Terra satellite and Earth Observing Systems (EOS)

To facilitate new research and enhance existing data regarding the interaction of dynamic geophysical systems, NASA is in the process of developing a comprehensive Earth Observing System (EOS). A multi-component program, one of the unifying aims of EOS units is to measure the impact of human activities on Earth's geological and atmospheric processes.

The first component in the EOS array of remote sensing instruments is the Terra satellite , launched into a near-circular, sun-synchronous Earth orbit in December, 1999.

The development of NASA's EOS (a part of NASA's Earth Sciences Enterprise [ESE]) will result in a group of satellites—each designed for a specific research purpose— that together will feed data to the Earth Observing System Data and Information System (EOSDIS) network that will make the information available to research groups around the world. As of April 2002, three EOS satellites were established in Earth orbit. NASA eventually plans to expand the EOS program to include some 18 satellites.

Terra's instrumentation includes an Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER), a Multi-angle Imaging Spectro-Radiometer (MISR), a Clouds and the Earth's Radiant Energy System (CERES) monitor, a Moderate-resolution Imaging Spectroradiometer (MODIS), and a Measurements of Pollution in the Troposphere (MOPIT) sensor.

ASTER is able to gather high-resolution Earth images ranging across the electromagnetic spectrum from visible to thermal infrared light. ASTER data will facilitate the development of maps based upon surface temperatures. MISR measures sunlight scattering from nine different angles. CERES, a two-component package, each of which scans radiation flux in different modes. MODIS provides wide-angle measurements in 36 spectral bands than will provide accurate estimates of phenomena such as cirrus cloud cover. At present, the extent of cirrus cloud cover is an important part of research efforts to determine whether they have a net cooling or warming effect on Earth's atmosphere. MODIS is capable of providing data enabling estimation of photosynthetic activity that in turn allows estimates of atmospheric carbon dioxide levels. MODIS is also capable of accurately measuring the extent of snow cover, or in the detection of heat from volcanic eruptions and fires. MOPITT utilizes gas correlation spectroscopy data in measuring radiation from Earth in three specific spectral bands. MOPITT data allows estimations of carbon monoxide and other gas (e.g., methane) levels in the troposphere.

In March 2002, the Terra satellite's Multi-angle Imaging Spectro Radiometer (MISR) instrument recorded data confirming the calving (breakaway) of a major iceberg measuring almost 200 mi² (5200 km²) off the Antarctic ice shelf. The iceberg, designated B-22, broke away from the West Antarctic mainland into the Amundsen Sea. In an effort to estimate and evaluate the effects of climate warming, researchers are attempting to correlate—and/or determine the cause of—a recent reported increase in iceberg calvings during the last decade of the twentieth century. As of May 2002, data was insufficient to positively determine a causal relationship to potential human-induced global warming . In fact, part of the EOS mission is to develop a database that will enable researchers to determine whether such dramatic events as the breakaway of B-22 was a result of global warming or an expected occurrence that is a normal part of cyclic regional climatic variation.

See also Atmospheric composition and structure; Atmospheric pollution; Insolation and total solar irradiation; Scientific data management in Earth Sciences; Spectroscopy; Weather balloon; Weather satellite