The first of NASA's Earth Observing System (EOS) Spacecraft, EOS AM-1, has reached a critical milestone with the delivery of its last science instrument, allowing completion of module testing and integration of the instruments and the spacecraft. The last instrument arrived on Aug. 25.

EOS AM-1 begins a new generation of Earth science - one that studies the Earth as a global system. EOS will carry a complement of five synergistic instruments. "We're absolutely thrilled to reach this milestone," said Dr. Robert Price, Director of NASA's Mission to Planet Earth Program Office at the Goddard Space Flight Center, Greenbelt, MD. "We're now well on our way to having the spacecraft ready for its June 1998 launch."

There are two JPL instruments on this platform that are designed to measure the amount of radiation that is absorbed and reflected by Earth's surface and atmosphere. The Multi-Angle Imaging Spectro Radiometer (MISR) is built by JPL; The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is provided by the Japan's Ministry of International Trade and Industry with scientific support provided by JPL. Both these instruments will help scientists study clouds, volcanoes, and how energy, carbon and water are exchanged between the air-land and the air-sea.

The next critical step for EOS AM-1 is to complete systems tests which validate the ability of the integrated spacecraft to withstand the harsh environment of space and to work with its ground system. Following that, the spacecraft will be delivered to Vandenberg Air Force Base, CA, for launch processing.

The EOS AM-1 spacecraft is being assembled and tested by Lockheed-Martin at its Valley Forge, PA, production facility.

The EOS series spacecraft are the cornerstone of NASA's Mission to Planet Earth (MTPE) Enterprise, a long-term coordinated research effort to study the Earth as a global system and the effects of natural and human-induced changes on the global environment. EOS AM-1 will use this unique perspective from space to observe the Earth's continents, oceans and atmosphere with five state-of-the-art instruments with measurement capability and accuracy never flown before. This unique approach enables scientists to study the interactions among these three components of the Earth system, which determine the cycling of water and nutrients on Earth.

"EOS AM-1 will study simultaneously clouds, water vapor, aerosol, particles, trace gases, terrestrial and oceanic properties, the interaction between them and their effect on atmospheric radiation and climate," said Dr. Yoram Kaufman, EOS AM-1 project scientist. "Moreover, EOS AM-1 will observe changes in Earth's radiation energy budget, together with measurements of changes in land/ocean surface and interaction with the atmosphere through exchanges of energy, carbon, and water. Clearly comprehending these interactive processes is essential to understanding global climate change," he said.

A polar-orbiting spacecraft, EOS AM-1 is scheduled for launch in June 1998 aboard an Atlas-Centaur IIAS launch vehicle from Vandenberg AFB. Because the AM series emphasizes observations of terrestrial surface features, its orbit is designed to cross the equator at 10:30 a.m., when cloud cover is minimalized.

MISR will measure the amount of sunlight that is reflected and absorbed by the Earth's surface and by particle's in the atmosphere. This information will help scientists determine how different types of clouds affect the amount of sunlight that is reflected back into space and what role clouds play in the overall global climate. MISR will also monitor the amount of aerosols -- tiny, solid particles -- in the atmosphere to understand where these particles come from and how they influence the climate. The instrument will also record information about land conditions and measure photosynthesis of plants on a global scale.

The ASTER instrument is also a radiometer and it will be used to monitor long-term local and regional changes on the Earth's surface. Such changes often lead to or occur as a response to global climate change. ASTER will study land use patterns, deforestation, desertification, glacial movements, coral reefs and volcanic activity.

The Cloud's and the Earth's Radiant Energy System (CERES) instrument will perform measurements of the Earth's "radiation budget," or the process in which the Earth's climate system constantly tries to maintain a balance between the energy that reaches the Earth from the Sun, and the energy that goes from Earth back out to space. The components of the Earth system that are important to the radiation budget are the planet's surface, atmosphere, and clouds.

Meanwhile, the Moderate-Resolution Imaging Spectroradiometer (MODIS) will measure atmosphere, land and ocean processes, including surface temperature of both the land and ocean, ocean color, global vegetation, cloud characteristics, temperature and moisture profiles, and snow cover. The Measurements of Pollution in the Troposphere (MOPITT) instrument is an infrared gas-correlation radiometer that will take global measurements of carbon monoxide and methane in the troposphere.

The CERES, MISR, and MODIS instruments are provided by the United States; MOPITT by Canada; and ASTER by Japan. Several hundred scientists from the U.S. and abroad have been preparing to take full advantage of EOS AM-1 observations to address key scientific issues and their environmental policy impacts.

EOS is managed by Goddard for NASA's Mission to Planet Earth strategic enterprise, Washington, DC.

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