Extended use of receiver groups: Theory, synthetic example, and noise considerations

Receiver grouping is commonly used in marine towed-streamer seismic acquisition. Measurements from several receivers in a group are stacked to increase the signal-to-noise ratio of the resulting data and form an analog spatial antialiasing filter. I propose a method for extracting inline derivatives of the wavefield as additional measurements from the groups. This is achieved by multiplying the signal from the individual receivers in a group with predefined weights that corresponds to a finite-difference (FD) operator. The inline derivative(s) makes it possible to use multichannel sampling theorems to reconstruct the signal on a denser grid. Extraction of FD data from clusters of receivers is not a new concept, but I find that, by using the geometry of conventional streamer groups, it is possible to obtain FD data which are well suited for multichannel interpolation. The key to finding suitable FD operators is to recognize that it is not the ideal differentiation response we seek, but the impulse response of the group multiplied with the ideal differentiation response. Furthermore, under a Gaussian noise assumption, I derive formulas for the resulting noise level from sinc and higher order sinc interpolations. I find that the random noise level in the reconstructed data, when using higher order sinc interpolation, is expected to be higher than when using conventional sinc interpolation and will vary with respect to the distance from the original sampling points. The statistical analysis shows that it is beneficial to find FD operators with as small an [Formula: see text] norm as possible. A synthetic example shows that the proposed method of extracting FD operators and subsequent interpolation works very well. I foresee that the proposed method can be used to reduce the density of receivers (hydrophones or geophones) when designing new streamers or with existing equipment to improve the inline sampling.

LUNAR SURFACE SAMPLING FEASIBILITY EVALUATION METHOD FOR CHANG’E-5 MISSION

<p><strong>Abstract.</strong> As China’s first unmanned spacecraft to collect lunar surface samples and return them to Earth, the Chang’E-5 detector is a crucial probe that will complete lunar surface sampling in China’s lunar exploration project. This lunar sampling will be the first successful lunar surface sampling return mission in China. Sampling decisions needs to be made based on topographical analysis results and characteristics of the area to be explored. Due to the unknown extraterrestrial terrain and uncertainty of sampled objects, we propose a sampling feasibility estimation for safely implementing lunar surface sampling.</p><p>Our strategy took into account the influence of factors that may interfere with the sampling process, and provided quantitative assessment of the sampling feasibility for the area to be explored. We combined the three-dimensional topography of the lunar surface with five parameters of the sampling area, flatness, slope, slope aspect, accessibility of the mechanical arm distal end, and safety of sampling conditions. The first three values were calculated based on a digital elevation model (DEM) of the landing area generated using stereo images. The other values were computed based on the mechanical properties of the arm and kinematic analysis of its articulated joints. Based on the above-mentioned quantitative parameters, they were weighed to obtain an evaluation value for the sampling feasibility of each DEM pixel. Meanwhile, a multichannel sampling area analysis graph was generated that combined all the above indicators as well as the sampling feasibility values, which provides a visualization for determining detection targets in the Chang’E-5 sampling mission.</p>