“The problem is that the GPS signal is very weak. It’s like a car headlight 20,000 kilometres away,” says consultant David Last, former president of the UK’s Royal Institute of Navigation. You can’t boost the signal any further because of the limited power supply on a satellite. <https://www.newscientist.com/article/dn20202-gps-chaos-how-a-30-box-can-jam-your-life/>
GPS Jamming Tests Frustrate Pilots, Controllers
Russ Niles - October 10, 2021 https://www.avweb.com/aviation-news/gps-jamming-tests-frustrate-pilots-controllers/
Just as civil aviation has become thoroughly addicted to GPS, the military
is trying to wean itself off that dependence and that’s causing some
fractious conflicts in the Southwest. The military uses the wide-open spaces
to purposely jam GPS signals to see how its equipment and personnel cope
with the “GPS denial.” But according to IEEE Spectrum <https://spectrum.ieee.org/gps-jamming>, the military and the FAA are not always on the same frequency when it comes to managing those tests and controllers and pilots have put their frustrations in writing in NASA’s Aviation Safety Reporting System. “Aircraft are greatly affected by the GPS jamming and it’s not taken seriously by management,” says one report gleaned
by IEEE Spectrum. “We’ve been told we can’t ask to stop jamming, and to just put everyone on headings.”
The military does notify the FAA about jamming activity but that doesn’t
always seem to get to the frontline workers in the system and the loss of
GPS can be dangerous. One of the reports involved a business jet that made a wrong turn and ended up in the highly restricted airspace of the White Sands Missile Range, which, ironically, is the source of much of the jamming.
Another pilot reported he lost his terrain mapping at a critical time and worried he’d end up in a smoking hole. When the jamming starts jamming up
the system, controllers have the option to request a “stop buzzer” to get
the military to turn off the electronic interference but some controllers complain they’ve been told not to make those requests and to just issue
vectors to affected traffic. The FAA told IEEE Spectrum that controllers
can, indeed, stop the tests if they think it’s necessary but those requests
are automatically reviewed by upper management. ------------------------------------------------------------------------
Air traffic controllers in a control tower monitoring the airfield. ETHAMPHOTO/GETTY IMAGES
FAA MILITARY GPS JAMMING NAVIGATION AIR TRAFFIC CONTROL SAFETY AEROSPACE
FAA air traffic controllers supervising flights over Arizona, New Mexico and Texas were confused and frustrated by an increase in military tests that interfered with GPS signals for civilian aircraft, public records show.
In March and April this year, flight controllers at the Albuquerque Air
Route Traffic Control Center filed reports on NASA's Aviation Safety
Reporting System (ASRS), a forum where aviation professionals can
anonymously share near misses and safety tips.
The complaints accused the FAA of denying controllers permission to ask the military to cut short GPS tests adversely affecting commercial and private aircraft. These so-called "stop buzzer" (or "cease buzzer") requests are supposed to be made by pilots only when a safety-of-flight issue is encountered.
"Aircraft are greatly affected by the GPS jamming and it's not taken
seriously by management," reads one report. "We've been told we can't ask to stop jamming, and to just put everyone on headings."
In a second report, a private jet made a wrong turn into restricted airspace over the White Sands Missile Range in New Mexico after being jammed. On that occasion, the air traffic controller called a stop buzzer. "[The] facility manager on duty later informed me we can't ask them to 'stop buzzer' and to just keep putting aircraft on headings," their ASRS report reads.
Putting an aircraft on headings requires giving pilots precise bearings to follow, rather than letting them perform their own navigation using GPS or other technologies. This adds work for controllers, who are already very
busy at certain times of day.
"Busy traffic, bad rides, frequency congestion, then GPS jamming," reads one report. "Limit the length and what time of the day that facilities can GPS
jam and have it taken seriously when we call and ask them to stop."
"Give controllers the ability to have White Sands stop GPS jamming during
high traffic periods," agrees the other.
The Pentagon uses its more remote military bases, many in the American West,
to test how its forces operate under GPS denial. A Spectrum investigation earlier this year discovered that such jamming tests are far more prevalent than had previously been thought, possibly affecting thousands of civilian flights each year.
The FAA does not share how many stop buzzer requests are made, but
Spectrum's investigation obtained FAA data detailing four stop buzzers over
the skies of California during a nine-week period in 2017. These included passenger jet flights operated by Frontier and Southwest.
The White Sands Missile Range (WSMR), whose tests appear to have caused the
GPS jamming in both recent complaints, estimates it receives "in the low
single digits" of stop buzzer requests a year.
