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by Patrick Barry
and Tony Phillips
"fasten seatbelts" light turns off, and you get up to ask
the stewardess for a pillow; it's going to be a long flight. Only a
kilometer ahead in the cloudless sky, a downward draft of sheering
winds looms. When the plane hits these winds, the "turbulence"
will shake the cabin violently and you could be seriously hurt.
You don't know about those winds, of course, and neither does the
pilot. Today's weather satellites can't see winds in clear
skies: they rely on the motion of clouds to infer which way the winds
"Believe it or not, their best indication of wind sheer right now
is warnings from aircraft that have gone through it ahead of them,"
says Bill Smith of NASA's Langley Research Center.
But a new satellite technology being pioneered by NASA and NOAA could
improve this shaky situation. It's called GIFTS, short for
Geosynchronous Imaging Fourier Transform Spectrometer. GIFTS is
an infra-red sensor that can detect winds in cloudless skies by
watching the motions of atmospheric water vapor. Water vapor is mostly
invisible to the human eye, but it reveals itself to GIFTS by the
infra-red radiation it absorbs.
Smith is the lead scientist for EO-3, a satellite designed to test out
this new technology. Slated for launch in 2005 or 2006, EO-3
will carry GIFTS to Earth orbit where it can produce 3-dimensional
movies of winds in the atmosphere below.
These wind data will not only improve safety, but also help the
airlines save money. Knowing the winds along a flight route allows
airlines to adjust the plane's fuel load accordingly, thus reducing
the weight that the engines must lift. Saved fuel means saved money
and less pollution.
GIFTS can help planes avoid another potentially lethal problem, too:
Ice forming on their wings. If a cloud contains
"supercooled" water droplets whose temperature is below
freezing, those droplets will form ice on the wings of planes that
pass through it. By looking at about 1700 different frequencies of the
light coming from clouds, GIFTS can measure the temperature of the
cloud top and determine whether it contains water droplets that could
cause aircraft icing. With information from GIFTS in hand, pilots can
simply avoid clouds that appear dangerous.
Once EO-3 demonstrates the accuracy of GIFTS, airlines will be able to
capitalize on this potential to make flying a cheaper and safer
Learn more about the GIFTS instrument and other advanced
technologies being tested on the EO-3 mission at
nmp.jpl.nasa.gov/eo3. Kids can go to The Space Place to play a
data compression game related to EO-3 at
article was provided by the Jet Propulsion Laboratory, California
Institute of Technology, under a contract with the National
Aeronautics and Space Administration.
carrying the GIFTS instrument, will be in a geosynchronous orbit for
extended monitoring of large regions of our planet and enabling
observation of weather patterns at higher resolution than possible
with existing geostationary satellites.
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