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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 no doubt."

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 country.

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: Narrative/Synopsis," click on “[words]." Then click on “Text contains Click Here."

4: In the pop-up window, enter some of the text that is quoted in this story. In the “Fields to search" field at the bottom, click “Narrative" (but you can also try “Synopsis").

5: If you're searching on more than one word, you need to format it inside parentheses, thus: (GPS JAMMING).

6: Click “Save." The pop-up will disappear.

7: Click “Run Search" at the bottom right.

8: Under “Display your results," click “View all reports."

The military is jamming GPS signals to develop its own defenses against GPS jamming. Ironically, though, the Pentagon's efforts to safeguard its own troops and systems are putting the lives of civilian pilots, passengers, and crew at risk. In 2013, the military essentially admitted as much in a report, saying that “planned EA [electronic attack] testing occasionally causes interference to GPS based flight operations, and impacts the efficiency and economy of some aviation operations."

In the early days of aviation, pilots would navigate using road maps in daylight and follow bonfires or searchlights after dark. By World War II, radio beacons had become common. From the late 1940s, ground stations began broadcasting omnidirectional VHF signals that planes could lock on to, while shorter-range systems indicated safe glide slopes to help pilots land. At their peak, in 2000, there were more than a thousand very high frequency (VHF) navigation stations in the United States. However, in areas with widely spaced stations, pilots were forced to take zigzag routes from one station to the next, and reception of the VHF signals could be hampered by nearby buildings and hills.

Everything changed with the advent of global navigation satellite systems (GNSS), first devised by the U.S. military in the 1960s. The arrival in the mid-1990s of the civilian version of the technology, called the Global Positioning System, meant that aircraft could navigate by satellite and take direct routes from point to point; GPS location and altitude data was also accurate enough to help them land.

The FAA is about halfway through its NextGen effort, which is intended to make flying safer and more efficient through a wholesale switch from ground-based navigation aids like radio beacons to a primarily satellite-enabled navigation system. Along with that switch, the agency began decommissioning VHF navigation stations a decade ago. The United States is now well on its way to having a minimal backup network of fewer than 600 ground stations.

Meanwhile, the reliance on GPS is changing the practice of flying and the habits of pilots. As GPS receivers have become cheaper, smaller, and more capable, they have become more common and more widely integrated. Most airplanes must now carry Automatic Dependent Surveillance-Broadcast (ADS-B) transponders, which use GPS to calculate and broadcast their altitude, heading, and speed. Private pilots use digital charts on tablet computers, while GPS data underpins autopilot and flight-management computers. Pilots should theoretically still be able to navigate, fly, and land without any GPS assistance at all, using legacy radio systems and visual aids. Commercial airlines, in particular, have a range of backup technologies at their disposal. But because GPS is so widespread and reliable, pilots are in danger of forgetting these manual techniques.

When an Airbus passenger jet suddenly lost GPS near Salt Lake City in June 2019, its pilot suffered “a fair amount of confusion," according to the pilot's ASRS report. “To say that my raw data navigation skills were lacking is an understatement! I've never done it on the Airbus and can't remember having done it in 25 years or more."

“I don't blame pilots for getting a little addicted to GPS," says Todd E. ­Humphreys, director of the Radionavigation Laboratory at the University of Texas at Austin. “When something works well 99.99 percent of the time, humans don't do well in being vigilant for that 0.01 percent of the time that it doesn't."

Losing GPS completely is not the worst that can happen. It is far more dangerous when accurate GPS data is quietly replaced by misleading information. The ASRS database contains many accounts of pilots belatedly realizing that GPS-enabled autopilots had taken them many kilometers in the wrong direction, into forbidden military areas, or dangerously close to other aircraft.

In December 2012, an air traffic controller noticed that a westbound passenger jet near Reno, Nev., had veered 16 kilometers (10 miles) off course. The controller confirmed that military GPS jamming was to blame and gave new directions, but later noted: “If the pilot would have noticed they were off course before I did and corrected the course, it would have caused [the] aircraft to turn right into [an] opposite direction, eastbound [jet]."

So why is the military interfering so regularly with such a safety-critical system? Although most GPS receivers today are found in consumer smartphones, GPS was designed by the U.S. military, for the U.S. military. The Pentagon depends heavily on GPS to locate and navigate its aircraft, ships, tanks, and troops.

