Concept of an X-Band Synthetic Aperture Radar for Earth Observing Satellites

Abstract

This paper presents a technical concept for an X-band phased array synthetic aperture radar mounted on a polar orbiting satellite. The interdependency of various parameters, such as geometric resolution, swath width and off-nadir angle, is shown as well as their influence on the sensitivity of the system. A description is given of the layout of the phased array system with a new dual polarized slotted waveguide array and attached GaAs transmit/receive modules. The antenna pattern is investigated for specified scanning ranges in elevation and azimuth direction. Descriptions are given of a possible high resolution mode (azimuth look steering mode) and a survey mode (scan SAR). Future SAR systems require a high stability in their system parameters or, at least, the possibility of calibrating their performance in an operational mode. External and internal radiometric calibration procedures are discussed. A method which monitors 64 sub-arrays and can be relatively easily implemented is suggested for internal calibration. Finally, the possibility of using lower orbits under the given limitations (power and antenna area) is considered in order to allow more flexibility in system design and performance.