Several instruments under study at the Jet Propulsion Laboratory to provide global coverage and surface imaging of Earth's changing environment have been selected for flight on the first of NASA's Earth Observing System (EOS) satellites.
The space-borne instruments and principal investigators at JPL confirmed for flight on the EOS-A1 satellite, the first of three satellites in the EOS-A series, include:
* The Atmospheric Infrared Sounder (AIRS) team, led by Dr. Moustafa Chahine, chief scientist at JPL.
* The Multi-Angle Imaging Spectro-Radiometer (MISR), led by Dr. David Diner, principal investigator of the experiment.
* The Stick Scatterometer (STIKSCAT) investigation, led by principal investigator Dr. Michael Freilich.
In addition, Dr. Alexander Goetz of the University of Colorado will oversee JPL's development of the High Resolution Imaging Spectrometer (HIRIS). The instrument was not selected for flight on EOS-A1 because of unresolved technical issues, but will be a candidate for flight on subsequent EOS satellites.
A team led by JPL's Dr. Richard Willson also will develop the Active Cavity Radiometer Irradiance Monitor (ACRIM), another instrument targeted for flight on a platform of opportunity.
EOS is the centerpiece of NASA's "Mission to Planet Earth," a global-scale research program that will study the Earth as an integrated environmental system, focusing on the interactions of the atmosphere, oceans, land surfaces and biosphere.
"Mission to Planet Earth" is NASA's contribution to the U.S. Global Change Research Program, a multi-agency federal program to observe the Earth, improve understanding of natural and human-induced global change and develop better models and predictive capabilities for interpreting environmental changes.
"The primary goal of the EOS-A satellites is to study the effects of potential global warming by conducting long-term research into the key parameters of the Earth's surface and atmosphere," said Dr. Charles Elachi, assistant laboratory director for JPL's Office of Space Science and Instruments. "Global changes are very complicated and require long-term monitoring," he said. "The EOS-A series will help determine the extent and causes of global climate changes through a program of long-term observations."
Launch of the first satellite, tentatively scheduled for 1998, will mark the beginning of a 15-year-long program of observations of the Earth system, which includes the oceans, land surface, and lower and upper atmospheres.
Specific observations from EOS-A1 will include measurements of the balance of radiation that is absorbed from the sun and emitted by Earth. This radiation balance heats and cools Earth's atmosphere and drives the circulation of the oceans.
Other measurements will include atmospheric circulation, air-sea interactions and the measurement of biological processes, such as the production of phytoplankton, a factor in helping regulate the flow of carbon in the sea. The exchange of carbon between the oceans, surface and atmosphere is essential to understanding potential global warming and the increase of carbon dioxide in Earth's atmosphere.
Nine of the 11 instruments will conduct simultaneous observations of related environmental variables, such as the role of clouds and water vapor on temperature and humidity, or the impact of surface winds on oceanic gas exchange.
"These atmospheric interactions are very important in understanding global warming," Elachi said. "It is critical that we monitor temperature fluctuations, atmospheric and surface patterns simultaneously to understand how they combine to produce certain environmental conditions."
Global views of the Earth system, possible only through use of the space-borne instruments, will enable scientists to make integrated measurements of these environmental patterns without interruptions from rapid atmospheric changes or sudden shifts of sunlight, Elachi said.
JPL's Atmospheric Infrared Sounder (AIRS) will measure atmospheric temperature profiles with an accuracy of 1 degree Centigrade and provide data on atmospheric water vapor, cloud cover, and sea- and land-surface temperatures.
The Multi-Angle Imaging Spectro-Radiometer (MISR) will obtain global observations of the amount of light that is reflected from the Earth's surface and atmosphere at multiple view angles.
MISR will help characterize the optical properties of atmospheric hazes, clouds and the Earth's surface to monitor environmental changes and predict climatic effects.
The Stick Scatterometer (STIKSCAT) is a microwave radar to measure surface wind speeds and directions over the oceans to study atmosphere-ocean interactions and improve global weather predictions.
The Active Cavity Radiometer Irradiance Monitor (ACRIM), which does not require the polar orbit of the EOS-A series, will make long-term measurements of the amount of sunlight reaching Earth's upper atmosphere and help determine the influence of variations in solar output on climate change.
The High-Resolution Imaging Spectrometer (HIRIS) will use its high imaging resolution of 30 meters to study biological and geophysical processes. HIRIS will be able to study complex interactions along the borders of different marine ecosystems, for instance, and determine the annual cycle of phytoplankton in the open sea and along the coastal waters.
The JPL EOS-A satellite instruments are being developed under the auspices of the Laboratory's Office of Space Science and Instruments.
The EOS project is managed by the Goddard Space Flight Center in Greenbelt, Md., for NASA's Office of Space Science and Applications. Overall program management is an international effort involving NASA, the European Space Agency, Japan and Canada.
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