Blok D (Блок Д meaning Block D) is an upper stage used on Soviet and later Russian expendable launch systems, including the N1, Proton-K and Zenit.
A low Earth orbit (LEO) is an orbit around Earth with an altitude of or less, and with an orbital period of between about 84 and 127 minutes.
Proton (Russian: Протон) (formal designation: UR-500) is an expendable launch system used for both commercial and Russian government space launches.
The Soviet crewed lunar programs were a series of unsuccessful programs pursued by the Soviet Union to land a man on the Moon, in competition with the United States Apollo program to achieve the same goal set publicly by President John F. Kennedy on May 25, 1961.
The Soyuz 7K-L1 "Zond" spacecraft was designed to launch men from the Earth to circle the Moon without going into lunar orbit in the context of the Soviet manned moon-flyby program in the Moon race.
Japan and China each launched their first satellites in 1970, bringing the total number of nations with independent launch capability to five.