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Orbital Sciences Corporation on Thursday launched its unmanned Cygnus cargo ship on the company's first regular supply mission to the International Space Station.
The liftoff of the Antares rocket carrying the ship took place at 1:07 pm (1807 GMT) from Wallops Island, Virginia, according to footage carried by the US space agency NASA's television network.
"It is a beautiful launch occurring on time... with perfect weather," a NASA commentator said.
The cargo vehicle separated from the rocket's second stage 10 minutes after the launch as planned.
Cygnus is due to dock at the ISS on Sunday, only the fifth mooring of a private vessel to the station. The first was California company SpaceX's Dragon in May 2012.
The Cygnus launch was initially planned for December but delayed after a cooling system breakdown on the ISS, which required American astronauts to make two spacewalks in order to replace an ammonia cooling pump.
The launch is Orbital's second trip to the ISS, following a successful demonstration launch in September.
That mission proved "that the company can reliably carry out regularly scheduled operational missions to the ISS for NASA," said David Thompson, Orbital's chairman and chief executive officer.
Orbital has a contract with NASA worth $1.9 billion for eight cargo resupply missions to the global space lab.
Orbital and SpaceX are two private companies that have stepped in to ensure the United States' ability to reach the orbiting outpost, after the retirement of the 30-year space shuttle program in 2011.
Upon arrival at the ISS, Cygnus will be secured by the station's robotic arm, operated by two of the six astronauts based at the outpost.
The ISS personnel -- three Russians, two Americans and one Japanese -- will then unload the Cygnus cargo, some 2,780 pounds (1,260 kilograms) of scientific equipment and supplies, as well as material from experiments looking at microbial resistance to antibiotics.
Unlike the SpaceX Dragon capsule, Cygnus will not be sent back to Earth and instead will be destroyed upon falling into the Earth's atmosphere.
Under the terms of its contract with NASA, Orbital must deliver 20 tons of cargo to the ISS over the course of eight flights scheduled until early 2016.
SpaceX meanwhile has already carried out three missions to the ISS with its Dragon capsule, part of a $1.6 billion deal with NASA which provides for 10 further flights to the outpost.
SpaceX has launched Dragon with its Falcon 9 rocket from Cape Canaveral in Florida.
SpaceX, Boeing and the Louisville-based Sierra Nevada firm have also been selected by NASA to develop a private vessel for transporting people to the ISS.
NASA also uses Europe's ATV vessel, Japan's HTV and Russia's Progress, which are destroyed in the atmosphere after their missions.