Automatic Dependent Surveillance-Broadcast
Categories: Aircraft stubs | Avionics
Automatic Dependent Surveillance-Broadcast (also called ADS-B) is a system by which airplanes constantly broadcast their current position and altitude, category of aircraft, airspeed, identification, and whether the aircraft is turning, climbing or descending over a dedicated radio datalink. This functionality is known as "ADS-B out" and is the basic level of ADS-B functionality.
The ADS-B system was developed in the 1990s. It relies on data from the Global Positioning System, or any navigation system that provides an equivalent or better service. The maximum range of the system is line-of-sight, typically less than 200 nautical miles (370 km).
The ADS-B transmissions are received by air traffic control stations, and all other ADS-B equipped aircraft within reception range. Reception by aircraft of ADS-B data is known as "ADS-B in".
The initial use of ADS-B is expected to be by air traffic control and for surveillance purposes and for enhancing pilot situational awareness. ADS-B is lower cost than conventional radar and permits higher quality surveillance of airborne and surface movements. ADS-B is effective in remote areas or in mountainous terrain where there is no radar coverage, or where radar coverage is limited. The outback of Australia is one such area where ADS-B will provide surveillance where previously none existed. ADS-B also enhances surveillance on the airport surface, so it can also be used to monitor traffic on the taxiways and runways of an airport.
ADS-B equipped aircraft may also have a display unit in the cockpit picturing surrounding air traffic from ADS-B data (ADS-B in) and TIS-B (Traffic Information Service-Broadcast) data derived from air traffic radar. Both Pilots and air traffic controllers will then be able to "see" the positions of air traffic in the vicinity of the aircraft, and this may be used to provide an ASAS (Airborne Separation Assurance System).
Airborne Collision Avoidance Systems may also make use of "ADS-B in", supplementing the existing TCAS collision avoidance system.
Airbus and Boeing are now expected to include ADS-B out (i.e. the transmitter of information) as standard on new-build aircraft from 2005 onwards. This is in part due to the European requirements for Mode S Elementary Surveillance (which uses 1090MHz Extended Squitter), and some common functionality with ADS-B out.
The currently (2005) used data links for ADS-B are: (i) 1090 MHz (the same frequency the transponder replies to secondary surveillance radar interrogations), (ii) 978 MHz (Universal Access Transceiver), and (iii) VHF Digital link mode -4 (VDL Mode 4). 1090 MHz Extended Squitter is the globally agreed standard for ADS-B for air carrier aircraft with existing Mode S transponders. The 1090ES has limited capacity and is, therefore, limited to supporting just ADS-B. The UAT has been used operationally in the United States since 1999 and supports air traffic separation services in Alaska. The UAT provides significant communications bandwidth and in addition to ADS-B, provides no-fee traffic (TIS-B) and weather (FIS-B) uplink services (see FAA's Safe Flight 21 link below). The VDL-4 has been used in several demonstration programs throughout Europe.
Projects and Trials
The FAA has been developing ADS-B since the early 1990s and has transitioned its demonstration programs into operational systems.
- Safe Flight 21/Capstone: 1999 – 2002, followed by Capstone II 2003 – 2006
- Safe Flight 21 East Coast Deployment of Broadcast Services 2003 - present
ADS-B initial projects and trials in Europe first started around 1995. Standardisation activities started at a similar time and have grown in intensity since. Both areas are now seeing a significant amount of work.
It is expected that implementations of pre-operational and then operational systems will occur in future years (for example, the SEAP project – South European ADS-B Project – and NUP II project are both looking at pre-operational trials in 2005).
Dates of some example ADS-B projects and trials/evaluations are:
- NEAN: January 1996 – December 1999
- OpEval-1 (Operational Evaluation-1 at Wilmington, Ohio) - July 1999
- NEAP: September 1997 – September 1998
- OpEval-2 (Louisville, Kentucky) - October 2000
- NUP and NUP II: 1998 – 2002, followed by NUP II and soon NUP II+
- TESIS (Test and Evaluation of Surveillance Information System) Memphis, Tennessee, July 2002
- ADS-MEDUP: 2000 – 2004
- FARAWAY: 1996 – mid 1998, followed by FARAWAY II: June 1998 – 2000
- Eurocontrol ADS Programme: 1997 - 2004
- Eurocontrol CASCADE Programme: 2004 - present