Design features of the ORION satellite antenna subsystem

The ORION satellites (first launch 1994) will provide flexible, high capacity Ku-band communications between and within North America and Europe. Four-fold frequency re-use allows the provision of thirty-four transponders per spacecraft, with two-way networking traffic to 1.2 metre rooftop VSAT terminals. The author provides an overview of the communications antenna subsystem and highlights some of the novel and sophisticated design features. These include the following: numerically shaped, gridded reflectors, computer optimised multihorn feed geometry, feed coefficients optimised under mutual coupling, reconfigurable beams via on-board switching, very low thermal-distortion reflectors, novel sunshield design, and two-axis boresight trimming. Selected analyses and measurement results are presented