ARGUS
From Halopedia, the Halo wiki
The ARGUS device was piece of bomb detection equipment used by the UNSC. It was mainly used against the Innsurrectionist terroist bombers, thoguh they often fooled them by coating they bombs in normal chemicals. The larger ARGUS detectors were deployed at major transportation hubs to limit the moving of bombs, and small tactical versions, were employed by Marines during raids. They were micro laser spectrometers designed to 'sniff' out chemicals used in explosives in the air. They were used on the ARGUS Drone.