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Since Mars is far away from Earth, the propagation delay between Mars and Earth is very large. To ensure the effective use of the link transmission bandwidth, China's first Mars exploration mission has put forward a demand for data compression for all scientific payloads. The on-board mature algorithms for data compression are mainly focused on optical images and microwave imaging radar applications. No articles have been published on data compression methods that are applied to subsurface-penetrating radar. Based on the background of this application, this paper proposes a logarithmic lossy compression algorithm which can meet the mission requirements for high compression ratios of 4:1 and 2.5:1. Its compression error is less than that of the block adaptive quantization (BAQ) algorithm. The algorithm is not only easy to implement on field-programmable gate array (FPGA) platforms, but also offers simple ground decompression and fast imaging. The experimental results show that high compression ratios of 4:1 and 2.5:1 can be realized, even if the data in and between traces do not have a strong correlation. And its relative error is less than 2%, which is a new type of high-efficiency data compression method that can be implemented on-board to meet with the demand of subsurface penetrating radar. [ABSTRACT FROM AUTHOR]

The unequal distribution of volcanic products between the Earth-facing lunar side and the farside is the result of a complex thermal history. To help unravel the dichotomy, for the first time a lunar landing mission (Chang'e-4, CE-4) has targeted the Moon's farside landing on the floor of Von Kármán crater (VK) inside the South Pole-Aitken (SPA). We present the first deep subsurface stratigraphic structure based on data collected by the ground-penetrating radar (GPR) onboard the Yutu-2 rover during the initial nine months exploration phase. The radargram reveals several strata interfaces beneath the surveying path: buried ejecta is overlaid by at least four layers of distinct lava flows that probably occurred during the Imbrium Epoch, with thicknesses ranging from 12 m up to about 100 m, providing direct evidence of multiple lava-infilling events that occurred within the VK crater. The average loss tangent of mare basalts is estimated at 0.0040-0.0061. The authors here report results from the ground-penetrating radar onboard the Yutu-2 rover from the Chagn'E 4 mission. The study presents up to 330 m deep subsurface structure of the Von Karman Crater inside the South Pole Aitken Basin. [ABSTRACT FROM AUTHOR]

As a main payload of the lander of Chang’E-5, lunar regolith penetrating array radar (LRPR) is a multi-input and multioutput ground penetrating array radar system. The following are the main characteristics of LRPR: it works at a fixed location, the layout of the antennas is irregular, and the amount of data for imaging is very rare. A prestack depth migration imaging method based on Kirchhoff integral is presented, which overcomes the problems of irregular antenna layout and the layered medium. The issue of sparse matrix imaging for LRPR is solved successfully by the method. The laboratory experiment demonstrates that the proposed method is very suitable for LRPR imaging, in which the targets are clearly distinguished and their depths are also consistent with the reality. [ABSTRACT FROM AUTHOR]

Chang'E-3 was launched on December 2, 2013, and successfully landed on the moon on December 14, 2013. It carried a 140-kg lunar rover named Yutu, which is designed to explore an area of 3 km2. Chang'E-3 mission is to achieve China's first soft landing and roving on the moon [1]. Lunar penetrating radar (LPR) is a key payload of the Yutu lunar rover in the Chang'E-3 mission. The scientific target of LPR is to explore the thickness distribution of the lunar regolith and the geological structure of rock under the lunar surface. To fulfill the target, LPR is equipped with two ultrawideband antennas, channel 1 (CH1) and channel 2 (CH2). The CH1's center frequency is 60 MHz, and the CH2?s center frequency is 500 MHz. LPR, which is mounted on the Yutu rover, can sound the structure of the lunar surface in a large range and over a long distance while the rover is moving. [ABSTRACT FROM PUBLISHER]

The Tianwen-1 of China is expected to land and explore on the planet Mars in May 2021, carrying a Mars Rover-mounted Subsurface Penetrating Radar (RoSPR) system. A VHF band ultra-wideband (UWB) monopole antenna integrated on the Mars Rover, and described in this paper, has been designed for the subsurface exploration of Mars tens of meters deep. Conventional antenna design methods usually prove difficult in taking into account several key parameters such as miniaturization, broadband characteristics and radiation efficiency. Moreover, there is almost no special research on the reliability of antennas. For this purpose, a miniaturized air-coupled monopole antenna integrated with the Mars Rover has been designed. The overall length of the antenna is 0.13 λ at the lowest operating frequency. In addition, the classical Wu–King profile is improved, which not only satisfies the operating bandwidth of the antenna, but also increases the gain by 3–4 dB. In the design, the innovative application of planar embedded resistance greatly enhances the reliability of the antenna and thereby ensures that the antenna can work on Mars for a long term. This is the first application of this antenna design method in the aerospace field. Because it is difficult to test the low-frequency antenna accurately, a 1:4 scale model of the antenna and Rover is fabricated to equivalently measure the radiation characteristics of the antenna. Furthermore, the performance and practicability of the antenna and radar system are verified on the glacier. [ABSTRACT FROM AUTHOR]

Abstract Lunar Regolith Penetrating Array Radar (LRPR) is one main payload of the Lander for Chinese Chang'E-5 (CE-5) mission. It is used to support the drilling and sampling device and to detect lunar regolith thickness and structure of the landing site. LRPR will only work in situ under static status, so the antenna array is employed. Since the antenna array is about 90 cm high from the ground, the layout is irregular, and the metal structure of the lander seriously interferes with LRPR, these factors make it very difficult to reconstruct the image of the drilling area, so the performance verification must be carried out. We propose a set of methods to process LRPR's data and reconstruct image. The verification experiments demonstrate that these methods are suitable for LRPR, the thickness and structure of the lunar regolith from zero to two meters can be clearly mapped, the vertical resolution is a few centimeters, and the electromagnetic properties of the subsurface can be estimated. Therefore, the performance of LRPR meets the requirements, and LRPR can successfully support drilling and sampling. [ABSTRACT FROM AUTHOR]