During thermal crossover, which sensor is affected most?

• A. EO (DTV)
• B. Infrared (IR)
• C. SWIR
• D. Visible

Answer: (B)

Thermal crossover hinges on how targets are detected when their temperature becomes similar to the surroundings. Infrared sensors rely on emitted thermal radiation from objects. When the target’s temperature matches the ambient environment, its emitted IR radiance becomes almost the same as the background, so the contrast drops and the sensor has a harder time seeing the target. Other sensors depend mostly on reflected illumination rather than on the object’s own emission. Visible and SWIR cameras image by catching reflected light, so they maintain contrast as long as there’s illumination. While SWIR can have some emission, it’s usually dominated by reflected energy, making it less sensitive to the isothermal condition than the infrared band. So the infrared sensor is the one most affected during thermal crossover.