Volcanic history of the Imbrium basin: A close-up view from the lunar rover Yutu

Hao

et al. 2016

Sci Rep

Self Cite

The seismic waveforms would be clipped when the amplitude exceeds the upper-limit dynamic range of seismometer. Clipped waveforms are typically assumed not useful and seldom used in waveform-based research. Here, we assume the clipped components of the waveform share the same frequency content with the un-clipped components. We leverage this similarity to convert clipped waveforms to true waveforms by iteratively reconstructing the frequency spectrum using the projection onto convex sets method. Using artificially clipped data we find that statistically the restoration error is ~1% and ~5% when clipped at 70% and 40% peak amplitude, respectively. We verify our method using real data recorded at co-located seismometers that have different gain controls, one set to record large amplitudes on scale and the other set to record low amplitudes on scale. Using our restoration method we recover 87 out of 93 clipped broadband records from the 2013 Mw6.6 Lushan earthquake. Estimating that we recover 20 clipped waveforms for each M5.0+ earthquake, so for the ~1,500 M5.0+ events that occur each year we could restore ~30,000 clipped waveforms each year, which would greatly enhance useable waveform data archives. These restored waveform data would also improve the azimuthal station coverage and spatial footprint.

Section: Discussionmentioning

confidence: 99%

“…4a. This figure was generated using the Generic Mapping Tools26 version 4.5.8 (http://gmt.soest.hawaii.edu). …”

Section: Figurementioning

confidence: 99%

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Restoration of clipped seismic waveforms using projection onto convex sets method

Hao

et al. 2016

Sci Rep

Self Cite

International Journal of Antennas and Propagation

“…The Chang'E 3 landed near the young crater C1, which has a diameter of approximately 450 m [18,19]. The landing position was approximately 50 m from the edge of the impact crater.…”

Section: The Interior Structure Of the Lunar Regolith At The Chang'e mentioning

confidence: 99%

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

Ding

Xing

et al. 2017

Self Cite

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.

Sci. China Phys. Mech. Astron.

“…The LPR measurements also detected three underlying basalt units at depths of 195, 215, and 345 m at the CE-3 landing area, and indicated significant volcanic eruptions in the Imbrium basin until 2.5 Ga, which is different from the gradual cessation of magma eruption in the Imbrium basin [15]. Correlated compositional and mineralogical investigations of the lunar soil at the landing site were determined by the Yutu rover with in situ measurements by APXS and VNIS.…”

mentioning

confidence: 95%

New achievements from CE-3 mission

Zou

Wang

Yan

et al. 2017

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The Chang'E-3 (CE-3) mission began with a smooth countdown and flawless launch on the Long March 3B rocket from the Xichang satellite launch center at 01:30 CST on December 2, 2013. It landed on the northeastern Imbrium basin (340.49°E, 44.12°N) at 21:11 CST on December 14, 2013, and the Yutu rover was deployed from the lander the next morning at 04:35.The lander was equipped with a number of remote-sensing instruments including the landing camera (LCAM), terrain camera (TCAM), extreme ultraviolet camera (EUVC), and lunar-based ultraviolet telescope (LUT). The Yutu rover successfully carried the panoramic camera (PCAM), VIS-NIR imaging spectrometer (VNIS), active particle-induced X-ray spectrometer (APXS), and lunar penetrating radar (LPR) [1][2][3].Three cameras (LCAM, TCAM, and PCAM) investigated the morphological features and geological structures near the landing area. The EUVC monitored activities in the Earth's plasmasphere at extreme ultraviolet wavelengths (measurement band center frequency 30.4±0.5 nm, bandwidth ≤5 nm). The LUT performed astronomical observations at near-ultraviolet wavelengths (245-340 nm). The VNIS (visible-nearinfrared 450-950 nm, short-wave infrared 900-2400 nm) and APXS detected the mineralogical and chemical compositions along the traverse path. The LPR obtained pioneering measurements of the lunar subsurface.After the lander released the Yutu rover, the eight science instruments began operating. The Yutu rover started traversing along a planned path covering a distance of 114 m. *Corresponding author (email: wangqin@bao.ac.cn) To analyze the topography, landform, and geology of the area surrounding the landing site (Sinus Iridum and 45 km× 70 km of the landing area), high-resolution topography data, image data, and geological data were obtained [4].Thus far, eight science instrument calibration procedures, data processing methods, and inversion models have been completed [5][6][7][8][9][10][11][12]. The total science data size was 6.69 TB as of April 4, 2016.The LPR detection and integrated TCAM & PCAM data interpretation have identified more than seven subsurface layers, suggesting that the landing region has experienced complex geological processes such as basalts and pyroclastic have filled in the Imbrium basin since the Imbrian (3.9-3.2 Ga) and Eratosthenian (3.2-1.5 Ga) epochs [3]. The LPR and PCAM data provides a higher resolution to estimate lunar regolith parameters such as permittivity, density, conductivity, and FeO+TiO 2 content. The surface regolith thickness of the CE-3 landing area is (1.24±0.10) m. Meteorite impacts might have been a vital influence to the thickness and growth rate of the regolith [13].The LPR consists of two types of antenna with two channels: 60 (Channel 1) and 500 MHz (Channel 2). The LPR observations at 500 MHz reveal four major stratigraphic zones from the surface to a depth of 20 m: a layered reworked zone (<1 m), ejecta layer (~2-6 m), paleoregolith layer (~4-11 m), and the underlying mare basalts. In addition, the LPR measurements indica...