From SKYbrary Wiki
The term "squitter" refers to a random broadcast of data occurring either intentionally or in response to noise.
Mode-S transponders automatically send periodic burst transmissions called "squitters". These transmissions are self generated and are not in response to interrogations from a secondary surveillance radar (SSR) system. The information sent in these burst transmission serves several purposes including:
- Airborne Collision Avoidance System (ACAS) - Squitter information includes aircraft location and vertical speed. This information is used by ACAS systems on other aircraft to identify potential conflicts.
- Automatic Dependent Surveillance Broadcast (ADS-B) - An extended squitter is a message or series of messages which broadcast an aircraft's identification, GPS position, projected aircraft trajectory and navigation system status to allow controllers to accurately track the aircraft.