Category Soviet Robots in the Solar System

A NEW BEGINNING RISES EROVI A CHERISHED LEGACY

The Phobos-Grunt spacecraft embraces the latest in space technology and erases the tradition of pressurized planetary spacecraft. The launcher will be the Zenit-Fregat. The Zenit rocket is a legacy of the Energiya-Ruran program, and the Fregat stage is a legacy from the Phobos and Mars-96 missions. For Phobos-Grunt to achieve the desired interplanetary trajectory, a burn of the spacecraft’s engine will be required after the Fregat burns out. The spacecraft will make the mideourse maneuvers, orbit insertion, and orbital maneuvers to rendezvous w ith and ultimately land on Phobos. the larger of the two Martian moons. Tradition also survives in the boldness of Russia’s return to robotic exploration: not just a modest step but an ambitious sample return mission, which seems appropriate for a program amongst whose unanswered legacies is a sample return from the Moon. Phobos-Grunt also continues the legacy of international cooperation, because it wall carry the first Chinese Mars spacecraft, Yinghuo 1, and release it into orbit around the planet.

The main goal of the Phobos-Grunt mission is to return a sample from Phobos to Earth for in-depth laboratory studies to help to answer key questions concerning the origin and evolution of the Solar System. The payload also includes instruments for navigation and for studying the Martian environment (television, space plasma and magnetic field detectors, and a dust particle detector) and instruments to study the surface of Phobos following the landing. The latter include a panoramic camera, gas

image254

Figure 21.1 Phobos-Grunt spacecraft. At bottom ls the Frcgat propulsion stage, then (in turn) adapter ring, spacecraft-lander system, Earth return system and entry capsule (courtesy NrO-Lavochkin).

chromatograph, gamma-ray spectrometer, neutron spectrometer, laser time-of’-llight mass spectrometer, secondary ion mass spectrometer, infrared spectrometer, thermal detector, long-wave subsurface radar and a seismometer. The robotic manipulator to be used for sampling carries a micro-television camera, an alpha, proton and x-ray spectrometer, and a Mossbauer spectrometer.

The Soviet lunar and planetary exploration program in the 20th Century left a legacy of scientific results and new knowledge. Tt is difficult to remember how little we knew about the Moon and planets at the beginning of the space age in 1957, and how much wc have learned as a result of sending out spacecraft. Table 21.1 provides a summary of the exploration milestones achieved by the Soviet program, most of which occurred during the first 15 years of the space age. Soviet scientists also made many scientific discoveries in the course of their missions. The early Luna missions established that whereas ihc near side of the Moon is dominated by the dark maria.

the far side is dominated by the bright highlands, an interesting dichotomy that has yet to he adequately explained. Lunar mass coneentrations were first discovered by Soviet spacecraft. Much of what we know of the atmosphere and surface of Venus eoincs from the Venera missions. And while the Soviets were thwarted at Mars, they were first to successfully land (albeit the lander failed after a few seconds), made the first in-situ measurements in the Martian atmosphere, the early discoveries about its ionosphere, and the lack of an intrinsic magnetic field.

The Phobos-Crunt mission represents a hope that Russia will resume a lunar and planetary exploration enterprise with the same boldness, innovation, and persistence that they demonstrated in the first 40 years of space exploration.

Table 21.1 ‘Firsts’ in lunar and planetary exploration by Soviet spacecraft

Lunar missions

First spacecraft to escape Earth’s gravity

Luna 1

1959. January 2

First spacecraft to fly by the Moon

Luna 1

1959. January 4

First spacecraft to impact another celestial body

Luna 2

1959. September 14

First photographs of the far side of the Moon

Luna 3

1959, October 6

First lunar lander

Luna 9

1966, February 3

First lunar orbiter

Luna 10

1966. April 3

First circumlunar mission with Earth return

Zond 5

1968. September 20

First robotic sample return mission

Luna 16

1970. September 21

First robotic rover (Lunokhod 1)

Luna 17

1970, November 17

Venus missions

First launch attempt to Venus

1VA Nod

1961. February 4

First spacecraft to impact another planet

Venera 3

1966, March 1

First planetary entry probe

Venera 4

1967, October 18

First planetary lander

Venera 7

1970. December 15

First Venus orbiter

Venera 9

1975. October 22

First photographs from the surface of a planet

Venera 9

1975. October 22

First radar imagery of Venusian surface

Venera 15

1983, October 10

First planetary balloon

Vega 1

1985. June 11

First comet distant flyby

Vega 1

1986. March 6

Mars missions

First planetary launch attempt

1M No. 1

1960. October 10

First spacecraft to impact Mars

Mars 2

1971. November 27

First lander on Mars (Tailed after landing)

