Auto Dependent Surveillance – Broadcast (ADS-B) is set to become the main aviation surveillance technology worldwide.
Reducing our reliance on radar
Surveillance involves monitoring the relative position of aircraft in flight so that Air Traffic Control can ensure the right amount of separation to prevent collisions.
The transition to satellite-based surveillance, which involves the use of Automatic Dependent Surveillance Broadcast (ADS-B) technology, will require equipment upgrades for aircraft and Air Traffic Control.
To make sure these changes happen smoothly, New Southern Sky will provide operators advance notice of new equipage requirements and guidance to help them make the right purchasing decisions.
We’ll also be making sure that implementation of ADS-B aligns with the timeline for the introduction of Performance Based Navigation (PBN), which is another key and interdependent element of our programme.
Automatic Dependent Surveillance Broadcast Technology (ADS-B)
Since the mid-20th Century, New Zealand Air Traffic Management has relied on ground-based radar for surveillance. Replacing this technology with a modern, satellite-based system is a key part of New Southern Sky and is the system recommended by ICAO to replace ageing radar technology.
Using a combination of satellites, transponders and Global Navigation Satellite System (GNSS) receivers, ADS-B involves aircraft self-reporting their GNSS derived position. It is compatible with other surveillance systems and will enable increased air traffic system capacity by improving positional accuracy on air traffic control displays.
This means Air Traffic Control, a service provided in New Zealand by Airways New Zealand, can determine a more accurate position, enabling a more efficient traffic flow and improved safety. Airways is playing a leading role in the roll-out of ADS-B.
New Southern Sky proposes that ADS-B will be introduced in a phased way. By the end of 2018, all aircraft flying above Flight Level 245 will need to have operational ADS-B. By the end of 2021, all aircraft flying in controlled airspace will require operational ADS-B. New Zealand will use the 1090 MHz extended squitter (ES) ADS-B system. The Universal Access Transceiver system (UAT) used in the US will not be implemented here. It is important that operators don’t buy or fit UAT equipment because it is not compatible with the 1090 MHz system.
Primary surveillance radar (PSR) transmits a radio signal that is reflected back to the radar by aircraft. The range and bearing of each aircraft detected is presented to the air traffic controller. PSR cannot identify aircraft, and does not rely on aircraft systems.
Secondary surveillance radar (SSR) not only detects and measures the range and bearing of aircraft, but also requests additional information from the aircraft itself, such as its identity and altitude.
Secondary surveillance radar relies on aircraft equipped with a mode A/C transponder, which replies to each interrogation signal by transmitting a response containing encoded identity and altitude data. Transponders are mandatory in New Zealand controlled airspace.
Multilateration (MLAT) is a more recent ground-based surveillance technique. A number of ground stations interrogate and receive replies from aircraft SSR transponders. The system calculates the position of the aircraft using the time difference between the arrival of a reply at four or more ground stations. Multilateration targets are typically updated once per second, compared with five-second intervals for radar targets. MLAT systems that cover broader areas are known as Wide Area Multilateration (WAM).
Automatic dependent surveillance-broadcast (ADS-B) transponders broadcast an aircraft’s position, altitude, velocity and other aircraft-derived data once or twice per second. Data received by ground stations is fed to air traffic control displays. This system provides controllers with richer and more accurate information, enabling more efficient traffic flow and improved safety. This system is known as ADS-B OUT.
Aircraft equipped with ADS-B IN can also receive ADS-B transmissions from other aircraft. ADS-B IN is expected to eventually replace the existing aircraft collision avoidance systems. Trials using ADS-B IN for specific types of self-separation, such as in-trail climb, are being conducted. Self-separation is unlikely to be adopted in New Zealand domestic airspace for many years.
Aviation surveillance today
In New Zealand, Airways provides surveillance coverage for most controlled en-route and terminal airspace using Monopulse Secondary Surveillance Radar (MSSR), with local areas of primary surveillance radar and multilateration.
- In the Auckland Oceanic Flight Information Region, communication is through Automatic Dependent Surveillance Contract (ADS-C).
- Surveillance contract (ADS-C4), Controller Pilot Data Link Communications (CPDLC) position reports, Flight Management Computer Waypoint Position.
- Reporting (FMC WPR)5 via data-link, and voice position reporting via HF radio and, in special circumstances, via satellite (SATVOICE).
- Multilateration is used for surface movement surveillance at Auckland International Airport.
- Wide-area multilateration coverage of the Queenstown area is being extended to cover most of Otago and Southland.