Zond 1 was a spacecraft of the Soviet Zond program. It was the second Soviet research spacecraft to reach Venus, although communications had failed by that time. It carried a 90-centimetre (35 in) spherical landing capsule, containing experiments for chemical analysis of the atmosphere, gamma-ray measurements of surface rocks, a photometer, temperature and pressure gauges, and a motion/rocking sensor in case it landed in water. An experimental Ion thruster was also carried for evaluation. The Zond-1 was a 3MV design, the second generation inter-planetary Soviet bus, improving over the 2MV design used for previous Mars and Venus missions. However, more importantly, significant advancements were in the 8K78 Molniya launch vehicle whose Block-L (upper stage) had crippled half a dozen interplanetary missions before.

Wikipedia: https://en.wikipedia.org/wiki/Zond_1. Related NASA reference: https://nssdc.gsfc.nasa.gov/planetary/chronology.html#1964. Description adapted from Wikipedia contributors (CC BY-SA 4.0; https://creativecommons.org/licenses/by-sa/4.0/).