| As the only satellite of the earth, the moon always attracts the most attention in space observation and exploration. In the past 60 years, the United States, the Soviet Union(Russia), China, Japan, India and other countries have launched many lunar crafts and made a deep research and understanding of the moon from all aspects. In the study of the moon, composition analysis of lunar surface minerals is one of the important goals, that is the premise and foundation of use of lunar resources in the future. Infrared spectrum analysis technology is an effective means to get the composition and specific elements of lunar surface minerals that is of great value to research the origin and evolution of the moon and take advantage of the moon’s resources. Specific method is that after spectral information of lunar surface minerals is obtained by spectrometers carried by moon crafts, reflectance and other physical parameters can be calculate through data inversion that is used to identify composition of moon surface minerals.Among spectrometers carried by lunar crafts, the typical are Moon Mineralogy Mapper(M3) developed by the United States whose spectral range is 400nm-3000 nm and VIS-NIR Imaging Spectrometer(VNIS) developed by China whose spectral range is 450nm-2400 nm, and spectral information obtained by them provides judge basis of composition of lunar surface minerals. To analyze the composition of the lunar surface minerals more effectively, spectral range detected should be extended, such as lunar mineral spectrometer that will be carried by Chang’E 5 moon craft extends spectral range to 3200 nm.Lunar mineral spectrometer has wide operating temperature range in the lunar surface, and its spectral data obtained by infrared channel III(spectral range 2200nm-3200nm) is not only related with the instrument temperature, but also includes effects of lunar surface mineral thermal radiance, so only key technical problem of temperature dependent be solved to meet the requirements of scientific exploration and application. This is also the main content of this study, and research work and innovation points are as follows:1. Mixing spectral model under wide temperature lunar surfaceBased on the radiance condition of lunar surface environment, through analyzing lunar surface under wide temperature range spectral energy transmit model, the spectral models of reflected solar radiance and its own emission radiance are established. According to the value range of parameters in the both spectral models, reflected solar radiance energy and emission radiance in spectrometer entrance pupil are quantified, mixing spectral model can be established. It provide basis for dynamic range design of infrared channel III and spectral data inversion. Lunar surface exploration based on 2200nm-3200 nm is made in the first time in China, so the detailed research and analysis of the mixed spectral model has certain innovation.2. Spectral calibration and radiometric calibrationFor the infrared channel III can be used to detect lunar surface spectral radiance when it is in lunar surface work in the future, laboratory calibration is needed. At first, the feasibility of spectral calibration method based on monochromator and radiometric calibration method based on blackbody is analyzed. Then, a prototype model based on the design principles and implementation method of the infrared channel III is built and used to achieve spectral detection in 2200nm-3200 nm spectral range. its performance parameters is consistent with the the infrared channel III and used to spectral calibration and radiometric calibration verification. Calibration results meet the engineering requirements, and calibration methods have been used to the infrared channel III, so this part of the work has a certain value in engineering.3. Analysis and correction of temperature characteristicsUnder wide temperature environment of lunar surface, because infrared channel III working temperature in orbit will have some differences with laboratory conditions, different spectral response of the same incident energy will appear. In order to ensure the infrared channel III radiometric calibration can be used in deep space wide environmental temperature range, this paper analyzes the temperature characteristics of the infrared channel III. On the basis of temperature characteristic analysis and experimental verification of the infrared detector and RF power amplifier, temperature correction model of infrared channel III under wide temperature range is established. Wherein the infrared channel III uses the Hg Cd Te detector and Chang’E NO.3 Infrared Imaging Spectrometer does not use this detector, therefore, the correction method of temperature characteristics of Hg Cd Te detector established and analyzed in this paper has some innovation.4. Reflectance spectral characteristics inversionReflectance inversion of lunar material is main objectives and key link of moon exploration. According to the lunar surface mixed spectral model, thermal removal inversion algorithm is established and the ground validate experiment is made that target detected is simulation lunar surface minerals. The experiment includes laboratory conditions without temperature factors and simulation lunar surface conditions with temperature factors. Spectrum model of the former contains only reflected spectral radiance, reflectance spectral characteristics can be obtained easily through using a diffuse gold plate as the reference plate, which can evaluate the performance of the instrument, but also in order to verify the algorithm and provide a prior knowledge about reflectance spectrum of the detected target. Through test data detected by ground validate experiment with temperature factors of detected target, thermal removal algorithms is used to inverse reflectance spectral characteristics of the samples, and results are given and error is analyzed. It provides reference and ideas for the on-orbit spectral data of the infrared channel III, so the content part of the work not only has important engineering value. also it has a certain degree of innovation.The research contents of this paper provide the relevant solutions for the infrared channel III of lunar mineral spectrometer on orbit application under wide temperature range of lunar surface. In the end, some shortage and suggestions for future research are pointed out. |
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