Mars 3

1971. December 2

First atmospheric probe of Mars (lost at landing)

Mars 6

1973, March 12

Phobos and Mars 96, 1988-1996

After a long run of very successful Venus missions beginning in 1967. including the highly successful Vega mission in 1985, and the clear lack of American follow-up to the Viking Mars orbiter/landers, the Soviets took the opportunity in the late 1980s to resume Mars missions. A new Universal Mars Venus Luna (UMVL) spacecraft was developed based on the highly successful Fro ton-launched Venera series. Two such spacecraft were built for the 1988 Mars opportunity, for a mission that would focus on the Martian moon Phobos. Once a spacecraft was in orbit around the planet, it would make a series of close encounters with Phobos, coming ever closer. When the geometry was just right, active remote sensing experiments would blast material off the surface of Phobos and two small landers would be deployed, one stationary and the other mobile. It was to be a very ambitious mission, including instruments from many international partners.

The Phobos 1 spacecraft w? as lost to a command error during the interplanetary cruise. Its partner achieved Mars orbit and returned very useful remote sensing data on Mars as it trimmed its orbit to approach Phobos. Unfortunately, communica­tions with Phobos 2 w^ere lost just days before its first planned rendezvous, and only very limited remote sensing data on this target were transmitted.

Encouraged by the Phobos effort, a Mars orbiter and ambitious surface mission w’as planned. This w’as originally scheduled for launch in 1992 using a new’ version of the IJM VL spacecraft but budget constraints led to it being descoped and slipped to

image50

Figure 5.13 The UMVL Phobos spacecraft.

image51

Figure 5.14 The Mars-9f> spacecraft (courtesy NPO-Lavochkin).

1994, and then further delayed to 1996. In addition to a large orbital science payload, the orbitcr had two small soft-landers similar to the previous Mars landers and two penetrators. This project involved even more international cooperation than the Phobos effort. However, this time only a single spacecraft wras built, and when it was launched on November 16, 1996. failures in the control system between the spacecraft and the Block D upper stage resulted in the escape burn causing re-entry. Having lost Mars-96 so embarrassingly, the Russian planetary exploration program entered a hiatus which continued through the end of the 20th Century. It is scheduled for renewal with the planned launch of the Phobos-Grunt sample return spacecraft in late 2011.

Surface topography

Altimetry based on the column density of carbon dioxide measured by the infrared photometer in the 2.06 micron absorption band was obtained along the orbiter tracks across the surface. The inferred altitudes were in general agreement with terrestrial radar observations.

Surface properties

The large diurnal variations of surface temperature indicated a low’ heat conductivity characteristic of a dry and dusty surface. Latitudinal surface temperature variations ranged from -110°C at the northern polar cap to + 1VC near the equator. Hquatorial temperatures averaged -40°C, and at 60°S latitude they were -70°C without much diurnal variation. Dark areas on the surface were 10 to 15 degrees warmer than the light areas. The surface cooled rapidly during the night in low latitudes, indicating a dry, porous soil with a low thermal conductivity. Subsurface temperatures down to a depth of 0.5 meter were no higher than -40°C. There were thermal ‘hot spots’ some 10°C warmer than their surroundings. Temperatures at the northern polar cap were close to the carbon dioxide condensation temperature. Surface pressures of 5.5 to 6 millibars ‘лете measured. Soil density, heat conductivity, dielectric permeability and reflectivity were derived from microwave and thermal radiometry. Soil densities of 1.2 to 1.6 g/cc were reported, with values increasing to

3.5 g/cc in some places. The surface was presumed to be covered with silicon dioxide dust to an average depth of about 1 mm. Heat flow anomalies on the surface were discovered.

Global properties

Global data on the Martian gravity and magnetic fields was acquired. No intrinsic planetary magnetic field was detected, and plasma data for the interaction of the ionosphere with the solar wind indicated a magnetic moment at least 4,000 times weaker than that of Earth. A key discovery were large local mass concentrations in the gravity field, similar lo Ihose of the Moon, which created significant changes in the orbits of the spacecraft. In addition, the polar diameter was measurably less than that at the equator.

Landers:

Although the Mars 2 lander crashed, it is significant as the first human artifact to reach the surface of Mars.

