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Sputnik is Russian for "satellite" (literal meaning 'travel companion'). Sputnik 1 was the first artificial satellite to achieve geocentric orbit, and was launched on October 4th 1957. Its more formal name was Object PS - Prosteishii Sputnik, meaning simplest satellite, as it was decided to launch something much more simple and therefore lighter than originally planned as a payload for the massive R-7 ICBM rocket in order to beat arch-rival America into space. In fact, the R-7 was designed to be capable of delivering a nuclear warhead principally to be targeted at the Soviet Union's 'main adversary' the United States of America.

Both the USA and USSR were planning to launch satellites in International Geophysical Year, which ran from July 1957 to December 1958 to coincide with the 11 year cycle of maximum sunspot activity. The USA had signalled its intention in a 1955 press release and the Soviet government authorized development of an artificial satellite for peaceful scientific purposes in January 1956. The R-7 was capable of launching a payload of over 1 tonne and it was planned to allow 200 - 300 kg for scientific instrumentation. However difficulties arose with the construction of the satellite (designated Object D), so the decision was made in November 1956 to delay the launch of Object D in favor of Object PS to comfortably enable launch within IGY. Sputnik 1 had a diameter of 0.58m and weighed 84 kg. It was fitted with a radio transmitter which functioned for 22 days, and two 2 beam antennas (one with 2.4 m beams and the other 2.9 m).

Sputnik 1 was pressurized with inert nitrogen at 1.3 atmospheres. The power for the transmitter etc was supplied by 3 silver-zinc batteries. If the temperature rose above 50 degrees Celsius or fell below 0 degrees then sensors were designed to trigger a change in Sputnik's radio signal. It re-entered the Earth's atmosphere in January 1958.

Sputnik 2, carrying the dog Laika, was launched a month after Sputnik 1 in time for the 40th anniversary of the birth of the Soviet Union. Unfortunately it is thought the dog died from heat and stress a few hours after launch.

Sputnik 3 was the first-planned satellite - Object D. Because of difficulties in completion and some rocketry problems it was eventually launched in May 1958, and was an ambitious automated scientific satellite carrying 12 experiments.