Definition
A datalink service in the United States ADS-B system that translates and rebroadcasts traffic information between aircraft equipped on different ADS-B frequencies. Aircraft in the U.S. transmit ADS-B Out on either 1090 MHz Extended Squitter or the 978 MHz Universal Access Transceiver (UAT). ADS-R, provided by ground stations, takes traffic data from one frequency and rebroadcasts it on the other so aircraft on each frequency can see traffic on the opposite frequency.
Plain English
U.S. aircraft use one of two ADS-B radio frequencies. ADS-R is the ground service that takes traffic from aircraft on one frequency and re-sends it on the other, so everyone can see each other regardless of which frequency they use.
Context Anchor
You may see ADS-R mentioned in ADS-B traffic, cockpit traffic display, and FAA surveillance system discussions.
Derivation
Rebroadcast means to broadcast again. The service receives an ADS-B transmission on one frequency and broadcasts it again on the other, which is exactly what the name describes.
Why Pilots Care
It lets pilots see nearby aircraft even when those aircraft broadcast on a different frequency than the pilot’s receiver, improving traffic awareness and safety.
Analogy
It is like a translator repeating the same message on a second radio channel so people using either channel can understand it.
Intuition Check
Do not read “dependent” as meaning weak or optional. In ADS-R, it means the aircraft’s reported position depends on information from the aircraft’s own navigation equipment.
Example Sentence 1
Because the Cessna had a 978 UAT and the inbound jet was on 1090ES, ADS-R was what allowed each of them to see the other on their traffic displays.
Example Sentence 2
With ADS-R in service the pilot saw the target on the traffic display even though the sending aircraft used a different broadcast frequency.