Luna 3

Luna 3 was a historic Soviet spacecraft launched in 1959. It was part of the Luna programme. This mission was the first to photograph the far side of the Moon. For all of human history, this side of the Moon remained a mystery. It is the hemisphere that always faces away from Earth. Luna 3 changed our understanding of the lunar landscape forever.

The spacecraft was a long, cylindrical canister with hemispheric ends. It was hermetically sealed and pressurized to maintain its internal environment. Solar cells were mounted on the outside of the cylinder. These cells provided electric power to the storage batteries inside. To manage heat, the probe had thermal control shutters. These shutters opened to expose a radiating surface if internal temperatures exceeded 30 °C. The probe also carried scientific tools like cosmic ray detectors. It used gas jets for its attitude control system.

The imaging system was called Yenisey-2. It used a dual-lens camera known as the AFA-E1. One lens had a 200 mm focal length to image the full Moon. The second lens had a 500 mm focal length to zoom in on specific regions. The camera used 35mm isochrome film. This film was specially treated to resist radiation and temperature changes. After the photos were taken, an onboard processor developed, fixed, and dried the film. A flying-spot scanner then converted the images into electric signals. These signals were transmitted to Earth using frequency-modulated analog video.

The mission required complex navigation and physics. Luna 3 was launched over the North Pole using a Luna 8K72 rocket. The spacecraft used a gravity assist maneuver to return to Earth. This maneuver used the Moon's gravity to change the spacecraft's orbit. It also changed the orbital plane of the probe. This calculation was based on research led by Mstislav Keldysh. The return path was designed to pass over the Northern hemisphere. This ensured Soviet ground stations could receive the signals.

On 6 October 1959, Luna 3 reached its closest approach to the Moon. It passed within 6,200 km of the lunar south pole. The photography sequence began on 7 October when a photocell detected sunlight. The cameras took 29 pictures over a period of 40 minutes. These images covered 70% of the far side of the Moon. The spacecraft was at distances between 63,500 km and 66,700 km during this time. Eventually, 17 photographs were successfully transmitted back to Earth.

The images revealed a landscape very different from the near side. The far side was mostly mountainous terrain. It lacked the large, dark areas seen on the side facing Earth. Scientists identified only two dark, low-lying regions called maria. One was named Mare Moscoviense, or the Sea of Moscow. The other was Mare Desiderii, or the Sea of Desire. Later, Mare Desiderii was found to contain a smaller mare called Mare Ingenii. Scientists believe the lack of dark lava on the far side is due to how lavas flowed during the Moon's formation.

The data from Luna 3 led to significant scientific achievements. In 1960, the USSR Academy of Sciences published an atlas of the far side. This atlas contained a catalog of 500 different landscape features. In 1961, the first Moon globes were created using these images. Scientists named several craters after famous figures like Marie Curie and Thomas Edison. Even today, researchers compare these early images to modern data.

This comparison shows how accurately the original Yenisey-2 system mapped the lunar surface. The mission remains a foundational moment in space exploration.