One mission separated Luna 1 and Luna 2, a launch failure that occurred with an unnamed probe on 18 June 1959. Luna 2 would be the Soviet Union’s sixth attempt to impact the Moon. It was the second of the Ye-1a series, modified to carry a heavier payload of 156 kg (344 lb) and had a combined mass of 390. 2 kg (860 lb). Luna 2 was similar in design to Luna 1, a spherical space probe with protruding antennas and instrumentation. The instrumentation was also similar to Luna 1, which included a triaxial fluxgate magnetometer, a piezoelectric detector, a scintillation counter, ion traps and two gas-discharge counters, while the Luna 2 included six gas-discharge counters. There were no propulsion systems on Luna 2 itself.