Sp-461 ers-envisat Symposium

Figure 7 : Prototype ASAR Calibration

Transponder Deployed at ESTEC

Figure 8 : ASAR Transponder Visibility over The Netherlands

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In-Flight Evaluation of Performance Para-

meters

The calibration transponders are not only used for

calibration, the also provide useful point targets

from which many performance parameters can be

derived. These include: spatial resolution, side-lobe

levels, point target ambiguity levels, radiometric

accuracy, radiometric stability and localization

accuracy.

The minimum backscatter level detectable by the

ASAR instrument (NES0) is determined from the

apparent backscatter obtained over a body of still

water such as a lake in an image.