CAPE CANAVERAL, Fla. - An unmanned Atlas 5 rocket blasted off from Cape Canaveral Air Force Station in Florida on Tuesday to put a second upgraded missile-warning satellite into orbit.

The 192-foot (58-meter) rocket lifted off from its seaside launch pad at 5:21 pm EDT/2121 GMT, carrying the US Air Force's second Space Based Infrared System Geosynchronous, or Geo2, satellite.

Once operational, the spacecraft will join an orbital surveillance network that continually scans the globe for telltale signs of missile launches.

"The infrared signature coming out the back end of a missile, we see that," Air Force Space Commander William Shelton said on Tuesday during a House Science Committee hearing about detecting incoming asteroids and other space objects.

"We'll be able to tell you what type of missile it is. We'll be able to tell you where that missile is going. We'll be able to tell you where it's going to impact," Shelton added.

"Those infrared sensors can be used for other things, but they can't be used for predictive things out beyond Earth," he said.

The satellite, built by Lockheed Martin joins an identical craft, Geo1, launched in May 2011. Each are equipped with two infrared sensors, one which continually scans the globe for missile launches, and the other which can stare at a fixed point.

The Space Based Infrared System supplements and eventually will replace the predecessor Defense Support Program satellite network which has been operating for 40 years.

"I would argue that the nation's missile warning system is critical now, perhaps even more so than it was during the Cold War," said James Planeaux, who oversees the Air Force's Infrared Space Systems directorate.

"Certainly, strategic and tactical missile threats have proliferated in both number and type. We're modernizing the nation's systems so we remain highly capable against today's threats."

The space-based network detected nearly 200 missile launches in 2011 and an additional 1,700 "special infrared events," Planeaux said.

"I believe with some of the activity we're seeing around the world even this year, we're seeing an increase in the number of global missile launches," Planeaux said.

On Friday, Defense Secretary Chuck Hagel announced plans to deploy 14 additional missile interceptors in Alaska to guard against increased threats from North Korea and Iran.

Data from the military's space-based monitoring network feeds missile interceptors positioning and tracking information.

Geo1 has not yet been put into operational service due to a data communications issue, but work to certify it for real-time monitoring should be completed by October 1, Planeaux said.

Geo2's certification is expected to follow before the end of the year.

Two more satellites are being built for launch in 2015 and 2016, respectively, and a follow-on contract for an additional pair is expected to be awarded this year, Planeaux added.

Tuesday's launch was the 69th for rocket manufacturer United Launch Alliance, a partnership of Lockheed Martin and Boeing that was established in 2006.