The AN/APG-81 is an Active Electronically Scanned Array (AESA) radar system designed by Northrop Grumman Electronic Systems for the F-35 Lightning II. The Joint Strike Fighter AN/APG-81 AESA radar is a result of the US government's competition for the world's largest AESA acquisition contract. Westinghouse Electronic Systems (acquired by Northrop Grumman in 1996) and Hughes Aircraft (acquired by Raytheon in 1997) received contracts for the development of the Multifunction Integrated RF System/Multifunction Array (MIRFS/MFA) in February 1996. Lockheed Martin and Northrop Grumman were selected as the winners of the Joint Strike Fighter competition; The System Development and Demonstration (SDD) contract was announced on 26 October 2001.