limited shelf life due to argon leakage. The IFF system receives power from a rechargeable battery which is part of the IFF interrogator box which plugs into the base of the gripstock's pistol grip. Guidance to the target is initially through proportional navigation, then switches to another mode that directs the missile towards the target airframe instead of its exhaust plume. There are three main variants in use: the Stinger Basic, Stinger-Passive Optical Seeker Technique (POST), and Stinger-Reprogrammable Microprocessor (RMP). These correspond to the FIM-92A, FIM-92B, and FIM-92C and later variants respectively. The POST and RMP variants have a dual-detector seeker: IR and UV. This allows it to distinguish targets from countermeasures much better than the Redeye and FIM-92A, which have IR-only. While modern flares can have an IR signature that is closely matched to the launching aircraft's engine exhaust, there is a readily distinguishable difference in UV signature between flares and jet engines. The Stinger-RMP is so-called because of its ability to load a new set of software via ROM chip inserted in the grip at the depot. If this download to the missile fails during power-up, basic functionality runs off the onboard ROM. The four-processor RMP has 4 KB of RAM for each processor. Since the downloaded code runs from RAM, there is little space to spare, particularly for processors dedicated to seeker input processing and target analysis. History The missile began as a program by General Dynamics to produce an improved variant of their 1967 FIM-43 Redeye. Production of the Redeye ran from 1969 to 1982, with a total production of around 85,000 missiles. The program was accepted for further development as Redeye II by the U.S. Army in 1971 and designated FIM-92; the Stinger appellation was chosen in 1972. Because of technical difficulties that dogged testing, the first shoulder launch was not until mid-1975. Production of the FIM-92A began in 1978. An improved Stinger with a new seeker, the FIM-92B, was produced from 1983 alongside the FIM-92A. Production of both the A and B types ended in 1987 with around 16,000 missiles produced. The replacement FIM-92C began development in 1984, and production began in 1987. The first examples were delivered to front-line units in 1989. C-type missiles were fitted with a reprogrammable microprocessor, allowing for incremental firmware updates. Later missiles designated D received improvements to improve their ability to defeat countermeasures, and later upgrades to the