For such a vital resource, GPS is exceedingly vulnerable to attack. By the time GPS signals reach the ground, they are so faint they can be easily drowned out by interference, whether accidental or malicious. Building a basic electronic warfare setup to disrupt these weak signals is trivially easy, says Humphreys: “Detune the oscillator in a microwave oven and you've got a superpowerful jammer that works over many kilometers." Illegal GPS jamming devices are widely available on the black market, some of them marketed to professional drivers who may want to avoid being tracked while working.

Other GNSS systems, such as Russia's GLONASS, China's BeiDou, and Europe's Galileo constellations, use slightly different frequencies but have similar vulnerabilities, depending on exactly who is conducting the test or attack. In China, mysterious attacks have successfully “spoofed" ships with GPS receivers toward fake locations, while vessels relying on BeiDou reportedly remain unaffected. Similarly, GPS signals are regularly jammed in the eastern Mediterranean, Norway, and Finland, while the Galileo system is untargeted in the same attacks.

The Pentagon uses its more remote military bases, many in the American West, to test how its forces operate under GPS denial, and presumably to develop its own electronic warfare systems and countermeasures. The United States has carried out experiments in spoofing GPS signals on at least one occasion, during which it was reported to have taken great care not to affect civilian aircraft.

Despite this, many ASRS reports record GPS units delivering incorrect positions rather than failing altogether, but this can also happen when the satellite signals are degraded. Whatever the nature of its tests, the military's GPS jamming can end up disrupting service for civilian users, particularly high-altitude commercial aircraft, even at a considerable distance.

The military issues Notices to Airmen (NOTAM) to warn pilots of upcoming tests. Many of these notices cover hundreds of thousands of square kilometers. There have been notices that warn of GPS disruption over all of Texas or even the entire American Southwest. Such a notice doesn't mean that GPS service will be disrupted throughout the area, only that it might be disrupted. And that uncertainty creates its own problems.

In 2017, the FAA commissioned the nonprofit Radio Technical Commission for Aeronautics to look into the effects of intentional GPS interference on civilian aircraft. Its report, issued the following year by the RTCA's GPS Interference Task Group, found that the number of military GPS tests had almost tripled from 2012 to 2017. Unsurprisingly, ASRS safety reports referencing GPS jamming are also on the rise. There were 38 such ASRS narratives in 2019—nearly a tenfold increase over 2018.

New internal FAA materials obtained by Spectrum from a member of the task group and not previously made public indicate that the ASRS accounts represent only the tip of the iceberg. The FAA data consists of pilots' reports of GPS interference to the Los Angeles Air Route Traffic Control Center, one of 22 air traffic control centers in the United States. Controllers there oversee air traffic across central and Southern California, southern Nevada, southwestern Utah, western Arizona, and portions of the Pacific Ocean—areas heavily affected by military GPS testing.

This data includes 173 instances of lost or intermittent GPS during a six-month period of 2017 and another 60 over two months in early 2018. These reports are less detailed than those in the ASRS database, but they show aircraft flying off course, accidentally entering military airspace, being unable to maneuver, and losing their ability to navigate when close to other aircraft. Many pilots required the assistance of air traffic control to continue their flights. The affected aircraft included a pet rescue shuttle, a hot-air balloon, multiple medical flights, and many private planes and passenger jets.

In at least a handful of episodes, the loss of GPS was deemed an emergency. Pilots of five aircraft, including a Southwest Airlines flight from Las Vegas to Chicago, invoked the “stop buzzer," a request routed through air traffic control for the military to immediately cease jamming. According to the Aircraft Owners and Pilots Association, pilots must use this phrase only when a safety-of-flight issue is encountered.

To be sure, many other instances in the FAA data were benign. In early March 2017, for example, Jim Yoder was flying a Cessna jet owned by entrepreneur and space tourist Dennis Tito between Las Vegas and Palm Springs, Calif., when both onboard GPS devices were jammed. “This is the only time I've ever had GPS go out, and it was interesting because I hadn't thought about it really much," Yoder told Spectrum. “I asked air traffic control what was going on and they were like, 'I don't really know.' But we didn't lose our ability to navigate, and I don't think we ever got off course."

Indeed, one of the RTCA task group's conclusions was that the Notice to Airmen system was part of the problem: Most pilots who fly through affected areas experience no ill effects, causing some to simply ignore such warnings in the future.

“We call the NOTAMs 'Chicken Little,' " says Rune Duke, who was cochair of the RTCA's task group. “They say the sky is falling over large areas…and it's not realistic. There are mountains and all kinds of things that would prevent GPS interference from making it 500 nautical miles [926 km] from where it is initiated."

