Lunar exploration is of significant importance in the development and utilization of in situ lunar resources, water ice exploration, and astronomical science. In recent years, ground-based radar (GBR) has gained increasing attention in the field of lunar exploration due to its flexibility, low cost, and penetrating capabilities. This paper reviews the scientific research on lunar exploration using GBR, outlining the basic principles of GBR and the progress made in lunar exploration studies. Our paper introduces the fundamental principles of lunar imaging using GBR and systematically reviews studies on lunar surface/subsurface detection, the dielectric properties inversion of the lunar regolith, and polar water ice detection using GBR. In particular, the paper summarizes the current development status of the Chinese GBR and forecasts future development trends in China. This review will enhance the understanding of lunar exploration results using GBR radar, systematically demonstrate the main applications and scientific achievements of GBR in lunar exploration, and provide a reference for GBR radar in future lunar exploration missions.

Earth-based radar (EBR) is an important type of remote-sensing instrument for planetary observation. EBR takes advantages in large-scale imaging swath, high repeatability, great flexibility, etc. The upcoming 233 MHz-frequency European Incoherent Scatter Scientific Association (EISCAT) 3D radar system will provide important features to lunar observation as introduced in this study. EISCAT_3D (E3D) radar is a powerful multi-static radar system. The 1.3 m-wavelength wave of E3D can penetrate deeper, about 30 m below lunar average surface which can reach the second layer, i.e. layer of ejecta. E3D radar supports dual/quadrature polarimetry, which gives it good flexibility and lower ambiguity in the inference of scatter’s properties. Also, there is less ambiguity in scattering regimes between icy and non-icy scatters for 1.3 m wavelength than for shorter wavelengths as given from the simulation results. Besides, the high topographic resolution (which requires forming interferometric baselines with distant telescope antennas) of E3D radar along with its penetration depth makes it possible for detection of sublunarean cavities by signatures of depression. As a whole, the 1.3 m-wavelength three-dimension (3-D) polarimetric imaging of the Moon by E3D radar, on a spatial resolution of about 200 m, will be valuable for obtaining new information about the geology and subsurface structure of the Moon, and can be used in search of buried water ice and sublunarean cavity, etc. Furthermore, we envision the collaboration of E3D radar with large telescope antennas in China, including Daocheng Solar Radio Telescope (DSRT) and Mingantu spectral radioheliograph (MUSER) for better imaging ability and detectivity.