LOS ANGELES (AP) _ After a five-year delay, an Earth-observing satellite will be launched to test new technologies aimed at improving weather forecasts and monitoring climate change.

The $1.5 billion NASA mission comes in a year of weather extremes from the Midwest tornado outbreak to the Southwest wildfires to hurricane-caused flooding in New England.

“We’ve already had 10 separate weather events, each inflicting at least $1 billion in damages,” said Louis Uccellini of the National Oceanic and Atmospheric Administration.

The satellite will lift off before dawn Friday from Vandenberg Air Force Base, Calif., aboard a Delta 2 rocket that will boost it into an orbit some 500 miles high.

The space agency already has a fleet of satellites circling the Earth, taking measurements of the atmosphere, clouds and oceans. But many are aging and need replacement.

The latest _ about the size of a small school bus _ is more sophisticated. It carries five different types of instruments to collect environmental data, including four that never before have flown into space.

One of the satellite’s main jobs is to test key technologies that will be used by next-generation satellites set to launch in a few years.

NOAA meteorologists plan to feed the observations into their weather models to better anticipate and track hurricanes, tornadoes and other extreme weather.

The information will “help us understand what tomorrow will bring,” whether it’s the next-day forecast or long-term climate change, said Andrew Carson, the mission’s program executive at NASA headquarters.

The satellite is part of a bigger program with a troubled history. Originally envisioned as a joint civil-military weather satellite project, ballooning costs and schedule delays caused the White House last year to dissolve the partnership.

Under the restructuring, the Defense Department is building its own military satellites while NASA is developing a new generation of research satellites for NOAA. Friday’s launch is considered the first step toward that goal.

The satellite was supposed to fly in 2006, but problems during the development of several instruments forced a delay. NASA invested about $895 million in the mission while NOAA and the Air Force contributed $677 million.

For the launch, NASA invited 20 of its Twitter followers to Vandenberg, where they will receive front-row seats to view the liftoff.

Once in orbit, the satellite, built by Ball Aerospace & Technologies Corp. in Boulder, Colo., will spend the next five years circling the Earth from pole to pole about a dozen times a day. Data will be transmitted to a ground station in Norway and routed to the United States via fiber optic cable. NASA will manage the mission for the first three months before turning it over to NOAA.

___

Online:

Mission details: http://www.nasa.gov/npp

___

Follow Alicia Chang’s coverage at http://twitter.com/SciWriAlicia