Tag Archives: Collision Avoidance

About ADS-B Lite

Automatic Dependent Surveillance – Broadcast (ADS-B) was conceived as an alternative to radar for tracking the location and movement of air traffic. Near airports Airborne Surveillance Radars (ASRs) scan the skies for aircraft. Identification Friend or Foe (IFF) interrogates the aircraft and a beacon on the aircraft called a transponder encodes a reply identifying itself to the radar operator.

ASR with IFF

ASR with IFF

Mode C transponders encode altitude and mode S transponders reply only when called. This helps in rejecting false replies unsynchronized in time (FRUIT). This is what a radar scope looks like before FRUIT has been removed.fruit_ppi

ADS-B broadcasts GPS location data twice per second on the radar’s 1090 MHz frequency in a reserved part of a transponder broadcast called Extended Squitter (ADS-B 1090 MHz ES). Since this location data is more accurate and more frequent than radar, the FAA has mandated that all aircraft operating within controlled airspace (altitudes above 18000 feet and close proximity to airports with control towers) have ADS-B by the year 2020. The FAA has also been directed to share the national airspace with UAVs. Their response to date has been to propose very restrictive rules that would make many commercial uses of drones unfeasible.

What if air traffic controllers could use voice commands to direct UAV use of controlled airspace, monitor compliance with ADS-B 1090 MHz knowing that the UAV would stay away from restricted airspace (geo-fencing), avoid collisions with structures and terrain and most importantly automatically avoid collisions with other ADS-B equipped manned or unmanned aircraft anywhere in the national airspace? Would that open the skies to commercially viable uses of UAVs? That is my vision for the ADS-B Lite project. It also overlaps NASA’s vision of an Unmanned Autonomous System (UAS) Traffic Management (UTM) system.