Lockheed Martin and Raytheon submitted competing final proposals for building a next-generation space surveillance radar network for the U.S. Air Force, the companies announced.

Lockheed Martin submitted its bid Nov. 13 and Raytheon filed the next day. Both companies have developed and demonstrated working prototypes of Space Fence that successfully tracked objects in space.

A final request for proposals for the new Space Fence was released Oct. 4. The Air Force expects to award a contract for the work in early 2013.

The first of two envisioned Space Fence sites will be located at Kwajalein Atoll in the Marshall Islands. The Air Force expects to have the Kwajalein site up and running as soon as late 2016. The service has not said where it would base the second site, the funding for which has not been clearly identified.

The long-delayed radar system is expected to track a far greater number of low Earth orbiting objects than the current VHF-band Space Fence, a line of radars deployed across the Southern United States during the 1960s. The new S-band system is expected to cost $3.5 billion.

Lockheed Martin Mission Systems & Sensors of Washington and Raytheon Integrated Defense Systems of Tewksbury, Mass., each won $107 million contracts in January 2011 for design work on the Space Fence that concluded over the summer.