Abstract
Knowledge of the subsurface structure not only provides useful information on lunar geology, but it also can quantify the potential lunar resources for human beings. The dual-frequency lunar penetrating radar (LPR) aboard the Yutu rover offers a Special opportunity to understand the subsurface structure to a depth of several hundreds of meters using a low-frequency channel (channel 1), as well as layer near-surface stratigraphic structure of the regolith using high-frequency observations (channel 2). The channel 1 data of the LPR has a very low signal-to-noise ratio. However, the extraction of weak signals from the data represents a problem worth exploring. In this article, we propose a weak signal extraction method in view of local correlation to analyze the LPR CH-1 data, to facilitate a study of the lunar regolith structure. First, we build a pre-processing workflow to increase the signal-to-noise ratio (SNR). Second, we apply the K-L transform to separate the horizontal signal and then use the seislet transform (ST) to reserve the continuous signal. Then, the local correlation map is calculated using the two denoising results and a time–space dependent weighting operator is constructed to suppress the noise residuals. The weak signal after noise suppression may provide a new reference for subsequent data interpretation. Finally, in combination with the regional geology and previous research, we provide some speculative interpretations of the LPR CH-1 data.
Highlights
Chang’E-3 (CE-3) landed at 340.4875 ◦ E, 44.1189 ◦ N on the Moon on 14 December 2013, in a new region in the largest basin that had not been explored before, that is, the Mare Imbrium [1].The dual-frequency lunar penetrating radar (LPR) aboard the Yutu Rover provides a special opportunity to understand the subsurface structure to a depth of several hundreds of meters from the low-frequency channel (CH-1, 60 MHz)
We proposed a weak signal extraction method based on local correlation to deal with the LPR CH-1 data, and we studied the structure of the lunar regolith
The weak signal after noise suppression can provide a new reference for subsequent data interpretation
Summary
Chang’E-3 (CE-3) landed at 340.4875 ◦ E, 44.1189 ◦ N on the Moon on 14 December 2013, in a new region in the largest basin that had not been explored before, that is, the Mare Imbrium [1]. Local correlation [12] is a typical local attribute used to measure the local similarity of two signals It has been utilized in several seismic signal processing fields, such as image contrast [13,14], time-frequency analysis [15], and random noise attenuation [16,17]. We proposed a weak signal extraction method based on local correlation to deal with the LPR CH-1 data, and we studied the structure of the lunar regolith. To extract these weak signals, we chose the K-L transform and seislet transform (ST) to process the LPR data. Combining with the regional geology and previous research, on LPR data, we provide some speculative interpretations of the LPR CH-1 data
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