||ES 771 Lecture|
James S. Aber
Only remote sensing from space can provide the
global, repeatable, continuous observations of processes
needed to understand the Earth system as a whole.
(Kennel, in Asrar and Dozier 1994)
NASA's MISSION TO PLANET EARTH
Global change is at the forefront of scientific research for the early 21st century. The United States Global Change Research Program--USGCRP has a central goal of establishing strong scientific understanding of the interactive physical, chemical, biological, geological, and human processes that influence the Earth's environmental systems. Satellite remote sensing is the means to provide integrated, comprehensive, long-term observations that are necessary to achieve global understanding.
Originally called Mission to Planet Earth (MTPE) and now simply Earth Science, the mission is an ambitious NASA space science program, which is the major NASA contribution to the U.S. Global Change Research Program. Many U.S. governmental agencies and international partners are also involved, including space agencies in Europe, Canada, and Japan. MTPE uses space- and ground-based instruments and data handling to provide the scientific basis for documenting and interpreting global change. Human intervention has caused unquestioned changes in the Earth's land cover, oceans, and atmosphere. Understanding these changes and their effects are among the most urgent scientific tasks.
Satellite observations of the Earth make up the core of MTPE programs. These satellites include several current systems: Landsat, SPOT, AVHRR, UARS, TOMS, plus manned space shuttle missions. Satellites and instruments under development will build on experiences gained with these operating systems. Many types of orbits and sensing instruments will be necessary to observe all aspects of the Earth's environment. A great variety of instruments are planned for low-, medium- and high-resolution data collection. Satellite orbits will include polar, high- and low-inclination, and geostationary configurations.
Taken from NASA's Earth Observing System.
| ||The Earth Observing System (EOS) is central to MTPE. As originally proposed in the late 1980s, EOS was to consist of two large satellites, carrying a total of 30 instruments, and costing $17 billion. However, NASA has restructured the EOS program several times in response to Congressional direction for lower cost and a more flexible approach. Budget restrictions call for a cap on cumulative budget of about $7 billion over the life of the mission (Asrar and Dozier 1994).|
As a result of these budget restrictions, the scope of EOS has been narrowed considerably, and EOS will rely more on contributions from international partners. NASA has opted for reducing certain requirements of instrumentation and data handling and for spreading out launch dates to lower costs even more. The research emphasis has been reduced from global change to global climate change (Asrar and Dozier 1994). The objectives of EOS are to:
EOS will achieve its goals by developing highly sophisticated satellite instruments and a massive data-handling system. The program consists of:
- Establish a comprehensive program to observe the Earth on a global scale.
- Conduct research to improve understanding of the physical, biological and cultural influences on the Earth's climate.
- Develop models for the Earth system to integrate and predict climatic changes.
- Assess impacts of natural and human activities on the Earth's climate.
The restructured EOS program now is comprised of several smaller satellites with a total of 20 instruments. Terra, the EOS flagship satellite, was launched successfully in December, 1999; its first data and science images were released in April, 2000. Terra carries five main remote-sensing instruments designed to probe the air, water, and land of the Earth. A sister satellite, Aqua, was launched in 2002.
- Long-term repeating series of Earth-orbiting satellites with highly sensitive instruments designed to observe the atmosphere, biosphere, cryosphere, hydrosphere, and lithosphere.
- Huge data processing, archive, and distribution system that will allow rapid and easy access to data in usable and understandable format.
- Interdisciplinary scientific research teams to apply satellite data toward better understanding of earth-surface processes and to develop predictive capability.
Subsequent satellite launches are planned every 18 to 24 months. Landsat 7, also launched in 1999, is part of MTPE, and a Landsat Advanced Technology Instrument (LATI) will be included in a later mission. Satellites will be replaced on a 5-year schedule. The goal is provide continuous coverage of environmental conditions over a 15-year period. The individual instruments selected are those that address the highest-priority scientific questions concerning global change, specifically climatic change. The following topics are identified as highest-priority science and policy subjects.
- Terra and Aqua satellites.
- Water and energy cycles: cloud formation, dissipation, and radiative properties; large-scale hydrology, including precipitation and evaporation.
- Ocean: exchange of energy, water, and chemicals between ocean and atmosphere, and within the ocean including sea ice and formation of bottom water.
- Troposphere: links to hydrologic cycle and ecosystems; chemical transformation of greenhouse gases (CO2, CH4 and N2).
- Stratosphere: chemistry of ozone, chlorofluorocarbons (CFCs), ozone depletion and UV radiation.
