Luna 3 and Ye-3. To the far side of the Moon.

 

Model of Luna 3 lunar probe. Credit: RKK Energiya

 

After successfully completing, with Luna 2, the goal of sending the impact probe to the Moon in September 1959, the next objective for the Soviet OKB-1 bureau was to obtain photographs of the far side of the Moon, which can never be observed from Earth. The Ye-2A No. 1 spacecraft that has achieved this goal was officially named in the Soviet press as the Automatic Interplanetary Station (Russian: Автоматическая межпланетная станция). The probe was retroactively renamed Luna 3 in 1963.

   The Ye-2A (Russian: E-2A) spacecraft was a cylindrically shaped canister with hemispherical ends and a wide flange near the top end. The probe was 130 cm long and 120 cm at its maximum diameter at the flange. Most of the cylindrical section was roughly 95 cm in diameter. The canister was hermetically sealed and pressurized at 0.23 atmospheres. Solar cells were mounted along the outside of the cylinder and provided power to the chemical batteries stored inside the spacecraft. Jalousies for thermal control were also positioned along the cylinder and would open to expose a radiating surface when the interior temperature exceeded 25 °C. The upper hemisphere of the probe held the covered opening for the cameras. Four omnidirectional antennae protruded from the top of the probe and two from the bottom. Gas jets for attitude control were mounted on the outside of the lower end of the spacecraft. Photoelectric cells were used to maintain orientation with respect to the Sun and Moon. The interior of the spacecraft held the cameras and film processing system, radio equipment, propulsion systems, batteries, gyroscopic units for attitude control, and circulating fans for temperature control. The probe had no propulsion system for course adjustment. 

Diagram of Luna 3 probe:
1. - camera porthole; 2. - attitude control engine; 3. - Sun sensor; 4. - solar batteries; 5. - thermal regulation shutters; 6. - thermal screens; 7. - antennas; 8. - scientific instruments 

      The scientific instruments on board were: Yenisey-2 photographic-TV imaging system, four micrometeoroid counters, four ion traps, Cherenkov radiation detector, sodium iodide scintillation counter and three gas discharge Geiger counters. Luna 3 was the first three-axis stabilized lunar space probe. It was to be spin stabilized under cruise, switch to 3-axis stabilization for photography, and then resume spin stabilization. The spacecraft total mass was 278.5 kg. 

   The Yenisey-2 photographic-TV imaging system consisted of a dual lens AFA-Ye1 camera, 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 unexposed film was repurposed from downed American reconnaissance balloons flown secretly by US Air Force as part of Project WS-119L (Project Genetrix) in 1956. The 200 mm (wide angle) objective could image the full disk of the Moon and the 500 mm (high resolution) lens could take an image of a region on the surface. 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. A frame could be scanned with a resolution of 1000 lines. 

Yenisey-2 imaging system. It included a dual-objective camera (AFA-Ye1) that took two pictures simultaneously using a 200 mm lens and a 500 mm lens. 

    On October 4, 1959, at 00:43:39 UT, the three-stage 8K72 launch vehicle (no. I1-8) successfully lifted the Ye-2A No. 1 probe from Tyuratam (now the Baikonur Cosmodrome) Site 1/5. Instead of a direct flight to impact the Moon, the spacecraft was placed into a highly elliptical orbit that would take it beyond the far side of the Moon, and then back to the vicinity of the Earth. Sources give somewhat various parameters of the orbit with perigee 40,300 km, apogee 476,500 km, inclination 73.8° or perigee 48,000 and apogee 468,000 km. Initial radio contact after the launch showed the signal from the probe was only about half as strong as expected and the interior temperature was increasing. The spacecraft spin axis was reoriented and some equipment shut down resulting in a drop in temperature from 40 °C to about 30 °C. 

 Diagram showing the trajectory of Luna 3    

   At a distance of 60,000 to 70,000 km from the Moon, the orientation system was turned on and the spacecraft rotation was stopped. The lower end of the station was oriented towards 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 image was taken at 03:30 UT at a distance of 63,500 km from the Moon's surface and the last 40 minutes later from 66,700 km. A total of 29 photographs were taken, covering 70% of the far side and a part of the near side, so as to provide a point of reference for evaluating formations on the far side. 

