The Delta IV rocket lifted off at 4:12 p.m. from the Vandenberg Air Force Base, about 209 kilometres northwest of Los Angeles.
"We've just seen the successful liftoff" of the rocket, launch commentator Don Spencer said in a webcast.
Since the launch involved a classified cargo for the National Reconnaissance Office, no details were immediately available about whether it was boosted to its intended orbit.
The reconnaissance office, which oversees the nation's constellation of spy satellites, has kept mum about the purpose of the mission and directed United Launch Alliance to cut off the live broadcast three minutes after liftoff.
Intelligence analysts think the rocket carried a radar imaging satellite capable of seeing at night and through bad weather. In recent years, the United States has worked to phase out its fleet of older, heavier radar reconnaissance satellites with smaller but equally capable ones, said Charles Vick, a space policy analyst with the
http://news.sympatico.ctv.ca/world/us_rocket_carrying_classified_payload_launches/b08e4977
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