of synoptic measurements to be made in France and in the Soviet Union.

Mariner 9 was successfully launched on May 30, preceded by the usual U.S. detailed explanation of its intended purposes and instrumentation. Also as usual corresponding details on the two Soviet craft were missing at that time, only to be revealed much later.

In-flight Progress

The Soviet releases of news presently were expanded to report both their flights would be measuring data from the interplanetary medium, although only Mars 3 carried the French experiment. The Russians said the directional antennas on the two craft would greatly increase the flow of data over that of earlier experiments.

On Juno 8, a course correction was made by Mars 3 to bring it more nearly to its intended trajectory. A similar course correction was carried out by Mars 2 on June 17.

By July 27, it was 'announced there had been 43 communications sessions with the craft, with continuing measurements of solar corpuscular radiation and of galactic cosmic rays.

On August 21, a similar announcement also added that each craft carried 8 separate spectrometers to determine the speed, temperature, and composition of the basic components of the solar wind over time, in the range of energies from 30 to 10,000 electron volts. This was the last known public reference to the flights for many months, and some Western observers began to suggest the flights had failed. (19)

As had been done with the fights from Venera 4 on, each Mars craft had its analog operating in a vacuum chamber on Earth to receive the precise commands being sent to the real craft, providing 'an opportunity to see how they responded, and also to aid in the solution of problems which might arise. For the real craft 'at the distances involved, the signal to fire a rocket and to receive confirmation back took longer than the firing itself.

Mars 2 Arrival

The Russians waited until November 30 to announce that on November 27, 1971, Mars 2 had entered on orbit around Mars, with an apoapsis of 25,000 kilometers, a periapsis of 1,380 kilometers, an orbit inclination of 48°54' to the Mars equator, and 'a period of 18 hours. As the payload first approached the planet, a capsule was separated from the main bus, and was delivered to the surface of the planet at 45°S., 58°E. It carried a pennant bearing the coat-of-arms of the Soviet Union . The main bus was to continue a study of the planet from orbit. There had been further course corrections on November 20 and 27.

Mars 3 Arrival

Not until December 7 did the Russians announce that Mars 3 had reached the planet in similar fashion, on December 2, 1971 . This time the Lander was referred to as a descent craft which parachuted to land 'at 45°S., 158°W., after which it transmitted signals to Earth. Both Mars 2 and 3 were described as opening the way to conducting a search for life, but were not themselves equipped for this purpose. The Mars 3 Lander also carried Soviet insignia to the surface. The Mars 3 bus was put into a more eccentric orbit with a low point 1,500 kilometers above the surface, and an 11-day period of orbit. Presumably the inclination was similar to that of Mars 2, and the high point should have been about 190,700 kilometers. Signals from the surface were transmitted by a weak omni directional system to the orbiting bus where they were recorded and later played at a slower data rate via the high gain antenna pointed toward Earth. Braking of the Lander was accomplished by aerodynamic ballistic entry, and after a marked slowing of the craft, a drogue chute was released, followed by the main parachute. A rocket braking system supplied the final reduction in velocity to permit a survivable landing. This brake was activated by 'a radio altimeter 20-30 meters above the surface. It was stated that the signals from the surface had been brief, and were replayed from the Mars 3 bus over the period December 2 to 5.

The landing site of the Mars 3 vehicle was in 'a relatively featureless rounded hollow about 1,500 kilometers across. Orbital television cameras with a resolution of 0.3 kilometers could detect no craters, even though beyond a surrounding area of ridges and cliffs, there were numerous craters.

On December 18 it was further reported when the Mars 3 Lander reached the surface and was stabilized, that after a lapse of 90 seconds, the several instruments and television system were activated. The TV began to take a panoramic view, but after 20 seconds of transmission, all signals from the Lander ceased. The small portion of picture, when retransmitted to Earth, revealed no noticeable contrast or details.

Obviously, the Lander portions of the two flights must have been a disappointment to the Russians. They were probably mechanically similar. Mars 2 failed to survive its landing, and Mars 3 ceased to function very shortly thereafter, when it might have been expected to operate for some hours or days before its batteries ran down. The cause of the failure is unknown.

Aviation Week on March 6, 1972 reported that the real problem was a failure in the relay antenna on the Mars 3 bus which malfunctioned, while the Lander probably continued to transmit data and pictures from the surface, which could not be relayed to Earth. Most observers today do not consider this the most likely explanation, and suggest rather that dust storm conditions on the surface overwhelmed the Lander.

