Story ID: 
Sensis considers expanding ADS-B
By: Bernard Fitzsimons
Caption: Sensis is building on its experience of automatic dependent surveillance-broadcast (ADS-B) in the FAA-sponsored Capstone trials in Alaska and the increasin
Word Count: 587
Sensis is building on its experience of automatic dependent surveillance-broadcast (ADS-B) in the FAA-sponsored Capstone trials in Alaska and the increasing use of its multilateration technology with the development of a 1,090-MHz receiver that is under consideration for deployment on the U.S. East Coast and preparations to deploy a multilateration system at Juneau, Alaska.
The Capstone system comprises 75 ground-based transceivers supporting the universal access transceiver datalink used by general aviation aircraft and 15 supporting air transport-standard 1090 extended squitter. Ken Tollstam, vice president of ATS sales and marketing, said the advantages ADS-B promises include three-nm separation en route, closer spacing on the approach and the ability to see other equipped aircraft, leading ultimately to a sense-and-avoid equivalent of see-and-avoid.
Making additional progress with ADS-B, Tollstam said, requires equipped aircraft in the air and system integration on the ground. He explained, “It’s no longer a technology issue. We have the equipment, but it’s a dependent technology. You must have the avionics to provide surveillance equivalent to today’s radar, and the majority of aircraft must be equipped, so there’s something of a stand-off. The airlines will equip only when there’s a benefit, and you can have the benefit only once the system is in place.”
For the time being, he said, U.S. aircraft have 1,090-MHz TCAS transponders but not mode-S. Airbus is installing mode-S on all its new airplanes, while Boeing is installing the wiring but leaving it to operators to buy the box. Regional jets are generally not equipped, but a significant proportion of new business jets are.
Operationally, trials in Alaska and Australia have shown the possibility of reducing separation and improving safety for operators and savings on surveillance technology for air navigation service providers (ANSPs). “Those are pockets where there is a specific need and the ANSPs are arranging for aircraft equipage,” Tollstam added. 
“Regional carriers operating in mountainous airspace could be another pocket.”One such pocket is Austria’s Inn Valley, where Innsbruck Airport has begun live operational use of a Sensis-supplied multistatic dependent surveillance (MDS) system. MDS uses multiple receivers to capture transponder pulses from aircraft and calculate their position and identity. The system gives air traffic controllers a surveillance picture with an accuracy of 23 feet on the ground and 200 feet in the air.
Mountain ranges towering more than 9,000 feet above the airport to the north and south make traditional radar surveillance financially and logistically prohibitive and force the airport to route arriving and departing traffic in the same direction. The Sensis MDS system uses low-cost, non-rotating sensors and, according to Austro Control COO Johann Zemsky, enables controllers to track aircraft from the gate to a range of 20 miles out.
The MDS technology is being deployed at other locations, including Frankfurt International airport and over the Gulf of Mexico. The ground stations can provide ADS-B positions as well as inputs to the multilateration system.
Installation of the equipment at Juneau is due to start in the spring and become operational next year after flight trials later this year. 
Implementation of ADS-B may follow a pattern similar to that of ILS, Tollstam speculated. He explained, “We are on the cusp of a shift in technology that depends heavily on changing the concepts of operations to produce real user benefits.” Applications specific to the business aviation world could include airports such as Jackson Hole, Wyo., where there is currently no surveillance.