by Patty Welsh
66th Air Base Group Public Affairs
7/21/2015 - HANSCOM AIR FORCE BASE, Mass. -- As
the 20th anniversary of Global Positioning System, or GPS, technology
is this month, the Aerospace Management Systems Division here explains
how the technology enables their work enhancing performance and safety
of air traffic management.
"The biggest improvement that GPS technology brought to air traffic
management is that the aircraft itself can reliably know its position
rather than relying on circa 1940s ground-based nav(igation) aids," said
Ben Brandt, MITRE senior technical advisor to the Division's
Communication, Navigation, Surveillance/Air Traffic Management or
In the United States the transition to GPS-based navigation is a central
tenet of the Next Generation Air Transportation System, or NextGen.
NextGen is a massive initiative between federal partners to modernize
America's air transportation system, and according to documentation
developed by the Federal Aviation Administration, it involves a shift to
satellite-based and digital technology. The Aerospace Management
Systems Division is the main Air Force conduit for participation in
The CNS/ATM program's main focus is to ensure Air Force aircraft can
operate in this NextGen airspace. Program personnel accomplish this by
tracking and contributing to civil aviation standards forums,
interpreting the standards into a set of requirements that can be
leveraged by any Air Force aircraft program, providing subject matter
expertise to aircraft programs in design or development and ultimately
conducting an independent assessment of a program's implementation to
ensure the aircraft can safely operate in the airspace with civilian
GPS technology helps with that interoperability.
The accuracy provided by GPS allows more aircraft to fit in the same
amount of airspace by reducing the space between aircraft while
maintaining the same level of safety, and enables Performance-Based
Navigation. PBN is described on the FAA website as a series of "new
routes and procedures that primarily use satellite-based navigation and
on-board aircraft equipment to navigate with greater precision and
accuracy. PBN provides a basis for designing and implementing automated
flight paths, airspace redesign and obstacle clearance."
"PBN is a primary focus area of NextGen," said Brandt.
For the CNS/ATM office, a core objective is to assess military GPS
receivers to ensure they can provide the necessary and appropriate
information to support capabilities such as PBN.
"The ultimate goal of our GPS-related efforts is to demonstrate that the
performance of our legacy and new M-Code GPS receivers can meet the
performance necessary to be interoperable with civilian air traffic
without requiring our Air Force aircraft to equip with both civil and
military GPS receivers," said Col. Joe Leonard, Division senior materiel
Another key tenet of Hanscom's work that relies on GPS technology and
will also support NextGen is Automatic Dependent Surveillance-Broadcast,
or ADS-B Out. According to program officials, the system relays the
GPS-computed position of the aircraft to the aircraft's transponder and
broadcasts it out from the aircraft once a second. This increased rate
of position notification is much more accurate than the average 4-5
second sweep-rate of traditional secondary surveillance airport radars.
"(ADS-B Out) allows for more precise reporting of position and
information, such as velocity, that can be used in applications other
than air traffic control" said Brandt.
For example, aircraft equipped with ADS-B In receivers can receive other
aircraft ADS-B Out signals and, through cockpit displays, provide
enhanced situational awareness to the pilot. The accuracy of the GPS
position also enables improved surface surveillance and
conflict-avoidance management at busy airports.
ADS-B Out is mandated to be implemented in U.S. airspace on Jan. 1, 2020, and in Europe June 7, 2020.
In addition to NextGen, Brandt says there are other efforts across the
globe under various names, but the philosophy remains the same,
replacing the capabilities provided by an extensive, dated network of
ground navigation aids with GPS-based technology.
"The use of GPS in civil aviation has grown significantly over the last
decade, but there are airlines operating aircraft still today that do
not use GPS," he said.
This is largely due to the previous use of selective availability, which
was an "intentional degradation of public GPS signals implemented for
national security reasons," according to the GPS.gov website. In 2000,
President Clinton authorized its discontinuation to ensure all users,
whether military or civilian, could receive the most accurate
According to Brandt, the ADS-B mandate will drive more civil aircraft to
use GPS, so its importance as critical infrastructure will continue to
The CNS/ATM program was originally stood up by the Secretary of Defense
in 1996 to address the addition of Navigation Safety equipment on Air
Force aircraft after a couple of high-profile incidents, including a
CT-43 crash into a mountain in Croatia that killed then Secretary of
Commerce Ron Brown.
Since that time, according to program officials, the CNS/ATM program has
become the Center of Excellence for the Air Force for all capabilities
related to civil airspace access. Recently the Division has teamed with
Air Force Life Cycle Management Center Avionics Engineering Division and
the Space and Missile Systems Center GPS User Equipment Office to
develop a set of recommendations on courses of action Air Force aircraft
can take to integrate ADS-B, Mode 5 IFF and the new M-Code GPS
capabilities, which will be presented to the AFLCMC commander during a
review in August.