Anti-radiation missile of radiation and explode when they got near it. SAM operators learned to turn their radar off when an ARM was fired at them, then turn it back on later, greatly reducing the missile's effectiveness. This led to the development of more advanced ARMs such as the AGM-78 Standard ARM and AGM-88 HARM missiles, which have inertial guidance systems (INS) built-in. This allows them to remember the radar's direction if it is turned off and continue to fly towards it. ARMs are less likely to hit the radar if the radar is turned off shortly after the missile is launched,
Sound speed gradient Sound speed gradient In acoustics, the sound speed gradient is the rate of change of the speed of sound with distance, for example with depth in the ocean, or height in the Earth's atmosphere. A sound speed gradient leads to refraction of sound wavefronts in the direction of lower sound speed, causing the sound rays to follow a curved path. The radius of curvature of the sound path is inversely proportional to the gradient. When the sun warms the Earth's surface, there is a negative temperature gradient in atmosphere. The speed of sound decreases with decreasing temperature, so this also