This story was updated with comments from Ligado Networks and the U.S. Defense Department on Sept. 9, 2022, at 4:19 p.m. EST.

WASHINGTON — Ligado Networks’ plan to establish a terrestrial 5G network could jeopardize some older U.S. Defense Department satellites, according to a congressionally mandated report released Friday. The company is preparing to start operationalizing its system as soon as next month.

The report, released by the National Academies of Sciences with Pentagon sponsorship, noted that satellite services provided to the department by Iridium Communications “will experience harmful interference” when their terminals are within 2,401 feet of Ligado’s terminals.

It also found that satellite systems provided by Iridium competitor Globalstar are “unlikely to experience harmful interference” as a result of the Ligado terrestrial network.

Congress required the report as part of the 2021 National Defense Authorization Act amid concerns from the Defense Department and 13 other federal agencies that Ligado’s 5G network would interfere with GPS, given both systems will operate in the L-band frequency at the range of 1 to 2 GHz.

“The findings from the [National Academies of Sciences] are consistent with the opposition from 14 federal agencies, more than 80 stakeholders and Iridium’s concerns that Ligado’s proposed operations will cause harmful interference,” Jordan Hassin, a spokesman for Iridium, told Defense News.

However, the report found the Ligado 5G network “will not cause most commercially produced general navigation, timing, cellular or certified aviation GPS receivers to experience harmful interference.” That said, it added, certain high-precision receivers sold before 2012 “can be vulnerable to significant harmful interference.”

Ligado spokeswoman Ashley Durmer told Defense News that the report confirms the company’s “licensed and authorized operations can co-exist with GPS.”

“A small percentage of very old and poorly designed GPS devices may require upgrading,” Durmer said. “Ligado, in tandem with the FCC [Federal Communications Commission], established a program two years ago to upgrade or replace federal equipment, and we remain ready to help any agency that comes forward with outdated devices. So far, none have.”

She expressed hope that the Pentagon “will stop blocking Ligado’s license authority and focus instead on working with Ligado to resolve potential impacts relating to all [Defense Department] systems, including but not limited to GPS.”

The Defense Department claimed its own tests found Ligado’s network “introduces harmful interference to critical national security capabilities,” though the Pentagon has not publicly released the data to support this.

The report said replacing older GPS receivers with newer, state-of-the-art versions “may provide a plausible solution,” but that is “not likely a satisfactory mitigation” when such replacements are not easily available.

“These systems typically must pass very long and expensive operational test certification; generally mitigations that include replacing or augmenting older devices would involve unsatisfactorily long delays,” the report read.

The Defense Department said in a statement that the findings are consistent with its “longstanding view that Ligado’s system will interfere with critical GPS receivers and that it is impractical to mitigate the impact of that interference.”

Sens. Jack Reed and James Inhofe led a bipartisan group of five other senators in a letter to the Federal Communications Commission last month, urging them to overturn the 2020 decision that paved the way for Ligado to establish its terrestrial 5G wireless network. Reed, D-R.I., is the chairman of the Senate Armed Services Committee, and Inhofe of Oklahoma serves as the top Republican on the panel.

But the Federal Communications Commission voted 3-2 last year to deny a petition to reverse the order. The National Telecommunications and Information Administration spearheaded that petition, which included the Defense and Transportation departments.

“The [National Academies of Sciences] study clearly demonstrates what the rest of the industry has known for years: the prior FCC order failed to fully consider the risk of harmful interference posed to mission-critical satellite systems,” Hassin said. “Iridium urges the FCC to take swift action to reverse the order before Ligado starts its technical demonstrations this fall.”

Bryant Harris is the Congress reporter for Defense News. He has covered U.S. foreign policy, national security, international affairs and politics in Washington since 2014. He has also written for Foreign Policy, Al-Monitor, Al Jazeera English and IPS News.

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