Phased array transmit antenna for a satellite

Active phased array antennas with electronically scanned beams offer advantages over high gain parabolic dish antennas used on spacecraft. Benefits include the elimination of deployable structures, no moving parts, and no torque disturbances that moving antennas impart to the spacecraft. The latter results in the conservation of spacecraft power, and the ability to take precision optical data while transmitting data. Such an antenna has been built under a contract from NASA Goddard Space Flight Center for the New Millennium Program EO1 satellite where it will act as the primary high speed scientific data communication link. The antenna operates at X-band, has an integral controller and power conditioner, communicates with the spacecraft over a 1773 optical data bus, and is space qualified for low Earth orbit (705 km altitude). The nominal mission length is one year, and the operational requirement is for one 10 minute transmission a day over Spitsbergen, Norway. Details of the antenna and its performance are given.