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EarthQuest 
Winter 1988

Remote Sensing - The International Community Comes of Age (continued from cover)

The promise is coming to fruition. Moreover, the scope of earth remote-sensing satellites has broadened to a truly international activity. The U.S., USSE, France, India, Japan, and the European Space Agency (ESA) provide the operational system of earth-sensing polar-orbiting and geostationary satellites today. In addition, these countries along with Canada, the People's Republic of China, and Italy are planning research missions on various components of the earth system.

The U.S. is involved on many fronts with Landsat, Geosat, the Earth Radiation Budget Experiment (ERBE), the Upper Atmosphere Research Satellite (UARS), the NASA Scatterometer (N-SCAT), and the Ocean Topography Experiment satellite (TOPEX/Poseidon, joint with France). Capabilities to provide measurements of gravity and magnetic fields are also under consideration. It is interesting to note that the impact of this new technology has been widely recognized and is being incorporated rapidly in the research missions planned by other nations.

The French satellite Système Probatoire d'Observation de la Terre (SPOT), launched in 1986, is a follow on to the U.S. Landsat program to provide an operational land use and inventory monitoring system. The Japanese Marine Observation Satellite (MOS), launched in 1987, provides observations of the state of the sea surface and the atmosphere. The Indian Remote-sensing Satellite (IRS) provides agricultural, geological, and hydrological data for management of natural resources. It was launched in 1987. The USSR also has significant missions in earth remote sensing, but few details are available. 

Looking to the near future, the ESA Remote-sensing Satellite (ERS-1) will provide all-weather imagery of oceans, coastal waters, ice fields, and land areas when it is launched in 1990. The Japanese Earth Resources-sensing Satellite (JERS-1), scheduled for launch in 1992, will provide global exploration of mineral and energy resources, data for management of agricultural and forestry resources, and environmental monitoring for land use planning. The Canadian Radarsat, scheduled for launch in 1994, will provide high-resolution studies of the arctic area, agriculture, forestry, water resources, and the ocean surface. Italy is planning a Laser Geodynamics Satellite-2 (LAGEOS-2) for measurement of continental plate motion, starting in 1993. Finally we note that the Japanese are planning for an Advanced Earth Observation Satellite (ADEOS), which will provide atmospheric and ocean color measurement. 

Most of these ongoing and planned missions are a prelude to a major system that is intended to be in place in the mid-1990s: the polar platforms. "Polar platforms" is used here as a shorthand for a satellite measurement system consisting of an Earth Observing System (Eos) that uses suites of integrated instruments aboard polar-orbiting platforms. Eos will include a NASA complement of instruments, a NOAA complement, and a complement of instruments provided by other nations (primarily Europe and Japan). It is anticipated that these polar-orbiting platforms will be supplemented in the 1990s by a proposed series of NASA earth system explorer research missions (the Earth Probes)and missions from other countries for those measurements - tropical rainfall, earth's gravity and magnetic fields - that require special orbits and configurations. 

The polar platforms have been viewed as one of three components of the NASA Space Station; the other two components are a core platform and a co-orbiting platform. Unlike the other two components, the polar platforms will be unmanned and visited by astronauts only as part of repair and servicing missions. They will be in a high-altitude (for better viewing) and high-inclination (for polar coverage) orbit, whereas the core and co-orbiting platforms will be in low-inclination (tropical), low-altitude orbit. Thus, the polar platforms must be launched and serviced separately. Their one link with the other two components of the Space Station will be commonality of parts, design, and servicing techniques. The polar platforms will build on and supplant the current set of satellite measurements, which will end in the mid-1990s. The operational payload will monitor the earth's magnetic field, atmospheric temperature and water vapor, ozone, aerosols, outgoing radiation, precipitation, sea-surface temperature, sea ice, ocean chlorophyll, sea-surface winds, wave height, ocean circulation, snow cover, land use, vegetable, crops, volcanoes, and parameters of the hydrologic cycle. Communications equipment will monitor emergency transmissions from ships and planes in distress.

Eos will consist of advanced optical, microwave, radar, and laser sensors that initially will supplement and someday may replace current operational instruments. These advanced sensors may eventually permit routine monitoring of atmospheric chemistry, global winds, and space plasma, and may provide positive mineral identification from space.

Funding is needed in the near-term U.S. budget cycles to ensure continuous measurements through the 1990s and beyond. At the present time, funding for one polar platform is included in the current Space Station budget; funding for a second will come for non-U.S. space agencies.

To ensure that these systems are implemented, support from the earth science and applications constituency is necessary. With the continued constraints on budgets, it is clear that those interested in describing, understanding, and eventually predicting global change must work hard to continue to educate decision makers in all countries of the importance of these global measurement systems.  

Dr. Baker is president of Joint Oceanographic Institutions, Inc., Washington D.C.

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