Antenna auto-calibration and metrology approach for the AFRL/JPL space based radar

The Air Force Research Laboratory (AFRL) and the Jet Propulsion Laboratory (JPL) are collaborating in the technology development for a space based radar (SBR) system that would feature a large aperture lightweight antenna for a joint mission later in this decade. This antenna system is a 50 m×2 m electronically steerable phased array in L-band (1260 MHz center frequency, 80 MHz bandwidth) and contains 384×12 transmit/receive modules. The radar is designed to operate in a variety of modes including synthetic aperture radar (SAR) and moving target indication (MTI). Stringent requirements are placed on phase center knowledge and antenna sidelobe levels during a data take, in the presence of temperature changes due to the orbital thermal environment, self heating, spacecraft platform vibrations, and mechanical deformation. We present an auto-calibration and metrology system concept to correct for phase errors and mechanical deformation during the mission.