Lunar absolute reflectance, which describes the fraction of solar radiation reflected by the Moon, is fundamental for the Chang'E-1 Imaging Interferometer(IIM) to map lunar mineralogical and elemental distribution...Lunar absolute reflectance, which describes the fraction of solar radiation reflected by the Moon, is fundamental for the Chang'E-1 Imaging Interferometer(IIM) to map lunar mineralogical and elemental distributions. Recent observations made by the Spectral Irradiance Monitor(SIM) onboard the Solar Radiation and Climate Experiment(SORCE) spacecraft indicate that temporal variation in the solar radiation might have non-negligible influence on reflectance calculation, and the SIM measurements are different from the two previously used solar irradiances, i.e., ATLAS3 and Newkur. To provide reliable science results, we examined solar irradiance variability with the SIM daily observations, derived lunar absolute reflectances from the IIM 2A radiance with the SIM, ATLAS3 and Newkur data, and compared them with the Chandrayaan-1 Moon Mineralogy Mapper(M3), the Robotic Lunar Observatory(ROLO) and the Kaguya Multispectral Imager(MI) results. The temporal variability of the SIM solar irradiance is 0.25%–1.1% in the IIM spectral range, and less than 0.2% during the IIM observations. Nevertheless, the differences between the SIM measurements and the ATLAS3 and Newkur data can respectively rise up to 8% and 5% at particular IIM bands, resulting in discrepancy between which might affect compositional mapping. The IIM absolute reflectance we derived for the Moon using the SIM data, except for the last two bands, is consistent with the ROLO and the MI observations, although it is lower.展开更多
The global map of potassium is represented in this paper from Chang'E-1 (CE-1) Gamma-ray Spectrometer (CGRS) for its one-year mission.Assuming a linear relationship between net count rate and its abundance,the ave...The global map of potassium is represented in this paper from Chang'E-1 (CE-1) Gamma-ray Spectrometer (CGRS) for its one-year mission.Assuming a linear relationship between net count rate and its abundance,the average potassium abundance of individual landing sites is used as ground-truth for the calibration to derive the global map of absolute concentration.Although CGRS spectra have a lower signal-to-noise ratio,the translated map still keeps relative variations.As calculated from Apollo,Lunar Prospector,and Kaguya,global potassium map from CGRS shows high concentrations on the lunar nearside and secondary concentrations located in the South Pole-Aitken (SPA) basin on the farside.The comparison with Lunar Prospector potassium map shows a good correlation,though abundances on the highlands of the farside are much lower than that of Lunar Prospector.Since the footprint of CGRS measurements is larger than the sampling radius of each landing site,the calibrated map shows a larger variation range of the scale than that of Lunar Prospector,which was derived using theoretical calculation;namely,the calibrated map has higher values in the areas with high concentration while having lower values for the areas with lower concentration.However,the derived potassium map is more consistent with the lunar sample data than that of Lunar Prospector.展开更多
Lunar titanium characterization is an important goal of the China Lunar Exploration Program. We suggest a method to determine the lunar titanium abundance using Chang'E-1 IIM (Interference Imaging Spectrometer) im...Lunar titanium characterization is an important goal of the China Lunar Exploration Program. We suggest a method to determine the lunar titanium abundance using Chang'E-1 IIM (Interference Imaging Spectrometer) imagery. Using samples from Apollo and Luna landing sites, the method firstly establishes the spectral parameters that possess good non-linear correlations with lunar titanium abundance. Secondly, the method estimates lunar titanium abundance using a DT-SVM (Decision Tree Method C5.0-Support Vector Machine) method. Namely, according to the established spectral parameters, it uses the C5.0 algorithm to classify the titanium abundance into the 4 classes of very low, low, intermediate and high. Then, in terms of the spectral parameters and the corresponding classes, it employs the SVM to estimate the titanium abundance. The method makes good use of hyperspectral information, analyzes the nonlinear correlations between spectral characteristics of lunar soils and the composition parameter, and well determines the titanium abundance. Validated by the Apollo and Luna station samples, the RMSE (root mean square error) is 0.72wt% TiO2 and the correlation coefficient of the measured and predicted values is 97.29%. So, the method proposed in this paper has a good predictive capability for TiO2 abundance on the lunar surface. The maps of TiO2 content in the partial region of Sinus Iridium, the Apollo 17 landing site and the Apollo 16 landing site are constructed by our method. This paper demonstrates the potential of IIM data for the investigation of lunar surface chemistry and mineralogy.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11003012,41373068,41473065 and U1231103)
