THE YE-2 AND YE-3 LUNAR FLYBY SERIES: 1959-1960

Campaign objectives:

Korolev’s second step after demonstrating the ability to hit the Moon was to obtain photographs of its far side, which can never be observed from Earth. The Television

Scientific Research Institute developed a camera for the mission; a facsimile system using film developed on hoard and scanned by a photometer for transmission. The camera was fixed and had to be pointed at the Moon by appropriately orienting and stabilizing the spacecraft, which required a З-axis pointing and control system rather than the spin stabilization used by the Ye-1 spacecraft. The Ye-2 would be the first to accomplish this vital mode of attitude control. In addition, the spacecraft had to be placed onto a trajectory that would enable it to view the far side of the Moon from a close range and under suitable illumination, and then return to the vicinity of Earth in order to transmit its pictures.

Spacecraft launched
First spacecraft:	Luna 3 (Ye-2 A No. l)
Mission Type:	Lunar Circumlunar Flyby
Country! Builder:	USSR OKB-1
Launch Vehicle:	Luna
Launch Date: Time:	October 4, 1959 at 00:43:40 UT (Baikonur)
Em ounter Da tej Time :	October 7, 1959
Mission End:	October 22, 1959
Outcome:	Success, photographed the lunar far side.
Second spacecraft:	Ye-3 No. l
Mission Type:	Lunar Circumlunar Flyby
Country: Builder:	USSR OKB-1
Launch Vehicle:	Luna
Launch Date: Time:	April 15, 1960 at 15:06:44 UT (Baikonur)
Outcome:	Upper stage failure.
Third spacecraft:	Ye-3 No.2
Mis si on Type:	Lunar Circumlunar Flyby
Country! Builder:	USSR OKB-1 "
Launch Vehicle:	Luna
Launch Date ‘: і ime:	April 19, 1960 at 16:07:43 UT (Baikonur)
Outcome:	Booster failure.

Keldysh’s Applied Mathematics Institute designed special orbits that would allow7 the spacecraft to photograph the far side of the Moon and then return to the vicinity of Earth over the USSR to transmit the pictures back at close range. There were only two launch opportunities for these restricted types of orbits, one in October 1959 for photography on approaching the Moon, and another in April 1960 for photography on receding from it. One Ye-2A spacecraft was launched in October and two of the Ye-3 type were assigned to the follow up. The first, Luna 3, was successful, but both of the more advanced spacecraft were lost to launch vehicle failures.

The Luna 3 mission was a momentous achievement for that time, and its pictures excited the w orld. But no one outside the USSR knew7 of the failures in the program. Of nine launches, six were total losses. Luna 1 failed to achieve its prime mission, but

Luna 2 was successful. And although Luna 3 look and transmitted pictures, they were of poor quality. Nevertheless, to the outside world it appeared that the Soviets had successfully launched three lunar missions of progressively greater complexity, and could do almost anything at will. In stark contrast, at the end of 1960 America appeared to be incompetent with nine embarrassing public failures yielding just one wide miss of the Moon.

After the success of Luna 3, the Soviet lunar program experienced a З-year hiatus as the focus shifted to the more challenging planetary targets, Venus and Mars, and a new robotic spacecraft was developed for soft landing on the Moon.

Spacecraft:

Two competing telecommunication systems were started for the lunar photography, one by Bogomolov labeled Ye-2 and the other by Ryazansky labeled Ye-2A. It was decided to use the Ye-2A system. The Ye-2A spacecraft designed by Gleb Maximov was a cylindrically shaped canister 130 cm in length with hemispherical ends and a 120 cm wide flange near the top. The cylindrical section was approximately 95 cm in diameter. The canister was hermetically sealed at 0.23 bar and held the cameras and film processing apparatus, communications equipment, thermal control fans, gyroscopes, and rechargeable silver-zinc batteries. Uplink was at 102 MHz and downlink at 183.6 MHz. A backup telemetry system operated at 39.986 MHz. The spacecraft had six omnidirectional antennas, four protruding from the top and two from the bottom. The thermal control system was to prevent the internal temperature from exceeding 25 C by using passive flaps mounted along the cylinder. There were micrometeoroid detectors, cosmic ray detectors, and solar cells for recharging the batteries on the exterior. The upper hemisphere of the probe housed the camera port, and the lower hemisphere housed the cold gas З-axis attitude control jets. There was no propulsion system with which to perform midcourse maneuvers. The spacecraft was to be spin stabilized under cruise, switch to 3-axis stabilization for photography, and then resume spin stabilization. Photoelectric cells were used to maintain orientation with respect to the Sun and Moon.

The follow up spacecraft, originally designated Ye-2F, were intended to acquire more and improved images of the lunar far side. As these were being prepared, there was a parallel rush to get the new’ four-stage R-7 and the Mars and Venus spacecraft ready for launch starting in the fall of 1960. The Ye-3 project was canceled when its camera system was judged too complicated and unreliable, and the Ye-2L spacecraft was re-designated Ye-3 shortly before launch. These two spacecraft were essentially the same as the Ye-2A but with improved imaging and radio systems.

