Luna 3

LunarOrbiter
Name=Luna 3


Organization=USSR
Contractors=OKB-1
MissionType=Planetary Science
Lunar Flyby
LaunchDate=October 4, 1959 at 00:43:39.7 UTC
LaunchVehicle=SS-6/R-7 (8K72)
MissionHighlight=Lunar flyby October 6, 1959, 14:16 UTC at distance of 6,200 km near south pole
MissionDuration=~207 days - Reentered April 29, 1960
Mass=278.5 kg
NSSDC_ID=1959-008A
Web= [http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1959-008A NASA NSSDC Master Catalog]
SatelliteOf=Earth
SemiMajor=250,682 km
Eccentricity=0.8379
Inclination=76.8°
Period=15 d
Apo=460,725 km
Peri=40,638 km
Orbits=~14
LunarLandingDate=
LunarLandingCoords=
LunarLiftoffDate=
Instruments=Yenisey-2 Camera/Film processor (Lunar photography)

The Soviet spaceprobe Luna 3 (E-3 series) was the third spacecraft sent successfully to the moon and was an early triumph in the human exploration of outer space. Though it returned 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.

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 Desiderii was later found to be composed of a smaller mare, Mare Ingenii (Sea of Ingenuity), and other dark craters.

Spacecraft design

The spacecraft 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 provided power to the chemical batteries stored inside the spacecraft.

Shutters for thermal control were positioned along the cylinder and opened to expose a radiating surface when the internal temperature exceeded 25 degrees Celsius. The upper hemisphere of the probe held the covered opening for the cameras. Four antennae 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. Photoelectric cells helped maintain orientation with respect to the sun and moon.

The spacecraft had no rockets for course adjustment. The interior held the cameras and film processing system, radio equipment, propulsion systems, batteries, gyroscopic units for attitude control, and circulating fans for temperature control. The spacecraft was spin stabilized for most of the flight, but engaged attitude control to take pictures. It was directly radio-controlled from the Soviet Union.

Mission

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 a course to the moon. Initial radio contact showed 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 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 spacecraft passed within 6,200 km of the moon near the south pole at its closest approach at 14:16 UT on October 6 1959 and continued on to the far side. On October 7 the photocell on the upper end of the spacecraft detected the sunlit far side of the moon and the photography sequence started. The first picture was taken at 03:30 UT at a distance of 63,500 km from the moon, and the last picture 40 minutes later from 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 earth. Attempts to transmit the pictures to the Soviet Union began on October 8 but were believed to be 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 October 18. Contact with the probe was lost on October 22. The probe was believed to have burned up in Earth's atmosphere in March or April 1960, but may have survived in orbit until after 1962.

Lunar photography

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 thena 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 earth were then given and the film was moved to a scanner where a bright spot produced by a cathode ray tube was projected through the film onto a photelectric 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 earth (frequency-modulated analog video, similar to facsimile). A frame could be scanned with a resolution of 1000 (horizontal) lines and the transmission could be done at a slow scan rate for large distances from earth and a faster rate at closer range.

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 earth, and 6 were published (frames 26, 28, 29, 31, 32, and 35); they were humanity'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 of 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).

References

External links

* [http://www.zarya.info/Diaries/Luna/Luna3.php Zarya - Luna 3 chronology]
* [http://www.mentallandscape.com/C_CatalogMoon.htm Soviet moon photographs]
* [http://www.svengrahn.pp.se/trackind/luna3/Luna3story.html Flight of Luna]
* [http://nssdc.gsfc.nasa.gov/imgcat/html/mission_page/EM_Luna_3_page1.html Luna 3 Image Catalogue at NSSDC]
* [http://astrosurf.com/nunes/explor/explor_luna3.htm Processed images from the Luna 3 mission]

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