A spokesperson for WSMR told Spectrum: "The US Army takes the safety of its operations extremely seriously. Calls for a cease buzzer are taken seriously and range control has not denied or ignored any cease buzzers. WSMR has also never requested or required any internal organization or outside agency to
not make use of the cease buzzer in the event of an emergency, or unsafe event."
The FAA provided the following statement:
"The FAA cooperates with Department of Defense to mitigate the effects of
the military's planned interference activities… to levels of acceptable
risk. The primary mitigation when GPS is lost is for a pilot to use another means of navigation. Air Traffic Control (ATC) will assist the pilot with navigation on rare occasions, upon request. Should multiple pilots encounter problems, then ATC has the option to stop the underlying cause through [a]
When a stop buzzer call is made by a controller, the FAA then has a review process to analyze the appropriateness of the action and the associated operational risk.
However, an FAA source also admitted that one ATC facility "expressed some confusion as to the scope of their authority to suspend operations using stop-buzzer protocols when GPS testing had ramped up significantly." The FAA now believes it has cleared up and abated those field concerns.
Although flight controllers may no longer be instructed not to issue stop buzzer calls when planes are in trouble, pilots continue to experience difficulties in the airspace around White Sands.
In May, the pilot of a light aircraft taking off at night in the Albuquerque area suddenly lost their GPS navigation and terrain warnings. Air traffic control told the pilot that WSMR was jamming, and instructed them to use
other instruments. That pilot was ultimately able to land safely, but later submitted their own ASRS report: "Being unfamiliar with this area and
possibly a different avionics configuration I feel my flight could have possibly ended as controlled flight into terrain."
Such an outcome–a likely deadly crash–would surely not meet anyone's
definition of "acceptable risk."
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is an investigative science and technology reporter based in Seattle, with a particular interest in robotics, transportation, green technologies, and medical devices.
Robert Munsey8 OCT, 2021
Just look at the National Defense Strategy and statement by Space Command "..Both China and Russia have weaponized space with the intent to hold
American space capabilities at risk. China's communist government has
exercised and continues to develop the capability to jam, targeting SATCOM,
ISR and GPS." https://www.defense.gov/News/Transcripts/Transcript/Article/1809882/remarks-by-acting-secretary-shanahan-at-the-35th-space-symposium-colorado-sprin/
The point is that anyone should expect the military to request GPS jamming
to allow units to train in a GPS denied environment. Readers should also
know that such requests HAVE to go through the particular service Spectrum Management Office (after the unit's SMO), then to the FCC and FAA for
approval. Such DOD requests are not always guarantee and quite frequently disapproved. With exceptions, most GPS jamming occurs during nocturnal hours when most civil aircraft are no flying. Also once approval is granted NOTAMs still have to be published. SO if civil aircraft flies over restricted
airspace in the published NOTAM, then there is a larger problem. ---------------------------------------------------
IT WAS just after midday in San Diego, California, when the disruption
started. In the tower at the airport, air-traffic controllers peered at
their monitors only to find that their system for tracking incoming planes
was malfunctioning. At the Naval Medical Center, emergency pagers used for summoning doctors stopped working. Chaos threatened in the busy harbour,
too, after the traffic-management system used for guiding boats failed. On
the streets, people reaching for their cellphones found they had no signal
and bank customers trying to withdraw cash from local ATMs were refused. Problems persisted for another 2 hours.
It took three days to find an explanation for this mysterious event in
January 2007. Two navy ships in the San Diego harbour had been conducting a training exercise. To test procedures when communications were lost, technicians jammed radio signals. Unwittingly, they also blocked radio
signals from GPS satellites across a swathe of the city.
Read more: The forgotten navigation system that could show GPS the door
Why would a GPS outage cause such disruption? These satellite signals now do
a lot more than inform your car’s satnav. GPS has become an “invisible
utility” that we rely on without realising. Cellphone companies use GPS time signals to coordinate how your phone talks to their towers. Energy suppliers turn to GPS for synchronising electricity grids when connecting them
together. And banks and stock exchanges use the satellites for time-stamps
that prevent fraud. Meanwhile, our societies’ reliance on GPS navigation is growing by the year.
Some are worried that we are now leaning too heavily on a technology that
can all too easily fail – and it doesn’t need a freak navy training exercise
to cause havoc. Their biggest concern is a GPS jammer – a plastic device
that can sit on car dashboards. These can be bought on the internet, and
tend to be used by say, truckers who don’t want their bosses to know where
they are. Their increasing use has already caused problems at airports and blocked cellphone coverage in several cities. One jammer can take out GPS
from several kilometres away, if unobstructed. No surprise, then, that researchers across the world are scrambling to find ways to prevent
disastrous GPS outages happening.
