How did photos of the invisible side of the moon: a big story
The first attempts to photograph Selena, like all the first space missions in general, had a pronounced character of the “space race” between the USA and the USSR. In August-September 1958, the Americans were the first to try to capture the lunar surface at close range, sending the first small and imperfect Pioneer probes into space.
Alas, due to malfunctions of the launch vehicles, none of these devices entered the calculated trajectory. Nevertheless, it must be assumed that it was the information on the preparation of American missions that served as a powerful incentive for S.P. Queen and his associates.
Two years after the triumph of the first satellite, on the morning of October 4, 1959, the Luna-3 (“product E-2A”) automatic interplanetary station (AMS) was launched in the Soviet Union. About three days later, on October 7, between 6:30 a.m. and 7:10 a.m. Moscow time, the station took photographs of the invisible side of the moon and transmitted the pictures on a television channel to Earth. All those involved in this event were able to contribute to their assets yet another “undoubted victory in outer space”: the Soviet Union was ahead of the United States for the sixth time, launching after its first satellite, the first animal in space, the first heavy automatic laboratory in orbit, the first artificial planet and the first getting into the neighboring celestial body the first object that was able to photograph the side of our natural satellite, forever hidden from the direct human eye. Meanwhile, the success of “Moon-3” was far from being only propaganda. It was based on thorough scientific and engineering developments in such areas as ballistics of spacecraft, control systems, optics, telecommunications, not to mention rocketry.
Outside and inside
Undoubtedly, the most difficult task was to calculate the flight path. Since the photographing of the lunar surface was supposed to be performed with a passive ballistic flight (the means of active correction of the trajectory were not yet mastered then), the calculation and subsequent implementation of the trajectory should be carried out with the highest accuracy. The choice of flight scheme was influenced by many factors. Among them, the main ones were the requirements of the necessary orientation, illumination and distance from the lunar surface at the time of shooting, the energy capabilities of the launch vehicle and the geographical location of the launch site. In addition, the shape of the trajectory was supposed to provide “dumping” of information at a time when the station was at a small distance from the Earth: it was required to obtain the maximum amount of information from the territory of the Soviet Union as soon as possible.
The flight scheme provided for a flyby of the Moon along a strongly elongated elliptical trajectory, the climax of which was near the boundary of the Earth's sphere of action. If no additional measures were taken, the station would return to Earth and burn out in the atmosphere already at the end of the first orbit and any long-term studies of the space between the Moon and the Earth would become impossible. The fact is that although the rocket almost informed Luna-3 the second cosmic velocity in magnitude (approximately 11.14-11.15 km / s), the direction of the vector was far from horizontal. As a result, without taking into account external disturbances from the Moon and the Sun, an open elliptical trajectory was obtained. This nuisance was due to the fact that the booster being developed, when launched from the territory of the USSR, could not give the AMS a second cosmic velocity for flying to the Moon, having positioned the vector strictly horizontally. By the way, the limited payload mass was an additional nuisance: gravitational losses were too large with a direct acceleration scheme.
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The situation could correct the start to the moon from the intermediate orbit of the Earth’s satellite. But he demanded to turn on the engine of the last stage twice. Alas, the Soviet missiles did not have such an opportunity. In 1959, ballistics found a beautiful solution, proposing to "correct" the trajectory with the help of ... the moon itself, due to its gravitational field. The trajectory was designed so that at some point, when the station was moving slowly enough, the moon’s sphere of action “flew” onto it. At the same time, lunar gravity significantly changed the orbit of the AMS, which eventually became an artificial Earth satellite. Thus, the gravitational maneuver was used for the first time in this mission, as a result of which the Luna-3 existed in space for six months instead of the prescribed week, until April 20, 1960.
Photographing the moon was made at a specially chosen moment. It did not coincide with the point of closest approximation to the Moon: the main requirement was to ensure the orientation of the AMS so as to capture on film as much of the invisible side of our celestial neighbor in the conditions of the necessary illumination. The station's orientation system included optical and gyroscopic sensors, logical electronic devices, and control engines. It was turned on by a signal from the Earth at that moment when the AMS was on the Moon-Sun line, that is, when the natural satellite of the Earth was in the full moon phase with respect to “Moon-3”.