Ye-2A launch mass: 278.5 kg

Payload:

1. Yenisey-2 photo-television facsimile camera system

2. Micrometeoroid detector

3. Ion traps (3)

4. Cherenkov radiation detector

5. Scintillation and gas discharge Geiger radiation counters

6. Mass spectrometer (not flown)

Fignrc 6.8 Luna 3 spacecraft.

Figure 6.*) Yenisey-2 photo-facsimile imaging system.

Several instruments from Luna 1 and 2 were flown in addition to the new camera system. A mass spectrometer based on an instrument that was flown sueeessfully on Sputnik 3 was planned but canceled owing to mass and time constraints.

Unlike the Americans who chose to use television v id icon tube cameras for their early deep space photography missions (except the Lunar orbiter series), the Soviets used a film camera system. This was mechanically complex and heavy but provided higher resolution, greater sensitivity, better quality, and was distortion free. The Yenisey-2 facsimile imaging system on the Ye-2 and -3 spacecraft consisted of a 35 mm film camera equipped with 200 mm f/5.6 and 500 mm f/9.5 lenses, an automatic film processing unit, and a photomultiplier film scanner with a resolution of L000 pixels line. The 200 mm objective was sized to image the full disk of the Moon. The camera cycled through four exposure times from 1 /200th to 1 /800th second. It exposed adjacent frame pairs simultaneously, one through each lens, and was capable of taking 40 frames at 1.000 x 1,000 pixel resolution using temperature and radiation resistant isochromatic film. The developed film could be scanned and rewound at ground command, and could be transmitted at either 1.25 lines/second or 50 lines/second depending on the range from Earth. The video signal was sent using the 3-W 183.6 MIIz transmitter. After the Cold War, it was revealed that the Soviets did not have radiation-resistant film and used US radiation-resistant film acquired by scavenging downed American spy balloons flown over the USSR from Western Europe.

Mission description:

Only the first of these missions survived its launch vehicle. The Luna 3 spacecraft (Yc-2A No. l) was successfully launched on October 4, 1959, into an elliptical Earth orbit that took it close to the south pole of the Moon, whereupon lunar gravitation redirected the trajectory back to the vicinity of the Earth, forming a figure-of-eight loop. The spacecraft, which the Soviet press dubbed the ‘Automatic Interplanetary Station’, experienced severe overheating with consequent ragged telemetry shortly after launch. This was alleviated somewhat by reorienting the spin axis and shutting off some equipment. To prepare for photography, the spin was stopped and the gyro-controlled З-axis orientation system activated. It flew within 6.200 km of the south pole of the Moon when at closest approach at 14:16 UT on October 6, and then crossed through the plane of the Moon’s orbit out over the sunlit far side. Early on October 7 the photocell on the top end of the spaceeraft detected the sunlit Moon at a distance of 65,200 km and initiated the 40 minute photography sequence. Twenty-nine frames w’ere exposed before the mechanical shutter jammed. The final image was taken at a distance of 66,700 km.

After photography w? as complete, the spacecraft resumed spinning and the first attempt was made to retrieve images. The signal strength was low and intermittent, and only one image with almost no detail was received. A second attempt was made near apogee at 470.000 km from Earth, but again the transmission quality w as poor. The antenna patterns on the spacecraft may not have been optimal. It was decided to wait for the most ideal situation when the spacecraft returned to the vicinity of the Earth ten days later. As the spacecraft approached Earth, several attempts to retrieve the images at fast playback did not yield good results. The signals were weak, with a lot of static and radio noise. To reduce the latter, Soviet engineers enforced radio silence in the Black Sea in the vicinity of the Yevpatoria receiving antenna. Finally, on October 18 the signals improved abruptly and 17 resolvable but noisy pictures were successfully received. By design, the mission was undertaken when a portion of the near side was illuminated to provide a point of reference, so only 70% of the far side was sunlit. Contact with Luna 3 was lost on October 22 and it burned up in the Earth’s atmosphere in April 1960.

Both Ye-3 spacecraft fell victim to their launchers. The third stage of the rocket carrying Yc-3 No. l cutoff prematurely. The kerosene tank had not been completely filled! At a range of only about 200,000 km from the Earth the spacecraft fell back and burned up in the atmosphere. The Yc-3 No.2 launch failed spectacularly when at the moment of liftoff one of the strap-on boosters failed to reach full thrust, placing abnormal loads on the vehicle. Three of ihe strap-ons separated at only a few meters altitude, resulting in violent maneuvers of the four separated pieces of the rocket and powerful explosions. There was considerable damage to the pad and buildings at the launch site. This brought a fiery end to the first series of Soviet lunar spacecraft and the final use of the 8K72 R-7E Luna launcher for lunar missions.

Figure 6.10 First image of the far side of the Moon returned by Lima 3. The dark area at lower left is Mare Smythii on the near side. The right-most three-quarters of the image shows part of the far side. The dark spot at upper right is Mare Moscoviense and the small dark circle at lower right is the crater Tsiolkovsky with its central peak.

Figure 6.11 Mosaic of Luna 3 images showing the far side of the Moon.

Results:

Luna 3 was the first spacecraft to photograph the lunar far side, but the 17 pictures successfully received were very noisy and of low resolution. Only six of these 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 Sea of Moscow and Sea of Dreams, the latter in honor of the Mechta first flyby mission.