Sp-461 ers-envisat Symposium

External Characterization

ASAR can be put into External Characterization Mode while overflying a calibration transponder. This involves

sending a series of pulses from each of the 32 rows in turn followed by each of the 10 columns in turn. These pulses are

detected both by the internal calibration loop and the receiver embedded in the transponder. Comparison of these data

together with instrument telemetry allows the characterization function to be computed (row and polarization

dependent). This is then used by the PDS Generic Processor. The baseline is to repeat measurement every six months.