During the 1950s - 1960s the USSR realized experiments with dogs for orbital space flights to see whether spaceflight with human beings have been possible. In this time, the USSR launched missions with special passenger slots for more than 55 dogs. The number of dogs in space is smaller, as majority of dogs fortunately flew more than one time. Most of survived and the few that died because technical failures, according to the data of the test. A notable exception is dog named Laika, which was the first animal sent into orbit, but whose death was expected from the beginning.
Belka (literally, "Squirrel") and Strelka ("Arrow") were the first dogs-cosmonauts that successfully turn on the Earth and spent a day in space aboard spaceship Sputnik-2 on 19 August 1960. Dogs were accompanied by a one rabbit, 42 mice, 2 rats, some dozens of flies, five plants and fungi. In the result of fly all space passengers survived. By the way, they were the first Earth-born creatures went into space orbit of the Earth and returned back alive.
There are some interesting facts about further destiny Belka and Strelka. After space fly, Strelka born six puppies who participated in many land-based space experiments, but never have gone into space. One of the pups was called Pushinka (or "Fluffy") and was presented in 1961 by Nikita Khrushchev to President John F. Kennedy's daughter. A Cold War romance flowered between Pushinka and a Kennedy dog named Charlie, resulting in the birth of 4 pups. Pushinka's descendants are still living today in USA and other countries.
About the exploit of Belka and Strelka today also remind the name of one satellite - “Dognik”. It flies around the orbit of Earth in an everlasting memory of the first space explorers – 2 little dogs.