Instruments on the Landers

 The December 18 Soviet, account of Mars 3 probably applied to both landers. Mars 3 carried atmospheric temperature and pressure sensors, a mass spectrometer to determine atmospheric components, a wind velocity meter, devices to measure the chemical and mechanical properties of the soil, and a television system to supply panoramic views of the surroundings. The Lander has not been pictured deployed, except possibly on a 1972 postage stamp, but probably was an outgrowth of the self-righting petal design used for Luna 9 and Luna 13. The landed weight (not revealed at the time) was 635 kilograms. (20)

The Orbital Buses and Their Activity

The Russians announced on December 15, 1971 that both Mars 2 and 3 had taken photographs of the planet at different distances and the pictures had been transmitted to Earth by facsimile after development, in an automatic on-board laboratory. On December 18, further details supplied described the camera system as including both a wide angle lens and a 4° narrow angle lens, and there were different light niters as well which could be shifted over the lenses on command. The continuing dust storm on Mars which hampered the much more ambitious picture taking by Mariner 9 plagued the Russians as well.

Another Soviet announcement said the French Stereo experiment carried by Mars 3 used a data compression system reducing by 100-fold the burden of transmitting significant results to Earth.

Pravda, carried a more complete account of the bus instrumentation in December 19 for both Mars 2 and 3:

An infrared radiometer to construct a Mars surface temperature distribution chart (8-40 microns).

An instrument to determine water vapor concentrations by spectral analysis of absorption in the 1.38 micron line.

An instrument to study surface relief by measuring the amount of carbon dioxide along a sighting line, according to the intensity of the 2.06 micron absorption band (an infrared spectrometer).

An instrument to study the reflectivity of the surface and atmosphere in the visible spectrum of 0.3 to 0.6 centimeter range, and for determining the dielectric permeability of the surface and temperature to a depth of 35-50 centimeters.

An instrument to determine the density of the upper atmosphere and the concentration of atomic oxygen, hydrogen, and argon—an ultra-violet photometer.

Two television cameras on the same axis, one wide angle, and the other narrow angle. (It was not clear how the television description squared with the alternate Soviet report of photographic film being developed on board for facsimile transmission to Earth.)

In general the two buses seem to have performed about as planned. On December 27, 1971 , the Russians announced the discovery of atomic hydrogen and atomic oxygen in the upper atmosphere of Mars. By January 9, 1972 , they said work was proceeding in orderly fashion, and that the dust storm seemed to be subsiding. Pictures taken with the red filter were showing dark areas of "seas" again, while ultraviolet pictures again showed bright clouds. A routine progress report was issued on January 29.

TASS further reported on March 1, 1972 that the dust storm was over. The soil temperature on Mars at a depth of several tens of centimeters was found to be largely independent of the time of day. The ionosphere was defined as beginning at a height of about 80-110 kilometers, with electron concentrations sharply increasing, then gradually diminishing with height. The orbital buses were said to be continuing to explore the structure and surface of Mars, taking pictures of the planet, and measuring the temperature, pressure, density, and chemical composition of its atmosphere. A second bulletin that day said that by March 1, Mars 2 had made 127 orbits of the planet, and Mars 3 had made 7 orbits around Mars. It concluded saying, "The program for the work of stations Mars 2 and Mars 3 which are orbiting Mars as its artificial satellites is nearing completion. (21) This was attributed to the growing distance of Mars from Earth.

Only over a period of time as analysis proceeded did more of the findings become available. On March 22, 1972 , it was reported that photography had played a minor role compared with the other data gathered. Mars 3 did three surveys of the planet during the dust storm and four more afterwards. The estimate was that billions of tons of material had been on the move during the dust storm. Water vapor was found to be about 1/2,000 that of the Earth, with a measurement in the range of from 50 to under 10 microns.

In April it was revealed the camera systems used had a 52mm focal length for the wide angle camera and an unspecified longer length for the narrow angle. Color filters were red, green, and blue. Some 12 frames were exposed and automatically developed on board, then scanned with 1000 lines of 1000 elements each for transmission to Earth where they were recorded both on magnetic tape and on electrochemical paper.

Although the main work program ended in March., the two orbiters were still being contacted in July at a distance of 385 million kilometers.

