ПІЕ YE-8 LUNAR ORBITER SERIES: 1971-1974

Campaign objectives:

In addition to the lunar surface rover and sample return missions, the Ye-8 modular spacecraft also flew orbital missions to support the engineering requirements of the planned manned missions. The principal requirements were to photograph the lunar surface at high resolution and conduct remote surface composition measurements to assist in selecting landing sites. Л secondary objective was to acquire data on the radiation and plasma in lunar orbit in order to understand the risks to humans. Two Ye-8LS orbiters were launched successfully as Luna 19 and 22. Their tracking data continued the accurate mapping of the lunar gravity field that Luna 14 initiated.

Spacecraft launched
First spacecraft:	Luna 19 (Ye-8LS No.202)
Mission Type:	Lunar Orbiter
Country і Builder:	USSR, NPO-Lavochkin
Launch Vehicle:	Proton-K
launch Date ‘: 7 Ъпе:	September 28. 1971 at 10:00:22UT (Baikonur)
Encounter Date; Tinie :	October 3, 1971
Mission End:	October 3, 1972
Outcome:	Success.
Second spacecraft:	Luna 22 (Ye-8LS No.206)
Mission Type:	Lunar Orbiter
Country! Builder:	USSR, NPO-Lavochkin
Launch Vehicle:	Proton-K
Launch Date ‘: 1 Ъпе:	May 29, 1974 at 08:56:51 UT (Baikonur)
Encounter Date:Tinie:	June 2, 1974
Mission End:	November 1975
Outcome:	Success.

Spacecraft:

The spacecraft was essentially the same as the lander stage for the lunar rover, but with a payload consisting of a pressurized module for the orbital instruments. This was a squat cylinder and, just like the Lunokhod, had a hinged lid that exposed solar panels on the underside.

Figure 12.20 Luna 19 spacecraft.

Luna 19 launch mass: 5,700 kg

Luna 22 launch mass: 5,700 kg

Payload:

1. Imaging system

2. Gravitational field, experiment

3. Gamma-ray spectrometer for surface composition

4. Radiation sensors

5. Magnetometer

6. Micrometeoroid detector

7. Altimeter

8. Radio occultation experiment

For these arbiters, new linear-scan cameras were developed based on the Luna 9 and 13 panoramic imagers. Basically the motion of the spacecraft provided the long axis of the image and the photometer scanned only perpendicular to the direction of orbital motion. The field of view was 180 degrees centered on the nadir and gave a ‘cylindrical fish-eye’ image. At 4 lines per second from an altitude of 100 km it had a resolution of 100 meters in the direction of travel and 400 meters perpendicular to it. Luna 22 carried an additional camera and engineering tests of solid lubricants for operation in vacuum and wafer tests of surface reflection properties.

The Ye-8 lunar orbiter series: 1971-1974 265

Mission description:

Luna 19 was launched on September 28, 1971, and on October 3 it entered a 2 hour circular lunar orbit at 140 km inclined by 41 degrees. Three days later the orbit was changed to an elliptical one of 127 x 385 km. Several months later the perilune was lowered to 77 km to undertake closer photography. After more than 4,000 orbits the spacecraft ceased operations on October 3, 1972.

Luna 22 was launched on May 29, 1974, and entered a 219 x 221 km lunar orbit at an inclination of 19.6 degrees on June 2. It made many orbit adjustments over its 18 month lifetime to optimize experiment operation, at times lowering its perilune to 25 km to improve photography. Sporadic contact was maintained after the supply of attitude control gas ran out on September 2, and the mission was concluded in early November 1974.

Figure 12,21 Section of a panoramic image from Luna 19 of Sinus Aestuum with the crater Eratosthenes at the right.

Figure 12.22 Luna 22 panorama fragment illustrating the ‘cylindrical fish-eye’ effect of the linear scanning photometer imager.

Results:

Luna 19 and 22 both returned images of the lunar surface from orbit, with Luna 19 apparently returning about 5 panoramas and Luna 22 ten panoramas. Both spacecraft extended the systematic study to locate mass concentrations (mascons) begun by the earlier Luna orbiters. They also remotely sensed the composition of the surface and directly measured the properties of the orbital environment including the radiation, plasma, magnetic fields and micrometeoroid flux. Altimetry measure­ments of lunar topography were made, and the electromagnetic properties of the regolith examined. The results must have been substantial but few results were published, particularly from Luna 22.