Raytheon Co. (NYSE: RTN) announced on Wednesday a $137.7 million contract with the U.S. Army to provide engineering work for the Patriot Air and Missile Defense System.

The deal is the third of four options originally part of a base contract awarded in 2009, totaling in $803 million to provide analysis, software, engineering, testing and logistics support.

The Patriot Defense System is designed to protect the United States from aerial attacks, including aircraft and missiles and is used by 12 nations globally.

The Tewksbury, Mass.-based defense company will make upgrades and improvements to defense centers in Andover, Mass., Tewksbury, Mass., Huntsville, Ala., and White Sands, N.M.

Shares fell in afternoon trading 27 cents to $50.58.