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Soviet probe plays communist anthem
Less than two months after succeeding with the world's first soft landing of a robotic vehicle on the surface of the Moon, Soviet engineers used that experience to launch a lunar orbiter. In April 1966, the Luna-10 entered orbit around the Moon, marking its arrival with a broadcast of the revolutionary song the Internationale.
The E6 (Luna-10) spacecraft. Copyright © 2016 Anatoly Zak
Luna-10 mission at a glance:
As often in the Soviet space program, the first robotic lunar orbiting mission acquired an additional propagandistic value, when it was chosen as a backdrop for the upcoming 23rd Congress of the Communist Party in Moscow, the most important political event in the USSR in several years. The triumphant first soft-landing of a probe on the Moon on February 3, 1966, gave confidence to a team of engineers led by Georgy Babakin and their political supervisors that the lunar orbiting "first" could be pulled off by the time of the Congress' opening in just two months time at the end of March.
The carrier for the first Soviet lunar orbiter was largely borrowed from the E6 (Ye-6) spacecraft, which had been previously used to carry automatic landers to the Moon, including the successful Luna-9. The proposed lunar orbiter received a designation E6-S, where "S" stood for "sputnik" or satellite.
Babakin's team at GSMZ Lavochkin quickly re-designed the existing lunar landing mission profile to reach orbit around the Moon. Instead of targeting a landing point on the Moon, the E6-S vehicle was programmed to navigate toward an imaginary target point in space located around 1,000 kilometers above the Moon. Once there, an engine firing would reduce the probe's velocity from 2.5 to 1.76 kilometers per second so that gravitational pull of the Moon could capture the spacecraft into an elliptical orbit. (773)
At the top of the E6 carrier vehicle, the lunar lander was replaced with a satellite of the Moon, which featured a newly designed compartment for scientific instruments. The spacecraft was also equipped with a radio system to measure parameters of its lunar orbit with high precision.
Various off-the-shelf hardware and scientific instruments apparently helped greatly speed up the development process. For example, for a number of years, Sergei Korolev's OKB-1 worked on the long-delayed E7 lunar orbiter, which undoubtedly laid technical foundation for a less complex E6-S mission. (509) The preliminary design for the ground control segment of the E7 mission was developed back in 1961 at NII-4 research institute of the Ministry of Defense, which was responsible for the Soviet space tracking network. (270) Also, key ballistic calculations for the lunar orbiting mission were also made far in advance. (773)
E-6S lunar orbiter
The E-6S lunar orbit was equipped with a suit of seven instruments, none of which required a complex attitude control system onboard the lunar orbiter, as would imaging payload:
A special deployable boom 1.5 meters long carried magnetometer sensors to keep them away from the satellite's own electric and magnetic sources. Although similar measurements during the Luna-2 mission in 1959 showed that the lunar magnetic field is barely one thousandth of that around the Earth, the new instrument designed for E-6S was 15 times more sensitive.
The Pioneer gamma-spectrometer was developed under leadership of Aleksandr Vinogradov and Yuri Surkov at Vernadsky GeoKhI and SNIIP institutes. The instrument consisted of a scintillator made out of a 40 by 40-millimeter Nal(T1) crystal and a 32-channel amplitude analyzer.
To support the scientific program, the orbiter contained the telemetry system, radio system, a programmer/timer, antennas and the power-supply system. The thermal control inside the pressurized body of the spacecraft was achieved with gas circulation.
At least one depiction of the Luna-10 probe also showed a pentagon-shaped pennant attached to the orbiter. (775)
Recording The Internationale
To fulfil its political role, the E6-S probe was given a unique task of broadcasting a musical tune back to Earth. Engineers quickly developed a technical solution for the exercise, but an ideological question which tune to play apparently became a stumbling block. The USSR's national anthem was an obvious first choice, but somebody within the political leadership decided that playing it from the Moon could be interpreted as the Soviet territorial claim to the Moon. The second choice was a patriotic song "My Native Land is Wide," but, it was also found too nationalistic for the purpose. (The opponents of the initial music choices probably could not envision American astronauts planting Stars and Stripes on the Moon 3.5 years later).
