A new surveillance technology called the Wide-Area Augmentation System (WAM) is now allowing air traffic controllers to track aircraft along the difficult approach to Juneau – a mountainous area where radar coverage isn’t possible.
“This technology will allow more aircraft to fly into Juneau and it will give air traffic controllers the tools they need to safely and efficiently handle these flights,” said FAA Administrator Randy Babbitt.
Air traffic controllers can now see aircraft approaching Juneau, something that wasn’t possible before WAM because of the rugged terrain surrounding the city. The mountains make radar coverage impossible since radar signals cannot pass through solid objects. Without radar coverage, controllers had to separate aircraft approaching Juneau by large distances in order to provide the appropriate safety margins. Air traffic controllers are now able to safely decrease the separation between them to five nautical miles.
WAM is comprised of a network of small sensors deployed around Juneau. The sensors send out signals that are received and sent back by aircraft transponders. No other aircraft equipment is required. The system triangulates the returning signals to determine the precise location of each aircraft. Controllers are able to see those aircraft on their screens as if they were radar targets.
WAM is being used in the near term while the agency rolls out Automatic Dependent Surveillance – Broadcast (ADS-B), the satellite-based surveillance system that will be deployed nationwide in 2013. WAM will then serve as a backup to ADS-B in the event of a GPS outage and provide an additional source of traffic broadcast to properly equipped aircraft. A WAM system is also operating in Colorado. (See SAJ Aug/Sept 2009 issue.)