From Halopedia, the Halo wiki
The Scorpion missile is a type of explosive ordnance used by the United Nations Space Command. These missiles are commonly mounted on the UNSC's AV-19 SkyHawk jets and occasionally GA-TL1 Longswords. They are equipped with motion tracking systems and proximity detonators that greatly increase their chances of crippling or destroying a target. They are also able to attain high cruising speeds and are very accurate, thanks to their advanced guidance systems, which quickly locate and lock onto a target.
During the Fall of Reach, Colonel James Ackerson dispatched a SkyHawk fighter to attack Spartan John-117 and the AI Cortana while the pair were on a testing run, in an effort to kill these threats to Ackerson's success. The SkyHawk launched a Scorpion missile at the Spartan, but it failed to kill him, as John-117 literally swatted the missile away with his energy shielded arm, a unique improvisation on the part of the Master Chief, made possible only by the aid of Cortana.
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