From Halopedia, the Halo wiki
ARGUS drones are small, disc-shaped, one-meter wide unmanned aerial vehicles equipped with ARGUS detection systems, which stay aloft by a single shrouded rotor. They are also equipped with targeting computers and one or more Lancet micro-missiles. Their function was to detect and, if possible, destroy explosives on motorways and in buildings. ARGUS drones are not infallible despite their widespread use, having wrongly identified explosives on an innocent civilian on at least one occasion.
Argus is a giant in Greek mythology who is said to have 100 eyes.
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