NASA’s Ice, Cloud and land Elevation Satellite (ICESat)
is sending home important scientific data and spectacular 3-D
views of Earth’s polar ice sheets, clouds, mountains, and
forestlands. The data are helping scientists understand how
life on Earth is affected by changing climate.

The principal objective of the ICESat mission, and its
Geoscience Laser Altimeter System (GLAS) instrument, is to
measure the surface elevations of the large ice sheets
covering Antarctica and Greenland and determine how they are
changing. Much of an ice sheet’s behavior and response to
changes in climate are apparent in their shape and how that
shape changes with time. The laser sends short pulses of green
and infrared light to Earth 40 times a second and collects the
reflected laser light with a one-meter telescope.

The measurements have provided revolutionary accuracy and
detail about the elevation of ice sheets and the elevation
structure of land surfaces. ICESat is providing scientists
with the most accurate measurements to date of the heights of
clouds. It is also providing critical observations of
atmospheric particles, called aerosols, over the ice sheets
and the rest of the world. These help climate modelers, who
reconstruct the past and project future climate.

“NASA has developed tremendous capabilities over the last
several decades for observing our Earth in two dimensions.
With ICESat, we can see the critical third-dimension, that is,
the vertical dimension of land, water, and the atmosphere, in
new and innovative ways,” said Waleed Abdalati, ICESat Program
Scientist, NASA Headquarters, Washington. “The first few
months of ICESat data have really been phenomenal. We can see
detail in ice and land features that were never visible before
from space.”

Scientists are using ICESat data to develop what are called
“Digital Elevation Models,” 3-D high-resolution images of ice
sheets in Greenland and Antarctica. Gathering these data from
space will allow scientists, to obtain an unprecedented view
of how and where ice sheets are growing and shrinking. This
information is critical to understanding how the Earth’s
changing ice cover affects sea level.

Earlier this year, ICESat’s first topographic profiles across
Antarctica revealed details never before seen of features such
as the ice streams of the Siple Coast, the Amery Ice Shelf,
and megadunes in the Antarctic interior.

“The amount and coverage of heavy dust and pollution loading
in many regions of the Earth that we are seeing in the initial
ICESat data are unexpected,” said James Spinhirne, principal
atmospheric scientist for ICESat at NASA’s Goddard Space
Flight Center, Greenbelt, Md. These include the rivers of dust
from the Sahara desert, massive dust storms, and large-scale
smoke from burning vegetation. The observations tie smoke,
dust and clouds directly to winds and global transport.

ICESat was launched January 12, 2003. It is the latest in a
series of NASA Earth observation spacecraft designed to study
the environment of our home planet and how it may be changing.
NASA’s Earth Science Enterprise is dedicated to understanding
the Earth as an integrated system and applying Earth System
Science to improve prediction of climate, weather and natural
hazards using the unique vantage point of space.

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