Sp-461 ers-envisat Symposium

Non Corrected Effects

Despite the comprehensive nature of the internal calibration system, it is not possible to use it to calibrate the passive

part of the antenna which falls outside of the calibration loop – this is achieved through end-to-end calibration using the

transponders. It is also not possible to correct for short term variations in the instrument, nor variations in the calibration

loop itself.

Ground Processing of Calibration Pulses

Using the amplitude and phase of the calibration pulses (P1/P1a, P2 and P3) for each row it is first necessary to

calculate the amplitude and phase of P2 relative to P3 and to subtract P1a vectorially from P1. From these values for

each of the 32 rows and together with the external characterization factor, it is possible to calculate the elevation beam

pattern. This is then used to detect any deviation to the reference instrument gain pattern as characterized on ground.

The typical update rate for this calculation is 5 to 35 seconds (mode dependent).