<Table> Union of Soviet Socialist Republics <Tr> <Td_colspan="2"> </Td> </Tr> <Tr> <Th_colspan="2"> United Nations membership </Th> </Tr> <Tr> <Th> Membership </Th> <Td> Former full member </Td> </Tr> <Tr> <Th> Dates </Th> <Td> 1945 (1945)--1991 (1991) </Td> </Tr> <Tr> <Th> UNSC seat </Th> <Td> Permanent </Td> </Tr> <Tr> <Th> Ambassadors </Th> <Td> <Ul> <Li> Andrei Gromyko 1946--1948 </Li> <Li> Yakov Malik 1948--1952 </Li> <Li> Valerian Zorin 1952--1953 </Li> <Li> Andrey Vyshinsky 1953--1954 </Li> <Li> Arkady Sobolev 1955--1960 </Li> <Li> Valerian Zorin 1960--1963 </Li> <Li> Nikolai Fedorenko 1963--1968 </Li> <Li> Yakov Malik 1968--1976 </Li> <Li> Oleg Troyanovsky 1976--1986 </Li> <Li> Yuri Dubinin 1986 </Li> <Li> Alexander Belonogov 1986--1990 </Li> <Li> Yuli Vorontsov 1990--1991 (last) </Li> </Ul> </Td> </Tr> </Table> <Tr> <Th_colspan="2"> United Nations membership </Th> </Tr>

When did the soviet union join the un