Most employees: Aerospace Corp. prepares liftoffs.

How many rocket scientists does it take to put a satellite into orbit? Ask Aerospace Corp.

The largest non-profit in the Los Angeles area, Aerospace has 3,100 employees in its E1 Segundo headquarters and another 700 in offices around the country. The company plans to add 130 more workers in 2005, according to spokesman George Torres. All are civilians, though many offices are on Air Force bases.

Scientists and engineers make up two-thirds of its workforce. More than 700 hold Ph.D.s, and more than 1,000 hold master's degrees. These are the people who invented global positioning systems, a network of satellites used for navigation that can pinpoint a location anywhere in the world. The organization is currently trying to improve the GPS systems used by coalition forces in Iraq.

Aerospace Corp. is the main consultant to the Air Force for space-related technology. Its engineers contribute to the design of the machines the Air Force uses to launch objects into orbit. They also design the objects themselves: satellites for weather, communications and surveillance.

"Every military launch vehicle that's ever flown, we've had a hand in it," said Tones.

If you've never heard of Aerospace Corp., there's a reason.

"In the beginning of our history, we were largely secretive about what we did," Torres said. "But as the years have gone by we've become more open."

Established in 1960, Aerospace is considered a Federally Funded Research and Development Center, set up by Congress to provide the Air Force with objective scientific advice. There are 37 such centers in the country, including Los Alamos National Laboratory in New Mexico, which is funded by the Department of Energy. Aerospace is one of 10 centers funded by the Department of Defense.

With revenues of almost $584 million in 2003, the company remains a non-profit by plowing excess funds back into research and development (about 7 percent of revenues in 2003). Almost 60 percent of revenues are spent on compensation, according to 2003 tax returns, an average of about $97,400 per employee.

Chief Executive William Ballhaus, a former Lockheed Martin executive and former NASA engineer, took home more than $600,000 in 2003, making him one of the top earners in the L.A. non-profit world. The company is quick to point out that chief executives at private sector aerospace companies earn well into the millions.

Aerospace Corp. has received almost $2.5 billion in Department of Defense contracts, its primary source of revenue, over the past six years. About 90 percent of the business comes from the Air Force and about 8 percent is with NASA. One of its current projects is trying to help put the space shuttle fleet back into orbit.