Soviet activity

THE SECOND GENERATION

After the success of Luna 3, the Soviets developed a new spacecraft designed to deliver a capsule to the lunar surface using the rough landing technique. Luna 4 was launched at 08:16 GMT on 2 April 1962, and after cruising in parking orbit it set off for the Moon. After an ineffective midcourse manoeuvre, the 1,422-kg vehicle made a flyby at 13:25 on 5 April at a range of 8,500 km and passed into solar orbit. After several further failures, the Soviet Union conducted a deliberate flyby mission.

FILLING THE GAP

Zond 3 lifted off at 14:38 GMT on 18 July 1965. After parking orbit, it was sent on a trajectory to pass by the illuminated leading limb of the Moon. Imaging began at 01:24 on 20 July at an altitude of 11,570 km and ended at 02:32 at 9,960 km, with the closest point of approach at 9,220 km. It had been intended to launch this probe in 1964 as a companion to Zond 2 on a mission to Mars, but it was held back. The pictures were not transmitted until the narrow-beam of the high-gain antenna was able to lock onto Earth, which occurred on 29 July at a range of 2.2 million km. The objective of this flight was to test deep-space communications for an interplanetary mission, and the Moon was merely a convenient photographic target. It transmitted two dozen pictures of Oceanus Procellarum and around onto the far-side to view the area which had not been visible to Luna 3.

The results indicated that although there were few maria on the far-side, and those were small, there were multiple-ring structures which for some reason had not been flooded by lava. The Orientale basin was seen in its entirety for the first time, since even at the most favourable libration barely half of it was observable in reprojected telescopic pictures. In addition to the concentric rings, there were radial patterns in evidence. There was a small patch of mare material inside the central ring, and small patches between the rings, but otherwise the entire structure was ‘on display’ in its

magnificence. It boggled the mind that Earth must once have been disfigured by such structures!