The Mars 3 lander gained the distinction of being the first successful landing on Mars, but it fell silent almost immediately. Figure 12.19 shows the data returned by

image165

Figure 12.19 Image from the Mars 3 lander.

the scanning-photometer imager, released in recent years, which analysis indicates to be mostly noise.

THE ACADEMY OF SCIENCES AND ITS RESEARCH INSTITUTIONS

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

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

image20

Figure 3.2 Institute for Space Research.

image21

Figure 3.3 R-7 Pad 1 at Baikonur today and as photographed by theU-2 (NASA & Bill Ingalls).

THE YE-6 LUNAR LANDER SERIES: 1963-1965

Campaign objectives:

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

Spacecraft launched

First spacecraft: Mission Type: Country; Builder: Launch Vehicle: Launch Date! Time: Outcome:

Ye-6 No.2 [Sputnik 25]

Lunar Lander USSR OKB-1 Molniya

January 4, 1963 at 08:49:00 UT (Baikonur) Failed to leave Earth orbit.

Second spacecraft: Mission Type: Countryj Builder: Launch Vehicle: Launch Date ‘: 7 "une: Outcome:

Ye-6 No.3 Lunar Lander USSR OKB-1 Molniya

February 3, 1963 at 09:29:14 UT (Baikonur) Launch vehicle veered off course.

Third spacecraft: Mission type:

Coun try j Builder: Launch Vehicle: Launch Date: Time: Encoun ter Dale і 17me: Mission End: Outcome:

Luna 4 (Yc-6 No.4)

Lunar Lander USSR OKB-1 Molniya

April 2, 1963 at 08:16:37 UT (Baikonur) April 5, 1963 April 6, 1963

Navigation failed in transit, missed Moon.

Fourth spacecraft: Mission Type:

Conn try і Builder: Launch Vehicle: Launch Date: Time: Outcome:

Ye-6 No.6 Lunar Lander USSR OKB-1 Molniya-M

March 21, 1964 at 08:15:35 UT (Baikonur) Upper stage failure. Did not reach orbit.

Fifth spacecraft: Mission Type: Country; Builder: Launch Vehicle: Launch Date! Time: Outcome:

Ye-6 No.5 Lunar Lander USSR OKB-1 Molniya-M

April 20, 1964 at 08:08:28 UT (Baikonur) Upper stage failure. Fourth stage failed to fire.

Sixth spacecraft: Mission Type: Country; Builder: Launch Vehicle:

Ye-6 No.9 (Cosmos 60) Lunar Lander USSR OKB-1 Molniya

Launch Dale ‘: 7 ‘line: Outcome:

March 12, 1965 at 09:30:00 UT (Baikonur) Failed to leave Earth orbit.

Seventh spacecraft: Mission type: Country; Builder: Launch Vehicle: Launch Date: Time: Outcome:

Ye-6 No.8 Lunar Lander USSR OKB-1 Molniya

April 10. 1965 (Baikonur)

Upper stage failure. Did not reach orbit.

Eighth spacecraft: Mission Type: Country і Builder: Launch Vehicle: Launch Dale/ Time: Em ounter Da tei Time: Outcome:

Luna 5 (Ye-6 No.10)

Lunar Lander USSR OKB-1 Molniya-M

May 9, 1965 at 07:49:37 UT (Baikonur)

May 12, 1965 at 19:10 UT

Crashed.

Ninth spacecraft: Mission Type: Country; Builder: Launch Vehicle: Launch Dale ‘: 7 ime: Em’ounter Da tei Time: Outcome:

Luna 6 (Ye-6 No. 7)

Lunar Lander USSR OKB-1 Molniya-M

June 8, 1965 at 07:40:00 UT (Baikonur) June 11, 1965

Midcourse maneuver failed, missed moon.

Tenth spacecraft: Mission Type:

Country і Builder: Launch Vehicle: Launch Dale ‘: 7 ime: Encounter Date; 7 7me: Outcome:

Luna 7 (Ye-6 No.11)

Lunar Lander USSR OKB-1 Molniya

October 4, 1965 at 07:56:40 UT (Baikonur) October 7, 1965 at 22:08:24 UT Crashed.

Eleventh spacecraft: Mission Type:

Country і Builder: Launch Vehicle: Launch Date: Time: Encounter Date; 7 ime: Outcome:

Luna 8 (Ye-6 No. 12)

Lunar Lander USSR OKB-1 Molniya

December 3, 1965 at 10:46:14 UT (Baikonur) December 6. 1965 at 21:51:30 UT Crashed.