Finally, the old Communist anthem "The Internationale" was qualified as "neutral" enough to play from the lunar orbit. The Composers' Union of the USSR -- the most authoritative music institution in the country -- supplied Babakin's team with a note sequence, complete with frequency and duration for each note. Engineers then fashioned an electronic music box, featuring solid-state oscillators made out of quartz and a programming device, which determined in which order generators would produce sounds and how long each note would last. As participants of the project recalled, the resulting performance would not exactly rival a symphony orchestra but it was more then satisfactory for an electronic synthesizer installed on a small lunar orbiter. (771)
The first attempt to launch the lunar satellite (E-6S No. 204) was made on March 1, 1966. The Molniya (8K78M N103-41) rocket lifted off from Site 31 in Tyuratam at 14:03:49 Moscow Time and a few minutes later, it successfully inserted its payload into an initial parking orbit. However during an unpowered flight, the vehicle apparently began rolling uncontrollably preventing the firing of the engine on Block-L N71650 to escape Earth's orbit. In accordance with the usual Soviet practice, the stranded spacecraft was officially announced as Kosmos-111 without any disclosure about its real mission. Still, the spacecraft would be soon identified in the West as a lunar orbiter, when its successor -- Luna-10 -- entered a similar parking orbit before embarking on a trip toward the Moon. (185)
The Western radar detected two objects associated with the March 1 launch in a 191 by 226-kilometer orbit with an inclination 51.85 degrees toward the Equator. Due to very low altitude, Kosmos-111 plunged back into the Earth's atmosphere on March 3, after just two days in orbit. (227)
Back on the ground, engineers quickly singled out the I-100 gyro-system as a culprit in the loss of the attitude control. The investigation showed that the instrument had displayed unreliable performance even during the pre-launch processing. The defect was registered during the tests somewhere in the midst of endless telemetry tapes, but remained unnoticed by specialists. As a result, the team including the head of the project Georgy Babakin received strong reprimands from the industry officials. (772)
Notebooks of Vasily Mishin, the head of TsKBEM design bureau, where the E6 project had originated, indicate that his deputy Evgeny Shabarov, who was responsible for launch operations, presented his review of the telemetry tapes from the failed launch on March 11, 1966.
From the Earth to the lunar orbit
Flight scenario and key milestones of the Luna-10 mission.
Typically for the Soviet era, the team immediately pressed ahead with a backup mission, after the failure of the initial attempt.
A Molniya rocket carrying the 1,583.7-kilogram E6-S No. 210 spacecraft lifted off from Site 31 in Tyuratam test range on March 31, 1966, at 13:46:59 Moscow Time. Again, the spacecraft successfully reached an initial parking orbit. Fortunately, this time, the vehicle's Block-L fourth stage successfully accelerated the probe to a speed of 10.9 kilometers per second in a direction of the Moon. Announced as Luna-10, the mission began a 3.5-day trek to its final destination.
On April 1, around 9 p.m., top Soviet space officials including Head of the Soviet Academy of Sciences Mstislav Keldysh and the Head of TsKBEM Vasily Mishin gathered at space calculation center of the TsNIIMash research institute for a mid-course correction of the Luna-10. The engine was fired at a distance of around 240,000 kilometers away from Earth and successfully placed the probe on a lunar flyby trajectory.
The moment of truth came on April 3, 1966, as Luna-10 approached the Moon. Vasily Mishin noted in his diary that the critical communications session with the probe had began at 19:04 Moscow Time. (774) As Luna-10 was 8,000 kilometers from the Moon, the probe oriented itself relative to the stars to point its engine against the direction of the flight. The braking engine firing began at 21:44 Moscow Time and lasted 57 seconds, creating the first artificial satellite of the Moon. Just 20 seconds later, at 21:45:39 Moscow Time, a 248.5-kilogram pressurized vehicle separated from its E6 carrier.
Luna-10 entered a 350 by 1,017-kilometer near-polar orbit with an inclination 71.9 degrees. It was taking the spacecraft two hours 58 minutes and 15 seconds to complete each revolution around the Moon.
Playing the Internationale
The first task of the mission control was to broadcast the performance of the Internationale into the Kremlin's palace, where the 23rd Congress of the Communist Party had already been in session since March 29. The historic transmission had to take place exactly at 10:00 Moscow Time on April 4 (as the Congress was to close).
On the eve of the event, controllers conducted a "rehearsal" of the broadcast and since everything worked well, they happily retired for the night. However, when they activated their musical device next morning in the final test, to their horror, they discovered that the melody stutters. It was determined that one of the oscillators had failed causing the device to skip a note. Terrified engineers were agonizing what to do next. Although 13 years had passed since the end of the Stalinist terror, but plenty of Soviet apparatchiks inherited enough paranoia to turn the broken record into a politically motivated sabotage.
Fortunately, controllers quickly came up with a solution. As the newly elected candidate to the Politburo Sharaf Rashidov announced the creation of the artificial lunar satellite and asked around 5,000 delegates to raise for the performance of the Internationale, mission control initiated the faulty broadcast from the lunar orbit, while simultaneously plugging a perfect recording from the previous night's transmission into the communications channel with Moscow! A small group of "conspirators" who organized the broadcast had kept their secret for three decades. The story was revealed only five years after the collapse of the USSR in the biography of Georgy Babakin published in 1996. (771)
The Internationale was then rebroadcast during Cosmonautics Day on April 12, on the May Day holiday, during the Victory Day celebrations on May 9, and, finally, at the opening of the Young Communist (Komsomol) Congress.
With its ceremonial duties out of the way, Luna-10 began its scientific mission. Due to lack of a data-recording device onboard the probe, measurements and experiments were conducted only when Luna-10 was in direct view of ground stations.
