Why does the Military Conduct GPS Jamming Exercises?

Picture a giant, invisible, upside-down cone rising up from the desert floor near Naval Air Weapons Station China Lake. It ranges over 500 miles in every direction, covers more than 500,000 square miles in total, and reaches up higher than any civilian aircraft can fly. Inside the cone, GPS-related systems fail to function.

testing

Such a planned outage was scheduled to be centered on the BTY VOR 214 degree radial at 059 NM on six different days in June, (from June 7 to June 30), running from 4:30 pm to 10:30 p.m. each day.

The outage could have affected GPS and Automatic Dependent Surveillance-Broadcast signals and “unplanned pitch and roll events” in Embraer’s Phenom 300. Therefore, the 300 was cautioned to stay away from the specified area.

In early June, citing reasons that were “internal”, the Navy canceled the GPS Interference Testing that was to emanate from the vicinity of the China Lake, California, Naval Air Weapons Station.

The Department of Defense conducts an estimated 50 GPS jamming events each year to train personnel to operate in an environment where the GPS signal is degraded or unavailable.

Navigation on sea, in the air, and on the ground all largely rely on GPS. Many weapon systems, like cruise missiles and GPS-guided bombs, also rely on the technology, at least partially, to hit their intended targets reliably and accurately. If the GPS signals are unavailable or unreliable, our fighting forces would be severely crippled. The enemy knows this, and our GPS satellites can be attacked in multiple ways, both kinetic (anti-satellite weaponry, orbital tampering, etc.) and non-kinetic (jamming, hacking, etc).

C4ISRNet.com published an interview with the head of the Navy’s Communications and GPS Navigation Program Office, Captain Mark Glover.

Captain Glover explained, “The GPS satellite signal at a user’s antenna is very low power. To put that in perspective, a 100-watt bulb is [10 to the 18th power] more powerful than a GPS satellite signal at the receiver’s antenna. Using a low-power jammer, the enemy can disrupt GPS operations.

To that end, denial and degradation of GPS can have myriad effects on our systems. Without protection, our ships, submarines and aircraft won’t be able to properly navigate. Some of our sensors might not function properly, and provide erroneous information to our war fighters. Plus, time and frequency is a critical part of our communications infrastructure. Disruption of time can prevent those networks and communications systems from functioning properly, as well.”

THE GROUND RULES

Before a GPS outage can be scheduled, the military proponent must submit its plans to the FAA, whose spectrum office analyzes the potential impact. That impact is then depicted graphically and sent to air route traffic control centers (ARTCCs) that would be affected. The ARTCCs and military then work together to minimize the impact on civilian aircraft, including setting limits on the duration of the jamming and the time of day it takes place. When agreement is reached between the military and the FAA, the FAA issues NOTAMS  and flight advisories.

To protect civilian traffic, the FAA can call a halt to the jamming if it believes the jamming is creating an unsafe situation for aircraft, for example if navigation is impaired in the vicinity of convective activity.

The graphics depicting the impact show the worst-case scenario in order to provide a margin of safety for aircraft, and most outages have a minimal impact on civilian aviation.

CHECKING GPS NOTAMS

GPS NOTAMS are included in the ARTCC NOTAMS,found in ForeFlight and in a ForeFlight briefing.

All the GPS NOTAMS can be found online at https://pilotweb.nas.faa.gov/PilotWeb/

Click on the”ARTCC Notices, TFRs and Special Notice page” button. This will display all the Centers in the United States. Select the Center(s) that you want to search, and click on the “View GPS NOTAMS” button.

Below is one of the GPS NOTAMs affecting aircraft in Albuquerque Center’s airspace.

ZAB  ALBUQUERQUE (ARTCC), NM.

!GPS 06/134 (KZAB A0205/16) ZAB NAV (YPG GPS 16-01) GPS (INCLUDING WASS, GBAS, AND ADS-B) MAY NOT BE AVBL WI A 219NM RADIUS CENTERED AT 332343N1142152W (BLH 108023) FL400-UNL DECREASING IN AREA WITH A DECREASE IN ALT DEFINED AS: 171NM RADIUS AT FL 250, 122NM RADIUS AT 10000FT, 126NM RADIUS AT 4000FT AGL, 087NM RADIUS AT 50FT AGL. THIS NOTAM APPLIES TO ALL AIRCRAFT RELYING ON GPS. ADDITIONALLY, DUE TO GPS INTERFERENCE IMPACTS POTENTIALLY AFFECTING EMBRAER PHENOM 300 AIRCRAFT FLIGHT STABILTY CONTROLS, FAA RECOMMENDS EMB PHENOM PILOTS AVOID THE ABOVE TESTING AREA AND CLOSELY MONITOR FLIGHT CONTROL SYSTEMS DUE TO POTENTIAL LOSS OF GPS SIGNAL. DLY 1830-2230 1606251830-1606262230

If you’re a “visual” pilot, you like things  graphically displayed on a sectional, like the TFR graphics we’ve grown accustomed to. However, the GPS NOTAMs make you work for it. We do know that it’s a giant inverted cone, centered on the BLH (Blythe, CA VORTAC) 108o Radial at 23nm. Directly over that point, it affects traffic at FL400 to infinity and beyond. The affects decrease in altitude, as you travel further away from the center (BLH 108023).

cone

Rune Duke, AOPA director of airspace and air traffic  said, “Anytime pilots are affected by a GPS outage event, we encourage them to report their experience. Without reporting by pilots, it’s difficult to know the extent and severity of impacts.”

You can report via email at gps@aopa.org .

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