Definition
A datalink service provided by FAA ground stations that retransmits ADS-B position reports between aircraft equipped on different ADS-B frequencies (978 MHz UAT and 1090 MHz Extended Squitter), so that suitably equipped aircraft can see each other in the cockpit traffic display regardless of which frequency they are broadcasting on.
Plain English
ADS-B aircraft broadcast their position on one of two radio frequencies. ADS-R is a ground service that listens on both frequencies and rebroadcasts the traffic so that aircraft on the other frequency can also receive it. Without this rebroadcast, aircraft using different frequencies would not see each other on their traffic displays.
Context Anchor
Seen in traffic display, ADS-B, and equipment discussions when explaining how traffic information can be shared between aircraft using different broadcast formats.
Derivation
The name describes the service step by step. Automatic: the aircraft sends its position without the pilot doing anything. Dependent: the position depends on the aircraft's own GPS, not on a ground radar measuring it. Surveillance: tracking aircraft for traffic and ATC purposes. Rebroadcast: a ground station receives the signal and sends it out again on the other frequency.
Why Pilots Care
It extends the range of traffic awareness by letting aircraft on UAT and 1090ES frequencies see each other through ground rebroadcast.
Intuition Check
Do not read “dependent” as meaning weak or unreliable. Here it means the system depends on the aircraft’s own reported position information. Do not read “rebroadcast” as aircraft repeating each other directly. In this term, the ground system receives the information and sends it out again.
Example Sentence 1
Thanks to ADS-R, the 1090 MHz traffic in the area showed up on our 978 UAT traffic display.
Example Sentence 2
Before takeoff the pilot checked the ADS-B coverage map to verify Automatic Dependent Surveillance Rebroadcast service was available along the route.