The S-125 SA-3 GOA medium altitude surface-to-air missile system uses a two-stage, solid-fuel missile built by the Isayev OKB. The S-125 missile includes a large 2.6 second burn-time solid propellant booster with rectangular fins that rotate through 90º at launch. The smaller main stage has an 18.7 second burn-time solid propellant sustainer motor, and has four aft fixed fins and four forward movable control. Following booster jettison the missile is tracked by the system's radar with guidance signals sent to an antenna on the rear fins.
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