NEW
NASA FIELD CAMPAIGN SEES THE FOREST FOR THE SATELLITE
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1 | | Aerial
view of the Harvard Forest. Photograph by David Foster | Something
different is "growing" in the Harvard Forest in central Massachusetts.
Researchers and their instruments have spread throughout the forest in an effort
to check the accuracy of land maps generated from NASA satellite data. These maps
provide valuable information about the Earth's land surface and different types
of ecological communities. Scientists
are gathering at the Harvard Forest Long Term Ecological Research (LTER) site
in Petersham, Mass. from August 1 through 8, to further improve land maps created
from MODIS (Moderate Resolution Imaging Spectrometer) and MISR (Multi-angle Imaging
Spectro-Radiometer) sensors aboard NASA's Terra satellite.
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2 | | Harvard
Pond, Photograph by David Foster | The
intensive campaign includes field, tower, and aircraft measurements and involves
two teams from Boston University (BU), the University of Arizona, and NASA's Jet
Propulsion Laboratory under the umbrella of the MODIS Land Team, and the "BigFoot
project." These teams are being hosted by Harvard Forest LTER through collaboration
with Steve Wofsy, Professor of Atmospheric and Environmental Chemistry, Harvard
University. The
BigFoot project, funded by NASA, works in collaboration with the MODIS Land Team
to analyze the landscape features of areas centered around existing "flux
towers," or towers with sensors that collect data on the relationship between
ecological communities, climate and the atmosphere. Based
on field campaigns, the MODIS Land Team and the BigFoot project will use different
methods to gather and create datasets of the land that will then be developed
into maps. Field data, Landsat satellite imagery, and various geophysical statistics
and models of ecosystem processes are all combined to create new maps. These new
maps will then be correlated to the resolution (500m and 1km) of the MODIS and
MISR data maps for comparison. By doing so, not only can various land and air
methods be checked against each other to see which are most accurate, but the
satellite maps themselves can be checked against other methods of gathering the
same information.
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3 | Harvard
Forest, Harvard University
since 1907, Long Term Ecological Research Site,
since 1988. Photograph by John O'Keefe | During
this campaign, the science teams will take detailed measurements of the temperate
broadleaf ecological community at the Harvard Forest from the land and by air.
The data will be compiled, integrated, and then compared with MODIS and MISR.
"These
land and aircraft measurements will be combined to produce a high resolution product
which can then be compared with a corresponding MODIS product," said Jeff
Morisette, MODIS Land Team Validation Coordinator. "Both the field data and
the satellites produce the same end product. They're trying to get the same information
but are using different modes of getting there. Comparing the two helps us understand
the uncertainty in the satellite-derived products" The
Harvard Forest LTER site is one of the initial 24 NASA Earth Observing System
(EOS) Land Validation Core Sites. These sites provide an infrastructure to support
in situ measurements and build on existing programs of long-term measurements.
The sites provide points on land where satellite, aircraft, and ground data collection
can all be synchronized and compared. Also, they are areas for which scientists
can readily access in situ data coupled with EOS imagery and data-rich maps.
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4 | Environmental
Measurements Station - Prospect Hill
Photograph by John O'Keefe |
Currently,
two Boston University teams are working in the Harvard Forest to develop the Leaf
Area Index / Fraction of Photosynthetically Active Radiation (LAI/FPAR) vegetation
maps from MODIS and MISR and Albedo/BRDF (Bidirectional Reflectance Distribution
Function) maps from MODIS.
The LAI shows how much vegetation exists in
an area as compared to the total ground area. The amount of greenness indicates
photosynthesis that occurs in plants (from absorbed sunlight) and the amount of
carbon they take in from the atmosphere. Also, FPAR measures the proportion of
available solar radiation that a canopy absorbs. Albedo is the fraction of solar
radiation that is reflected by the land/plant surface back into the atmosphere.
With respect to the land surface, it quantifies the amount of energy that is absorbed
by the biosphere, or the part of the Earth where life exists. BRDF describes how
reflected light is affected by the angle at which the sun's rays hit an object.
In
addition to the work by BU, other teams and the "BigFoot" project, the
"FLUXNET Project," a NASA and Department of Energy validation activity,
is also utilizing the Harvard Forest. As
part of the AmeriFlux network, FLUXNET provides researchers access to high quality
measurements of carbon dioxide, water vapor, and energy fluxes and more. The collection
of data from many worldwide terrestrial ecosystems (including managed systems)
are contributing to research on understanding how carbon, water, and nutrient
cycles of terrestrial ecosystems respond to environmental and climatic disturbances,
especially through the development and validation of ecosystem models and the
validation of remotely-sensed products.
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5 | | Sunset
over Harvard Forest, Photograph by David Orwig | The
Earth Observing System (EOS) is the centerpiece of NASA's Earth Science Enterprise
(ESE). It consists of a science component and a data system that supports a coordinated
series of polar-orbiting and low inclination satellites for long-term global observations
of the land surface, biosphere, solid Earth, atmosphere, and oceans. Back
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