VANDENBERG AIR FORCE BASE, Calif. » After a years-long delay, an Earth-observing satellite blasted into space early Friday on a dual mission to improve weather forecasts and monitor climate change.

A Delta 2 rocket carrying the NASA satellite lifted off shortly before 3 a.m. from the central California coast. The satellite separated from the rocket about an hour after launching, unfurled its solar panels and headed toward an orbit 500 miles above Earth.

NASA invited a small group of Twitter followers to watch the pre-dawn launch from Vandenberg Air Force Base, where weather conditions were ideal. Skies were clear and there was little wind.

"It was a thrill to watch the bird go up this morning in the beautiful clear night sky with the stars out there," Mary Glackin of the National Oceanic and Atmospheric Administration said at a post-launch news conference.

The satellite joins a fleet already circling the planet, collecting information about the atmosphere, oceans and land. The latest — about the size of a small SUV — is more advanced and carries four new instruments capable of making more precise observations.

Mission project scientist Jim Gleason said he could not wait for the data to "start flowing." NOAA meteorologists planned to use the information to improve their forecasts of hurricanes and other extreme weather while climate researchers hope to gain a better understanding of long-term climate shifts.

Besides collecting weather information, the satellite will track changes in the ozone, volcanic ash, wildfires and Arctic sea ice.

Many satellites currently in orbit are aging and will need to be replaced. The newest satellite is intended to be a bridge between the current fleet and a new generation that NASA is developing for NOAA.

The $1.5 billion mission’s path to the launch pad has been rocky. It was part of a bigger civilian-military satellite program that the White House axed last year because of cost overruns. The satellite was originally scheduled to fly in 2006, but problems during development of several instruments led to a delay.

Engineers will spend some time checking out the satellite’s instruments before science operations begin. Built by Ball Aerospace & Technologies Corp. in Boulder, Colo., the satellite is expected to orbit the Earth for five years.