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About the same time as Landsat-C (1978 ?) thermal data are expected 
to be available, NASA plans to orbit the first of its Applications 
Explorer Mission (AEM-A) satellites, one devoted to thermal sensing of 
limited areas of the Earth's surface (U.S. NASA, 1975). . The spatial 
resolution and thermal sensitivity of this satellite, called the Heat 
Capacity Mapping Mission (HCMM) lies between the capabilities of NOAA 
satellites and Landsat-C. 
The diurnal and annual variation of surface temperature is perhaps 
the most dynamic characteristic of our planet's surface. The NOAA 
satellite series and other advanced satellites planned for launch in 
the next few years offer opportunities to those who wish to perform the 
scientific research necessary to convert this new data into useful 
knowledge. For future imaging systems, see the NASA report (1973) on 
advanced scanners and imaging systems for Earth observations. 
The United States' GOES (Geostationary Operational Environmental 
Satellites) willeventually number 5, thereby giving complete global 
coverage both day and night with visible and infrared sensors (VISSR). 
Imagery at high latitudes is very oblique hence only really useful at 
high latitudes for meteorological work. The nearly continuous record- 
ing of thermal emission from the planet's surface and atmosphere, 
however, will provide important data to a number of geological 
experiments at mid and low latitudes. 
Microwave 
Assessment of current status of microwave remote sensing, although 
not all inclusive, shows a significant increase in activity. This is 
due to the development and planning of major space programs in the United 
States and by the European Space Agency. Major areas of research which 
have continued to lag are adequate development of,the quantitative rela- 
tionships between materials and their microwave "signatures" .and 
radiometrically calibrated active systems. 
Microwave systems, both active and passive, have been designed for 
many specific applications. Data from active systems have been utilized 
for many geoscience applications including storm location, height and 
distance measurement, interpretation of geologic structure, mapping the 
Moon and planets, measuring agricultural fields and forested areas, 
determining ice and snow conditions, and monitoring oil spills and sea 
state. Passive microwave systems have been used to a lesser extent, but 
their potential is being explored especially as the data relate to soil 
moisture measurements and ice distributions, and water content of snow.