The Moon is tidally locked, so the same hemisphere has faced the Earth for as long as there have been eyes to look at it. Until October 1959, roughly forty one percent of the lunar surface had never been seen by anybody, ever, and there was no way to find out what was on it.
The guesses were reasonable and turned out to be wrong. Most astronomers expected the far side to look much like the near side: dark basaltic plains, the maria, with cratered highlands in between.
A Camera That Had to Be a Darkroom Too
Luna 3 launched on 4 October 1959, two years to the day after Sputnik, and the imaging problem it faced was brutal. Television sensors in 1959 were far too insensitive for the job. Photographic film was much better, and film has one obvious drawback: it has to come back, or else be developed where it is.
So the engineers built a self contained photographic laboratory into a spacecraft weighing 278 kilograms. The Yenisey-2 system carried 35 millimetre film and two lenses, 200 and 500 millimetre, exposing two frames at a time. After the exposures the film was drawn into a processing unit inside the vehicle that developed, fixed and dried it automatically. Then the dried negative was pulled past a flying spot scanner, a bright point of light that traced across the frame while a photomultiplier on the other side measured how much got through, turning the image line by line into a varying voltage.
That voltage went to Earth as a facsimile signal, in the manner of a newspaper wire photo. There were two transmission modes, a slow high quality one for when the probe was close and a fast degraded one for long range.
The film itself was radiation hardened stock, and the persistent account, repeated by people who worked on the programme, is that it came from American Genetrix reconnaissance balloons that had drifted over Soviet territory and been recovered. Soviet film of the period fogged too easily.
Forty Minutes of Work
On 7 October 1959, from between 63,500 and 66,700 kilometres out, Luna 3 photographed the far side for about forty minutes. It exposed 29 frames covering roughly seventy percent of the hidden hemisphere, with the Sun behind the spacecraft so the surface was fully lit.
Full illumination is excellent for coverage and terrible for detail, because shadows are what make relief visible. The results are flat, washed out and grainy.
The first transmission attempts, at extreme range, produced almost nothing usable. The team waited as the probe swung back toward Earth and tried again on 18 October from much closer, recovering about seventeen frames of which a handful were genuinely legible. Then contact was lost for good.
By any photographic standard the pictures are poor. They are also one of the most consequential image sets ever produced, because they answered a question that had been open for the whole of human history.
What Was There
The far side was almost all highland. The great dark maria that dominate the near side were essentially absent, with two exceptions large enough to name: a modest dark plain that the Soviet Academy called Mare Moscoviense, the Sea of Moscow, and a crater with a bright central peak on a dark floor, named for Konstantin Tsiolkovsky, the Russian theorist of spaceflight.
Both names took an argument. The convention was that maria carried names describing weather or states of mind, and Moscow is a city. The Soviet delegation pointed out that tranquility is a state of mind and proposed that Moscow was one too. The International Astronomical Union accepted it in 1961 and it is still on the maps.
The asymmetry the pictures revealed is real and is still being explained. The near side crust is thinner and the far side crust is thicker, so on the near side rising basalt could flood the basins and on the far side it mostly could not. The strongest current explanation involves the Earth itself: in the first hundred million years the Moon was much closer and the Earth was still hot enough to radiate significantly, keeping one hemisphere warmer and changing how its crust crystallised.
That is the kind of question that only becomes askable once somebody produces a bad photograph of the right thing.
The Manoeuvre Nobody Noticed
There is a second first buried in this mission. To get where it needed to be, Luna 3 was sent past the Moon’s south pole and allowed the Moon’s own gravity to bend its path, swinging it up over the far side and then back toward the northern hemisphere of the Earth for the transmission.
That is a gravity assist, and it is generally recognised as the first one ever performed. The technique that later threw Voyager out of the solar system was first used to get a camera into position above a hemisphere nobody had seen.
Where It Sits in the History of Looking
There is a straight line from 1959 back three and a half centuries. When Galileo turned a telescope on the Moon in 1609 and drew what he saw, the news was that the surface was rough: mountains, valleys, an imperfect body rather than a polished sphere. He was working at the limit of his instrument and his drawings are, by modern standards, inaccurate.
Luna 3’s frames are at the limit of their instrument in exactly the same way. Both are ugly images that settled a question, and in both cases what mattered was not the resolution but the fact that the thing had been looked at.
Nine years after Luna 3, the crew of Apollo 8 went around the back of the Moon and saw it with their own eyes, and reported that the photographs had not conveyed how battered it was. Orbiters have since mapped the whole surface to a couple of metres. The finest astronomical photographs we have now are assembled from hundreds of hours of exposure and are good enough to hang on a wall.
None of them did what the grainy ones did. There is only one first look at a hemisphere.
No products in the cart. 