Study On Ground-based Spectral Imaging Measurement Of The Moon And Lunar Radiometric Model

With further development of space remote sensing and continuous improvement of the quantitative application requirements of remote sensing products,it is increasingly more necessary and important for high-precision calibration of spaceborne remote sensors.Reliability,application scope and depth of remote sensing data greatly depend on calibration accuracy.However,there are many problems for onorbit calibration of spaceborne sensors,such as temporal degradation,inconsistency between international multi-source data,these are the issues that need to be addressed urgently.Lunar calibration is a new in-orbit calibration method in the 21 st century.Based on long-term stability of the lunar surface,the relationship between the radiometric responses of remote sensors and standard radiometric values is established to realize stability monitoring and absolute calibration of in-orbit remote sensors via periodically observing the moon.At present,the domestic Fengyun series of satellites have lunar observation capabilities,and the nighttime low-light measurements from the Night Band in the satellite also need to provide lunar radiometric values in the night.Therefore,a high-precision lunar photometric model is urgently required for these remote sensors.To date,the ROLO model from the United States is the most frequently used lunar photometric model at the reflective solar bands,its absolute accuracy is about 5%~10%.In order to improve the ROLO model and construct a high-precision lunar model with independent intellectual property rights,it is critical to obtain highprecision observational data.Ground-based lunar radiometric measurement can implement high-precision and high-frequency calibration to ensure the accuracy and long-term consistency of observational data.Therefore,with the application requirements of in-orbit instrument calibration and the testing problem of the future space-based radiometric measurements,supported with the 863 project "Lunar Calibration in Visible Spectral Region ",we carried out study on ground-based spectral imaging measurement of the Moon and lunar radiometric model.The main contents of this paper include:1)Based on the requirements of high-precision lunar radiometric measurements,a research on the scheme of ground-based radiometric imaging observation is developed,orbital forecasting has been realized for lunar ground measurements,and the feasibility of the scheme is studied through simulation.In order to realize the long-term data acquisition for observation system,an intelligent collection algorithm for high-quality data is developed based on the dynamic range,spatial resolution,and atmospheric conditions under different lunar phases for hyper-spectral lunar imager with a slit.Based on the preliminary scheme of lunar measurements,a lunar hyperspectral imaging automated radiometric observation system is constructed,which is capable of tracking and scanning,with the spectral range from 400 nm to 1000 nm.2)The measurements of spectral calibration,radiometric calibration and instrument optical performance for the hyperspectral lunar imager are performed in the laboratory.On the basis of accurate spectral calibration,a detailed study in radiometric calibration of the instrument is carried out,and the observational data is traceable to Système Internationale(SI)radiometric units.The performance of the imaging spectrometer is measured,including the stability,linearity,and signal-tonoise of the instrument,and the star method is proposed to realize calibration of optical axis parallelism for the lunar observation system,and measure the focal length and spatial response function of the slit imaging spectrometer.3)Based on research on space-based radiometric reference source of the moon,a ground-based lunar radiometric measurement is carried out to verify the performance of the instrument and ability of lunar observations.A scheme of instrument stability monitoring is design in the field.Based on the measurements of the atmospheric aerosol and temperature,humidity and pressure profiles,comparative analysis of atmospheric parameters from different data sources is conducted,and the MODTRAN radiative transfer modeling is used to calculate the nighttime atmospheric extinction.To obtain spectral irradiances and radiance images outside the atmosphere,hyperspectral radiometric quantification algorithms are studied,including the data redundancy,imaging geometry correction,atmospheric correction and so on.4)Based on the requirement of lunar calibration for space-based remote sensing instruments,the international frequently-used lunar irradiance model is focused.By using ground-based hyperspectral irradiance,comprehensive analyses and validation of lunar models is performed in the absolute precision,relative accuracy,band-toband stability,phase reddening and so on.Based on the phase angle dependence and absolute deviation of lunar model,the improvement of the current lunar model is carried out,which is traceable to the ground radiometric reference,and the quality of the ground-based observational data is assessed.This research work has greatly improved the quality of remote sensing data,application ability,and achieved the fusion and versatility of multi-source remote sensing data.In the future,the full-space stereoscopic monitoring system composed of a space station,various types of earth observing satellites,communication satellites,aircraft platforms,and ground monitoring stations will be established,and global cooperation research provide necessary technical support.