Complex sentence: Luna 1960B (E- 3 series) was the third Soviet attempt to photograph the far side of the Moon, the first being the highly successful Luna 3 mission and the second being the unsuccessful Luna 1960A.
Split into simpler sentences: Luna 1960B (E- 3 series) was the third Soviet attempt to photograph the far side of the Moon. The first being the highly successful Luna 3 mission and the second being the unsuccessful Luna 1960A.