- Land surface: hydrology and ecosystem processes, sources and sinks of greenhouse gases, exchange of moisture between land and atmosphere, changes in land cover, especially vegetation.
- Glaciers and polar ice sheets: observation and modeling of glacier activity, predictions of sea level and global water balance.
- Solid earth: volcanic eruptions and their role in climatic change.
MODIS The Moderate Resolution Imaging Spectroradiometer (MODIS) is a cross-track optical scanner that will collect data in 36 discrete spectral bands (0.4 to 14.4 µm) at resolutions ranging from 250 m to 1 km. MODIS will provide repeatable global coverage every 1-2 days. It is designed to bridge the data gap between high- and low-resolution systems. It will detect land and ocean surface temperatures, ocean color, land vegetation and surface cover, and cloud cover and properties.
MODIS is a key instrument that will be carried on each of the Terra/Aqua satellites. It is designed to provide comprehensive coverage of the Earth's land, ocean and atmosphere. MODIS has proven extremely popular with the public and valuable for scientific monitoring of the Earth. Team leader: Salomonson, NASA Goddard Space Flight Center.
- MODIS for more information.
ASTER The Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER) is a suite of advanced high-resolution radiometers. Its primary goal is to acquire high-resolution imagery of selected areas, as well as black-and-white stereo images. It will have a total of 14 visible and infrared bands.
ASTER will bridge the spatial range between ground observations and MODIS moderate resolution. It will be used for long-term monitoring of local and regional changes on the Earth's surface. The instrument will be scheduled to acquire imagery of selected and high-priority targets for environmental observations. Important applications are mapping surface temperature, measuring clouds, and generating high-resolution digital elevation models (DEMs). Team leader: Tsu, Geological Survey of Japan.
- Three visible and near-infrared bands (VNIR) between 0.5 and 0.9 µm (15 m resolution). The VNIR subsystem will have both nadir and backward-looking telescopes. This will provide for along-track stereoviews and high-resolution imagery of land, water, and clouds.
- Six short-wavelength infrared bands (SWIR) from 1.6 to 2.43 µm (30 m resolution). The mirror can point ± 8½° from nadir, which allows coverage for all parts of the Earth's surface during the satellite's 16-day mapping cycle.
- Five thermal infrared bands (TIR) between 8 and 12 µm (90 m resolution). The mirror can point ± 8½° from nadir, which allows coverage for all parts of the Earth's surface during the satellite's 16-day mapping cycle.
- ASTER for more information.
EOSDIS The EOS Data and Information System (EOSDIS) will serve as the primary data management and applications system for the next several decades. EOSDIS will be responsible for control and operation of satellites in orbit, archiving of all EOS data, and making these data readily available to all scientists. The development of EOSDIS will begin with existing Distributed Active Archive Centers (DAACs) and Affiliated Data Centers (ADCs). A prototype Version 0 Information Management System (IMS) began operation in 1994.
EOSDIS will be one of the largest, most complex data archive and handling systems every built. When fully operational, it will receive data at the rate of about one terabyte (1012 bytes) per day. During the 15-year period of EOS, EOSDIS will archive some 10 perabytes (1015 bytes) of data. In contrast, combined Landsat MSS and TM data for the period 1972-1997 amounts to only 120 terabytes (Holm 1997). EOS instruments will generate every 3 months more data than the first 25 years of Landsat!
- Visit the DAACs.
EOSDIS is distinguished from previous satellite-data systems in the commitment to provide useable information to a broad and interdisciplinary spectrum of scientists. Data will be collected and archived in a systematic way to represent all environmental features on a global basis. Standard, reliable products will be readily available in user-friendly formats at reasonable costs to the entire scientific community.
- Asrar, G. and Dozier, J. 1994. EOS science strategy for the earth observing system. AIP Press, American Institute of Physics, 119 p.
- Dozier, J. and Moore, B. III 1992. EOS science and priorities for remote sensing technology. Geotimes June, 1992, p. 12-15.
- Holm, T.M. 1997. National satellite land remote sensing data archive. Photogrammetric Engineering & Remote Sensing 63:1180.
- Price, R.D. et al. 1994. Earth science data for all: EOS and the EOS data and information system. Photogrammetric Engineering & Remote Sensing 60:277-285.
- Wilson G.S. and Backlund, P.W. 1992. Mission to Planet Earth. Photogrammetric Engineering & Remote Sensing 58:1133-1135.
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