Northrop Grumman Corp. on Wednesday said that its fourth-quarter earnings fell 9 percent mainly because of lower revenue at three of its core businesses.

The Los Angeles defense contractor, which is in the process of moving its corporate headquarters to the Washington, D.C. area, reported net income of $376 million ($1.27 a share), compared with $413 million ($1.31) a year earlier.

The quarter included a debt-buyback charge that reduced the most recent quarter’s result by 51 cents a share. But excluding that as well as some gains and other charges, Northrop’s adjusted profit from continuing operations was $376 million ($1.27) compared with $375 million ($1.19) a year earlier,

Revenue fell 4 percent to $8.61 billion as sales fell at its core aerospace, electronics and information systems units, but operating income grew due to improved efficiency and lower costs, the company said. Revenue at its Los Angeles County-based aerospace unit, for example, fell 4 percent, hurt by lower sales for civil space and missile defense programs, but profit was up 11 percent.

Analysts surveyed by Thomson Reuters on average expected per-share profit of $1.01 on revenue of $8.8 billion.

“Northrop Grumman had a very good fourth quarter and a strong finish to 2010,” Chief Executive Officer Wes Bush said in a statement.

At the end of the quarter, funded backlog was up 1.3 percent to more than $34.3 billion. For the coming year, Northrop expects to earn $6.40 to $6.60 per share, not including one-time items but including the impact of its shipbuilding spin-off. Analysts were expecting per-share profit of $6.99.

Shares were up $1.04, or 1.5 percent, to $72.13 in midday trading on the New York Stock Exchange.