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This article is about the AI. For radar, see Doppler radar.
FoRInvasion - Doppler.png
Biographical information

Began service:

Before 2552

Ended service:



Male programming

Political and military information


United Nations Space Command,


Space Dock Quartermaster

Service number:



Doppler (AI Serial Number: AI-8575), was a UNSC artificial intelligence. In 2552, he was the Space Dock Quartermaster for Gamma Station in orbit of Reach.


On August 29, just prior to the Fall of Reach, Doppler hailed the UNSC Circumference as it approached the station. However, due to security regarding Operation: HYPODERMIC, which the prowler was a part of, Doppler was told by an ONI official to access Office of Naval Intelligence Instruction ONI-Seven-Eta. The data temporarily scrambled Doppler's memory, causing him to forget about the prowler and about the official who tricked him.[1] The prowler was then isolated from the REACH DOC NET, preventing Doppler from accessing the ship should he discover it again.

As the battle began, though, Doppler discovered Covenant intrusion software that was penetrating the DOC NET, against which his own counter-intrusion measures were ineffective. This software had also discovered the location of the Circumference, the NAV data of which Doppler was unable to delete. The AI sent a distress signal that reached the UNSC Pillar of Autumn alerting them that the prowler had failed to delete its NAV database as per the Cole Protocol.[2] When the SPARTAN-II team led by John-117 arrived at Reach Station Gamma, they tried to contact Doppler but were unsuccessful, indicating that he had self-destructed in accordance with the Cole Protocol.


Doppler took the appearance of an English scholar, dressed in a red jacket, a bowtie, and spectacles. He may have been named after the Austrian physicist Christian Doppler, who discovered the wave behavior known as the Doppler effect.


List of appearances[edit]


  1. ^ Halo: Fall of Reach - Invasion, Issue 1
  2. ^ Halo: The Fall of Reach, page 302