The development of inflatable array antennas

Inflatable array antennas are being developed to significantly reduce the m ass, the launch vehicle's stowage volume, and the cost of future spacecraft systems. Three inflatable array antennas, recently developed for spacecraf t applications, are a 3.3 rn x 1.0 m L-band synthetic-aperture radar (SAR) array, a 1.0 m-diameter X-band telecom reflectarray, and a 3 m-diameter Ka- band telecom reflectarray. All three antennas are similar in construction, and each consists of an inflatable tubular frame that supports and tensions a multi-layer thin-membrane RF radiating surface with printed microstrip p atches. The L-band SAR array achieved a bandwidth of 80 MHz, an aperture ef ficiency of 74%, and a total mass of 15 kg. The X-band reflectarray achieve d an aperture efficiency of 37%, good radiation patterns, and a total mass of 1.2 kg (excluding the inflation system). The 3 m Ka-band reflectarray ac hieved a surface flatness of 0.1 mm RMS, good radiation patterns, and a tot al mass of 12.8 kg (excluding the inflation system). These antennas demonst rated that inflatable arrays are feasible across the microwave and millimet er-wave spectrums. Further developments of these antennas are deemed necess ary, in particular, in the area of qualifying the inflatable structures for space-environment usage.