The program was reported formally completed by August 22, 1972 . By then Mars 2 had completed 362 orbits and Mars 3, 20 orbits of the planet. They had returned interplanetary data, and done integrated studies of the surface and atmosphere of Mars in visible, IR, and UV ranges, plus radio studies. They measured therma1 differences by region find variations in altitudes. The estimate on water vapor was lowered to 1/5,000 that of Earth. The TV studies revealed the structure, height, composition, and temperature of the upper atmosphere. The radio studies gave the pressure and temperature at the surface. Dust particle size and concentration was measured. The magnetic field was measured. The, temperature was found to be between 13° C. and —9?>° C., except at the North Pole where it was —110° C. The temperature drops quickly with darkness. There was about a 10° difference between seas and continents with the seas being warmer. Mountains up to 3 kilometers high were found, and depressions ran to a depth of 1 kilometer. The maximum water vapor reading was 5 microns (1/2,000 of Earth). The air was mostly carbon dioxide, but at high altitudes, separated into carbon monoxide and atomic oxygen, while water also broke into atomic hydrogen and atomic oxygen. The temperature rose with altitude The ionosphere was about one tenth as dense as that of Earth, with its maximum strength at 140 kilometers. The magnetic field was about 8 times as strong as in the interplanetary medium. Air glow showed in photographs of the terminator.


The year 1973 was more difficult than 1971 in terms of the energy requirements for sending payloads to Mars. Consequently, when the Soviet flights came, they fell into a different pattern. There were two pairs of flights, each made up of an orbiter and a Lander, with ability to switch communications between members of pairs in order to increase redundancy. Launching a total of four D-l-e vehicles represented a very considerable Soviet investment.

The Launches of Mars 4- Mars 5. Mars 6, and. Mars 7

Mars 4 was launched on July 21, 1973 at 2231 Moscow time. Soviet observatories were able to make optical observations as the payload sped toward Mars after departure from an Earth orbiting platform. Soviet accounts spoke of the elaborate controls at the launch center with monitoring television screens and reference data available at the touch of a button. In the Atlantic were three ships to monitor the escape from the platform. These were the Akademik Sergey Korolev, the Bezhitsa, and the Ristna. Molniya was used as a link to the U. S. S. R.

Mars 5 was launched on July 25. 1973 at 2156 Moscow time, and it departed from its Earth orbital platform at 2315 Moscow time. It was described as being like Mars 4, intended to study Mars and its surroundings space.

Mars 6 was launched August 5 at 2046 Moscow time. It was described as different from the two earlier flights, and intended to work primarily with Mars 4. It was also said to carry French experiments for solar studies. This time the three ocean tracking ships named before also had the Morzhovets in the Atlantic to help out. Soviet observatories extended their reach to make optical searches for Mars 6. The Crimean observatory found the payload at distances up to 465,000 kilometers from Earth, and the carrier probe rocket was located first at 435,000 kilometers.

Mars 7 was launched on August 9, at 20:00 Moscow time, being put into an intermediate Earth orbit, and then pent on its way. It was to work closely with Mars 5, and Mars 7 was like Mars 6 in carrying French solar study equipment. The Alma Ata observatory was reported to be doing optical tracking of both Mars 7 and its carrier rocket.

The Flight En Route .

Midcourse corrections were made to Mars 4 on July 30 and to Mars 5 on August 3. This time the French experiment for solar studies en route was called Zhemo. This was for study of the distribution and intensity of fluxes of solar protons and electrons. Other French equipment of the Stereo type was for making solar radio emission studies.

Course corrections were applied to Mars 6 on August 13 and to Mars 7 on August 16. Though still generalized, a more complete description than usual of the mission of the four craft was issued on September 22 relating to the studies to be done both from orbit and on the surface of the planet, including studies of the physical characteristics of the surface rock, and surrounding terrain including use of photography and also studies of the atmosphere. As the voyages continued, update reports were issued about monthly.

3. Arrival at Mars

Mars 4 reached Mars on February 10, 1974 . The retrorocket failed to fire, so it did not enter orbit around the planet, instead making a close pass at 2,200 kilometers. It was able to take photographs for development on board and transmission to Earth by facsimile scan the payload continued to gather interplanetary data thereafter.

