Northrop Grumman Aerospace Systems will eliminate 500 jobs, mainly in Southern California, in anticipation of a decline in U.S. defense spending, the Los Angeles-based company announced Sept. 27.

The planned reductions, which will include a combination of voluntary and involuntary layoffs, are concentrated at Northrop Grumman’s El Segundo, Manhattan Beach and Redondo Beach facilities. Redondo Beach is home to the company’s satellite-building operation. Those three locations currently employee about 12,500 people.

Northrop facilities in New York and Florida also will be affected, Northrop Grumman spokesman Jim Hart said.

Layoff notices will be issued by Oct. 15 and take effect Dec. 31, Hart said.

“We regret the need to take this action,” Robert McNulty, Northrop Grumman Aerospace Systems’ sector vice president for human resources and administration, said in a statement. “It is a necessary step to address affordability initiatives of our customers and allow us to effectively compete in a very cost-conscious marketplace.”