The authors give the results of the designing of the antenna sub-system of the multi-channel microwave scanning radiometer designed for measurement of the temperature patterns of the Earth's surface and installed on a low-orbit satellite. The antenna of the multi-range radiometer is designed on the basis of the offset parabolic reflector. The exciter is the multi-range wide-band horn excited by the side waveguides with the findamental wave H11 (see fig.1). The horn is oriented at 45° to the focal axis of the paraboloid so that to form the conical scanning sector, the generating line of which constitutes a 45° angle with the satellite axis (see Fig.2), as the reflector rotates around the sighting line, which connects the phase centre of the horn with the centre of the offset reflector.