   After the photography was complete the spacecraft resumed spinning, passed over the north pole of the Moon and returned towards the Earth. Attempts to transmit the photographs to Earth began on October 8, but were believed to be unsuccessful due to the low signal strength. As Luna 3 got closer to Earth a total of 17 resolvable but noisy photographs were transmitted by October 18. Contact with the probe was lost on October 22. The probe was believed to have burned up in the Earth's atmosphere in March or April of 1960, but may have survived in orbit until after 1962.

   Only six of the received pictures of the Moon were published. A tentative atlas was compiled showing the far side to be very different to the near side, being predominantly bright highland terrain, without extensive mare. Two small dark regions were named Mare Moscoviense (Sea of Moscow) and Mare Desiderii (Sea of Dreams). Mare Desiderii was later found to be composed of a smaller mare, Mare Ingenii (Sea of Ingenuity) and other dark craters. 

Luna 3 model. Collection of the Museum of Astronautics, Moscow. Credit: Wikimedia Commons 

   Following the spectacular success of Luna 3, the Soviets attempted to obtain more detailed images of the far side of the Moon using two Ye-3 probes in 1960. These were modified Ye-2A probes with an improved radio telemetry system but with an original imaging system. Their goal was to image the far side of the Moon from a much closer distance and in better lighting conditions than Luna 3. 

   During the launch of the first of the spacecraft, Ye-3 No. 1, on April 15, 1960, the engine of the third stage (Blok Ye) of the rocket shut down 3 seconds prematurely because its kerosene tank had not been completely filled. As a result the achieved velocity was about 130 meters per second slower than required. The spacecraft reached maximum altitude of about 200,000 km and then fell back and burned up in Earth’s atmosphere probably on April 19. The flight of the spacecraft was officially kept secret for many years. 

   After the failed launch, it was decided to immediately launch the backup probe, Ye-3 No. 2. Immediately after the lift-off that took place, according to various sources, on April 16 or April 19, 1960, one of the four strap-on boosters of the first stage failed to reach full thrust, placing abnormal loads on the rocket. Three of the strap-ons separated at only a few meters altitude, resulting in violent maneuvers of the four separated pieces of the rocket and powerful explosions. The core with its Blok Ye upper stage and payload crashed 800 meters from the pad. There was considerable damage to the pad and buildings at the launch site. 

 

Lift-off of the 8К72 launch vehicle carrying a lunar probe (date unknown). Credit: RKK Energiya

 

This is the first image returned by Luna 3, taken by the wide-angle (200 mm) lens. It showed the far side of the Moon was very different from the near side, most noticeably in its lack of lunar maria (the dark areas). The right three-quarters of the disk are the far side. The dark spot at upper right is Mare Moscoviense, the dark area at lower left is Mare Smythii. The small dark circle at lower right with the white dot in the center is the crater Tsiolkovskiy and its central peak. The north is up in this image. Credit: Roscosmos

 

 

This wide-angle view, taken by the 200 mm focal lenght lens, shows the far side comprising most of the image, with the near side making up about one-quarter of the disk at left. It is a composite image using several Luna 3 images to help suppress the noise. The dark patch at upper right is Mare Moscoviense and the dark areas at below and left of center are Mare Marginus and Mare Smythii. These are on the border between the near and far sides. The small dark circle at lower right is the crater Tsiolkovskiy. The image is centered at 15 N, 120 E, the north is at 11:30. Credit: Roscosmos 

 

This photograph, taken by the 500 mm focal lenght lens, shows the far side at right and the near side making up about one-third of the image at left. The circular dark patch below and left of center is Mare Smythii, on the boundary between the near and far sides. Just above this is Mare Marginus. The dark circle at upper right is Mare Moscoviense and at lower right is the crater Tsiolkovskiy with its light central peak. The image is centered at 10 N, 110 E, the north is at 11:30. Credit: Roscosmos  

 

 

References:

Asif A. Siddiqi. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. Washington, DC: NASA History Program Office, 2018. ISBN 978-1-62683-042-4.
Don P. Mitchell. The Hidden Side of the Moon.
NASA/NSSDCA. Luna 3.
NSSDC Image Catalog. First images of the far side of the Moon returned by Luna 3.
Wesley T. Huntress Jr., Mikhail Ya. Marov. Soviet Robots in the Solar System: Mission Technologies and Discoveries. Springer Praxis Books, 2011. ISBN 978-1-4419-7897-4.

 

© 2025, Andrew Mirecki