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Sputnik 1

Sputnik 1
Sputnik 1.jpg
Replica of Sputnik 1
Mission type Technology demonstration
Operator Soviet space program
Harvard designation 1957 Alpha 2
COSPAR ID 1957-001B
SATCAT no. 00002
Mission duration Final: 21 days
Orbits completed 1440
Spacecraft properties
Manufacturer OKB-1
Ministry of Radiotechnical Industry
Launch mass 83.6 kg (184 lb)
Dimensions 58 cm (23 in) diameter
Power 1 watt
Start of mission
Launch date 4 October 1957, 19:28:34 (1957-10-04UTC19:28:34) UTC
Rocket Sputnik 8K71PS
Launch site Baikonur 1/5
End of mission
Disposal Spacecraft failure
Last contact 26 October 1957 (1957-10-27)
Decay date 4 January 1958
Orbital parameters
Reference system Geocentric
Regime Low Earth
Semi-major axis 6,955 km (4,322 mi)
Eccentricity 0.05201
Perigee 215 km (134 mi)
Apogee 939 km (583 mi)
Inclination 65.1°
Period 96.2 minutes
Epoch 4 October 1957, 15:12:00 UTC

Sputnik 1 (/ˈspʌtnɪk/; Russian: Спутник-1 [ˈsputnʲɪk] "Satellite-1", or ПС-1 ["PS-1", i.e., Russian: Простейший Спутник-1, Prosteyshiy Sputnik-1, "Elementary Satellite 1"]) was the first artificial Earth satellite. The Soviet Union launched it into an elliptical low Earth orbit on 4 October 1957. It was a 58 cm (23 in) diameter polished metal sphere, with four external radio antennae to broadcast radio pulses. It was visible all around the Earth and its radio pulses were detectable. This surprise success precipitated the American Sputnik crisis and triggered the Space Race, a part of the larger Cold War. The launch ushered in new political, military, technological, and scientific developments.

Tracking and studying Sputnik 1 from Earth provided scientists with valuable information, even though the satellite itself wasn't equipped with sensors. The density of the upper atmosphere could be deduced from its drag on the orbit, and the propagation of its radio signals gave information about the ionosphere.

Sputnik 1 was launched during the International Geophysical Year from Site No.1/5, at the 5th Tyuratam range, in Kazakh SSR (now known as the Baikonur Cosmodrome). The satellite travelled at about 29,000 kilometres per hour (18,000 mph; 8,100 m/s), taking 96.2 minutes to complete each orbit. It transmitted on 20.005 and 40.002 MHz, which were monitored by amateur radio operators throughout the world. The signals continued for 21 days until the transmitter batteries ran out on 26 October 1957.Sputnik burned up on 4 January 1958 while reentering Earth's atmosphere, after travelling about 70 million km (43 million mi) and spending three months in orbit.