The first privately built Cygnus cargo ship to visit the International Space Station detached from the orbiting lab Tuesday (Oct. 22) and is poised to destroy itself in Earth's atmosphere in a fiery finale to its successful test flight.

The unmanned Cygnus spacecraft built by Orbital Sciences Corp. of Dulles, Va., was released by astronauts using the station's robotic arm at 7:30 a.m. EDT (1130 GMT) as both space vehicles sailed high above the Atlantic Ocean, east of Argentina. The spacecraft is expected to fire its rocket thrusters Wednesday (Oct. 23) to leave orbit and burn up in Earth's atmosphere.

On the space station, astronauts and cosmonauts bid farewell to the visiting cargo ship. Italian astronaut Luca Parmitano of Italy thanked Orbital and Cygnus ground control teams, adding that it was a honor to watch over the spacecraft's first test flight. [See photos from Orbital Sciences' 1st Cygnus test flight]

"It was a real pleasure to work both with Cygnus and all the people on the ground," Parmitano radioed NASA's Mission Control in Houston.

Cygnus test flight success

The departure of Cygnus caps a successful test flight of the new spacecraft by Orbital and sets the stage for the first official cargo delivery to the space station in December. Orbital Sciences has a $1.9 billion contract with NASA to deliver supplies to the space station with at least eight Cygnus spacecraft.

The next Cygnus spacecraft is expected to launch to the space station in December to fly Orbital's first official cargo delivery mission for NASA.

This first Cygnus launched toward the space station on Sept. 18 atop an Orbital-built Antares rocket from NASA's Wallops Flight Facility on Wallops Island, Va. The spacecraft arrived at the station on Sept. 29, about seven days later than planned due to a software glitch and the launch of a new crew to the orbiting lab on Sept. 25.

Orbital's disposable Cygnus spacecraft are silver cylinders about 17 feet (5 meters) long that are built for the company by Thales Alenia Space in Italy. Cygnus is powered by an Orbital-built service module containing two solar wings for power, as well as rocket thrusters. Each Cygnus is capable of carrying up to 4,409 pounds (2,000 kg) of supplies, though the first test vehicle was packed with only 1,543 pounds (700 kilograms) of supplies and gear, Orbital officials said.

Commercial spaceflight's giant leap

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Cygnus spacecraft leaves International Space Station, will burn up in atmosphere