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Surveillance at Colorado mountain airports

The ski industry represents a large source of annual revenue for the State of Colorado, and a sizable percentage of skiers arrive at their destinations by air. During ski season and, in particular, periods of Instrument Meteorological Conditions (IMC), Ski Country Airports experience delays, diversions and denied service for both General Aviation and air carriers. For this reason, the Colorado Department of Transportation (CDOT) became interested in seeking ways to enhance the efficiency and capacity of these airports. Lack of radar coverage below 9,000 to 10,000 feet MSL has been one of the significant factors contributing to reduction in capacity at mountain airports during IMC. CDOT's Division of Aeronautics met with the FAA (ATO-T and ATO- E) in an effort to develop a solution to the capacity issue. It was quickly determined that due to the low operational numbers at airports serving ski communities, a sufficient benefit/cost ratio did not exist to justify FAA funding of a radar solution. Therefore, the State of Colorado made the unprecedented decision to fund the project. In 2005, the Colorado Division of Aeronautics requested the FAA to join it in conducting a feasibility study to determine an optimal solution to the limited surveillance in the Colorado mountains. The Division of Aeronautics made the decision to require the system to support existing Mode A/C, S and Mode S 1090 Extended Squitter (ES) aircraft transponder equipage. This constraint narrowed the possible solutions to legacy secondary radars and Wide Area Multilateration (WAM), a component of ASDE-X. The line-of-sight issue created by the mountainous terrain at these airports resulted in imposition of the additional constraint that the system be expandable and scalable. This last condition further limited the solution set to a multi- sensor distributed surveillance system. Of the two, WAM satisfied the constraints placed on the system by the Colorado Division of Aeronautics. Surveillance service for the airports selected to be included in the Colorado Surveillance Project is provided by Denver Air Route Traffic Control Center (ARTCC) in Longmont, Colorado. The Host Computer System (HCS) is the current automation platform in use in the Denver ARTCC. To minimize operability issues within the HCS automation the surveillance system will emulate an Air Traffic Control Beacon Interrogator (ATCBI)-6 radar. Processed data will be sent to Denver ARTCC via the Common Digitizer (CD)-2 format. Ten mountain airports were initially selected as possible beneficiaries of the new surveillance system. It was decided to divide the project into two phases. Phase I will provide surveillance service for the airports in Craig, Hayden, Rifle and Steamboat Springs, Colorado. Phase II will provide surveillance for the remaining seven airports, and will begin following successful completion and certification of Phase I. This paper will detail the rationale for selection of WAM as the preferred system, concepts of operation and system requirements. The paper will also present a vision of the system's end state configuration as it relates to NexGen and the blending of airspace within the NAS.