What role does the atmosphere play in military infrared applications?

The atmosphere plays a crucial role in military infrared applications primarily by transmitting infrared radiation. This transmission allows for the detection and observation of thermal signatures from various objects, such as vehicles or personnel, which is essential for reconnaissance and targeting. Infrared sensors rely on the ability of the atmosphere to allow infrared radiation to pass through, ensuring that the emitted heat from objects is detectable by these sensors.

By effectively transmitting infrared radiation, the atmosphere enables various applications in military settings, such as night vision systems, target acquisition, and surveillance operations. This capability is vital for enhancing situational awareness without compromising the stealth of deployed forces. The other options do not accurately describe the atmospheric behavior relevant to military infrared applications, as the atmosphere does not completely absorb infrared radiation nor does it reflect or filter it in significant measure compared to its transmission characteristics.