Question: When did the Soviets launch the first Earth satellite?
About the article "Cold War", section "Sino-Soviet split, space race, ICBMs".

Candidate passages:
The Timeline of Earth science satellites shows, in chronological order, those successful satellites with a program of Earth science.
Sputnik 1, while the first satellite ever launched, did not conduct Earth science.
Explorer 1 was the first satellite to make an Earth science discovery when it found the Van Allen belts. 
The first artificial satellite was Sputnik 1, launched by the Soviet Union on October 4, 1957, and initiating the Soviet Sputnik program, with Sergei Korolev as chief designer (there is a crater on the lunar far side which bears his name).
This in turn triggered the Space Race between the Soviet Union and the United States.
Sputnik 1 helped to identify the density of high atmospheric layers through measurement of its orbital change and provided data on radio-signal distribution in the ionosphere.
The unanticipated announcement of "Sputnik 1'"s success precipitated the Sputnik crisis in the United States and ignited the so-called Space Race within the Cold War.
"Sputnik 2" was launched on November 3, 1957 and carried the first living passenger into orbit, a dog named Laika.
In May, 1946, Project RAND had released the Preliminary Design of an Experimental World-Circling Spaceship, which stated, "A satellite vehicle with appropriate instrumentation can be expected to be one of the most potent scientific tools of the Twentieth Century.
"The United States had been considering launching orbital satellites since 1945 under the Bureau of Aeronautics of the United States Navy.
The United States Air Force's Project RAND eventually released the above report, but did not believe that the satellite was a potential military weapon; rather, they considered it to be a tool for science, politics, and propaganda.
In 1954, the Secretary of Defense stated, "I know of no American satellite program.
"On July 29, 1955, the White House announced that the U.S. intended to launch satellites by the spring of 1958.
This became known as Project Vanguard.
On July 31, the Soviets announced that they intended to launch a satellite by the fall of 1957.
Following pressure by the American Rocket Society, the National Science Foundation, and the International Geophysical Year, military interest picked up and in early 1955 the Army and Navy were working on Project Orbiter, two competing programs: the army's which involved using a Jupiter C rocket, and the civilian/Navy Vanguard Rocket, to launch a satellite.
At first, they failed: initial preference was given to the Vanguard program, whose first attempt at orbiting a satellite resulted in the explosion of the launch vehicle on national television.
But finally, three months after Sputnik 2, the project succeeded; Explorer 1 became the United States' first artificial satellite on January 31, 1958.
In June 1961, three-and-a-half years after the launch of Sputnik 1, the Air Force used resources of the United States Space Surveillance Network to catalog 115 Earth-orbiting satellites.
Early satellites were constructed as "one-off" designs.
With growth in geosynchronous (GEO) satellite communication, multiple satellites began to be built on single model platforms called satellite buses.
The first standardized satellite bus design was the HS-333 GEO commsat, launched in 1972.
The largest artificial satellite currently orbiting the Earth is the International Space Station. 
Naro-1 became the first South Korean launch vehicle to achieve Earth orbit on January 30, 2013, when it was successfully used to launch the Science and Technology Satellite 2C (STSAT-2C).
Naro-1 launched from the Naro Space Center, located 480 kilometers south of Seoul, 
Explorer 3 (international designation 1958 Gamma) was an artificial satellite of the Earth, nearly identical to the first United States artificial satellite Explorer 1 in its design and mission.
It was the second successful launch in the Explorer program. 
The Amazônia-1 satellite (or SSR-1), scheduled to launch in December 2016, using the rocket, is the first earth observation satellite entirely developed by Brazil.
Operations will be joint with the CBERS-3 and 4 satellites.