NASA is sending two specially equipped aircraft into the skies over the East Bay on Friday to better understand air pollution.

The aircraft -- a Lockheed P-3B carrying 24 scientists and crew members and Beechcraft 200 King Air with four crew members -- have an array of high-tech measuring instruments, sampling the air as they fly.

The project will help identify where pollution is coming from -- and how it moves. The data will improve air pollution forecasting in the Bay Area.

"Surprisingly, few studies have explored the vertical distribution of pollution in the Bay Area, particularly in wintertime," said Laura Iraci, an atmospheric research scientist at Ames Research Center, based at Moffett Field. Earth science researchers at NASA Ames will help analyze the data.

A similar route was taken Thursday by a different aircraft, called Alpha Jet, which measured ozone, carbon dioxide and methane. Its findings were surprising: due to Thursday's offshore breeze, the air was worse over the ocean than in Bay Area cities.

The planes plan to fly a loop on Friday, departing from Palmdale in Los Angeles County and heading north up to Yuba City in the Sacramento Valley and returning south via the Bay Area, gathering samples over Interstate 680.

Scientists are specifically interested in measuring particulates and other air pollutants above the surface layer of the atmosphere. Satellites have so far been unable to distinguish between air pollution that is high in the atmosphere -- or near the surface, where people breathe.

The P-3B carries a chemistry kit and particle sensors. The B200 has sensors looking down on the pollution from above.

Friday's flights will be the eighth "science flight" of the NASA's Discover-AQ campaign, a four-year program to improve experts' ability to monitor air quality for public health and the environment.

Contact Lisa M. Krieger at 650-492-4098.