Half of the planned radio sites for Automatic Dependent Surveillance-Broadcast (ADS-B) “essential” services have been built under Segment 1 of the FAA contract, which calls for construction of 330 sites by September.

There were 165 radio sites built at this writing, 90 of them operational, according to ADS-B prime contractor ITT Corp. A typical radio site features one omnidirectional Universal Access Transceiver (UAT) antenna and four sectorized 1090ES antennas, supporting a dual-frequency approach to communicating with aircraft.

ADS-B essential services consist of Traffic Information Service-Broadcast (TIS-B) and Flight Information Service-Broadcast (FIS-B) transmissions to properly equipped aircraft.

Twelve ADS-B stations -- nine of which were installed and operational -- will be located on offshore oil platforms in the Gulf of Mexico. Nine terrestrial sites are located around the Gulf. Some of the platform-based ADS-B stations will be collocated with Automated Weather Observing System (AWOS) installations by All Weather Inc. (AWI), of Sacramento, CA.. AWI is a subcontractor to ITT in providing 35 AWOS systems for surface weather measurements on Gulf oil platforms and further systems for Alaska. VHF radio terminals to transmit AWOS data are being installed by FAA.

Also under Segment 1 of the contract, ITT will stand up four sites for “critical services,” the presentation of downlinked ADS-B targets on controller displays, supporting radar-like aircraft separations. Two of those sites -- the Louisville, KY., Terminal Radar Approach Control (Tracon) and Houston Air Route Traffic Control Center (ARTCC), were declared operational by FAA in November and December, respectively. Operational status of third site, at the Philadelphia Tracon, was imminent; the fourth site at Anchorage was due in April.

ITT is expected to provide ADS-B coverage for three types of service volumes: enroute, terminal and surface. Enroute service volumes correspond to the geographic areas managed by ARTCCs in the continental United States; terminal service volumes to Tracons. Surface service volumes will be based at the 35 major airports that either have or will receive Airport Surface Detection Equipment, Model X (ASDE-X) surface traffic management systems.

As of September, ITT plans to complete deployment of ADS-B services for 19 enroute service volumes: Jacksonville, Boston, Juneau, South Alaska, Anchorage-Fairbanks, McGrath, Yukon, Nome, Kotzebue-Northern Alaska, Albuquerque, Seattle, Cleveland, New York, Atlanta, Washington, Los Angeles, Chicago, Oakland and Minneapolis.

Remaining enroute and terminal service volumes will be provisioned in Segment 2 of the contract, extending to 2014.

Bill Carey, editor-in-chief of Avionics magazine, has 25 years of experience as a business, technology and aviation journalist with daily newspapers, newsletters and magazines. He previously served as managing editor of Avionics magazine and as European Bureau Chief for Avionics and Rotor & Wing in London from 1993 to 1995.

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