GPS works thanks to radio signals from satellites. The dominant provider is still the US military’s NavStar network, with at least 24 satellites
operating at any given time, positioned so that you can always see four of
them from anywhere on the planet’s surface.
Each satellite continually broadcasts its location and the time as measured
by its on-board atomic clock. A GPS receiver compares the time with its own clock, and then calculates how far it must be from each satellite. Once it locks on to at least four satellites and has accounted for errors, it will discover its precise location (see graphic). Nowadays, many receivers also
use GPS for cheap and convenient access to the accurate time given by the satellites’ clocks.
“The problem is that the GPS signal is very weak. It’s like a car headlight 20,000 kilometres away,” says consultant David Last, former president of the UK’s Royal Institute of Navigation. You can’t boost the signal any further because of the limited power supply on a satellite.
New Scientist Default Image
Last has first-hand experience of how easy it is to block a GPS signal, and
the effects it can have on modern technology. In 2010, he conducted an experiment in the North Sea, aboard the THV Galatea, a 500-tonne ship. The Galatea is the pride of its fleet, with all the latest navigation equipment. Last wanted to find out how it would cope without GPS. So he used a simple jamming device that overwhelmed the GPS signal by broadcasting noise on the same frequency as the satellites.
When Last activated the jammer, the ship went haywire. According to the electronic display on the ship’s bridge, the Galatea was suddenly flying at Mach speeds over northern Europe and Ireland. Then alarms sounded. The
ship’s navigation backup – its gyrocompass – crashed, because it uses GPS to provide corrections. The radar did the same. Even the ship’s satellite communications failed, because GPS points the antenna in the right
direction. “The crew were well trained and briefed, so they knew what was
going on,” says Last. “But, like us, they were surprised.”
Last deliberately simulated a simple, commercially available jammer. Though illegal to use in the US, UK and many other countries, these low-tech
devices can be bought on the internet for as little as $30. Sellers claim they’re for protecting privacy. Since they can block devices that record a vehicle’s movements, they’re popular with truck drivers who don’t want an electronic spy in their cabs. They can also block GPS-based road tolls that
are levied via an on-board receiver. Some criminals use them to beat
trackers inside stolen cargo. “We originally expected that jammers might be assembled by spotty youths in their bedrooms,” says Last. “But now they’re
made in factories in China.”
Last is worried that jammers could cause as much havoc on land as he
discovered on the Galatea, and he’s not alone. In November 2010, a NASA-appointed executive committee for “space-based positioning, navigation
and timing” warned that jamming devices could cause disaster if activated in cities. It is not known how many are out there, but the panel is concerned
that the risk of interference is growing fast. And in future, devices called “spoofers” – which subtly trick GPS receivers into giving false readings –
may make the problem even worse (see “Faking it”).
An event last year at Newark Liberty International Airport in New Jersey
showed that it only takes one jammer to cause disruption. Airport
controllers had installed a new GPS-based landing system, so that aircraft could approach in bad visibility. But it was shutting itself down once or
twice a day. It took several months to find the culprit: a driver on the
nearby New Jersey Turnpike using a portable GPS jammer to avoid paying the highway toll. This trucker was cruising past twice a day, crippling an
airport as he went.
Future generations of air-traffic control won’t work without GPS – nor will train routing. The US Federal Railroad Administration has GPS at the heart
of its plan for smart management of rail traffic. GPS is also increasingly relied upon for guiding emergency services to the scene.
What’s more, a lot more than navigation ability is lost when GPS fails
today. “We rely upon GPS without even being aware of it,” says Donald
Jewell, who helped to establish GPS from its inception in the US air force,
and is now editor of GPS World magazine. It is estimated that more that a billion GPS receivers are now in operation, he says, and more than 90 per
cent use the signals only for the accurate time provided by the satellites.
Cellphones are a key user of this invisible utility. Towers must synchronise with each other to pass calls to other towers as you move – a GPS time
signal offers a cheap and accurate way to do this. The timing offset for
each tower is also used to identify it. In fact, many wireless communication technologies use GPS timing for synchronisation. That’s probably why the harbour traffic control and emergency pagers failed in San Diego in 2007.
Time is money
GPS timing can time-stamp financial transactions, such as stock-market
trading. And ATMs sometimes communicate wirelessly, using a time-based encrypted code that requires synchronisation. Though it is not known why the cash machines stopped working during the San Diego event, this might have something to do with it.
