To better understand how dry landscapes respond to wind-driven changes,
scientists can monitor how fast sand dunes migrate. Researchers Vermeesch
and Drake used pairs of high-resolution optical satellite images taken at
differing times by the Advanced Spaceborne Thermal Emission and Reflection
Radiometer (ASTER) instrument on NASA's Terra spacecraft to monitor the
migration of sand dunes in the Bodele depression of northern Chad in time
intervals ranging from one month to 6.5 years. The scientists used the
displacement maps from the satellite image pairs to distinguish dunes from
interdunes and obtain fine-scale measurements of dune heights and volumes,
allowing them to estimate movements of sand over time. Their work
confirmed that the Bodele dunes are some of the fastest moving sand dunes
on Earth.
With its 14 spectral bands from the visible to the thermal infrared
wavelength region and its high spatial resolution of 15 to 90 meters
(about 50 to 300 feet), ASTER images Earth to map and monitor the changing
surface of our planet.
ASTER is one of five Earth-observing instruments launched December 18,
1999, on NASA's Terra satellite. The instrument was built by Japan's
Ministry of Economy, Trade and Industry. A joint U.S./Japan science team
is responsible for validation and calibration of the instrument and the
data products.
The broad spectral coverage and high spectral resolution of ASTER provides
scientists in numerous disciplines with critical information for surface
mapping and monitoring of dynamic conditions and temporal change. Example
applications are: monitoring glacial advances and retreats; monitoring
potentially active volcanoes; identifying crop stress; determining cloud
morphology and physical properties; wetlands evaluation; thermal pollution
monitoring; coral reef degradation; surface temperature mapping of soils
and geology; and measuring surface heat balance.
The U.S. science team is located at NASA's Jet Propulsion Laboratory,
Pasadena, Calif. The Terra mission is part of NASA's Science Mission
Directorate.
More information about ASTER is available at http://asterweb.jpl.nasa.gov/.
Size: 47.4 by 24.8 kilometers (29.4 by 15.4 miles)
Location: 17 degrees North latitude, 18 degrees East longitude
Orientation: North up
Image Data: ASTER Bands 1,2,3
Original Data Resolution: 15 meters (49.2 feet)
Date Acquired: March 2, 2006
