Information about the variability,and spatial distribution of iron abundance is important to understand lunar geological history and for future resource utilization. In this paper we present a preliminary model to produce an iron abundance map using images taken by an Imaging Interferometer on board the satellite Chang'E-1. Compared with the Clementine UVVIS images,the images from the Chang'E-1 satellite also allowed for the extraction of FeO abundance distributions on the Moon. However,the prelimi-nary model results suggest an underestimation of ～2 wt.% for the FeO content of the mare region and an overestimation of ～3 wt.% for the highland region.
The imaging interferometer(IIM)aboard the Chang’E-1 lunar orbiter is the first multispectral imaging spectrometer for Chinese lunar missions.Before science applications(e.g.,FeO and TiO2mapping)of the IIM raw data,the radiance variation due to changes in illumination and viewing geometry has to be removed from the radiometrically calibrated IIM Level 2A images.To achieve this,we fit the IIM Level 2A radiance data with a Lommel-Seeliger photometric model consisting of an exponential term and a fourth order polynomial in the phase function,without distinguishing between lunar maria and highlands.The exponential and the fourth order polynomial parameters are derived separately by fitting to two datasets divided at a solar phase angle threshold,avoiding a decrease in the phase function close to zero phase angle.Different phase angle thresholds result in coincident fitting curves between 20°and 75°,while large discrepancies occur at other phase angles.Then the derived photometric model is used to normalize the IIM Level 2A data to radiance values at an incidence and phase angle of 30°and emission angle of 0°.Our photometric model is validated by comparing two photometrically normalized IIM radiance spectra covering the same areas,showing a relative deviation consistent with the IIM preflight calibration.
The distribution of titanium abundance on the lunar surface is important knowledge for lunar geologic studies and future resource utilization.In this paper,we develop a preliminary model based on"ground truths"from Apollo and Luna sample-return sites to produce a titanium abundance map from Chang’E-1 Imaging Interferometer(IIM) images.The derived TiO2 abundances are validated with Clementine UVVIS results in several regions,including lunar highlands neighboring the Apollo 16 landing site,and high-Ti and low-Ti maria near the standard site of Mare Serenitatis(MS2) .The validation results show that TiO2 abundances modeled with Chang’E-1 IIM data are overestimated for highlands(～0.7 wt.%) and low-Ti maria(～1.5 wt.%) and underestimated for high-Ti maria(～0.8 wt.%).
