Definition
Fusion is a surveillance data processing method that combines target reports from multiple sources -- such as primary radar, secondary radar, and Automatic Dependent Surveillance-Broadcast (ADS-B) -- into a single, integrated track for each aircraft displayed to the controller. The number of stars shown next to the word Fusion in the Pilot/Controller Glossary indicates the level of detail or category of the entry within the source document.
Plain English
Fusion is the way air traffic control systems blend information from radar and ADS-B together so each aircraft shows up as one clean target on the controller's screen, instead of multiple overlapping ones from different sensors.
Context Anchor
Seen in air traffic control discussions involving STARS, the Standard Terminal Automation Replacement System used by controllers in terminal radar facilities.
Derivation
From Latin 'fusio,' meaning 'a pouring together' or 'melting.' The word captures the idea of separate streams of information being merged into a single combined stream -- which is exactly what the system does with surveillance data from different sensors.
Why Pilots Care
Under fusion, controllers see a single track for your aircraft built from the best available data, which can improve accuracy and coverage compared with older single-source radar displays. It also means ADS-B-equipped aircraft may be tracked in areas where radar coverage alone would be limited.
Grounding Statement
If two sensors report the same airplane, fusion helps the ATC system show one best position instead of cluttering the display with separate tracks.
Intuition Check
Fusion does not mean nuclear fusion or anything related to stars in the sky here. In this term, STARS is the name of an air traffic control display system, and fusion means combining surveillance information into one track.
Example Sentence 1
The facility transitioned to a fusion display, so each aircraft now appears as one merged target rather than separate radar and ADS-B returns.
Example Sentence 2
Fusion of radar and ADS-B data maintained continuous tracking even when one sensor momentarily lost the aircraft.