A system for estimating a pointing error of an antenna (ANT) of a satellite, the satellite includes a payload (CU) comprising a multichannel transmitter or receiver comprising a multichannel antenna (ANT), one analogue processing chain per channel and a set of digital integrated circuits (PN), the system comprising an estimation device (EST), implemented aboard the satellite or in a ground station, for estimating a pointing error of the antenna, the device for estimating a pointing error being configured to: acquire, for at least two channels of the transmitter or of the receiver, at least two test signals, each test signal having been transmitted or received by the antenna along a different direction (θA, θB), for at least one pair of acquired test signals, determine, for each test signal, a relative complex gain between the test signal received or transmitted respectively on two distinct channels, determine a comparative measurement between the two test signals from either the ratio between the two relative complex gains and/or the difference between the phases of the two relative complex gains, determine a pointing error (dθ) of the antenna on the basis of the comparative measurement, of the expected directions of transmission or of reception of the test signals (θA, θB) and of a model of the gain of the antenna for each channel and in a plurality of directions.