Iridium Main Mission Antennas — A phased array success story and mission update

The Iridium satellite communications system, beginning with first launch on May 5, 1997, has provided worldwide coverage since its fully operational status in November 1998. Iridium Main Mission Antennas (MMAs) help provide this uninterrupted service. This paper describes the Iridium system and Main Mission Antenna design and provides an update on MMA mission life and continued performance. The novel MMA phased array panels supply the L-band satellite to ground links for the Iridium system. Key aspects of the antennas are discussed including the RF beam performance, patch radiators, T/R modules, and an onboard power system which minimizes DC power consumption and provides on-orbit redundancy. A mission update for the MMAs is presented including ongoing system support and a longevity study that analyzed component operating data to generate antenna failure and lifetime predictions. Continuing support is discussed including use of a flight worthy MMA and test equipment used to simulate on-orbit antenna performance. Updated MMA control software, which provides enhanced satellite operational flexibility and more robust mission performance, is also described.