MOSCOW (AP) — The launch of Sputnik 60 years ago opened the space era and became a major triumph for the Soviet Union, showcasing its military might and technological prowess. It also stunned the rest of the world.

Details of the development and the launch of the first artificial satellite were hidden behind the veil of secrecy that surrounded the Soviet space program and only became known decades later.

A look at some little-known facts behind the Oct. 4, 1957, launch of the unmanned spacecraft:

A BYPRODUCT OF THE SOVIET MISSILE PROGRAM

Amid a tense Cold War arms race with the United States, the Soviet Union focused its efforts on building the world's first intercontinental ballistic missile capable of delivering a hydrogen warhead to the U.S. The R-7 missile was built by a team led by Sergei Korolyov, and tests of the rocket began in 1957.

Korolyov, a visionary scientist and a shrewd manager at the same time, pressed the reluctant military brass to use one of the first R-7s to put a satellite in orbit. He warned Soviet leaders that the U.S. was also developing a satellite and won the Kremlin's permission for the launch.

SIMPLE DESIGN

While there already was a project for a full-fledged scientific satellite, Korolyov ordered his team of engineers to design a primitive orbiter to save time and beat the U.S. into space. The craft, which was built in only a few months, was named PS-1, for "Prosteishiy Sputnik" — the "Simplest Satellite."

The satellite, weighing less than 84 kilograms (about 184 pounds) and slightly larger than a basketball, was a pressurized sphere of polished aluminum alloy with two radio transmitters and four antennas.

An earlier satellite project envisaged a cone-shape vehicle, but Korolyov opted for the sphere.

"The Earth is a sphere, and its first satellite also must have a spherical shape," he was quoted as saying.

THE START OF SPACE AGE

While the rest of the world was stunned by the Soviet accomplishment, the Kremlin's leadership seemed to be slow to grasp the scope of the event.

The first official Soviet report of Sputnik's launch was brief and buried deep inside the pages of Pravda, the Communist Party's daily newspaper. Only two days after the launch did it come out with a banner headline and quotes of the foreign accolades.

LIGHT AND SOUND IN THE SKY

Sputnik contained a radio transmitter, broadcasting a distinctive "beep-beep-beep" sound.

Pravda published a description of Sputnik's orbit to help people watch it pass. However, it didn't mention that the light seen moving across the night sky was in fact the spent booster rocket's second stage, which was in roughly same orbit as the satellite. The tiny orbiter itself was invisible to the naked eye.

Sputnik orbited the Earth for three months before burning up in the atmosphere.

LEADING SPACE RACE

Thrilled by the global furor caused by Sputnik's launch, the Kremlin immediately ordered Korolyov to launch a new satellite to mark the Nov. 7 anniversary of the 1917 Bolshevik Revolution. His team succeeded in building a spacecraft in less than a month, and on Nov. 3 launched Sputnik 2, which weighed about 508 kilograms (1,120 pounds). It carried the world's first passenger, a dog named Laika. While the dog died of the heat soon after the launch, the flight proved that a living being could survive in space.

On April 12, 1961, the Soviet Union made another giant leap ahead of the United States when Yuri Gagarin became the first human in space.

The Soviet lead in space prompted the U.S. to pour money into research and technology. In 1969, the U.S. won the race to land the first man on the moon, while the Soviet program collapsed in a series of booster rocket explosions.

UNKNOWN HERO

Amid the shroud of secrecy around the Soviet rocket and space program, Korolyov was never mentioned in any contemporary accounts of the launch. His key role was known only to a small circle of senior Soviet officials and space engineers.

Korolyov was only allowed to publish the non-secret parts of his research under the pseudonym "Professor K. Sergeyev," while Leonid Sedov, a member of the Soviet Academy of Sciences with no connection to space program, was erroneously praised in the West as the Father of Sputnik.

Soviet leader Nikita Khrushchev rejected the Nobel committee's offer to nominate Sputnik's designer for a prize, insisting it was the achievement of "the entire Soviet people."

Korolyov's daughter, Natalia, recalled later that her father sometimes felt bitter about the secrecy. "We are like miners — we work underground," she quoted him saying. "No one sees or hears us."