(a) Raw data obtained by CE-4 LPR second channel (500 MHz) from January 2019 to September 2020. The sampling interval is 0.3125 ns and the average trace interval is 3.75 cm. The colors represent relative electric field strength of echoes received by antenna. The radargram is shown in a dynamic range of –15 to 15 to reveal more details in deeper regolith. (b) LPR data after bandpass filtering, background removal, time-zero correction, and spherical exponential compensation.