Nadir Panel - internal view

The Nadir (Earth facing) panel contains most of the electronic units. This has the advantage of limiting interconnections to other panels and reducing cable lengths. The approach also allows for a certain amount of the system to be tested and validated without having to break down the validated items. Because of the tolerances involved in mating waveguide/RF units, the X-Band subsystem is delivered and mounted on a dedicated plate. The DORIS USOs (Ultra stable oscillators) can just be seen - these had to have special shock dampers designed to allow the unit to survive the environment during launch.