GPS interference can be affected by the terrain, aircraft altitude and attitude, direction of flight, angle to and distance from the center of the interference, equipment aboard the plane, and many other factors, concluded the task group, which included representatives of the FAA, airlines, pilots, aircraft manufacturers, and the U.S. military. One aircraft could lose all GPS reception, even as another one nearby is completely unaffected. One military test might pass unnoticed while another causes chaos in the skies.

This unreliability has consequences. In 2014, a passenger plane approaching El Paso had to abort its landing after losing GPS reception. “This is the first time in my flying career that I have experienced or even heard of GPS signal jamming," wrote the pilot in an ASRS report. “Although it was in the NOTAMs, it still caught us by surprise as we really did not expect to lose all GPS signals at any point. It was a good thing the weather was good or this could have become a real issue."

Sometimes air traffic controllers are as much in the dark as pilots. “They are the last line of defense," Duke told Spectrum. “And in many cases, air traffic control was not even aware of the GPS interference taking place."

The RTCA report made many recommendations. The Department of Defense could improve coordination with the FAA, and it could refrain from testing GPS during periods of high air traffic. The FAA could overhaul its data collection and analysis, match anecdotal reports with digital data, and improve documentation of adverse events. The NOTAM system could be made easier to interpret, with warnings that more accurately match the experiences of pilots and controllers.

Remarkably, until the report came out, the FAA had been instructing pilots to report GPS anomalies only when they needed assistance from air traffic control. “The data has been somewhat of a challenge because we've somewhat discouraged reporting," says Duke. “This has led the FAA to believe it's not been such a problem."

NOTAMs now encourage pilots to report all GPS interference, but many of the RTCA's other recommendations are languishing within the Office of Accident Investigation and Prevention at the FAA.

New developments are making the problem worse. The NextGen project is accelerating the move of commercial aviation to satellite-enabled navigation. Emerging autonomous air systems, such as drones and air taxis, will put even more weight on GPS's shaky shoulders.

When any new aircraft is adopted, it risks posing new challenges to the system. The Embraer EMB-505 Phenom 300, for instance, entered service in 2009 and has since become the world's best-selling light jet. In 2016, the FAA warned that if the Phenom 300 encountered an unreliable or unavailable GPS signal, it could enter a Dutch roll (named for a Dutch skating technique), a dangerous combination of wagging and rocking that could cause pilots to lose control. The FAA instructed Phenom 300 owners to avoid all areas of GPS interference. Embraer said that it fixed the issue in 2017.

As GPS assumes an ever more prominent role, the military is naturally taking a stronger interest in it. “Year over year, the military's need for GPS interference-event testing has increased," says Duke. “There was an increase again in 2019, partly because of counter-UAS [drone] activity. And they're now doing GPS interference where they previously had not, like Michigan, Wisconsin, and the Dakotas, because it adds to the realism of any type of military training."

So there are ever more GPS-jamming tests, more aircraft navigating by satellite, and more pilots utterly reliant on GPS. It is a feedback loop, and it constantly raises the chances that one of these near misses and stop buzzers will end in catastrophe.

When asked to comment, the FAA said it has established a resilient navigation and surveillance infrastructure to enable aircraft to continue safe operations during a GPS outage, including radio beacons and radars. It also noted that it and other agencies are working to create a long-term GPS backup solution that will provide position, navigation, and ­timing—again, to minimize the effects of a loss of GPS.

However, in a report to Congress in April 2020, the agency coordinating this effort, the U.S. Department of Homeland Security, wrote: “DHS recommends that responsibility for mitigating temporary GPS outages be the responsibility of the individual user and not the responsibility of the Federal Government." In short, the problem of GPS interference is not going away.

In September 2019, the pilot of a small business jet reported experienced jamming on a flight into New Mexico. He could hear that aircraft all around him were also affected, with some being forced to descend for safety. “Since the FAA is deprecating [ground-based radio aids], we are becoming dependent upon an unreliable navigation system," wrote the pilot upon landing. “This extremely frequent [interference with] critical GPS navigation is a significant threat to aviation safety. This jamming has to end."

The same pilot was jammed again on his way home.

This article appears in the February 2021 print issue as “Lost in Airspace."

This article was updated on 26 January 2021.

Mark Harris is an investigative science and technology reporter based in Seattle, with a particular interest in robotics, transportation, green technologies, and medical devices. He’s on Twitter at @meharris  and email at mark(at)meharris(dot)com. Email or DM for Signal number for sensitive/encrypted messaging. 

Each has made CMOS camera chips with pixel pitches of just 0.56 micrometers

To get 0.56-micrometer CMOS image-sensor pixels, Samsung had redesign the “fences” [white] that keep out stray light.

