needs to- be quantified as compared to a C-band system alone for crops, forest 

 types, and soil moisture. This issue should be addressed now. Multidate 

 like-polarization data are needed for both L- and C-band to address this 

 issue. 



3. Dual-Polarization Utility 



The added performance of a dual-polarization (like and cross) system 

 needs to be determined as compared to a like-polarized system alone for crops 

 and snow cover. Multidate dual-polarization C- and L-band data are needed for 

 this issue. 



4. Spatial Resolution, Revisit Interval, and Swath Width for Soil Moisture 



According to one computer simulation study, sensing soil moisture can be 

 done at relatively low resolution (~100 m) for the 15° C-band HH 

 configuration. The simulation work is being continued with more realistic 

 model assumptions concerning the spatial distributions of plant and soil 

 characteristics. Also, the interleaved constraints of viewing angle range, 

 spatial resolution, swath width, and revisit interval need to be considered 

 to determine if a practical and useful SAR mission configuration can be 

 designed for soil moisture surveying. To support the research for this issue, 

 the team recommends a nominal 30 m (4 looks) spatial resolution since one may 

 degrade that resolution if desired. 



C. SUMMARY OF PRELIMINARY MISSION REQUIREMENTS 



The renewable resources SAR mission requirements summarized in Table 3 are 

 preliminary and based on our present understanding of the available literature 

 of radar backscatter research. Some of these findings may be modified as a 

 result of the proposed experimental program discussed earlier. These SAR 

 minimum requirements may be viewed as a least common denominator to the crop 

 classification and soil moisture potential applications. They would allow a 

 system with enough flexibility to permit the test and evaluation from space of 

 the preliminary information extraction procedures based on truck radar 

 spectrometer and airborne radar scatterometer measurements and analyses 

 coupled with theoretical models. 



Thus, the minimum system is a VV-polarized, C- and L-band SAR which 

 operates simultaneously in both a low-angle and high-angle mode. The low- 

 angle mode is principally for soil moisture mapping and the high-angle mode 

 for crop type and forest species condition and identification. In addition, 

 the synergism of a combination of visible/infrared data and SAR data (1-4 

 channels) may enhance system performance as compared to any one data source 

 alone. Although the optimum revisit interval for soil moisture mapping may be 

 as short as 1-2 days, in an operational mode, it is felt that the 10-day 

 revisit interval required for crop classification would allow an adequate test 

 of the soil moisture mapping concept in a research mode. Since no operational 

 uses are envisioned for the research spacecraft SAR addressed here, it is not 



2-4 



