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April
30, 2008: Today, NASA-funded researchers released
to the general public a new "4D" live model of Earth's
ionosphere. Without leaving home, anyone can fly through the
layer of ionized gas that encircles Earth at the edge of space
itself. All that's required is a connection to the Internet.
"This
is an exciting development," says solar physicist Lika
Guhathakurta of NASA headquarters in Washington, DC. "The
ionosphere is important to pilots, ham radio operators, earth
scientists and even soldiers. Using this new 4D tool, they
can monitor and study the ionosphere as if they're actually
inside it."
Click
on the screenshot to view a 19 MB video demo:
![see caption](images/4dionosphere/screenshot2_strip.jpg)
Above:
A screen-shot of the 4D ionosphere. Clicking on the image
launches a 19 MB video
demo. You can download and launch your own 4D ionosphere
by following these simple
instructions.
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 the ionosphere—or
communicate not 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 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 GPS position errors
as large as 100 meters. Imagine a pilot flying on instruments
descending toward a landing strip only to discover it is a football
field to the right.
"Understanding
the ionosphere is clearly important. That's why NASA's Living
with a Star (LWS) program funded this work," says Guhathakurta,
LWS program scientist. Space Environment Technologies, Inc.
of California received the LWS grant and they partnered with
Space Environment Corp. of Utah and the US Air Force to develop
the 4D ionosphere.
"The
best way to appreciate the 4D ionosphere is to try it,"
says W. Kent Tobiska, president of Space Environment Technologies
and chief scientist of its Space Weather Division. He offers
these instructions:
"One,
download and install Google
Earth."
"Two,
visit our web
site and click on the link 'Total Electron Content.'"
Right:
Kent Tobiska demonstrates the use of the 4D Ionosphere: 19
MB video.
Wait
for the file to load and presto—you're flying through the
ionosphere: screenshot.
"Colors
represent electron content," Tobiska explains. "Bright
red is high density; that's where radio communications are
restricted to few or no frequencies. Blue denotes low density;
no problem there."
Using
the intuitive Google Earth interface, users can fly above,
around and through these regions getting a true 3D view of
the situation. Make that 4D. "The fourth dimension is
time. This is a real-time system updated every 10 minutes,"
he says.
The
4D model can be fun and even a little addictive, warns Tobiska,
who 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."
Below:
An increasing number of international business flights cross
Earth's Arctic to save time, fuel and money. [Larger
image]
![see caption](images/4dionosphere/polar_routes_map_strip2.jpg)
The
ionosphere is particularly important to these lucrative 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 4D 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,
says Tobiska, that CAPS reveals the ionosphere not only as
it is now, but also as it is going to be the near future.
"Forecasting is a key aspect of CAPS available to our
customers from, e.g., the Dept. of Defense and the airline
industry."
Start
your own flight here.
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Author: Dr.
Tony Phillips | Editor:
Dr. Tony Phillips | Credit: Science@NASA
|