Fig. 1: Chang’e-4 radargram for the 60 MHz channel.
From: First look by the Yutu-2 rover at the deep subsurface structure at the lunar farside
a LPR CH-1 radargram of CE-4 landing site using an Automatic Gain Control (AGC) method49 for amplitude compensation. The yellow line represents the aggregated data traces to show the enhanced subsurface echoes A–E. This approach also minimizes “anomalous” signal points along the travel path that might arise from the random distribution of rocks and debris among more heterogeneous layers. b Interpreted LPR CH-1 radargram of CE-4 landing site using image enhancement techniques. The cumulative length of the traversed path is 284.6 m. Yellow lines represent enhanced subsurface echoes A–E (a); light blue lines are subtle boundaries denoting differences in “stripe” directions and sharpness; dashed lines denote higher uncertainty in location. The two red vertical lines indicate waypoint 37 and 42, respectively. Please note that LPR data were not collected at a fixed speed. For example, the jump from 180 to 240 m at the end of X axis is because LPR CH-1 collected much fewer data at the end of the traverse path than at the beginning stage when rover traveled around a small crater. The enlarged images of the end of the traverse are given in Supplementary Fig. 3. c The interpreted stratigraphy structure inferred from the LPR results. ε = 4.5(≤52 m) and 6.5(>52 m) is used for time-to-depth conversion.
