established Danger Zone. The boundaries of the Danger Zone were extended considerably following BRAVO, The Air Control System for aircraft used on CASTLE was of an advanced nature. It proved considerably superior to the systems used on previous operations.* Prior to CASTLE there had never been a positive Air Control System in the Pacific Proving Ground during a shot series. The Air Opera- tions Center (AOC) and the USS ESTES exercised positive control of all aircraft in the Proving Ground and at all times knew the location of every participating aircraft. This was made possible by the installation of IFF scopes in the Air Operations Center and on the USS ESTES. This in- ; stallation gave the control centers (the AOC and the Combat Information Center on the USS ESTES) the capability of directing the aircraft and of ascertaining their location in case of any emergency. This new system will be adapted for use on all future tests, both overseas and continental. (For additional information on this system see the FinalReport of the Commander, Air Task Group 7.4, Operation CASTLE.) Participation of the Air Force in Operation CASTLEwas of great benefit, particularly in the field of increased knowledge of weapon effects on aircraft. * Details of this knowledge will be found in the text. Task Group 7.4 personnel affiliated with the Air Control System were generally in agreement that the only possible improvement to the System used on CASTLE would be the addition of a GCI (Ground Controlled Intercept) . mn a