Sputnik 1

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Sputnik 1
Sputnik 1
Organization: Soviet Union
Major Contractors: Korolev Design Bureau
Mission type: Earth Science
Satellite of: Earth
Launch Date: October 4, 1957 at 19:12 UTC
Launch Vehicle: R-7/SS-6 ICBM
Decay: January 4, 1958
Mission Duration: 3 weeks
NSSDC ID: 1957-001B
Webpage: NASA NSSDC Master Catalog
Mass: 83.6 kg
Semimajor Axis: 6,955.2 km
Eccentricity: .05201
Inclination: 65.1°
Orbital Period: 96.2 minutes
Apoapsis: 939 km
Periapsis: 215 km
Orbits: ~1,400

Sputnik 1 (Russian: Спутник-1, Satellite 1) was the first artificial satellite to be put into orbit, on October 4, 1957. Coming at the height of the Cold War, the launching of Sputnik caught the West by surprise, and in the U.S. led to a wave of self-recriminations, the beginning of the space race, and a movement to reform science education.

Spacecraft design

The satellite weighed about 83 kg (184 pounds). The Sputnik 1 satellite was a 58.0 cm-diameter aluminium sphere that carried four whip-like antennas that were 2.4-2.9 m long. The antennas looked like long "whiskers" pointing to one side. It had two radio transmitters (20 and 40 MHz) and is believed to have orbited Earth at a height of about 250 km (150 miles). Analysis of the radio signals was used to gather information about the electron density of the ionosphere. Temperature and pressure were encoded in the duration of radio beeps, indicating the satellite was not punctured by a meteorite. Sputnik 1 was launched by an R-7 rocket. It incinerated upon re-entry on January 3, 1958.

Sputnik was the first of several satellites in the Soviet Union's Sputnik program, the majority of them successful. Sputnik 2 followed as the second satellite in orbit, also the first to carry an animal, the dog Laika. The first failure occurred with Sputnik 3.


The Sputnik 1 spacecraft was launched from Baikonur Cosmodrome at Tyuratam (370 km southwest of the small town of Baikonur) in Kazakhstan, then part of the Soviet Union. The Russian word "Sputnik" means "travel companion" ("satellite" in the astronomical sense). The full official name, however, translates as "Artificial Earth Satellite" (ISZ in Russian literature). In 1885 Konstantin Tsiolkovsky first described in his book Dreams of Earth and Sky ( ISBN 1-4147-0163-2) how such a satellite could be launched into a low altitude orbit. It was planned as a contribution to the International Geophysical Year (1957-1958), with three of the five Sputnik satellites reaching orbit during that period.

The actual sequence of decision-making as to the form of Sputnik 1 was convoluted. A tonne-and-a-half, cone-shaped artificial satellite capable of making many physics measurements in space was first planned by Academician Keldysh, but when the Soviets read that the American Project Vanguard had two satellite designs, a small one which was just to see if they could get something into orbit, the Soviets decided to have what translates as the "Simplest Satellite" too, one which was one centimeter larger in diameter, and much heavier, than Vanguard's "real" satellite. They had to see whether the conditions in low Earth orbit would permit the bigger satellite to remain there for a useful length of time. When, months after Sputnik 1, the Vanguard test satellite was orbited, Khrushchev ridiculed it as a "grapefruit." Once the Soviets found they could orbit a test satellite too, they planned to orbit Keldysh's space laboratory satellite as Sputnik 3, and did so after one launch failure.

Nitrogen pressurized sphere : Micrometeorite detection
Radio : Propagation of radio signals
Thermometer : Micrometeorite detection

The spacecraft obtained data pertaining to the density of the upper layers of the atmosphere and the propagation of radio signals in the ionosphere. The instruments and electric power sources were housed in a sealed capsule and included transmitters operated at 20.005 and 40.002 MHz (about 15 and 7.5 m in wavelength), the emissions taking place in alternating groups of 0.3 s duration. The downlink telemetry included data on temperatures inside and on the surface of the sphere.

Because the sphere was filled with nitrogen under pressure, Sputnik 1 provided the first opportunity for meteoroid detection (no such events were reported), since losses in internal pressure due to meteoroid penetration of the outer surface would have been evident in the temperature data. The satellite transmitters operated for three weeks and were monitored with intense interest around the world, until the on-board chemical batteries failed. The orbit of the then-inactive satellite was later observed optically to decay 92 days after launch ( January 4, 1958) after having completed about 1400 orbits of the Earth, travelling a cumulative distance of 70 million kilometers. The orbital apogee declined from 947 km after launch to 600 km by December 9.

The Sputnik 1 rocket booster also reached Earth orbit and was visible from the ground at night as a first magnitude object. The satellite itself, a small but highly polished sphere, was barely visible at sixth magnitude, and thus more difficult to follow optically. Several replicas of the Sputnik 1 satellite can be seen at museums in Russia and another is on display in the Smithsonian National Air and Space Museum in Washington, D.C.

Space race

The United States had also been working on satellites, primarily through teams working for the US Navy as Project Vanguard. Their first launch had originally been intended to go before Sputnik, but was delayed several times before eventually blowing up on the pad. A rush effort then started under the US Army's Jupiter project and succeeded launching Explorer I in January 1958. This is considered the start of the Space Race between the two superpowers, as an aspect of the Cold War. Both nations attempted to out-do each other in space exploration, eventually culminating in the launch of the Apollo 11 mission to the Moon.

Historical preservation

In 2003 a back-up unit of Sputnik 1 called "model PS-1" was sold on eBay (minus the classified military radio parts that were removed in the 1960s). It had been on display in a science institute near Kiev. It is estimated that between four and twenty models were made for testing and other purposes.

A Sputnik 1 model was given as a present to the United Nations and now decorates the entry Hall of its New York City Headquarters.

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