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ADS-B: An Evolution in Air Traffic Control
On June 30, 1956, two commercial planes collided in clear skies over the Grand Canyon, killing more than 100 people. Following that tragedy—and in the wake of more than 65 similar, often fatal, crashes between 1950 and 1955—the Federal Aviation Administration (FAA) was formed, which led to a significant leap in U.S. aviation safety.
Since World War II, air traffic control systems have relied on radar and radio communications systems that took advantage of wartime advances in these technologies. It was the creation of the FAA (a successor to earlier civil aviation authorities) that enabled full-scale regulation of U.S. commercial airspace, however. Over the past half-century, the agency has continued to use those same radar and radio technologies to manage the increasing complexities of commercial aviation.
Today, MITRE is working with our FAA sponsors to engineer the next momentous transformation in air traffic control—the shift from the radar-based system to one taking advantage of the global satellite network. A key part of this evolution is a technology that MITRE has supported since its earliest days: Automatic Dependent Surveillance-Broadcast, or ADS-B.
The ADS-B system enables airplanes to transmit critical information on their location, speed, and altitude to other planes in their vicinity and to ground stations connected to air traffic control centers. The system uses Global Positioning System (GPS) technology to determine a plane's exact location and whether it's climbing, descending, or turning, broadcasting this data in real time. Armed with this information, pilots can maintain situational awareness of other aircraft around them, allowing for safer and more efficient flights. Air traffic controllers and ground automation systems benefit from a highly accurate depiction of the aircraft's position and direction, which will lead to safer operations and improved efficiencies in the air traffic control system in the future.
MITRE Part of An Award-Winning ADS-B Team
Our groundbreaking work on this program, begun in the early 1990s and undertaken with 25 government and industry partners, was recently recognized when ADS-B received the most prestigious honor in aviation: the Robert J. Collier Trophy (see "Highest Honors: The Robert J. Collier Trophy," below). In the past, this award has gone to such pioneers as Orville Wright, Howard Hughes, Chuck Yeager, and the crew of Apollo 11. At a ceremony at MITRE marking the occasion, Jonathan Gaffney, president of the National Aeronautic Association, which awards the Collier Trophy, described ADS-B as "the first great leap forward in air traffic control since radar."
"ADS-B vastly improves what controllers can do and how effectively they can work," says Jonathan Hammer, a MITRE simulation modeling engineer and ADS-B program manager. "With radar, only controllers on the ground could see what was happening in the airspace. Now, other aircraft have this same visibility. ADS-B becomes another pair of eyes for the pilot."
Another major advantage of ADS-B is its ability to bolster the capabilities of ground-based air traffic control systems, says Jeff Mittelman, a MITRE multi-discipline systems engineer who serves as "Outcome Leader," or strategic planner, for the company's ADS-B work program. "During poor visibility conditions, ADS-B will allow pilots and air traffic control systems to work as though the weather was good," he says. At the same time, the system increases the quality and timeliness of weather data visible to pilots, greatly improving flight safety. (For more information on the advantages of ADS-B, see "ADS-B Benefits," at left.)
Reduced Cost of Ownership for FAA Infrastructure
ADS-B's ongoing development and wider implementation—expected to unfold over the next decade as ADS-B infrastructure is put in place and many existing radars are replaced—will enable the FAA to greatly reduce its cost of ownership for air traffic control infrastructure, explains Mittelman. "Cutting down on the radar infrastructure will translate into cost savings."
The FAA believes the gains in safety and efficiency expected to result from widespread implementation of ADS-B will help it meet the huge growth in air traffic predicted in the coming years, with one billion passengers estimated to fly annually worldwide by 2015.
In 2005, the FAA determined that the ADS-B technology had been proven and was ready to operate throughout the national airspace system. ADS-B is used today by commercial and private pilots flying single and twin-engine aircraft in Alaska, where MITRE spearheaded an extensive testing program called Capstone, and by commercial companies such as UPS, Federal Express, and United Airlines in the lower 48 states. It's estimated that by 2013, the main ADS-B infrastructure will be in place and by 2020 most aircraft will transmit ADS-B information, says Hammer.
"The implementation timeline will depend on how aggressive industry and the FAA are," he says. "The technology is pretty close, but from an operations and procedural standpoint there is still a long way to go. Much depends on when industry becomes convinced of the benefits of the cockpit display, which will offer significant benefits but require more expensive avionics."
MITRE's Ongoing Leadership Role
"We played a leadership role in technology development, doing the fundamental R&D and playing the role of facilitator to bring industry and government together," says Hammer. "We have also been involved in standards development and in getting international agreement on technical standards." The work required the input of some 100 people from across three MITRE operational centers over the last dozen years—an illustration of the company's commitment to teamwork and attention to details both large and small.
"From a technical perspective, we had a very broad involvement in the ADS-B vision and concept development. We helped with the design, engineering and architecting of ADS-B, along with prototype design and fielding," Mittelman says. Prototypes were developed in the mid-1990s, the Capstone testing took place in the early 2000s, and national procurement is underway currently.
The Capstone effort was an attempt to improve aviation safety in Alaska and prove the ADS-B technology at the same time. This involved the installation of ground infrastructure, GPS-based avionics, and data link communications in commercial aircraft serving certain remote areas of the state.
Improving Aviation Safety in Alaska
For many people in Alaska, aviation (using mostly small aircraft) is the only means of getting needed supplies. Air taxi services, air ambulance services, and air delivery services operated for years without the benefit of surveillance radars. Bad weather, harsh geography, and inadequate equipment often made flying dangerous and accidents commonplace.
MITRE worked closely with the Alaskan aviation industry, the FAA, manufacturers, controllers, pilots, contractors, and others to deploy the initial system, develop Capstone software and infrastructure, and test the emerging ADS-B system. On January 1, 2001, the Anchorage Air Route Traffic Control Center received the first ADS-B position report and vectored two aircraft to the airport in Bethel without the use of surveillance radar, a historic event that paved the way for further ADS-B testing in the state. As a result of the Capstone work, the air accident rate in the ADS-B-equipped portion of Alaska's airspace fell by 50 percent between 2000 and 2005.
A key component to the program's success was MITRE's research into the cockpit infrastructure necessary for providing ADS-B services. Our invention of the Universal Access Transceiver (UAT), a device that can communicate with the ground and with nearby aircraft to exchange the ADS-B position data represented an important leap forward for the overall system.
MITRE designed the UAT, a wideband data link technology operating on a single global channel, to provide a communications system with a simple and robust design based on proven techniques. UAT uses readily available components to keep costs down and can be incorporated into radios in smaller and lower-flying aircraft. Following the first successful flight demonstrations of ADS-B as part of Capstone, UAT technology was transferred to UPS Aviation Technologies, now known as Garmin Ltd., (on the instructions of the FAA) for commercial production of the sets used in the Capstone exercises.
In light of this history with ADS-B, Jim Reagan, a MITRE multi-discipline systems engineer and director of the company's Systems Evolution and Domain Integration group, summed up the company's work on the program during the Collier Trophy ceremony.
"We've been thought leaders, inventors, pioneers, and skeptics," Reagan said. "We were there at the beginning, and we remain a partner of the FAA and industry."
—by Maria S. Lee
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