ARGUS

The ARGUS device was piece of bomb detection equipment used by the UNSC. They were micro laser spectrometers designed to 'sniff' out chemicals used in explosives in the air and to alert UNSC personnel of these dangerous explosives if found. It was mainly used against the Insurrectionist terrorist bombers, who used simple countermeasures to easily fool the devices. They mixed the Explosive compounds into non-reactive substances, such as a bar of soap or the rubber of a tire. Although the UNSC was able to add these mixtures into it's database after they were used, it was rare to ever catch something dangerous like this beforehand. The larger ARGUS detectors were deployed at major transportation hubs to limit the movement of bombs, and smaller tactical versions were employed by Marines during raids.They can be utilized in both airborne drones and hand held variants. .

History
In 2524, the ARGUS device was utilized successfully in Operation: TREBUCHET after a raid on an Insurrectionist cell operating in Tribute to locate a tanker rigged to explode, but the UNSC forces were unable to successfully stop it's owners before they managed to detonate it near a local restaurant, killing three marines and an unknown number of civilians.

The ARGUS device is also not infallible; Avery J. Johnson was witness to at least one incident where an innocent civilian was killed due to suspected explosive detected in his vehicle. These suspicions proved to be false.

Historical Reference
"ARGUS" is most likely used as a reference to Argus from Greek mythology. In the myth, Argus was a guardian with one thousand eyes (The ARGUS drones supposedly also had this "all-seeing" ability to detect bombs).