May 2, 2008
At the Space Weather Workshop in Boulder, Colorado, NASA-funded researchers have released to the general public a "4-D" live model of Earth's ionosphere. Without leaving home, anyone can fly through the dynamic layer of ionized gases that encircles Earth at the edge of space. All that's required is a connection to the Internet. Airline flight controllers can use this tool to plan long-distance business flights over the poles, saving money and time for travelers.
"This is an exciting development," says solar physicist Lika Guhathakurta of NASA headquarters in Washington, D.C. "The ionosphere is important to pilots, ham radio operators, earth scientists and even soldiers. Using this new 4-D tool, they can monitor and study the ionosphere as if they're actually inside it."
The ionosphere is, in a sense, our planet's final frontier. It is the last wisp of Earth's atmosphere that astronauts leave behind when they enter space. The realm of the ionosphere stretches from 50 to 500 miles above Earth's surface where the atmosphere thins to near-vacuum and exposes itself to the fury of the sun. Solar ultraviolet radiation breaks apart molecules and atoms, creating a globe-straddling haze of electrons and ions.
Ham radio operators know the ionosphere well. They can communicate over the horizon by bouncing their signals off of it. Or, they don't communicate at all when a solar flare blasts the ionosphere with X-rays and triggers a radio blackout. The ionosphere also has a big impact on Global Positioning System (GPS) reception. Before a GPS satellite signal reaches the ground, it must first pass through ionospheric gases that bend, reflect and attenuate radio waves. Solar and geomagnetic storms that unsettle the ionosphere can cause position errors as large as 100 meters. Imagine a pilot flying on instruments, descending toward a landing strip only to discover that it's a football field.
"Understanding the ionosphere is clearly important. That's why NASA's Living with a Star (LWS) program funded this work," says Guhathakurta.
Space Environment Technologies Inc. of California received the LWS grant and partnered with Space Environment Corp. of Utah and the U.S. Air Force to develop the 4-D ionosphere.
"The best way to appreciate the 4-D ionosphere is to try it," says W.
Kent Tobiska, president of Space Environment Technologies and chief scientist of its Space Weather Division. You can start your own space flight at terra1.spacenvironment.net/~ionops/++ES4Dintro.html.
Within minutes of downloading the files, Google Earth will appear on your computer screen, the globe wrapped in an atmosphere of vivid color. "Colors represent electron content," Tobiska explains. "Bright red is high density. That's where radio communications are restricted to few or no frequencies. Blue is low density. No problem there."
Using the intuitive Google Earth interface, users can fly above, around and through these regions getting a true 3-D view of the situation. Make that 4-D. "The fourth dimension is time. This is a real-time system updated every 10 minutes."
The 4-D model can be fun and even a little addictive, Tobiska warns. He likes to use it to pilot an imaginary plane over the Arctic. "A growing number of commercial business flights are crossing the Arctic Circle," he says. "It's the shortest distance between, say, Chicago and Beijing and many other major cities."
The ionosphere is particularly important to these flights. While they are over the Arctic, planes lose contact with most geosynchronous satellites and must rely on "old-fashioned" radio communications, a link that could be severed during a radio blackout. Using the 4-D model, a flight controller could examine the ionosphere from the flyer's point of view and use that information to anticipate problems that could cause a flight to be delayed or diverted.
The proper name of the system is CAPS, short for Communication Alert and Prediction System. Earth-orbiting satellites feed the system up-to-the-minute information on solar activity. The measurements are then converted to electron densities by physics-based computer codes.
It is important to note, Tobiska says, that CAPS reveals the ionosphere not only as it is now, but also as it will be in the near future.
Contributing partners to the development of CAPS include the Space Environment Corp. of Utah, Air Force Research Laboratory of Massachusetts, and IPS MeteoStar of Colorado.