Mars 5 reached Mars on February 12 at 1845 Moscow time firing its retrorockets to be placed in an orbit around Mars with an apoapsis of 32,500 kilometers and a periapsis of 1,760 kilometers. The orbit was inclined at 35 degrees to the Martian equator, and had a period of 25 hours. All of these steps were accomplished by an on-board autonomous navigation system.

Mars 6 reached the vicinity of Mars on March 12, 1974 . While its bus continued in heliocentric orbit, it separated a descent module which used aerodynamic braking in the atmosphere and then a parachute system to reach the surface of the planet. It landed at 24° S., 25 degrees W.

Mars 7 reached the vicinity of Mars three days earlier on March 9. Its bus also continued in heliocentric orbit. Its descent module separated as planned, but a malfunction of an onboard system made it miss the planet by 1,300 kilometers.

Follow-up Details of the Flights

Even the first announcement noted that the probes through use of a wide range of observed wavelengths had been able to answer questions on Mars relief, temperature, heat conductivity, soil structure and composition, chemical composition of the lower atmosphere, and structure of the upper atmosphere. More water vapor was found in some places this time than had been the case two years earlier

It was then disclosed that contact with Mars 6 had ceased 148 seconds after the parachute had opened, in the immediate proximity of the surface. All data up to that point were relayed from the landing module to the bus for further relay later to Earth. Dried river beds were detected.

Soviet papers carried follow up articles by leading Soviet scientists who were drawing conclusions from the most recent flights, almost as if to fill the gap in real information, as it was too early for new data to be fully interpreted R. M. Sagdayev, Director of the Institute of Space Research, said that Mars was more Earth-like than had been supposed, and he spoke of its being geologically active at least in the past and possibly having had water at some stages. He gave a refined figure for the orbital period of Mars 5 as 24 hours, 53 minutes He explained that Soviet measurements of thickness of atmospheric strata were revealing differences in ground elevation which were not apparent from photographs. He noted that the IR data and daily changes told about soil thermal conductivity and hence structure. Study of the surface in visible and near-IR wavelengths as to brightness and polarization could answer questions of soil composition. The gamma spectrometer readings revealed the nature of rocks. The photometer gave localized readings as high as 60 microns for water traces in the atmosphere, several times what had been read by Mars 3, and giving a 5-fold range among tested localities on this flight. He said the UV photometer revealed some ozone traces. He reported the outer atmosphere as atomic hydrogen at 1,216 angstroms. The magnetic field is 30 gammas near the planet, helping to divert away the solar wind.

He said that Mars 4 and 5 both took pictures of Mars at resolutions ranging from 1 kilometer down to 100 meters, from a distance of about 2,000 kilometers. Through the use of the adjustable filters, color pictures had been created. In the southern hemisphere, several strips 1,000 kilometers long had been taken. He also said that the Mars 6 Lander had been separated at a distance of 48,000 kilometers from the planet, and the bus had passed the planet at 1,600 kilometers. Aerodynamic braking had lasted 5 minutes. Pressure at the landing site had been 6 millibars, about 1/100 the level of Earth. (22)

What was especially significant is that Mars 6 managed to send bad; from its Lander the first direct readings of pressure, temperature, and chemical composition of the atmosphere.

The Russians finally published color photographs of Mars taken by Mars 4 and 5. They revealed that the plains are orange, the mountains blue, and the craters bluish-green. Mountains may range up to 8 or even 11 kilometers high with gentle slopes (23) Later V.S. scientists criticized the pictures as lacking adequate calibration for scientific purposes. (24)

The first complete review of findings was published in January and February 1875, with a whole issue of the journal devoted to the four payloads. (25)

Apparently the Landers for Mars 6 and 7 were 635 kilograms each. (26) Other summary findings were carried in the COSPAR report on 1974 activities. (27) The findings were consistent with the earlier brief reports, but gave greater details. Mars 6 had hit at atmosphere at a speed of 5.6 kilometers per second at 12:05:53 Moscow time. Air drag slowed the speed to 600 meters per second by 12:08:32 , when the parachute opened. It readied the surface at 12:11:00 , and the radio signals ceased at that moment. This meant it had taken 2 minutes, 39 seconds to slow in ballistic flight, and 2 minutes, 33 seconds more for the parachute to bring it to the surface.

