ABSTRACT
Selecting a proper frequency band for a SAR system is application-driven within technical constraints. We assume the L-band for Moon-Based SAR (MBSAR) due to its longer penetration depth. However, the radio signal propagation at the L-band is susceptible to ionospheric disturbance. In the scenario of MBSAR, the ionospheric effects are more severe due to long synthetic aperture time and curved trajectory, rendering the atmospheric freezing model and linear path trajectory that is typically assumed for LEOSAR no longer applicable. The ionospheric effects encompass background ionospheric effects and the effects arising from ionospheric irregularities. This chapter takes the background ionosphere as an example to look into its spatiotemporal variation characteristics and their impacts on MBSAR imaging. Leveraging the insights gleaned from this analysis, we quantitatively inspect the geometric distortion and image defocusing of the MBSAR under spatiotemporally varying background ionospheric effects. The point target responses are simulated to illustrate imaging distortions in terms of the geometric deviation and defocusing.
