NEW YORK - Just weeks before the first man shot into outer space in 1961, the Soviets launched a dress rehearsal with a duplicate of the space capsule carrying a cosmonaut mannequin and a live dog.

The Vostok 3KA-2 spacecraft -- a twin of the Vostok 3KA-3 that later carried cosmonaut Yuri Gagarin -- is being auctioned in New York on April 12, the 50th anniversary of the manned mission.

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The capsule, scorched during its re-entry into the Earth's atmosphere, was to go on exhibit at the Sotheby's auction house galleries on Thursday. It's estimated to sell for between $2 million and $10 million.

Sotheby's said the owner, who wished to remain anonymous, bought it privately from the Russians years ago and felt the 50th anniversary was an appropriate time to sell it.

The capsule's interior, which contained about 1,800 pounds (815 kilograms) of instrumentation, has been stripped for security reasons. Made of aluminum alloy and measuring a little more than 7 feet (2.1 meters) in diameter, it retained "secret" classification until 1986.

The life-size spacesuited mannequin, nicknamed Ivan Ivanovich, has been on loan at the Smithsonian National Air and Space Museum in Washington since 1997. It was bought at Sotheby's by the Perot Foundation in 1993.

The faux astronaut shared the small capsule with a mutt named Zvezdochka, or Little Star, which made it back from space safely.

The test mission made one low Earth orbit before its re-entry 115 minutes later and landing in a snow-covered gully near Izhevsk, an industrial city in what's now the European part of Russia.

Just 18 days later, the 3KA-3 manned capsule, later renamed Vostok 1, carried Gagarin on the world's first space flight. Like the mannequin, Gagarin was ejected from the capsule and parachuted down.

The Vostok 1 is now housed in the Rkk Energia Museum near Moscow.

The first manned space flight came four years after the launch of Sputnik, the first manmade satellite.