Boeing Co. and Lockheed Martin Corp. are preparing responses to the U.S. Air Force’s request for proposals for the GPS 3 constellation, the companies announced July 16.

The Air Force plans to acquire eight GPS 3A satellites, with the first scheduled to be placed into orbit in 2013, the service announced July 12. Proposals are due Aug. 27, and the Air Force plans to award a contract for the first eight satellites as well as options for four more by the end of 2007. The contract could be valued at up to $1.8 billion. The Air Force also plans to order eight GPS 3B and 16 GPS 3C satellites.

The next-generation GPS spacecraft will provide improved position, navigation and timing services to warfighters and civilian users.