be able to fire upon the target without having to turn its radar sets on at all. Otherwise, the fighter can turn the radar on and achieve a lock immediately before firing if desired. The fighter could also close to within cannon range and engage that way. Whether or not they use their radar, the IRST system can still allow them to launch a surprise attack. An IRST system may also have a regular magnified optical sight slaved to it, to help the IRST-equipped aircraft identify the target at long range. As opposed to an ordinary forward looking infrared system, an IRST system will actually scan the space around the aircraft similarly to the way in which mechanically (or even electronically) steered radars work. The exception to the scanning technique is the F-35's DAS, which stares in all directions simultaneously, and automatically detects and declares aircraft and missiles in all directions, without a limit to the number of targets simultaneously tracked. When they find one or more potential targets they will alert the pilot(s) and display the location of each target relative to the aircraft on a screen, much like a radar. Again similarly to the way a radar works, the operator can tell the IRST to track a particular target of interest, once it has been identified, or scan in a particular direction if a target is believed to be there (for example, because of an advisory from AWACS or another aircraft). IRST systems can incorporate laser rangefinders in order to provide full fire-control solutions for cannon fire or launching missiles (Optronique secteur frontal). The combination of an atmospheric propagation model, the apparent surface of the target, and target motion analysis (TMA) IRST can calculate the range. The United States Air Force is currently seeking an IRST system for its F-15 aircraft. List of modern IRST systems The best known modern IRST systems are: Chengdu J-10B/C Shenyang J-11/15/16 Chengdu J-20 (EORD-31 with 360 degree IRST coverage named Distributed aperture system) Shenyang FC-31 (Electro-optical targeting system) Classe Orizzonte frigate (Safran Vampir MB) ROKS Dokdo amphibious assault ship (Safran Vampir MB) Sejong the Great-class destroyer (Safran Vampir NG) Anzac-class frigate (Safran Vampir NG) Canberra-class landing helicopter dock (Safran Vampir NG) Hobart-class destroyer (Safran Vampir NG) Cassard-class frigate (Safran EOMS-NG) Floréal-class frigate (Safran EOMS-NG) Horizon-class frigate (Safran EOMS-NG) Baynunah-class corvette (Safran EOMS-NG) Gowind-class OPV for Argentina (Safran EOMS-NG) Aircraft carrier Charles de