Abstract: A communication payload system for a satellite having a beam forming network, an amplifier associated with each output port of the beam forming network, and a plurality of hybrid matrices and a calibration pick-up antenna. Each hybrid matrix has a plurality of inputs connected to selected amplifiers and a corresponding number of outputs. One output of each hybrid matrix is connected to a power absorber adapted to function as an output calibration port producing a calibration sample and the remaining outputs connected to feed radiating elements. A calibration system applies power to selected output ports and calculates calibration corrections in response to the values of the calibration samples and the values of the power radiated by each feed radiating element which are applied to the beam forming network to maintain the calibration of the payload system.