The mass spectrometer was not set to function until after touchdown, so did not return data. Other sensors during the flight down to the surface disclosed that 35 ± 10 percent of the atmosphere was an inert

gas, perhaps argon. At the landing site, the air pressure was measured as being 6 millibars, and the temperature 230° K. (-3° C.).

Meanwhile the orbiting vehicle, Mars 5, was returning a wide variety of other data. It made a radio probe of the atmosphere at 8-32 cm. It used a radio telescope at 3.5 cm. Its infrared radiometer worked in the 8-26 cm. range. The spectrometer with an interference filter worked in the 2-5 ym range. A narrow band photometer with interference filter studied the CO 2 band at 2ym. Another narrow band photometer with interference filter studied the H 2 O band at 1.38 ym. There was a photo-television complex of instruments to take pictures, develop the film, and scan these for facsimile transmission to Earth. Another photometer with interference filter covered the 0.3-0.8 ym range. Two polarimeters covered 9 narrow bands in the range of 0.35-0.8 /mi. Another photometer studied the ozone band at 2,600 angstroms. A different photometer measured the intensity of scattered solar light in the Lyman alpha range of 1,215 angstroms. There was also a gamma photometer.

Several experiments were duplicated among the four main vehicles. Magnetometers were carried on Mars 4 and 7, as were plasma traps. Multichannel electrostatic instruments were carried by Mars 4 and 5. Mars 6 and 7 carried micrometeorite sensors and cosmic ray sensors. It was Mars 7 that also carried a French solar radio wave experiment.

Mars 5 made a study of the chemical composition of the atmosphere measuring the amount of water vapor and ozone. Mars 3, after the dust storm two years earlier had found only 10-20 ym of water vapor. But Mars 5 found some readings of up to 80 ym of water vapor, with variations of 2 to 3 fold even within short distances of a few hundred kilometers. Mars 5 found that the amount of ozone by volume was 10 to the-5 percent, with the layer at 30 kilometers.

Between them, Mars 4 and 5 took 60 photographs, often of high quality. Those with resolutions as good as 1 kilometer were taken with a camera whose focal length was 52 mm. Other pictures with a resolution ranging up to 100 meters were taken with a camera with a focal length of 350 mm. Pictures scanned for return to Earth were done so either at 1,000 by 1,000 fineness or at 2,000 by 2,000 fineness. Mars 4 used a red filter. Mars 5 used a blue filter.

Apparently, not only was there the photo-television system, but also an optico-mechanical TV scanning system. In addition to the general filters referenced above, Mars 5 used other red, blue, and green filters, and a special orange light filter. From the pictures taken, rectified maps were produced which provided control points and links with the pictures taken two years earlier by Mariner 9. In one region it was possible to do a geomorphological study.

In summary, although the payloads collectively did much less than hoped of them, the mission was not the total loss some Western publications seem to have assumed. Further details are carried in the referenced Soviet reports.

A small amount of supplementary detail was carried in another Soviet publication. The Mars 4 and 5 photo TV systems were described as designed to attain 700 and 100 meter resolutions at best for survey purposes. The camera already described as having a focal length of 52 mm was called Vega. It was f/2.8, providing a 23 by 22.5 mm frame and its look angle was 35°42'. The other camera already described as having- a focal length of 350 mm was called Zufar. It was f/4.5, again with a 23 by 22.5 mm frame, and its look angle was 5°40'. (28)



18. Flight International, London , March 27. 1971. p. 793.

19. Flight International, London , Oct. 7, 1971 , p. 592.

20. Oja, Heikki, In Spaceflight, London , July 1975, p. 279, quoting a Soviet scientist.

21. TASS, March 1, 1972 , 1446 GMT

22 Pravda, Moscow , March 17,1974 , p. 3.

23. TASS November 11, 1974 , 0912. citing Zemlya 1 Vselennaya.

24. Aviation Week, New York . February 10, 1975 , p. 11.

25. Komichesklye Issledovanlya, Moscow . Vol. XIII, No. 1 (Not available to this study).

26. Oja, Hpikki, in Spaceflight, London , July 1975, p. 279.

27. Space Research Conducted in the U.S.S.R. In 1974, COSPAR Report, I8th Plenary Session. Translated into English and republished as JPRS 65778. September 29, 1975 by the Joint Publications Research Service, pp. 2-21.

28. Tekhnika Kinoi Televideniya, Moscow . No. 9,174, pp. 55-60.

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