Derived from the MiG-25 "Foxbat", the MiG-31 provides enhanced capabilities against low-level threats, and was intended to Guard the Soviet UnionÆs long borders. Important changes include a strengthened airframe (allowing supersonic performance at low altitude) and an electronically scanned phased array radar (the first of its type in service, allowing the MiG-31 to track 10 targets simultaneously in excess of 200 km). The FoxhoundÆs primary armament is the AA-9 "Amos" long range air-to-air missile.%n