Shun Dai

Data processing and initial results of Chang'e-3 lunar penetrating radar

To improve our understanding of the formation and evolution of the Moon, one of the payloads onboard the Chang’e-3 (CE-3) rover is Lunar Penetrating Radar (LPR). This investigation is the first attempt to explore the lunar subsurface structure by using ground penetrating radar with high resolution. We have probed the subsurface to a depth of several hundred meters using LPR. In-orbit testing, data processing and the preliminary results are presented. These observations have revealed the configuration of regolith where the thickness of regolith varies from about 4 m to 6 m. In addition, one layer of lunar rock, which is about 330 m deep and might have been accumulated during the depositional hiatus of mare basalts, was detected.

Performance evaluation of lunar penetrating radar onboard the rover of CE-3 probe based on results from ground experiments

Lunar Penetrating Radar (LPR) onboard the rover that is part of the Chang’e-3 (CE-3) mission was firstly utilized to obtain in situ measurements about geological structure on the lunar surface and the thickness of the lunar regolith, which are key elements for studying the evolutional history of lunar crust. Because penetration depth and resolution of LPR are related to the scientific objectives of this mission, a series of ground-based experiments using LPR was carried out, and results of the experimental data were obtained in a glacial area located in the northwest region of China. The results show that the penetration depth of the first channel antenna used for LPR is over 79 m with a resolution of 2.8 m, and that for the second channel antenna is over 50.8 m with a resolution of 17.1 cm.

Pitfalls in GPR Data Interpretation: False Reflectors Detected in Lunar Radar Cross Sections by Chang’e-3

Chang’e-3 (CE-3) has been the first spacecraft to soft land on the moon since the Soviet Union’s Luna 24 in 1976. The spacecraft arrived at Mare Imbrium on December 14, 2013, and the same day, Yutu lunar rover separated from lander to start its exploration of the surface and the subsurface around the landing site. The rover was equipped, among other instruments, with two lunar penetrating radar systems having a working frequency of 60 and 500 MHz. The radars acquired data for about two weeks while the rover was slowly moving along a path of about 114 m. At navigation point N0209, the rover got stacked into the lunar soil and after that only data at a fixed position could be collected. The low-frequency radar data have been analyzed by different authors and published in two different papers, which reported totally controversial interpretations of the radar cross sections. This paper is devoted to resolve such controversy by carefully analyzing and comparing the data collected on the moon by Yutu rover and on earth by a prototype of LPR mounted onboard a model of the CE-3 lunar rover. Such analysis demonstrates that the deep radar features previously ascribed to the lunar shallow stratigraphy are not real reflectors, rather they are signal artifacts probably generated by the system and its electromagnetic interaction with the metallic rover.

Numerical Simulations of the Lunar Penetrating Radar and Investigations of the Geological Structures of the Lunar Regolith Layer at the Chang’E 3 Landing Site

In the process of lunar exploration, and specifically when studying lunar surface structure and thickness, the established lunar regolith model is usually a uniform and ideal structural model, which is not well-suited to describe the real structure of the lunar regolith layer. The present study aims to explain the geological structural information contained in the channel 2 LPR (lunar penetrating radar) data. In this paper, the random medium theory and Apollo drilling core data are used to construct a modeling method based on discrete heterogeneous random media, and the simulation data are processed and collected by the electromagnetic numerical method FDTD (finite-difference time domain). When comparing the LPR data with the simulated data, the heterogeneous random medium model is more consistent with the actual distribution of the media in the lunar regolith layer. It is indicated that the interior structure of the lunar regolith layer at the landing site is not a pure lunar regolith medium but rather a regolith-rock mixture, with rocks of different sizes and shapes. Finally, several reasons are given to explain the formation of the geological structures of the lunar regolith layer at the Chang’E 3 landing site, as well as the possible geological stratification structure.

The subsurface penetrating radar on the rover of China's Mars 2020 mission

Chinas Mars probe including an orbiter and a landing rover will be launched by 2020. A subsurface penetrating radar (SPR) instrument has been selected to be a part of the payload on the rover. The main scientific objective of the SPR is to characterize the thickness and sub-layer distribution of the Martian soil. The SPR consists of two channels. The low frequency channel of the SPR will provide a penetration depth of 10 to 100 meters with a resolution of a few meters within the Martian soil. The higher frequency channel will penetrate to a depth of 3 to 10 meters with a resolution of a few centimeters within the Martian soil. The SPR first version prototype was designed and some field tests have been conducted with it.

Lunar regolith structure model and echo simulation for Lunar Penetrating Radar

A Lunar Penetrating Radar (LPR) based on time domain Ultra Wide Band (UWB) technique is currently within the scope of Chinas Chang-E 3 (CE-3) lunar mission, with the purpose of studying the subsurface structure of the Moon. Exploring the UWB microwave radiation and transfer properties of lunar regolith and establishing a reasonable inverse model are essential for the estimation of the thickness of lunar regolith. In this study, a multi-layer microwave transfer model is established. The model is further used to numerically simulate and analyze the variations of the echo obtained from the LPR attached on CE-3 with time, location and thickness of lunar regolith. The thickness of lunar regolith is calculated by the comparison between the simulated radar B-scan images based on the model and the detective result taken form CE-3 lunar mission. The potential scientific return from LPR echoes taken form landing region is also discussed.