Fig. 1

The Chang’E-3 landing site and a zone of phase reversals exist in the top 50 ns of the radargram. a Image returned by the Lunar Reconnaissance Orbit (M102285549LE + RE; 1.66 m/pixel) showing that the Chang’E-3 landing site (red star) and the traverse route of the Yutu rover are both on the continuous ejecta deposits of the Ziwei crater. b Traverse route of the Yutu Rover from navigation points N101 to N208 (black dots). Navigation points that start with ‘1’ represent the first lunar day, while those beginning with ‘2’ represent the second lunar day. The red star represents the position of the lander. The segment between N106 and N108 is marked in green, which represents the surface projection of the observed low-permittivity zone. The background image was acquired by the descent camera of the Change’-3 Lander (ID: CE3_BMYK_LCAM-3006). c Radargram obtained by the high-frequency LPR channel. The radargram is processed following a standard routine outlined by Feng et al. (2017). The left y-axis is the apparent depth that corresponds to an assumed dielectric constant of 1, and the two-way travel time of the electromagnetic wave is shown in the right y-axis. The surface projection of the low-permittivity zone is denoted as green lines. d Regional radargram for the zone of phase reversals of reflections. The horizontal distance is identical to those used in panel c, and the y-axis is the two-way travel time. e Radargram with annotations of phase reversal locations. The negative peak of the reflected signal is marked in red, and the positive peak is marked in green. The three yellow dashed lines f–h correspond to traces of data where the A-scan is extracted. Red and green arrows point to the negative and positive peaks, respectively, where the phase reversals are identified