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

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

Spacecraft:

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

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

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

Lunar lander

 

Gas ttjnks for astroorientalion

 

Control system

 

Astroorientalion
system

 

Radio

 

Oxygen lank Fuel tank

 

M

 

Radioaltimeter

 

engine

 

Radioaltimeter

antenna

 

Main engine

 

Figure 9.1 Ye-6 lunar soft-lander spacecraft.

 

Figure 9.2 Drawings of the Ye-6 spacecraft and lander.

 

image72image73

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

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

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

Luna 4 launch mass:

1.422 kg

Luna 5 launch mass:

1.476 kg

Luna 6 launch mass:

1.442 kg

Luna 7 launch mass:

1.506 kg

Lima 8 launch mass:

1.552 kg

Lander payload:

1. Panoramic camera

2. Radiation detector

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

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

Mission description:

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

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

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

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

image74

Figure 9.3 Ye-6 flight profile (from Space Travel Encyclopedia)’. 1. Launch; 2. Parking orbit; 3. Translunar injection; 4. Fourth stage separation; 5. Telemetry for trajectory determination; 6. Trajectory correction; 7. Original trajectory; 8. Corrected trajectory; 9. Landing sequence initiation; 10. Determine lunar vertical; 11. Orient to lunar vertical; 12. Radar altimeter activated; 13. Altimeter fires retrorocket system; 14. Retrorocket burn:l 5. Landing.

image75

Figure 9.4 Ye-6 soft landing profile (from Space Travel Encyclopedia): 1. Balloons inflated, encapsulated lander ejected at 14 m/s; 2. Impact with several bounces to final complete stop; 3. Balloon hemispheres separated by firing stitches around circumference 4. Petals are deployed from upper hemisphere to insure lander rests upright.

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

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

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

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

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

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

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

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

Results:

None.

And back to Venus yet again

TIMELINE: 1982-1983

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

Launch date

1982

No missions

1983

2 Jun Venera 15 orbiter Successful radar mapper

7 Jun Venera 16 orbiter Successful radar mapper

PIERCING TIIE CLOUDY VEIL OF VENUS: 1983

Campaign objectives:

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

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

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

Spacecraft launched

First spacecraft:

Venera 15 (4V-2 No.860)

Mission Type:

Venus Or biter

Country/ Builder:

USSR NPO-Lavochkin

Launch Vehicle:

Proton-K

Launch Date: Time:

June 2, 1983 at 02:38:39 UT (Baikonur)

Encounter Date! Time:

October 10, 1983

Mission End:

March 1985

Out come:

Successful.

Second spacecraft:

Venera 16 (4V-2 No.861)

Mission Type:

Venus Or biter

Соті try j Builder:

USSR NPO-Lavochkin

Launch Vehicle:

Proton-K

Launch Date: Time:

June 7, 1983 at 02:32:00 UT (Baikonur)

Encoun ter Date/ 7 ime:

October 14. 1983

Mission End:

May 28. 1985

Outcome:

Successful.

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

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

Spacecraft:

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

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

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

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Figure 17.T Venera 15 during tests at Lavochkin.

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Figure 17.2 Venera 15 museum model. SAR tilted at 10 degrees to the long axis on top of the SAR/Altimeter instrument compartment above cylindrical propellant tank.

Payload:

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

2. Omega radiometric altimeter

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

4. Cosmic ray detectors (6)

5. Solar plasma detectors

6. Magnetometer (Austria)

7. Radio occultation experiment

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

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figure 17.3 Venera IS SAR strip taken during a single periapsis pass (from Don Mitchell).

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

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

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

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

Mission description:

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

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

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

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

Results:

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

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

Coronae large circular or oval features with deep concentric rings

Domes flat, nearly circular raised features some with central calderas

Arachnoids – collapsed domes with radial cracks

Tessera – large regions of linear ridges and valleys

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

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

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Figure 17.4 Venera 15 and 16 global imaging at about 1 km resolution. The elevated Lakshmi planum is at upper right with Maxwell Montes (from Don Mitchell).

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Figure 17.5 Landforms found by Venera 15 and Venera 16. From upper left clockwise: Anahit and Pomona Coronas, Fortuna Tessera, Arachnoids in Bereghinya, and Duncan crater.

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

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

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

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Figure 17.6 Venera 15 and Venera 16 altimeter data. Lakshmi planum at left (from Don Mitchell).

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Figure 17.7 Venera 15 and Venera 16 cartography of Lakshmi planum with Maxwell Montes and caldera at right (from Don Mitchell).