This work presents the results of the Lunar Regolith Penetrating Radar (LRPR), installed at the bottom of the Chang’E-5 (CE-5) lander, which is the first antenna-array radar deployed for the investigation of an extraterrestrial body. Radar imaging results unveiled a hyperfine structure for the top 2.5-m-thick lunar regolith with an unprecedented high resolution of 5 cm. The interpretation of the results permitted to state that subsurface regolith is dominated by fine grains with abundant rock fragments. The radar imaging results were also used to drive the drilling process until a fragment jammed the core inlet at about 100-cm underground. Laboratory measurements of the samples returned at Earth allow to estimate the real part of relative permittivity and the loss tangent, which are 3.04 ± 0.02 and 0.014 ± 0.002, respectively.

Accurate relative permittivity is essential to the further analysis of lunar regolith. The traditional hyperbola fitting method for the relative permittivity estimation using the lunar penetrating radar generally ignored the effect of the position and geometry of antennas. This paper proposed a new approach considering the antenna mounting height and spacing in more detail. The proposed method is verified by numerical simulations of the regolith models. Hence the relative permittivity of the lunar regolith is calculated using the latest high-frequency radar image obtained by the Yutu-2 rover within the first 24 lunar days. The simulation results show that the relative permittivity is underestimated when derived by the traditional method, especially at the shallow depth. The proposed method has improved the accuracy of the estimated lunar regolith relative permittivity at a depth of 0–3 m, 3–6 m, and 6–10 m by 35%, 14%, and 9%, respectively. The thickness of the lunar regolith at the Chang’E 4 landing site is reappraised to be 11.1 m, which improved by ~8% compared with previous studies.

The Chinese Chang’E-5 probe landed in the Mons Rümker of Oceanus Procellarum on the near side of the Moon. The lunar regolith penetrating radar (LRPR) carried by the Chang’E-5 probe allows for the determination of in situ lunar regolith dielectric properties, which are probably related to the age and chemical composition of the regolith. In this paper, we analyze the Chang’E-5 LRPR data with the frequency shift method to estimate the loss tangent of the lunar regolith within a depth of ∼2.8 m. The loss tangent of the Chang’E-5 landing site is constrained to be 0.0148 ± 0.0016, which is substantially higher than that of the typical lunar regolith. The high loss tangent is found to be characteristic of the young basalt age (∼2.0 Ga) and high TiO${}_2$+FeO content (28.21 ± 1.57%) of the Chang’E-5 landing site. Integrated analysis of results from Chang’E-3, Chang’E-4, and Chang’E-5 show that the younger is the geologic age of the mare unit, the greater is the loss tangent of the lunar regolith, and the weaker is the radar electromagnetic signal penetrating ability.

This paper presents an imaging approach for Multiple Input Multiple Output Ground Penetrating Radar (MIMO GPR) systems working in down-looking contactless mode. The approach exploits a linear approximation of the scattering phenomenon and is based on a ray-based propagation model, which takes into account the presence of the air-soil interface. Accordingly, the Interface Reflection Point concept is extended to the case of MIMO GPR. The proposed approach performs the imaging in the 2D scalar case and applies the Truncated Singular Value Decomposition regularization scheme to perform the inversion. The effectiveness of the approach is assessed by processing synthetic and real data. The real data are referred to the lunar soil and have been collected by means of the Lunar Regolith Penetrating Radar, installed on the Chang’E-5 lander.

The Rover-mounted Subsurface Penetrating Radar (RoSPR) is one of the scientific payloads onboard China’s first independent Mars exploration mission, Tianwen-1. The radar aims to characterize the thickness of the upper Martian soil and investigate the subsurface stratigraphy by collecting and processing the data. This article is mainly divided into two parts, the introduction of data pre-processing and analysis of pre-processed radar signals, aiming at helping scientists make more effective use of radar data. The first part describes the operating principle of the RoSPR and the procedure of radar data pre-processing at all levels. Data pre-processing is mainly designed to transfer the raw data format to a common PDS (Planetary Data System) and eliminate the influence of the instrument. In the signal analysis part, the performances of both self-check signals and echo signals of low- and high-frequency channels are analyzed, which indicate a stable radar system and are useful for background removal. Phase and time calibration is of great importance for improving data quality and making the radar data more accurate. Moreover, further processing is required to obtain clear radar images, such as filtering, background removal and gain setting.

As humanity’s first sample return mission from the lunar farside, China’s Chang’E-6 mission provides a unique window into understanding the dichotomy in lunar nearside-farside evolution. Chang’E-6 landed in the southwestern Apollo basin (~2.79 Ga) within the South Pole–Aitken basin, providing a valuable record of early solar system impacts. Equipped with a Multi-Input-Multi-Output Lunar Regolith Penetrating Radar, the mission enabled the first detailed investigation of the shallow subsurface structure at the farside. By employing a tailored data processing approach, we obtained high-resolution subsurface images and revealed a distinct two-layer structure to a depth of 3 m. The upper layer (~1.7 m thick) consists of fine-grained, highly weathered regolith, while the lower layer (extending to 3 m) contains coarse, unweathered ejecta. Furthermore, by integrating data from Apollo and Chang’E missions, we identified a potential relationship between the lunar surface geological age and the shallow regolith’s electromagnetic losses. Specifically, geologically older regions exhibit lower electromagnetic attenuation, suggesting a possible link between regolith maturity and electromagnetic properties. These findings provide critical insights into the geological evolution of the Moon, and also offer unprecedented opportunities for correlating in-situ radar measurements with laboratory analyses of the farside samples, fundamentally advancing our understanding of lunar exploration.