Brightness Temperature Calculation of Lunar Crater: Interpretation of Topographic Effect on Microwave Data From Chang'E

Abstract

In order to quantitatively interpret topographic effect on Chang'E (CE) microwave data, a detailed method to compute brightness temperature (TB) over a lunar crater is proposed, which incorporated the effect of surface tilts. The method improves the effective solar irradiance model of the lunar surface to obtain the temperature profile of the lunar crater. The calculated TB at 37 GHz with the proposed computation method, which is based on three digital elevation models (DEMs) from different sources, are consistent with the observed TB from the CE-2 microwave radiometer. The simulated behavior of TB across crater Hercules reproduces the TB undulation observed by CE in a single swath. TB is significantly affected by the lunar dust of a lunar crater and affected by albedo and emissivity in a lesser degree. Based on the explanation with simplified models, the TB variation over a crater is proved to be significantly affected, through physical temperature, by the crater shape described by DEMs. With the simplified crater model, the amplitude of the TB oscillatory curves is proved to depend on the crater shape.Index Terms-Brightness temperature (TB), Chang'E (CE), digital elevation model (DEM), lunar crater.

Mare Deposits Identification and Feature Analysis in Mare Australe Based on CE‐2 CELMS Data

“…Considering that the great change of the regolith temperature only occurs in the upper 15 cm from the lunar surface (Hu et al, 2013;Wang et al, 2010); Meng et al (2017), Meng, Hu, et al, 2018;Meng, Wang, Chen, et al, 2019) proposed that the difference between the noon T B and the night T B of the same frequency, named dT B , is directly related to the regolith thermophysical parameters within the penetration depth of the corresponding microwave. Therefore, the dT B maps were generated in this study ( Figure 5).…”

The Moon in the Microwave: Shedding New Light on the Lunar Farside

“…The Level 2C Chang'E−2 (CE‐2) Microwave Radiometer (MRMs) data (NAOC, 2016; Zheng et al., 2019, 2012) were used in this study, following system calibration and geometric correction with the Planetary Data System (McMahon, 1996). The MRM underwent onboard adjustments to ensure its reliability and accuracy using a two‐point calibration method (for details see Chan et al., 2010; Wang et al., 2010; Zheng et al., 2012; Hu et al., 2014; Hu et al., 2017, Zheng et al., 2019). We used spherical harmonic fits for the TB variations with local time (Wang et al., 2010) to suppress the lunar phase effect.…”

“…Normalized TBs at midnight were chosen to minimize the topographic effects on the emission (Hu et al., 2014). Surface temperature variations at night are dependent on the local differential heat energy storage and release accumulated by surface materials during the day, with a minimal contribution by internal sources (heat flow).…”

“…We used spherical harmonic fits for the TB variations with local time (Wang et al, 2010) to suppress the lunar phase effect. Even though a few calibration issues are still pending (Hu et al, 2014), the relative distribution shown in TB maps is now considered to be consistent within the chosen latitudes of interest (Hu et al, 2017(Hu et al, , 2021Zheng et al, 2019).…”

“…Dating back from Zheng et al (2012), several studies have published single-channel microwave maps of the entire lunar surface, mostly concentrating on the continuous improvement of data calibration (Hu et al, 2014(Hu et al, , 2017(Hu et al, , 2021Siegler et al, 2020). In 2019, Zheng et al updated their maps and discussed some broad mineralogical implications.…”