Northrop Grumman Corp. has won a $20.9 million Navy contract to make radar sets for Virginia-class submarines, the Pentagon announced late Tuesday.

The eight radar systems will provide surface surveillance. The work will be done at the Los Angeles defense contractor’s Charlottesville, Va. facility. The contract is expected to be finished by late 2016.

Northrop shares were down $1.07, or 2 percent, to $51.68 in midday trading Wednesday on the New York Stock Exchange.