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The New Wave: Introducing Jonathan Makela

Forecasting Communication and Navigation Outages

By Doug Peterson

October 2006

During the Gulf War of 1991, there was anecdotal evidence that American soldiers riding around in their Humvees would suddenly lose the signals coming to their on-board global positioning system (GPS) and even their communication system. Most soldiers assumed that the enemy was jamming their signals, but in truth the culprit was probably the Earth’s ionosphere, not Iraqi soldiers.

The Earth’s ionosphere regularly exhibits “plasma instabilities” -a phenomenon that occurs shortly after sunset and is especially pronounced in regions close to the equator, such as Iraq. And according to CSL professor Jonathan Makela, these plasma instabilities are notorious for disrupting communication and navigation systems.

Makela, a young professor who came to CSL from the Naval Research Laboratory in November of 2004, is a key researcher in the growing movement to forecast when and where these plasma instabilities can wreak havoc with radio signals.

According to Makela, instabilities occur in the ionosphere, a region roughly 200 to 1,000 kilometers (124 to 621 miles) above the Earth. Every day, the sun energizes, or ionizes, this region. As a result, electron density is high in the ionosphere, especially in the “F region” 300 to 400 kilometers (186 to 249 miles) above the Earth.

After sunset, this layer of high-electron density mixes with a region of low-electron density, creating an unstable situation, much as if you had a heavy fluid over a layer of lighter fluid. When radio signals pass through this turbulence, they can be temporarily lost.

“If you’re receiving the signal on the ground, you’ll see your power fluctuate wildly, and that can cause trouble for the tracking loops within your receiver, and you won’t be able to track the signal any more,” Makela says.

Because this phenomenon is greatest near the equator, prior to 10 years ago most scientists assumed that instabilities weren’t a problem in the mid-latitude regions, such as North America. As he puts it, “Over a decade ago, everybody was very excited about what was going on at the equator because of the instabilities and what was occurring at the polar regions with displays like the Aurora Borealis. They just assumed that everything in between was quiet and boring and not important.”

Today, Makela and other scientists understand that serious disruptions can also occur in the mid-latitude regions. This is crucial because the majority of the world’s population lives in these areas.

In mid-latitude regions, the signals are not usually totally lost, as they often are near the equator. But gradients in the ionosphere can still cause global positioning systems to be inaccurate by 20 to 30 meters (66 to 98 feet).

“This may not sound like a lot,” Makela says. “But when you think about using GPS to land airplanes, which is how it may be in a decade, that starts to be a big problem.”

What Makela and other researchers are trying to do is understand the physics behind these phenomena to get a clearer idea of what causes instabilities. If scientists are able to predict when and where the instabilities occur, systems can make adjustments to prevent the loss or disruption of signals.

Makela’s team currently has imaging equipment set up in Chile (the American sector), Hawaii (the Pacific sector), and is hoping to field equipment in the African sector -three of the four sectors near the equator.

When Makela started this work as a graduate student 10 years ago, the massive imaging equipment stood up to 4 feet high. But while he was doing his post-doc work at the Naval Research Laboratory following his PhD from Cornell University, he designed custom-built imaging equipment that is much more compact -only 12 inches long.

Makela is also looking forward to the 2008 launch of the C/NOFS satellite, which will help gather a lot of the background data essential to forecasting plasma instabilities, as well as the resulting outages in communication and navigation systems.

“Hopefully,” he says, “that satellite will bring us into a new era of forecasting capabilities.”

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