Last month, two companies said they have reached the next stage in shrinking the pixels on CMOS camera chips. Both Santa Clara–based Omnivision and South Korea’s Samsung claimed pixels with a pitch of just 0.56 micrometers (measured from the center of one pixel to the center of the next), which is about as large as the wavelength of green light.

Samsung currently produces camera chips with 0.64-micrometer pixels, Omnivision released a 0.61-micrometer sensor in January. Omnivision says a 200-megapixel-resolution image sensor with the new 0.56-micrometer pitch will go to customers later this year, and consumers can expect to find them in their smartphones in 2023. Samsung did not say when its imagers would appear, describing the innovation at IEEE International Solid-States Circuits Conference (ISSCC) in February.

Light enters a CMOS imager pixel via a microlens, then passes through a color filter before striking a silicon photodiode. In the photodiode, the light causes charge to accumulate, which is then sensed and the amount digitized by separate circuits. Making all this smaller leads to a host of potential problems.

For example, small pixels are more subject to cross talk, where light entering at a slight angle to the pixel passes through to its neighbor, reducing contrast. So engineers have to build structures that will block this cross talk. Both companies rely on technology called deep trench isolation for this. That is, each pixel’s silicon is separated from its neighbor by a barrier that runs all the way down through the silicon. At the top of the pixel, where the light enters, they use a comparatively short “fence” of dielectric between the silicon and the pixel’s integrated microlenses.

Deep trench isolation structures [long vertical towers] keep light from entering from neighboring pixels. Metal fences [top] also help with this. Samsung boosted the fencing's abilities by inserting a gap of air [bright white] within each.Samsung

Seeking to strengthen the barrier against stray light, Samsung made modifications to the fence. Reasoning that a lower-index-of-refraction material would keep the light out better, Samsung went to the extreme—an air gap. Air has the lowest index of refraction of any material compatible with the CMOS manufacturing process, Samsung’s Sungbong Park told engineers at ISSCC. Through a process of deposition and etching, Samsung engineers made an air cavity within the fence, reducing cross talk by 1.2 percent and boosting quantum efficiency—the ratio of photons converted to electrons—by 7 percent.

Another problem with simply scaling down pixels is that you can store less charge in them before they become saturated, limiting the pixel’s dynamic range. (Dynamic range is the ability to sense in both low and bright light.) Samsung’s 0.64-micrometer device can hold the equivalent of 6,000 electrons, Park said. Shrink that region down to 0.56 micrometers without changing anything and you’re left with only 3,400. Samsung increased the volume by slimming down the isolation walls and adjusting the profile of dopant elements in the photodiode, bringing the capacity back up to 6,000 electrons.

In addition to slimming down the deep trench isolation barrier, Samsung altered its composition. Engineers replaced some of the insulation with material having a higher dielectric constant, making it better at preventing current from flowing when there is no light falling on the pixel.

Both companies also use chip stacking to make more room for pixels. In order to be interpreted by a digital processor, the value at each pixel must first be digitized. At one time, this meant that the photodetecting parts of the pixels all had analog-to-digital converter circuits beside them. But these days, those circuits are built on a separate chip, which is bonded to the photodetector chip, leaving room for more pixels. While Samsung has its own image-chip fabs, Omnivision relied on Taiwan Semiconductor Manufacturing Corp. for both the circuit chip and the photodetector chip.

There will be even tinier pixels in the future, Park assured engineers. Shrinking pixels “is not easy, but we will find a way just as we always have,” he said.

This young professional is a media spokesperson, author, and mentor

Kathy Pretz is editor in chief for The Institute, which covers all aspects of IEEE, its members, and the technology they're involved in. She has a bachelor's degree in applied communication from Rider University, in Lawrenceville, N.J., and holds a master's degree in corporate and public communication from Monmouth University, in West Long Branch, N.J.

It’s hard to believe that Ramneek Kalra was once an introvert. The Young Professional is an IEEE Impact Creator, brand ambassador, and influencer.

He’s also a prolific writer. He has penned several research papers and is the author of an IEEE-USA book. In addition, he is the new editor of the IEEE IC Vaani, the India Council newsletter.

Kalra says he found his voice in 2016 after becoming a member of the IEEE student branch at Guru Gobind Singh Indraprastha University in Dwarka, Delhi. Before joining, he says, he feared that sharing his knowledge with others would dilute his own.

“That was the misconception I had,” he acknowledges. “But when I joined IEEE and explored public speaking and even the management of the student branch itself as chair in my final year, I got the feeling that IEEE was my place, and that it could help me grow personally as well as professionally.”

