The Soviet space probe Luna 3 (E-3 series) was the third spacecraft sent successfully to the Moon, and it was an early feat in the human exploration of outer space. Though it returned several rather poor pictures by later standards, the historic, never-before-seen views of the Moon's far side caused excitement and interest when they were published around the world, and a tentative Atlas of the Far Side of the Moon was created after image processing improved the pictures. This space probe has been commonly called "Lunik 3", at least in the western world.
These views showed mountainous terrain, very different from the near side, and only two dark, low-lying regions which were named Mare Moscovrae (Sea of Moscow) and Mare Desiderii (Sea of Desire). Mare Luna Desiderii was later found to be composed of a smaller mare, Mare Ingenii (Sea of Ingenuity), and other dark craters.
The Space Probe Design
The space probe was a cylindric canister with hemispheric ends and a wide flange near the top. The probe was 130 cm long and 120 cm at its maximum diameter at the flange. Most of the cylindric section was roughly 95 cm in diameter. The canister was hermetically sealed and pressurized at 0.22 atmosphere (23 kilopascals). Solar cells were mounted on the outside of the cylinder, and they provided power to the storage batteries located inside the space probe.
Shutters for thermal control were positioned along the cylinder and opened to expose a radiating surface when the internal temperature exceeded 25 celsius. The upper hemisphere of the probe held the covered opening for the cameras. Four antennas protruded from the top of the probe and two from the bottom. Other scientific equipment was mounted on the outside, including micrometeoroid and cosmic ray detectors, and the Yenisey-2 imaging system. Gas jets for attitude control were mounted at the lower end of the spacecraft. The photoelectric cells helped maintain orientation with respect to the Sun and the Moon.
This space probe had no rockets for course adjustment. The interior held the cameras and the film processing system, radio equipment, propulsion systems, batteries, gyroscopic units for attitude control, and circulating fans for temperature control. The space probe was spin-stabilized for most of the flight, but it activated attitude control to take pictures. Luna 3 was directly radio-controlled from the Soviet Union.
After launching on an 8K72 (number I1-8) rocket over the north pole, the Blok-E escape stage was shut down by radio control to put Luna 3 on its course to the Moon. Initial radio contact showed that the signal from the probe was only about half as strong as expected, and the internal temperature was rising. The spacecraft spin axis was reoriented and some equipment was shut down, resulting in a temperature drop from 40° C to about 30° C. At a distance of 60,000 to 70,000 km from the moon, the orientation system was turned on and the spacecraft rotation was stopped. The lower end of the craft was pointed at the sun, which was shining on the far side of the moon.
The space probe passed within 6,200 km of the moon near its south pole at the closest lunar approach at 14:16 UT on 6 October 1959, and it continued on over the far side. On 7 October, the photocell on the upper end of the space probe detected the sunlit far side of the moon, and the photography sequence was started. The first picture was taken at 03:30 UT at a distance of 63,500 km from the moon, and the last picture was taken 40 minutes later from a distance of 66,700 km.
A total of 29 pictures were taken, covering 70% of the far side. After the photography was complete the spacecraft resumed spinning, passed over the north pole of the moon and returned towards the Earth. Attempts to transmit the pictures to the Soviet Union began on 8 October but the early attempts were unsuccessful due to the low signal strength. As Luna 3 drew closer to earth, a total of 17 viewable but poor quality photographs were transmitted by 18 October. Contact with the probe was lost on 22 October 1959. The space probe was believed to have burned up in the Earth's atmosphere in March or April 1960, but it might have survived in orbit until after 1962.
The purpose of this experiment was to obtain photographs of the lunar surface as the spacecraft flew by the moon. The imaging system was designated Yenisey-2 and consisted of a dual-lens camera AFA-E1, an automatic film processing unit, and a scanner. The lenses on the camera were a 200 mm focal length, f/5.6 aperture objective and a 500 mm, f/9.5 objective. The camera carried 40 frames of temperature- and radiation-resistant 35 mm isochrome film. The 200 mm objective could image the full disk of the moon and the 500 mm could take an image of a region on the surface. The camera was fixed in the spacecraft and pointing was achieved by rotating the craft itself.
Luna-3 was the first successful 3-axis stabilized spacecraft. During most of the mission, the spacecraft was spin stabilized, but for photography of the moon, the spacecraft oriented one axis toward the Sun and then a photocell was used to detect the moon and orient the cameras towards it. Detection of the moon signalled the camera cover to open and the photography sequence to start automatically. The images alternated between both cameras during the sequence. After photography was complete, the film was moved to an on-board processor where it was developed, fixed, and dried. Commands from the Earth were then given to move the film into a scanner where a spot produced by a cathode ray tube was projected through the film onto a photoelectric multiplier. The spot was scanned across the film and the photomultiplier converted the intensity of the light passing through the film into an electric signal which was transmitted to the Earth (via frequency-modulated analog video, similar to a facsimile). A frame could be scanned with a resolution of 1000 (horizontal) lines and the transmission could be done at a slow-scan television rate at large distances from the Earth and a faster rate at closer ranges.
The camera took 29 pictures over 40 minutes on 7 October 1959, from 03:30 UT to 04:10 UT at distances ranging from 63,500 km to 66,700 km above the surface, covering 70% of the lunar far side. Seventeen (some say twelve) of these frames were successfully transmitted back to the Earth, and six were published (frames numbered 26, 28, 29, 31, 32, and 35). They were mankind's first views of the far hemisphere of the moon.
The imaging system was developed by P.F. Bratslavets and I.A. Rosselevich at the Leningrad Scientific Research Institute for Television and the returned images were processed and analyzed by Iu.N. Lipskii and his team at the Sternberg Astronomical Institute. The camera AFA-E1 was developed and manufactured by the KMZ factory (Krasnogorskiy Mekhanicheskiy Zavod).
Published in July 2009.
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