An unmanned Atlas V rocket has blasted off to put the first of a new generation of NASA communications satellites into orbit.
The 191-foot (58-metre) rocket launch is the first of 13 planned launches in 2013 from the Cape Canaveral Air Force Station just south of NASA's Kennedy Space Center.
Once in position 22,300 miles (35,900 km) above the planet, the Tracking and Data Relay Satellite, known as TDRS and built by Boeing, will join a seven-member network that tracks rocket launches and relays communications to and from the space station, the Hubble observatory and other spacecraft circling Earth.
"TDRS-K bolsters our network of satellites that provides essential communications to support space exploration," said Badri Younes, deputy associate administrator for Space Communications and Navigation at NASA Headquarters in Washington.
"It will improve the overall health and longevity of our system."
Two other TDRS spacecraft were decommissioned in 2009 and 2011 respectively and shifted into higher "graveyard" orbits.
A third satellite was lost in the 1986 space shuttle Challenger accident.
NASA used its space shuttle fleet for launching the satellites until 1995, then switched in 2000 to unmanned Atlas rockets, manufactured by United Space Alliance, a partnership of Lockheed Martin and Boeing.
With six operational satellites and a seventh spare, NASA can track and communicate with spacecraft in lower orbits, such as the space station, which flies about 250 miles (400 km) above Earth.
Before 1983 when the first TDRS was launched, NASA relied on ground-based communications, occasionally supplemented with airplanes and ships, which was expensive to maintain and provided only a fraction of the coverage of an orbiting network.
Three second-generation TDRS spacecraft were launched from 2000 to 2002.
This week's launch was the first of three planned third-generation satellites needed to replace aging members of the constellation.
"It's been a long time since we launched the last one," NASA's TDRS project manager, Jeffrey Gramling, said at a news conference before the launch.
Most of the spacecraft are well beyond their 10-year design life, he added.
"With this launch, NASA has begun the replenishment of our aging space network," said Gramling.
"This addition to our current fleet of seven will provide even greater capabilities to a network that has become key to enabling many of NASA's scientific discoveries."
Initially developed to support the space shuttle and space station programs, the TDRS network now serves a variety of NASA spacecraft and commercial users such as Space Exploration Technologies and foreign space agencies flying cargo ships to and from the station, a $100 billion research laboratory staffed by rotating crews of astronauts and cosmonauts.
The new spacecraft, which cost between $350 million and $400 million, will take about 10 days to reach its intended orbit. It will then go through a three-month checkout before it is put into service, Gramling said.
The 12th and 13th TDRS satellites are targeted for launch in 2014 and December 2015.