The Sharpness Method Based on Window Interception Improves the Stability of Mars TEC Estimation

The Martian ionosphere will cause signal delays and dispersion, affecting the imaging precision of Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) and the analysis of subsurface features. The Total Electron Content (TEC) is an important reference for the analysis of ionospheric effects, and it can be jointly established by the first-order and second-order terms of ionospheric phase dispersion. Among them, the first-order term of ionospheric dispersion can be obtained by group delay, and the second-order term can be obtained by the Contrast Method (CM). For the CM algorithm, this paper delves into the stability of the decision-making process in both the maximum-value method and sharpness methods, and brings the theory of sharpness methods into the correlation between azimuth frames. The Sharpness Method can be used to determine whether the data has sharp or smooth changes. In this study, we apply this method to evaluate the smoothness of phase parameters in the azimuth direction by continuously adjusting some parameters to find the smoothest phase term output between frames. This mainly involves two aspects: first, the determination of the first-order term of the phase, during which we continuously adjust the matching parameters of the group delay; second, the determination of the second-order term, we add a variable window to the original image Interception function, and judged the distance sharpening method. Then, during this process, we also continuously adjusted the parameters related to the window length and threshold size of the surface position, and finally output the smoothest result of the second-order term in the azimuth direction. Finally, by further calculating the surface, our method is more robust than traditional TEC estimation.