LITTLETON, Colorado (Reuters) - Lockheed Martin Corp has begun final assembly of a new U.S. weather satellite that will allow the U.S. government to provide far earlier warnings about potentially deadly tornadoes and solar flares when it is launched in early 2016.

Lockheed this week powered on a key part of the satellite for the first time in a special "clean room" at a sprawling facility south of Denver, where engineers are assembling the satellite and testing components before the whole spacecraft moves to environmental and thermal vacuum testing in July.

The company won a $1.09 billion contract in 2009 to build two 30-foot, 14,000-pound Geostationary Operational Environmental Satellite R-Series (GOES-R) satellites for NASA and the National Oceanic and Atmospheric Administration, which have since exercised options for two additional satellites.

The first of the new satellites is on track for delivery to the government by October 2015, followed by launch into geosynchronous orbit about 35,000 km (22,300 mi) above the Earth in early 2016, Steve Jolly, chief engineer for the GOES-R program, told Reuters during the first media tour of the cavernous "high-bay" room where the satellite is being built.

To minimize any debris, visitors and workers wear special coveralls, head bonnets and slippers over their shoes, while fans blow air down through the room to reduce the possibility that even a stray bit of dust could harm the performance of the sophisticated cameras on board once they get out to space.

The GEOS-R satellites are being assembled at a Lockheed facility tucked away in a canyon south of Denver where the company built the nation's first intercontinental ballistic missile in 1955, and continues to work on a range of other military and intelligence satellites today. Engineers are now using small portable computers and large flat screens for testing the satellite, said Mike Ingalls, who heads the systems integration and testing for the satellite.

Jolly said the new satellite would give the government revolutionary new weather forecasting capabilities, offering imagery with four times better resolution and five times more data. "It's just phenomenal," Jolly said. "It can scan the entire (western) hemisphere in five minutes."

Using a new lightning tracker, also built by Lockheed, the satellite will be able to predict formation of tornadoes up to 20 minutes sooner than currently possible, Jolly said, adding, "Twenty minutes can be a matter of life or death."

The new satellite is based on Lockheed's A2100 spacecraft, which is also used for commercial communications satellites.

The satellite also includes a new sensor that will monitor solar activity in ultraviolet wavelengths, helping predict potentially disruptive solar flares and other "space weather."

The GOES system has been in use by the United States for 40 years. Three GOES satellites are in orbit at any given time; one covers the Pacific Ocean and western United States, one covers the Atlantic Ocean and eastern United States, and one is a spare, available if needed.

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