Sputnik 1 (, Russian: Спутник-1, Satellite 1), often referred to as simply Sputnik, was the first artificial Earth satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957 as part of the Soviet space program. It sent a radio signal back to Earth for three weeks before its three silver-zinc batteries became depleted. Aerodynamic drag caused it to fall back into the atmosphere on 4 January 1958.
It was a polished metal sphere 58 cm (23 in) in diameter with four external radio antennas to broadcast radio pulses. Its radio signal was easily detectable by amateur radio operators, and the 65° orbital inclination made its flight path cover virtually the entire inhabited Earth.
The satellite's success was unanticipated by the United States. This precipitated the American Sputnik crisis and triggered the start of the Space Race. The launch was the beginning of a new era of political, military, technological, and scientific developments. The word sputnik is Russian for satellite when interpreted in an astronomical context; its other meanings are spouse or travelling companion.
Tracking and studying Sputnik 1 from Earth provided scientists with valuable information. The density of the upper atmosphere could be deduced from its drag on the orbit, and the propagation of its radio signals gave data 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 a peak speed of about 8 km/s (18,000 mph), taking 96.20 minutes to complete each orbit. It transmitted on 20.005 and 40.002 MHz, which were monitored by radio operators throughout the world. The signals continued for 22 days until the transmitter batteries depleted on 26 October 1957. On 4 January 1958, after three months in orbit, Sputnik 1 burned up while reentering Earth's atmosphere, having completed 1,440 orbits of the Earth, and travelling a distance of approximately 70,000,000 km (43,000,000 mi).
Спутник-1, romanized as Sputnik-Odin (pronounced [ˈsputnʲɪk.ɐˈdʲin]), means 'Satellite-One'. The Russian word for satellite, sputnik, was coined in the 18th century by combining the prefix s- ('fellow') and putnik ('traveler'), thereby meaning 'fellow-traveler', a meaning corresponding to the Latin root satelles ('guard, attendant or companion'), which is the origin of English satellite. (In the West, dating from the 1930s, the term fellow traveler was already used as a pejorative to describe people who were philosophically sympathetic to communism.)
Satellite construction project
On 17 December 1954, chief Soviet rocket scientist Sergei Korolev proposed a developmental plan for an artificial satellite to the Minister of the Defense Industry, Dimitri Ustinov. Korolev forwarded a report by Mikhail Tikhonravov, with an overview of similar projects abroad. Tikhonravov had emphasised that the launch of an orbital satellite was an inevitable stage in the development of rocket technology.
On 29 July 1955, U.S. President Dwight D. Eisenhower announced through his press secretary that, during the International Geophysical Year (IGY), the United States would launch an artificial satellite. Four days later, Leonid Sedov, a leading Soviet physicist, announced that they too would launch an artificial satellite. On 8 August, the Politburo of the Communist Party of the Soviet Union approved the proposal to create an artificial satellite. On 30 August, Vasily Ryabikov—the head of the State Commission on the R-7 rocket test launches—held a meeting where Korolev presented calculation data for a spaceflight trajectory to the Moon. They decided to develop a three-stage version of the R-7 rocket for satellite launches.
On 30 January 1956, the Council of Ministers approved practical work on an artificial Earth-orbiting satellite. This satellite, named Object D, was planned to be completed in 1957–58; it would have a mass of 1,000 to 1,400 kg (2,200 to 3,100 lb) and would carry 200 to 300 kg (440 to 660 lb) of scientific instruments. The first test launch of "Object D" was scheduled for 1957. Work on the satellite was to be divided among institutions as follows:
The USSR Academy of Sciences was responsible for the general scientific leadership and the supply of research instruments.
The Ministry of the Defense Industry and its primary design bureau, OKB-1, were assigned the task of building the satellite.
The Ministry of the Radio technical Industry would develop the control system, radio/technical instruments, and the telemetry system.
The Ministry of the Ship Building Industry would develop gyroscope devices.
The Ministry of the Machine Building would develop ground launching, refuelling, and transportation means.
The Ministry of Defense was responsible for conducting launches.
Preliminary design work was completed in July 1956 and the scientific tasks to be carried out by the satellite were defined. These included measuring the density of the atmosphere and its ion composition, the solar wind, magnetic fields, and cosmic rays. These data would be valuable in the creation of future artificial satellites; a system of ground stations was to be developed to collect data transmitted by the satellite, observe the satellite's orbit, and transmit commands to the satellite. Because of the limited time frame, observations were planned for only 7 to 10 days and orbit calculations were not expected to be extremely accurate.
By the end of 1956, it became clear that the complexity of the ambitious design meant that 'Object D' could not be launched in time because of difficulties creating scientific instruments and the low specific impulse produced by the completed R-7 engines (304 seconds instead of the planned 309 to 310 seconds). Consequently, the government rescheduled the launch for April 1958. Object D would later fly as Sputnik 3.