Energy suppliers use GPS time to keep alternating current from various power plants in phase across the grid. If frequency cycles are not matched, two supplies will partially cancel each other out, creating inefficiency. A
precise time signal allows operators to pinpoint the start of each cycle.
The US power grid, for instance, requires synchronisation between the
supplies of over 5000 companies. Yet in 2006, a temporary GPS outage due to sunspot activity <http://www.springerlink.com/content/yvp8227244218371/>
meant that energy companies were not able to see where the power was going, which resulted in false billing. Blackouts due to GPS failure are not out of the question.
Given the potential for disruption, law-enforcers are trying to crack down
on GPS jamming. In February, the US Federal Communications Commission
announced a new effort to fine jammer sellers and owners <http://www.fcc.gov/Daily_Releases/Daily_Business/2011/db0209/DOC-304575A1.pdf>.
The problem for western authorities is that most sellers are in east Asia
and laws tend only to cover the use of a jammer, not its ownership.
That’s part of the reason why navigation researchers are calling for a
back-up. To discuss what to do next, many of them will gather for a meeting next week at the National Physical Laboratory in Teddington, UK.
Fortunately, there’s a backup right under our noses, and the idea been
around since the 1940s. Just like GPS, it provides navigation and accurate timing. It’s called Enhanced LORAN (eLORAN).
Basic LORAN (for long range navigation) is similar to GPS but uses
ground-based radio signals rather than from satellites. It doesn’t have
global coverage, but does beat GPS on some things. LORAN operates at a far longer wavelength than GPS signals and is more powerful. Both of these
features make it virtually impossible to jam.
A new version, eLORAN, uses more reliable transmitters and features improved caesium atomic clocks. With software modifications, it is accurate to about
10 metres, as well as providing a time signal of similar accuracy to GPS. It would be easy to modify future receivers to switch over to eLORAN without
the user even noticing, says Last.
In Europe, a team at the UK’s General Lighthouse Authorities has been
testing eLORAN, and is now recommending that the UK government rolls it out. Across the Atlantic, however, the US government is taking its current LORAN
out of service. And it has so far rejected all advice to fund eLORAN: which would cost about $20 million per year – less than it costs to launch one GPS satellite. “We still hold out hope that someone with some foresight and technical know-how in our government will see the light,” says Jewell.
Happily, a few decades from now a GPS signal might not be required at all
for many things. If atomic clocks get cheaper, then they could be built into everything that needs accurate time. And eventually you’ll be able to
navigate without any external signals, thanks to devices called “inertial measurement units”, which track your movements from a known start point.
Today, these IMUs use gyroscopes to measure orientation, plus accelerometers
to tell how fast it is accelerating. Using this information, plus time, the acceleration is converted into speed and distance to reveal relative
Today, IMUs drift about 1.5 kilometres per hour of travel, and are large and expensive. Yet the US Defense Advanced Research Projects Agency plans to improve performance with a microchip-sized atomic clock and an equally diminutive, accurate acceleration sensor.
In the meantime, however, a generation is growing up that has never known
life without GPS. As jammers proliferate, GPS outages like San Diego are
likely to become more common. So next time you lose your cellphone signal, blame the little black box on a car dashboard a few kilometres away.
Get there in a flash
Your satnav might one day find its route thanks to the faint flashes of
Both GPS and LORAN (see main story, above) are navigation techniques that
rely on radio signals to pinpoint your location, but these signals can’t penetrate underground or deep inside buildings.
Now the US Defense Advanced Research Projects Agency (DARPA) is testing the idea of using radio pulses from lightning instead. These natural atmospheric radio sources – or “sferics” – have a very low frequency, so can penetrate
deep underground and even underwater. The military is interested because it would improve navigation in caves and tunnels or for submarines.
DARPA’s S-BUG receivers detect radio waves emitted by lightning thousands of kilometres away – at any given moment there are around 2000 storms active on the planet. Another device feeds the receiver the exact location and
emission time of the sferic so that it can calculate how far away it is.
Once several sferics are recorded, the receiver can then use this to
discover its location.
DARPA is still testing S-BUG. But once a lightning receiver network is fully
in place, existing GPS users should require nothing more than an antenna and
a software upgrade to use the system, says programme manager Stephanie
Todd Humphreys can trick you into thinking you are somewhere else. He uses a “spoofer” device that causes a GPS receiver to give an inaccurate reading.
Humphreys, at the University of Texas at Austin, has no mischief in mind,
but built the device to demonstrate how straightforward it is to do. Such spoofers are not on the market yet, but when they are, could cause all sorts
Unlike a GPS jammer, which has fairly obvious effects, the spoofer’s impact
is slow and subtle. “The victim usually won’t realise they’re being
spoofed,” says Humphreys. “It leaves no trace.”
