The Cybersecurity and Infrastructure Security Agency (CISA) at the Department of Homeland Security (DHS) recently released a three page “CISA Insights” document titled “Global Positioning System (GPS) Interference.” The January 2022 GPS jamming incident in Denver is discussed on the first page as an example of bad things that can happen and why GPS users should take precautions against interference.

Issued eleven months after the event, the report provides little new information, and leaves several important questions unanswered.

Delay in locating and ending interference

One of the most important questions is why it took so long to locate and end interference from a strong signal impacting such a large area.

The Federal Aviation Administration (FAA) was the first agency to become aware of the issue and the report credits the Enforcement Bureau of the Federal Communications Commission (FCC) with finding and terminating the spurious transmission.

Despite an “established national coordination process,” the interference was unabated for 33 hours.

While the report does not give details of the delay, likely reasons include the large number of agencies involved, diffuse authorities and responsibilities, the lack of a national interference detection system or a GPS/PNT “command center,” and several decades of funding and staffing reductions for FCC’s Enforcement Bureau.

How and why it happened

One of the primary reasons for doing an analysis of an accident like this is to prevent similar events in the future. Yet the CISA report provides no helpful information in this regard. It does not identify the source, nor the chain of events leading to the presumably accidental interference.

Those who might take steps to ensure that their operations don’t accidentally interfere with GPS signals learn nothing from the document.

A similar GPS jamming event occurred in October 2022 in the Dallas area. That one lasted 44 hours and the source was never identified. One wonders if this could have been prevented if the CISA report had been issued earlier and included more information.

Why the general public was not warned

The FAA issued a Notice to Airmen as soon as it became aware of the problem. The CISA report says surface (road and highway), rail, and telecommunications users were also impacted. Undoubtedly other types of users were also affected. Yet despite the outage lasting almost a day and a half, no public warning was issued to inform and protect non-aviation interests.

At a minimum, such a warning could have saved companies a lot of trouble and effort. A trouble report during the event from one public safety system operator provides an example of the unnecessary effort expended because a company did not know about the on-going disruption:

“Approximately 1530 on 21 DEC 22 two of our base transceiver systems began to lose sync. The GPS receivers, control cabling, and surge protectors were replaced with no change to loss of sync. There are no other BTS affected other than three sites in Aurora, Colorado … also problems with the local public safety P25 simulcast systems which have lost GPS lock in this area. Spok provides critical encrypted health care communications at these facilities.”

Warning the public could also help prevent more serious consequences, like the loss of life and property.

Troubling assertion

In this case, no losses of life or property have been connected to the disruption.

Yet the CISA report makes a more affirmative statement that “No accidents or injuries occurred because of the GPS interference incident.”

While we all certainly hope that was the case, and it may well be true, the CISA statement is troublingly certain.

A fairer and more accurate statement would be that “…none occurred, that we know of…” This would acknowledge that GPS is a safety of life system in many applications, and the seriousness of interference events.

Striving to do better

After its discussion of the Denver incident the report says improving GPS interference detection and mitigation is a CISA priority. And they are leading an interagency review to improve things.

This will be an uphill battle.

One challenge is DHS and other departments and agencies have limited authorities. The FCC is legally responsible for ensuring transmitters don’t trespass into unauthorized frequencies. However, its resources are limited and, as an independent agency not part of the administration, its participation in cross-governmental efforts is entirely voluntary.

Another is the lack of a clear, authoritative leader and champion for positioning, navigation, and timing (PNT) issues within the federal government.

Executive branch policy scatters PNT-related tasks thinly across the administration. These are to be coordinated by a senior level executive committee tasked to make recommendations “…to the President, through the Assistant to the President for National Security Affairs, or the Executive Secretary of the National Space Council…”

It is not hard to imagine that the details of PNT policy are rarely, if ever, brought to the attention of the President. This can lead to a stalemate between much more junior White House officials and greatly inhibit action.

Let’s hope the CISA report, limited as it is, highlights for leadership the many challenges faced by folks across government who care about GPS reception and national PNT issues. And that, as they collaborate on good solutions, they get the policy and budget support they deserve.