m (10.3 ft) long, weigh 126 kg (278 lb) and use command guidance. There is also a backup low-light optical tracking system for heavy ECM environments. The latest 9M33M3 missiles have an increased total weight of 170 kg (375 lb) in order to provide the extended range coverage and larger warhead. Propulsion is provided by a dual-thrust solid fuel rocket motor. Both versions feature a missile speed of around Mach 2.4 (peaking at around Mach 3) for a maximum target engagement speed of around Mach 1.4 for the original missile and Mach 1.6 for the M2\M3 missiles. The warhead for the initial and M2 versions weighs 19 kg (42 pounds), increased to 40 kg (88 lb) in the M3 version to improve performance against helicopters. All versions have impact and proximity fuzes. There have been unconfirmed reports of other possible versions of the missile with both infrared and semi-active radar terminal homing seekers. Each TELAR is able to launch and guide two missiles against one target simultaneously. Kill probability is quoted as being 0.35–0.85 for the Osa and 0.55–0.85 for the Osa-AK and Osa-AKM (presumably depending upon target aspect, speed, maneuverability and radar cross section). Reaction time (from target detection to launch) is around 26 seconds. Time to prepare for engagements from being in transit is around 4 minutes and missile reloading takes around 5 minutes. Each battery of four TELARs is usually accompanied by two reload vehicles carrying 18 missiles in sets of three, with a crane mounted on the reload vehicles to assist in moving the missiles. When launched the booster motor burns for two seconds, this permits the radar to gather and control it at very short ranges (about 1.6 km). The sustainer motor has a 15-second burn, bringing the missile to a top speed of about Mach 2. Once launched the missile is command-guided for the whole flight, and the warhead is detonated by its proximity fuze or possible command. The warhead is said to have a lethal radius of 5 m at low altitude against an F-4 Phantom size target. Radars 1S51M3 ("Land Roll") – C band target acquisition radar, H band conical scan target tracking radar and two J band pulse mode fire control radars (range 35 km/22 miles for acquisition, 30 km/19 miles for tracking and 25 km/16 miles for guidance). Mounted on the TELAR. P-40 ("Long Track") – E band early warning