He boils down the benefits of IEEE membership into three themes: participation, volunteering, and networking. For the past six years, he’s been doing all three.

Kalra says he knew he wanted to become an engineer after his mother bought him a science kit for his 11th birthday. He decided on a career as a computer science engineer after learning HTML and Java in the 11th grade. For a class project, he wrote management software for his local bank.

While pursuing his bachelor’s degree in computer science at Guru Gobind Singh Indraprastha, one of his professors encouraged students to join the newly established IEEE student branch there. It was the first time Kalra had heard of the organization. He became the branch’s first computer science student and “broke the misconception that IEEE is only for electrical and electronics engineers,” he says.

“My main intention for joining,” he says, “was to explore, volunteer, and participate.”

For the first two years, he was the branch’s webmaster. During his senior year in 2019, he served as its chair. He credits his time with the branch for helping him acquire skills such as event planning, team management, and finding sponsors to support the branch’s programs.

“I got the feeling that IEEE was my place, and that it could help me grow personally as well as professionally.”

He was also busy writing research papers on each of his computer science projects including biometric authentication, smart metering solutions, and traffic management using 5G and edge computing. In his first semester, he created a program to speed up checking out books from the university’s library. For his efforts, he received the school’s Technocrat Award.

Word got out about Kalra’s programming skills. The director of India’s largest national broadcasting company, All India Radio, in New Delhi, learned about Kalra’s library checkout program and asked him to write software to streamline the broadcaster’s accounting processes. The project took six months.

“That was the first time I got recognized as an engineer,” Kalra says. His programs are still being used today.

Kalra has an Indian patent application pending for an automatic bus ticketing and verification machine, which allows citizens to use their thumbprint to purchase a digital bus ticket. He was inspired to create the system after waiting in many long lines to purchase a ticket with money.

Several of his papers have been published in the IEEE Xplore Digital Library. Once again, his membership proved valuable.

“When I started my journey in research paper writing, I wasn’t aware of how to write a research paper or even how to write one using proper technical English, which is required,” he says. “IEEE resources, including the IEEE Author Center, actually helped me out a lot.”

Kalra has been invited to present his research at several IEEE conferences. He credits the public speaking opportunities with helping him strengthen his English.

Kalra says that in his final year of school, he was so busy working on IEEE projects, writing papers, and presenting at conferences that his advisor admonished him for neglecting to search for a job after graduation. But Kalra’s time volunteering paid off.

His volunteer activities and background in event management and team management, as well as his communication skills, helped him land a job in 2019 as a project engineer with Wipro. The interviewer and the HR representative of the IT services company in Greater Noida, Uttar Pradesh, were impressed with the work Kalra did for IEEE, he says.

Kalra credits IEEE for giving him the confidence to talk about his abilities.

Kalra left Wipro in 2021 to join a cloud computing organization in India. There he spreads the word about IEEE, encouraging his colleagues to join and explore the benefits.

Even with his new job, Kalra still finds time to volunteer. As an IEEE brand ambassador, he educates students and others on how to properly display IEEE branding on websites, newsletters, banners, event materials, and other items. He gives workshops about the guidelines to student branches.

In his role as an IEEE Impact Creator, he shares his insights on engineering, computing and technology with the media.

He’s also an active Young Professional with the IEEE Computer Society. He chairs its history and research subcommittee, which is part of the society’s Distinguished Visitors initiative.

In addition, he is the founding chair of the Quarter Tech Talk Table, which was initiated by Young Professionals and Impact Creators. As the new editor for IEEE IC Vaani, he contributed to transforming it to a digital format, which was recently launched.

He encourages preuniversity students to pursue an engineering career. He is a member of the IEEE Educational Activities Board’s preuniversity education coordinating committee. He participates in IEEE TryEngineering, IEEE Women in Engineering’s Student-Teacher and Research Engineer/Scientist (STAR) program and its new Project-Based Learning Camp for students in Grades 7 to 12.

And if he wasn’t busy enough, last year he wrote Idea to Product: A Research Pathway for Students, published by IEEE-USA. The book is free for members, and he also described the process in an IEEE Collabratec hosted session.

His next book, he says, will be on his participation, volunteering, and networking model. It will cover the benefits of IEEE and aim to encourage members to remain with the organization, he says, so they, too, can feel that it is their professional home.

In this webinar you will learn more about solutions for high test speeds and throughput as well as how to cover multiple tests with one set-up.

Jürgen Kausche, Product Manager for EMC and RF test systems and projects