Volume Measurement of Lunar Soil in the Chang'E-6 Sampling Container Using A Single Camera

Abstract

The Chang'E-6 mission aims to return lunar soil samples from the far side of the Moon. For assisting Chang'E-6 mission deciding the optimal time to stop scooping, a comprehensive measurement method including image acquisition scheme and measurement algorithm was proposed to measure the volume of lunar soil in the container in the paper. A camera is used to capture images at two different positions, serving as the left and right image of stereo. By capturing images with different exposures times, the information both in the low-illumination and high-illumination area was obtained. A robust multi-target template detection method is proposed, which can avoid the erroneous target extraction problem based on threshold. We avoid the complex target point cloud extraction by detecting the lunar soil area in the image. The experimental results in the lunar simulation environment on Earth demonstrate that the method can measure the volume of lunar soil accurately. The absolute error of the measured volume is less than $30 cm^3$. On June 3rd 2024, the volume of lunar soil measured using our method after sampling 8 shovels on the moon is $1393 cm^3$. The measurement results had assisted Chang'E-6 team to determine that the lunar soil in the sampling container had met the established objectives and it is the optimal time to stop scooping.