文摘Lunar absolute reflectance, which describes the fraction of solar radiation reflected by the Moon, is fundamental for the Chang'E-1 Imaging Interferometer(IIM) to map lunar mineralogical and elemental distributions. Recent observations made by the Spectral Irradiance Monitor(SIM) onboard the Solar Radiation and Climate Experiment(SORCE) spacecraft indicate that temporal variation in the solar radiation might have non-negligible influence on reflectance calculation, and the SIM measurements are different from the two previously used solar irradiances, i.e., ATLAS3 and Newkur. To provide reliable science results, we examined solar irradiance variability with the SIM daily observations, derived lunar absolute reflectances from the IIM 2A radiance with the SIM, ATLAS3 and Newkur data, and compared them with the Chandrayaan-1 Moon Mineralogy Mapper(M3), the Robotic Lunar Observatory(ROLO) and the Kaguya Multispectral Imager(MI) results. The temporal variability of the SIM solar irradiance is 0.25%–1.1% in the IIM spectral range, and less than 0.2% during the IIM observations. Nevertheless, the differences between the SIM measurements and the ATLAS3 and Newkur data can respectively rise up to 8% and 5% at particular IIM bands, resulting in discrepancy between which might affect compositional mapping. The IIM absolute reflectance we derived for the Moon using the SIM data, except for the last two bands, is consistent with the ROLO and the MI observations, although it is lower.
基金Financial supports from the Science and Technology of Development Fund of Macao (Grant Nos. 004/2011/A1,003/2008/A1 and 042/2007/A3)
文摘The global map of potassium is represented in this paper from Chang'E-1 (CE-1) Gamma-ray Spectrometer (CGRS) for its one-year mission.Assuming a linear relationship between net count rate and its abundance,the average potassium abundance of individual landing sites is used as ground-truth for the calibration to derive the global map of absolute concentration.Although CGRS spectra have a lower signal-to-noise ratio,the translated map still keeps relative variations.As calculated from Apollo,Lunar Prospector,and Kaguya,global potassium map from CGRS shows high concentrations on the lunar nearside and secondary concentrations located in the South Pole-Aitken (SPA) basin on the farside.The comparison with Lunar Prospector potassium map shows a good correlation,though abundances on the highlands of the farside are much lower than that of Lunar Prospector.Since the footprint of CGRS measurements is larger than the sampling radius of each landing site,the calibrated map shows a larger variation range of the scale than that of Lunar Prospector,which was derived using theoretical calculation;namely,the calibrated map has higher values in the areas with high concentration while having lower values for the areas with lower concentration.However,the derived potassium map is more consistent with the lunar sample data than that of Lunar Prospector.
基金supported by the National Natural Science Foundation of China (Grant No. 40902099)the Fundamental Research Funds for the Central Universities,China University of Geosciences (Wuhan) (Grant No. CUG100702)
文摘Lunar titanium characterization is an important goal of the China Lunar Exploration Program. We suggest a method to determine the lunar titanium abundance using Chang'E-1 IIM (Interference Imaging Spectrometer) imagery. Using samples from Apollo and Luna landing sites, the method firstly establishes the spectral parameters that possess good non-linear correlations with lunar titanium abundance. Secondly, the method estimates lunar titanium abundance using a DT-SVM (Decision Tree Method C5.0-Support Vector Machine) method. Namely, according to the established spectral parameters, it uses the C5.0 algorithm to classify the titanium abundance into the 4 classes of very low, low, intermediate and high. Then, in terms of the spectral parameters and the corresponding classes, it employs the SVM to estimate the titanium abundance. The method makes good use of hyperspectral information, analyzes the nonlinear correlations between spectral characteristics of lunar soils and the composition parameter, and well determines the titanium abundance. Validated by the Apollo and Luna station samples, the RMSE (root mean square error) is 0.72wt% TiO2 and the correlation coefficient of the measured and predicted values is 97.29%. So, the method proposed in this paper has a good predictive capability for TiO2 abundance on the lunar surface. The maps of TiO2 content in the partial region of Sinus Iridium, the Apollo 17 landing site and the Apollo 16 landing site are constructed by our method. This paper demonstrates the potential of IIM data for the investigation of lunar surface chemistry and mineralogy.
