# Time-Frequency Attribute Analysis of Channel 1 Data of Lunar Penetrating Radar
## 1 Introduction  
Exploration of the lunar subsurface structure is a powerful force for the analysis of the stratigraphic thickness, time, and contact relationships, which exert a vital role not only on theorizing the evolution of the subsurface structure, but also on estimating the total resources of the lunar subsurface. In order to detect the shallow geological structure of the moon, spaceborne radar and synthetic aperture radar (SAR) are mainly used. As early as 1972, Apollo 17 carried out on-board radar detection [1]. It operated at 5, 15, and 150 MHz. In addition, it mainly detected the underground geological structure of the moon. Since 20 November 2007, the Lunar-Radar Sounder (LRS) on Japan's Kaguya probes (SELENE) has been surveying the moon underground. The LRS uses the high-frequency (HF) band (5 MHz) to enable the acquisition of subsurface data at depths of several kilometers [2]. The small SAR was launched on the moon in September 2007 and it carried out the Indian Chandrayaan mission. It mapped the scattering characteristics of the moon's pole and determined the existence and extent of polar ice [3, 4]. The Mini-RF instrument on the Lunar Reconnaissance Orbiter (LRO) is a SAR, and it works with bistatic radar from the Arecibo Observatory to conduct data analysis of the region. The results show that there may be near-surface sediments of water ice [4, 5]. Unlike the spaceborne radar described above, the lunar radar on Chang'E-3 (CE-3) is a field instrument for underground structure detection [6]. The dual-frequency radar (DFR) offers a greatopportunity to map underground structures to depths of a few hundred meters from the CH-1 and its near-surface stratigraphic structure re-aggregates from the CH-2 [7] of Mare Imbrium. The Yutu rover (YR) landed at a height of 340.4875\({}^{\circ}\) E, 44.1189\({}^{\circ}\) N in a new area that had never been surveyed in the largest basin, the Mare Imbrium. Ancient basalts and young basalts are distributed here, and the last volcanic activity also stopped here [8]. The CE-3 Lunar Penetrating Radar (LPR) data provide a new perspective for analyzing subsurface structures. In the beginning, the LPR data primary results were put forward by the National Astronomical Observatory of the Chinese Academy of Sciences (NAOC) [9]. The preliminary analysis of LPR, especially CH-1, showed that there are nine underground layers from the surface to a depth of about 360 m [6]. The existence of three basaltic areas detected by the LPR is the same as the distribution of the three major basaltic areas in Mare Imbrium [10; 11; 12; 13; 14]. By processing the original CH-2 data, the near-surface structure was inferred. The parameters of cemented carbide were calculated by [PERSON] et al. [15] and [PERSON] et al. [16]. [PERSON] et al. [17] and [PERSON] et al. [18] developed a new method for processing CH-2 data. [PERSON] et al. proposed a rock extraction method by using local similarity constraints to realize rock location and quantitative analysis [19]. The basis for interpretation when using CH-1 data is its credibility. However, [PERSON] et al. demonstrated some false reflectors in the CH-1 data [20]. In order to analyze and decompose the CH-1 data, an analysis method that can be used in nonlinear data is necessary. In recent years, empirical mode decomposition (EMD) [21] has developed into a data analysis method. EMD has demonstrated appropriate versatility in the application of signals for extracting from random data with a complex noise environment. Although EMD has proven to be useful, it still has some unresolved difficulties. The main disadvantage of EMD is the constant appearance of pattern blending. Signals of different scales can be combined into an intrinsic mode function (IMF). In order to conquer the frequent occurrence of pattern mixing, a new method of noise assisted data analysis (NADA) has been proposed. Its name is ensemble EMD (EEMD) [22]. The core idea of this method is to average the results of EMD and apply it to the original signal.