2K11 Krug Missile System

The 2K11 Krug (Russian: 2К11 «Круг»; English: circle) is a Soviet and now Russian medium-range, medium-to-high altitude surface-to-air missile (SAM) system. The system was designed by NPO Novator and produced by Kalinin Machine Building Plant. Its GRAU designation is "2K11." Its NATO reporting name is SA-4 Ganef, after a word of Yiddish origin meaning "thief" or "rascal".

The missiles are launched with the aid of four solid fuel rocket motors inside boosters attached to the outside of the missile. Once they have burned and the missile is aloft, a liquid-fuelled ramjet sustainer engine is ignited. It reaches speeds of up to Mach 4 and has an effective range of 50–55 km (31–34 miles) depending upon the version. It carries a 135 kg (300 lb) fragmentation warhead. Possible engagement altitudes range from 100 m to 27 km (330-88,500 feet). The 3M8 missile was designed and produced by NPO Novator.

The TEL vehicles are tracked based on a GM-123 chassis and carry two missiles each on an elevating turntable for up to 360-degree rotation and 70-degree elevation. The two primary versions of the missile in service are the 9M8M1 (former designation 3M8M1) (2K11M "Krug-M") and 9M8M2 (former designation 3M8M2) (2K11M2/3 "Krug-M1"), both of which are believed to be known to the US DoD as SA-4B. The original 9M8 (former designation 3M8) (SA-4A) was first introduced into service in 1965 and followed by the upgraded 9M8M (2K11A "Krug-A") in 1967 before the 9M8M1 in 1971 and the 9M8M2 in 1973. The 9M8M2 actually has a lower maximum engagement altitude and shorter range in exchange for better performance in engaging aircraft close to the battery. 

The Krug had several features that improved the survivability of the radar against anti-radiation missiles. In PI mode (ПИ) the system only briefly illuminated the target and the computer calculated it's prolonged path based on data received from early warning radars. After a longer passive period the main radar illuminated the calculated flight direction of the target for a few seconds and recalculate path of the target if necessary (if the distance between the calculated track and the actual position is greater than 7 km). As a result, the system emitted detectable signals only for a few seconds in every few minutes, making it difficult to jam or launch an anti-radar missile against Krug. The system was also able to tracking the target in full-passive automated PNS (ПHC) mode based on the data provided by "Long Track" mobile EWR via radio datalink. In this mode it was almost impossible to detect the Krug system until the moment of missile launch, because Krug did not emit radiation at all. More details