Image Formation Algorithm for Topside Ionosphere Sounding with Spaceborne HF-SAR System

The exploration of ionosphere is significant for satellite communication and navigation etc. Spaceborne HF-SAR is utilized for the observation of topside ionosphere, in order to acquire higher spatial resolution, global scale ionospheric electron density map and irregularities distribution. The operation mode and system parameters are introduced. The echo signal of spaceborne HF-SAR has long synthetic aperture time, large range migration, and small depth of focus due to the low carrier frequency. Considering these characteristics of spaceborne HF-SAR, a two dimension time-frequency domain correlation image formation algorithm is presented. The effectiveness of the algorithm is validated by computer simulation results.