Comparison and evaluation of the Chang'E microwave radiometer data based on theoretical computation of brightness temperatures at the Apollo 15 and 17 sites

Autor: Kang T. Tsang, Ao-Ao Xu, Yongchun Zheng, Kwing L. Chan, Guo-Ping Hu
Rok vydání: 2017
Předmět:
Zdroj: Icarus. 294:72-80
ISSN: 0019-1035
Popis: There are significant differences (in the order of 3 to 20 K) between the lunar brightness temperatures (TBs) as measured by the microwave radiometers (MRM) onboard Chang'E (CE)−1 and −2. To determine which set is more accurate, we have carried out a dataset comparison using theoretical calculations of the TBs (four frequency channels) versus local time at the Apollo 15 and 17 landing sites, where the thermal parameters are well-constrained by the in-situ measurements. Based on these parameters, we sought to constrain fits between theory and observation, as uncertainties still exist in parameters involved in the microwave transfer computation. We found that: (i) CE-1/2 TBs have almost constant biases (negative, different for different channels) from the theoretical TBs. The averaged biases for each channel are smaller for CE-1; (ii) TBs of the high frequency channels (19.35/37 GHz) show a better fit with theory than the low frequency channels. The channel 4 (37 GHz) TBs from CE-1 are consistently shifted by about 1 K from the theoretical values. Adjustments in the order of 20 K are instead needed for the two CE-2 low frequency channels (3/7.8 GHz). Based on this comparison, we conclude that the CE-1 dataset to be more accurate than CE-2 one in terms of temperature accuracy (not spatial resolution). We also offer a possible explanation for the significant TB differences between CE-1 and CE-2, and propose a possible recalibration method as a starting point towards the realignment of the two datasets.
Databáze: OpenAIRE
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