During the cruise phase of the Luna-10 mission, the project's team was deployed at NIP-10 ground station near Simpheropol in Crimea, a base for the 25-meter TNA-200 antenna operating in meter-band and used for transmitting and receiving information from spacecraft. (270) However trajectory measurements, which would be critical for tracking the evolution of Luna-10's orbit around the Moon required radio communications in decimeter range. These antennas were located at NIP-16 ground station near Yevpatoria, also in Crimea. To support this effort, a group of engineers was dispatched to NIP-16. Due to lack of hotel rooms at the site, a multi-age and multi-gender group, which included high-level scientists, had to be housed in a large military tent with very little comfort. (771)
First details on the scientific results of the Luna-10 mission were published in a press release of the official TASS news agency on April 10, 1966. It said that on April 5, measurements of magnetic field at different parts of the lunar orbit had shown little variation, staying within a range of 15-20 gammas. These values were just slightly higher than those recorded in the interplanetary space away from all celestial bodies during a magnetically quiet period. Even that weak readings could not be immediately attributed to the Moon's magnetic field, because the tail of Earth's own magnetic field could cause the effect, TASS said. (775) During a following press-conference on April 16, 1966, the lunar magnetic field was reported as varying between 17 and 35 gammas. (776)
Chemical composition of soil
With the help of its gamma spectrometer, Luna-10 conducted first measurements of natural gamma-radiation emanating from thorium, uranium and their decay products as well as from calium-40 isotope in the lunar soil. This information allowed to determine chemical composition of the soil.
The conclusion was that radioactivity of the lunar soil is lower than that of granites on Earth and does not exceed that of basalt. The analysis of this information prompted Soviet scientists to suggest a simultaneous origin of the Earth and the Moon from a common gaseous and dust cloud. (775) Luna-10's observations also showed that around 90 percent of lunar radiation results from a reaction with cosmic rays leaving only 10 percent for soil's own natural radiation. (777)
Interestingly, after monitoring the evolution of the Luna-10's orbit, the Soviet scientists initially characterized the Moon's gravitational field as close to a central body. They apparently did not notice any major gravitational anomalies, which could prevent bringing future orbital missions much closer to the surface. (773)
"The anomalies of the Moon's gravitational field are not great," a TASS press release said on June 3, 1966. (776)
These conclusions were contrary to future discoveries of the so-called mascons on the Moon, or local concentrations of mass, which could affect the orbit of satellites flying over it.
Preliminary data received from Luna-10 by April 10, 1966, from meteor detectors showed higher density of meteors in the lunar orbit than in the interplanetary space. (775)
Luna-10 recorded some increase in intensity of low-energy particle fluxes, particularly electrons. (776)
End of mission
On June 3, 1966, TASS announced that Luna-10 had exhausted its battery power on May 30 and ceased operation after a 56-day mission. According to the agency, it was possible to complete the entire scientific program and even conduct additional communications sessions for measuring the probe's orbit and check the status of its instruments. (776)
At the end of its operation, the spacecraft was reported in a 378.8 by 985.3-kilometer orbit with an inclination 72 degrees and orbital period of 2 hours 58 minutes and 3 seconds.
During its mission, Luna-10 covered 7 million kilometers and made 460 revolutions around the Moon. The probe conducted 219 communications sessions with ground control. Theses included 74 trajectory measurement sessions, 17 long-duration measurements of radiation, near-lunar plasma, concentrations of micrometeoroids and studies of Moon's thermal radiation.
Ground control also received nine spectra of gamma-radiation from the lunar surface and 10 magnetic profiles of the near-lunar space. (773)
By the end of April 1966, six scientists and engineers at the top of the Luna-9 and Luna-10 project received Lenin's Prize, the highest Soviet scientific honor. A special diploma from the International Aviation Federation, IAF, commemorating the Luna-10 mission was also awarded. (771)
The inactive Luna-10 spacecraft remained in the orbit of the Moon for "several years".
Georgy Babakin led the development of the E-6S series. Credit: NPO Lavochkin
The architecture of the E6-S spacecraft.
The E6-S lunar-orbiting spacecraft in pre-launch configuration. Credit: NPO Lavochkin
The official photo of the E6-S orbiter. Credit: NPO Lavochkin
Museum replicas of the Luna-10 orbiter. Copyright © 2000 Anatoly Zak
The carrier stage, which was used to deliver Luna-10 into lunar orbit. Copyright © 2000 Anatoly Zak
The Pioneer spectrometer for the E6-S spacecraft. Copyright © 2011 Anatoly Zak
Soviet-era illustrations of the E6 orbiter entering lunar orbit. In reality, the probe's strap-on avionics containers would be jettisoned before the braking maneuver. Credit: NPO Lavochkin
Pendants flown aboard the Luna-10 mission.
Soviet postage stamps dedicated to the Luna-10 mission. Anatoly Zak's collection
NASA's Lunar Orbiter spacecraft was under development in parallel with the Soviet E6-S. Copyright © 2001 Anatoly Zak