Mission Type: Flyby
Launch Vehicle: 8K72 (no. I1-8)
Launch Site: NIIP-5 / launch site 1
Spacecraft Mass: 278.5 kg
References:
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, Monographs in Aerospace History No. 24, by Asif A. Siddiqi

National Space Science Data Center, http://nssdc.gsfc.nasa.gov/

This spacecraft, of the Ye-2A class, was the first Soviet probe designed to take pictures of the far side of the moon using the Yenisey-2 imaging system (replacing the Yenisey-1 used on the abandoned Ye-2 probe).

The TV system consisted of a 35-mm camera with two lenses of 200-mm (wide-angle) and 500-mm (high-resolution) focal lengths and a capacity to read up to 40 images. Strictly speaking, the probe was not meant to reach escape velocity; instead, the launch vehicle inserted the spacecraft, called the Automatic Interplanetary Station (AMS) in the Soviet press, into a highly elliptical orbit around the Earth at 48,280 x 468,300 kilometers, sufficient to reach lunar distance.

During the coast to the moon, the AMS suffered overheating problems and poor communications, but the vehicle eventually passed over the moon's southern polar cap at a range of 7,900 kilometers on 6 October before climbing up over the Earth-moon plane.

At a distance of 65,200 kilometers from the moon, on 7 October, cameras began taking the first of 29 pictures of the far side of the moon. The exposed film was then developed, fixed, and dried automatically, after which a special light beam of up to 1,000 lines per image scanned the film for transmission to Earth.

Images were finally received the next day (after a few aborted attempts). Seventeen of the images were of usable quality and showed parts of the moon never before seen by human eyes. The spacecraft, named Luna 3 after 1963, photographed about 70 percent of the far side and found fewer mare areas on the far side, prompting scientists to revise their theories of lunar evolution.