Thermal Removal Method for Chang’e-5 Multispectral Data Using a Heat Conduction Model and Real Terrain

The lunar mineral spectrometer (LMS) onboard the Chang’e-5—China’s lunar exploration mission—collected in situ multispectral data up to
$3~\mu \text{m}$
over a large area of the lunar surface for the first time. As Chang’e-5 operated near the Moon’s noon local time, the spectral data are influenced by thermal radiation. In particular, the LMS multispectral data are in the form of characteristic spectral bands with discontinuities that make it difficult to directly apply the existing empirical models for thermal removal. Here, we present a thermal removal method based on the 1-D heat conduction model and real terrain data. A centimeter-scale temperature distribution map of the multispectral measurement region is calculated, which ranged from 330 to 362 K. We calculated the temperatures of four hyperspectral regions using an empirical model, compared them with those of the same region using the proposed method, and obtained a relative error of less than 1%. Afterward, we removed the effects of thermal radiation in the multispectral data using a thermal removal model with the temperature of the multispectral region. We compared multispectral data after thermal removal using our proposed method with hyperspectral data after thermal removal using an empirical model at similar locations. The results showed good consistency between the data corrected by both methods. This article proposed method does not depend on the setting of the spectral band, and it can provide a reference for thermal removal of Chang’e-5 multispectral data and that of subsequent in situ noncontinuous spectral detection data.