The concern is that the frequency band being proposed by Ligado is adjacent to the band used by the Global Positioning System (GPS) and poses a strong risk of interference with GPS signals, including the potential interruption of GPS signals at low altitudes.
In announcing the FCC order, FCC Chairman Ajit Pai said that the conditions FCC has imposed on Ligado, “ensure that adjacent band operations, including the [GPS] are protected from harmful interference.”
However, GPS users across many sectors do not agree with that optimistic assessment. Allowing Ligado to operate its network “risks endangering the performance of GPS systems onboard aircraft, and that’s very important, because GPS is the main navigation system,” said Noppadol Pringvanich, IATA’s Head ATM Engineering & Aviation Radio Spectrum.
He noted that accurate position reports from GPS are also used by cockpit safety systems such as the Terrain Avoidance and Warning Systems (TAWS). “Just imagine if, because of the interference (from the Ligado network), GPS is interrupted and the TAWS doesn’t know where the aircraft is,” said Pringvanich.
In addition, the proposed network affects aircraft SATCOM systems that are the main channel for communications between pilots and air traffic services in transoceanic flights. Pringvanich explained: “Even though the SATCOM system is mainly used in oceanic operations, the pilot needs to make sure it is working before the aircraft departs. But if you have a Ligado station near the airport, it may cause interference. If you cannot lock on your SATCOM, you cannot verify that the system is operational so you may not be able to depart. This will have costly operational and retrofitting implications.”
Opposition to the FCC’s action is not confined to the aviation sector, nor to private industry. Numerous federal agencies and departments have also raised concerns, including the US Departments of Defense (DOD), Transportation (DOT), and Homeland Security (DHS).
A joint statement from the DOD and DOT identified a number of uses of GPS, including the 9/11 emergency response system, securing financial systems, ordering and receiving shipments, automobile navigation systems, facilitating commercial trucking and construction work, and even using a cell phone.
“Our Departments rely on GPS each day for all those reasons as well as to coordinate tactical national security operations, launch spacecraft, track threats, and facilitate travel by air and sea,” noted the statement. “The Ligado decision by the Federal Communications Commission will put all these uses of GPS at risk."
DHS, meanwhile, said it “remains concerned that an approval creates a high degree of uncertainty for our public and private sector partners.”
Lawmakers have also weighed in against the FCC’s decision. In a joint statement, the leaders and ranking members of the Senate and House Armed Services Committees encouraged the FCC to withdraw its approval of Ligado’s application, which “threatens to undermine our GPS capabilities, and with it, our national security.”
Chad Heflin, IATA’s Assistant Director, Member and External Relations, concluded: “IATA is working with a broad coalition of airlines, trade associations, and other groups to persuade the FCC to reverse its order. If that effort fails, then IATA and others may have to seek legal or legislative remedies.”