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June
28, 2007
NASA SATELLITE CAPTURES FIRST VIEW OF 'NIGHT-SHINING' CLOUDS
A NASA satellite has captured the first occurrence this summer of
mysterious
iridescent polar clouds that form 50 miles above Earth's surface.
The
first observations
of these clouds by the Aeronomy of Ice in the Mesosphere (AIM)
satellite
occurred above 70 degrees north on May 25. Observers on the ground
began seeing
the clouds on June 6 over northern Europe.
AIM is the first
satellite mission dedicated to the study of these unusual clouds.
These mystifying clouds are called Polar Mesospheric Clouds, or PMCs,
when they
are viewed from space and referred to as "night-shining" clouds, or
noctilucent clouds, when viewed by observers on Earth. The clouds form
during
the Northern Hemisphere's summer season that begins in mid-May and
extends
through the end of August. They are being seen by AIM's instruments
more
frequently as the season progresses. The clouds also are seen in the
high
latitudes of the Southern Hemisphere during the summer months.
Very little is known about how these clouds form over the poles, why
they are being
seen more frequently and at lower latitudes than ever before, or why
they have
been growing brighter. AIM will observe two complete polar mesospheric
cloud
seasons over both poles, documenting for the first time the entire,
complex
life cycle of PMCs.
"It is clear that PMCs are changing, a sign that a distant and rarified
part of our atmosphere is being altered, and we do not understand how,
why or
what it means," stated AIM principal investigator James Russell III,
Hampton University, Hampton, Va. "These observations suggest a
connection
with global change in the lower atmosphere and could represent an early
warning
that our Earth's environment is being altered."
The AIM instruments are returning valuable information on the global
extent and
variability of these clouds and preliminary information on their
particle sizes
and shapes. Early indications are that the clouds occur at high
latitudes early
in the season then move to lower latitudes as time progresses. The AIM
science
team is studying these new data to understand whether the changes in
the clouds
may be related to global climate change.
When the Northern Hemisphere summer season ends in mid- to late August,
the AIM
science team will not have to wait long before the Southern
Hemisphere's season
starts. This occurs about three months later in mid- to late November.
The
Southern season lasts until approximately mid-March of 2008. Early
results from
the AIM mission will be reported at a major international conference
focused on
PMCs and other high altitude layered phenomena to be held at the end of
August
2007 in Fairbanks,
Alaska.
The satellite was launched on April 25, only four weeks before the
first
science observations began. During the satellite-commissioning phase
and now in
routine observations, all three state-of-the-art instruments have been
working
exceptionally well and returning high quality data.
The Cloud Imaging and Particle Size instrument offers a 2-D look at the
clouds,
collecting multiple views from different angles. The cameras are
providing
panoramic PMC images of the Arctic polar cap daily. The Solar
Occultation For
Ice Experiment is measuring new information on cloud particles: their
variability with altitude, the chemicals within the clouds and the
environment
in which the clouds form. The Cosmic Dust Experiment is recording the
amount of
space dust that enters Earth's atmosphere to help scientists assess the
role
this dust plays in PMC formation.
The AIM mission coincides with the two-year, worldwide scientific
community's
International Polar Year, and the mission is expected to make unique
contributions to the International Polar Year's objective of advancing
polar
research.
AIM is the ninth Small Explorers mission under NASA's Explorer Program
and is
managed by the Explorers Program Office at the Goddard Space Flight
Center, Greenbelt,
Md.
The AIM Project Data Center
is located at Hampton University.
For related images on this story, please visit:
http://www.nasa.gov/aim
###
Contact:
Dwayne
Brown/Tabatha Thompson
Headquarters, Washington
202-358-1726/3895
Cynthia O'Carroll
Goddard Space Flight Center, Md.
301-286-4647
Nina Stickles
Hampton University,Hampton, Va.
757-727-5457
This
text
derived from:
http://www.nasa.gov/home/hqnews/2007/jun/HQ_07145_AIM_First_Light.html
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