Northrop Grumman Corp. has agreed to buy Columbia, Md.-based intelligence company Essex Corp. for about $551.5 million.

The acquisition will expand the Los Angeles-based defense company’s stance in the intelligence community, Chief Executive Ronald Sugar said in a statement. The move is in line with the company’s efforts to diversify its business and move toward more non-traditional defense contracting work.

Essex share holders will receive about $24 a share in cash, with the total deal nearing $580 million including debt.

The company also said Thursday that it expects annual earnings per share from between $4.40 and $4.45, up from prior guidance of $4.20 to $4.25. The revised guidance includes an after-tax gain of approximately $72 million (21 cents) from the sale of common shares of TRW Automotive Holdings Corp. which the company expects to be finalized Friday.

Shares in Northrop were down 8 cents to $64.96 in early trading Thursday.