LOS ANGELES (AP) -Earth’s atmosphere will soon get a health checkup from a new NASA satellite designed to learn more about the ozone layer, pollution and how the planet’s climate is changing.

The $785 million Aura mission is scheduled for launch before dawn Sunday aboard a Delta II rocket.

“Aura is a mission that’s designed to understand and protect the very air that we breathe,” mission scientist Phil DeCola said Friday at a briefing from Vandenberg Air Force Base, northwest of Los Angeles.

Carrying four instruments, the 6,542-pound spacecraft will climb to an orbit 438 miles high and should remain aloft for six years.

The launch will complete the first series of NASA’s Earth Observation System, joining the land-watching Terra satellite and the Aqua satellite, which studies the planet’s water cycle.

Earth’s atmosphere is 99 percent nitrogen and oxygen, but Aura’s interest is in the tiny portion made of other gases, including the stratospheric ozone layer.

“Aura is focused on a fraction of the remaining 1 percent, the trace gases and aerosol particles that are almost as important as oxygen itself in sustaining life on Earth,” DeCola said.

The ozone layer blocks deadly ultraviolet radiation, but pollution has depleted the layer, resulting in a hole over Antarctica. Aura will study changes in the layer caused by ozone-depleting chemicals and greenhouse gases.

Aura will also help scientists understand how air pollution in one part of the world can affect the global atmosphere and how global climate changes can influence air quality in specific areas, DeCola said.

On the Net:

NASA Aura mission: http://aura.gsfc.nasa.gov/

AP-ES-07-10-04 0433EDT

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