A defence used by merchant ships against German aircraft was a battery of rockets carrying aerial mines. These consisted of a parachute with a warhead below, beneath which was a long cable with a drogue chute attached. When a plane encountered the cable the warhead detached from its chute and began to fall. The pull of the drogue chute ensured that the warhead hit the aircraft rather than falling behind it. Aerial mines could be deployed by artillery as a hazard to attack helicopters. Fitting a hydrogen balloon in place of the upper parachute would keep the mine aloft longer. Mines might also be deployed by aircraft in combat.
Update. Since July 1944 many Soviet bombers were equipped with special package DAG-10 for 10 2-kg air grenades AG-2 (those spherical grenades with parachute exploded in 3-4 s after release and destroyed attacking fighters by 130 fragments (weight 3-80 g) within a radius of 10-50 m). Also DAG-5 were used for 5 air grenades. In principle AG-1/AG-2 air grenades were developed for the rear defense of battle planes IL-2 (first single-seat modifications without gunner) in 1941. Used quite widely since the middle 1942. DAG means Derzhatel' Aviatsionnyh Granat = Rack for Air Grenades
One interesting detail concerning the Pe-2 was its use of the AG-2 aerial grenade. A store of them were carried in the tail, to be ejected and explode about 80 meters (260 feet) behind the aircraft and scatter shrapnel in the path of a pursuer. The Soviets claimed that about 1 out of every 5 aerial kills obtained by the Pe-2 were obtained with this weapon.