Research On On-orbit Measurement Control And Fine Remote Sensing Technology Of Solar Irradiance Spectrometer

As a star in the center of the solar system,the radiation of the sun is the most important external energy of the earth.The energy of solar radiation is related to the spectral range.Accurate and traceable solar irradiance measurement results are of great significance to the study of solar change,atmospheric physical and chemical process and climate change.Solar irradiance spectrometer carried on FY-3E satellite is a newly developed load to obtain the solar spectral irradiance in the spectral range of 165nm to 1650nm.With high spectral resolution,high signal-to-noise ratio,high stability and high-precision calibration index requirements on the ground and on-orbit,it is the most advanced instrument of its kind in the world.In order to ensure the successful completion of load development and on-orbit detection and calibration tasks,this paper studies the on-orbit measurement control and fine remote sensing technology of solar irradiance spectrometer,mainly including the following aspects:(1)In order to verify the feasibility of optical mechanical scheme,verify the performance index,and determine the signal processing mode of each band,an intelligent detection system is designed and implemented to drive a variety of signal processing equipment and cover the whole band.The system consists of hardware and control software.The hardware includes light source,mechanical motion subsystem,signal acquisition subsystem and computer.The control software is realized by Lab VIEW in Windows environment.It has the functions of parameter configuration,motor control,continuous wavelength scanning,fixed-point wavelength scanning,real-time display of measured spectral curve,automatic calculation of signal-to-noise ratio,Gaussian fitting,automatic reading bandwidth,local data storage and playback.The experimental results show that the intelligent detection system meets the index requirements of wavelength accuracy better than±0.05nm,repeatability better than0.01nm and spectral bandwidth less than 1nm.It provides experimental data basis for load project demonstration and principle performance index verification,and lays the foundation for load development.(2)In order to ensure that the instrument is preheated for 30 minutes before the sun enters the detection window,a high-precision solar angle prediction method considering accuracy and simplicity is proposed.This method uses the time broadcast by the satellite platform,uses the simplified VSOP87 theory,and considers nutation and aberration correction to obtain the solar apparent right ascension and apparent declination.According to the orbital instantaneous root broadcast by the satellite platform,the perturbation motion equation considering only J₂ perturbation is used to predict the orbital instantaneous root,and the transformation matrix from the geocentric inertial coordinate system to the orbital coordinate system is obtained.The attitude correction matrix of the satellite is calculated through the satellite attitude angle,and then through the calibrated change matrix from the instrument body coordinate system to the satellite coordinate system,the solar vector under the instrument body coordinate is finally obtained.Comparing the prediction results with STK simulation results,it shows that the error of the X,Y and Z components in solar vector predicted by this method are in the range of±0.003°,with high accuracy,which can meet the needs of on-orbit applications.At the same time,the main error sources are analyzed.(3)Aiming at the hardware structure design of solar irradiance spectrometer without encoder,a high-precision control method of stepping motor is proposed,which can position accurately without encoder.When controlling the wavelength scanning mechanism,this method judges the effectiveness of the hall signal by controlling the forward and reverse rotation of the motor and running a fixed number of steps.When the hall signal is valid,it will execute the operation of returning to the starting position normally,otherwise it will enter the mode of fault returning to the starting position.The motor drive is subdivided into 16 substeps,and each fine step is only 0.1125°.The control method of the turntable mechanism is to quickly return to the starting position,after overshoot,one-step reverse rotation with appropriate delay to move out of the hall effective area and then identify the starting position.The experimental results show that this method meets the requirements of spectral resolution less than 1nm,wavelength repeatability less than 0.01nm,wavelength calibration accuracy less than 0.05nm and calibration accuracy stability less than0.2%.At the same time,it reduces the volume,reduces the weight and realizes the miniaturization of the system.(4)In order to ensure the smooth progress of on-orbit detection and calibration of solar irradiance spectrometer,an on-orbit intelligent operation control process system is designed and implemented.The working mode of the solar irradiance spectrometer is designed according to the requirements.The on-orbit intelligent operation control process system automatically completes the process control and working mode switching according to the orbit count.The daily measurement completes the daily solar measurement,and the weekly calibration,monthly calibration,quarterly calibration and annual calibration complete the calibration tasks in different periods,so as to monitor the on-orbit changes of the instrument,correct the long-term decay of optical system and detector.The on-orbit data results show that the on-orbit operation status meets the design expectations,and the solar spectrum data measured on-orbit are given.The calibration results show that the on-orbit spectral resolution of the instrument is less than 1nm,the wavelength repeatability is less than 0.01nm,and the wavelength calibration accuracy is less than 0.05nm,which meets the index requirements.