b. Nonrenewable Land Resources 



Maintenance of relative brightness levels across the swath 

 is important for mapping and correlating tonal features. 

 Radiometric control is extremely important to the 

 effective manipulation (ratioing, slicing, etc.) of SAR 

 data and in stereo mapping or mosaic production. A 

 relative calibration value of 1.5 dB within the swath and 

 +3 dB between swaths is considered to be essential. 



c. Ice 



Insufficient C-band imagery of sea ice is available to 

 assess the difference in radar backscatter coefficients 

 between various ice types. A relative calibration of 2 dB 

 is considered, at this time, to be adequate for most 

 purposes. 



d. Oceans 



An absolute calibration of the radar to 2 dB is required 

 for the quantitative analysis of SAR ocean data. 



e. Discussion 



The Renewable Land Resources Team has justified the need 

 for a radar system that will maintain a relative 

 calibration of 0.5 dB within a given scene. This is more 

 than adequate to meet the requirements stated by the 

 Nonrenewable Land and Ice Teams and therefore is shown as 

 a desirable characteristic to be considered in the design 

 of a satellite SAR system. The absolute calibration 

 figure of 2 dB, required by the Oceans Team, may be 

 impossible to achieve due to the wide variation in 

 incidence angles possible with a steerable antenna and 

 unpredictable attenuation of the signal due to constantly 

 changing atmospheric conditions. 



9. Radiometric Resolution, Signal-to-Noise Ratio, and Dynamic Range 



a. Discussion 



A number of team members have attempted to define specific 

 limits within which radiometric resolution, signal-to- 

 noise ratio, and dynamic range parameters should be 

 established to meet their requirements. However, after 

 discussion of specifications presented in their reports, 

 it was agreed that team members require additional 

 information before they can make firm recommendations 

 regarding these parameters. Action to be taken is 

 detailed in recommendation number 3 in this report. 



5-17 



