III. NONRENEWABLE RESOURCES MISSION REQUIREMENTS SUMMARY 



Report Based on NASA FIREX Nonrenewable Resources 



Study Team Workshop 



Washington, D.C, 



December 1981 



This mission requirements summary, prepared by the U.S. Nonrenewable 

 Resources Study Team covers (1) the major potential nonrenewable resources 

 applications objectives for orbital free-flying Synthetic Aperture Radar (SAR) 

 imagery acquired at either L-band (1.275 GHz) and/or C-band (5.3 GHz), (2) key 

 radar parameters and specific research issues (e.g., recommended angles, 

 frequencies, or polarizations) which must be addressed in order to adequately 

 specify the SAR satellite mission requirements, (3) an experimental program 

 using aircraft SAR data which could address those key research issues, and (4) 

 a preliminary specification of the mission requirements for SAR to be used in 

 a future satellite-based research program. This satellite program is referred 

 to in this document as FIREX (Free-Flying Imaging Radar Experiment). 



A. POTENTIAL NONRENEWABLE RESOURCES APPLICATIONS OBJECTIVES 



The Nonrenewable Resources Study Team proposes three objectives for 

 FIREX: (1) to complete the investigation of satellite radar's sensitivity to 

 topography, (2) to develop the use of backscatter radiance as a discriminator 

 among geologic features, and (3) to conduct radar stereo imaging research. 

 The Study Team emphasizes that these objectives require the highest possible 

 geometric and radiometric control of the radar data. 



The primary recognized advantage of radar in remote sensing geology is 

 radar's sensitivity to topography. This sensitivity is greatest at incidence 

 angles less than 25° and greater than 60°. Seasat provided high quality radar 

 data at a 22° incidence angle. FIREX should first provide calibrated 

 registered imagery at a high-look angle of 60°-65° for use in structural 

 mapping. Space-borne SAR sensitivity to topography should be further explored 

 by additionally imaging at an intermediate-look angle of 30°-35°; the 

 combination of intermediate- and high-look angle data permits 30° convergence 

 stereo which has been shown to be a powerful tool in geomorphology. Finally, 

 a low-look angle mode of 15°-20° should be included to permit studies of 

 subtle topographic expression. 



At a single wavelength, single-look angle, and single polarization, a 

 given geologic unit may not have a unique signature since its radiometric 

 brightness on an image depends on local slopes, surface moisture, vegetation 

 cover, etc. Geologic interpretation of radar imagery is based on the analysis 

 of image recognition elements which include tone, texture, shape, pattern, and 

 context. However, when it is possible to vary the wavelength, or incidence 

 angle, or polarization, a much more powerful imaging capability is made 

 available because independent looks are acquired which can be used to 

 discriminate among different geologic structures. 



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