Northrop wins Air Force satellite work

Northrop Grumman Corp., the third- largest U.S. defense contractor with a division in Rolling Meadows, won satellite system-modification work from the U.S. Air Force valued at as much as $2.34 billion.

The award to improve the National Polar-orbiting Operational Environmental Satellite System calls for a pair of development satellites with a production option for two more. The work is expected to be completed in September 2016, the Defense Department said in a statement Monday.

The satellite system is used to monitor global conditions related to weather, atmosphere, oceans, land and near-space environments. It is run jointly by the Air Force, the Commerce Department and the National Aeronautics and Space Administration.

Shares of Northrop fell 8 cents to $77.12 at 4:27 p.m. in New York Stock Exchange composite trading. They have gained 14 percent this year. Lockheed Martin Corp. is the largest U.S. defense con tractor, and Boeing Co. is second biggest.