Humphrey’s GPS spoofer looks like a wireless internet router. It picks up genuine GPS signals and synchronises its output to resemble them. Any nearby receiver will treat this output as a genuine signal from a GPS satellite.
The spoofer then gradually alters its time output, changing from the true
value by, say, 3 nanoseconds per second. Since GPS receivers use the time signature in a signal to find location or as an easily accessible clock, the error builds up.
“The biggest risk is probably complicit spoofing, where someone deliberately misleads their own GPS,” says Humphreys. For example, unscrupulous fishing
boat captains could spoof GPS to fake their location and fish in forbidden waters. “If mass-produced, they could be made for perhaps $400 to $500,”
says Humphreys. Such a spoofer could push another ship off course, just as ship-wreckers used to lure vessels onto rocks with false lighthouse lights.
Criminals could also spoof GPS timing for profit. The US National
Association of Securities Dealers requires financial traders to time-stamp transactions with an accuracy of within 3 seconds. “The bad guys would spoof the timing at their preferred site and, watching an upward trend, buy stock
a few seconds in arrears,” says Humpreys. “Those three seconds could be
worth a lot of money.” --------------------------------------------------------------
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FAA FILES REVEAL A SURPRISING THREAT TO AIRLINE SAFETY: THE U.S. MILITARY'S
Military tests that jam and spoof GPS signals are an accident waiting to
MARK HARRIS21 JAN 202111 MIN READ
Image of a plane being tracked by GPS.
PHOTO-ILLUSTRATION: STUART BRADFORD
EARLY ONE MORNING LAST MAY, A COMMERCIAL AIRLINER was approaching El Paso International Airport, in West Texas, when a warning popped up in the
cockpit: “GPS Position Lost." The pilot contacted the airline's operations center and received a report that the U.S. Army's White Sands Missile Range,
in South Central New Mexico, was disrupting the GPS signal. “We knew then
that it was not an aircraft GPS fault," the pilot wrote later.
The pilot missed an approach on one runway due to high winds, then came
around to try again. “We were forced to Runway 04 with a predawn landing
with no access to [an instrument landing] with vertical guidance," the pilot wrote. “Runway 04…has a high CFIT threat due to the climbing terrain in the local area."
CFIT stands for “controlled flight into terrain," and it is exactly as
serious as it sounds. The pilot considered diverting to Albuquerque, 370 kilometers away, but eventually bit the bullet and tackled Runway 04 using
only visual aids. The plane made it safely to the ground, but the pilot
later logged the experience on NASA's Aviation Safety Reporting System, a
forum where pilots can anonymously share near misses and safety tips.
This is far from the most worrying ASRS report involving GPS jamming. In
August 2018, a passenger aircraft in Idaho, flying in smoky conditions, reportedly suffered GPS interference from military tests and was saved from crashing into a mountain only by the last-minute intervention of an air
traffic controller. “Loss of life can happen because air traffic control and
a flight crew believe their equipment are working as intended, but are in
fact leading them into the side of the mountain," wrote the controller. “Had [we] not noticed, that flight crew and the passengers would be dead. I have
There are some 90 ASRS reports detailing GPS interference in the United
States over the past eight years, the majority of which were filed in 2019
and 2020. Now IEEE Spectrum has new evidence that GPS disruption to
commercial aviation is much more common than even the ASRS database
suggests. Previously undisclosed Federal Aviation Administration (FAA) data
for a few months in 2017 and 2018 detail hundreds of aircraft losing GPS reception in the vicinity of military tests. On a single day in March 2018,
21 aircraft reported GPS problems to air traffic controllers near Los
Angeles. These included a medevac helicopter, several private planes, and a dozen commercial passenger jets. Some managed to keep flying normally;
others required help from air traffic controllers. Five aircraft reported making unexpected turns or navigating off course. In all likelihood, there
are many hundreds, possibly thousands, of such incidents each year
nationwide, each one a potential accident. The vast majority of this
disruption can be traced back to the U.S. military, which now routinely jams GPS signals over wide areas on an almost daily basis somewhere in the
How to access reports on NASA's Aviation Safety Reporting System
1: To investigate a report, go to the ASRS database: https://asrs.arc.nasa.gov/
2: On the top ribbon, click “Search ASRS Database," and then choose “Search ASRS Online." Click on “Start Search."
3: Follow the steps under “How to Search" at the top. Then, under 7 “Text: