Design And Technology Research Of The Whisk Broom Imaging System On Geostationary Orbit

Compared with the low-orbit imaging spectrometer,the geostationary imaging spectrometer has the advantages of high image signal-to-noise ratio and short revisit period when detecting the earth's atmosphere.These advantages are crucial for improving the ability to analyze atmospheric components.The research group has launched the research work of the prototype of the geostationary imaging spectrometer,the purpose is to verify the feasibility of the related technology,so as to provide a technical reference for the design of the spectrometer load.The geostationary imaging spectrometer acquires the spectral image data of an observation band by gazing at each imaging zone;then,through stepwise motion and gaze imaging,it gradually covers all observation ranges step by step,and this process is scanning imaging.The research content of this paper is the pre-research design of the scanning imaging control system of the spectrometer,mainly from the aspects of drive system design,scanning scanning control scheme design,CCD imaging system design and scanning imaging comprehensive control.According to the requirements of scanning mirror pointing stability,step angle accuracy and other requirements,the scanning-sweep drive system proposes a"stepping motor+harmonic reducer" to constitute the drive execution component,and an absolute-value photoelectric encoder as an angle measurement component.The scanning-sweep drive circuit is designed to realize the integration of motor control,communication and encoder data reading in the FPGA system.In order to enhance the pointing stability of the pendulum sweep mechanism,the static moment angle characteristics of the stepper motor were analyzed and tested;through the vacuum thermal experiment,the temperature rise rate of the motor drive chip in the space environment was measured.In order to reduce the out-of-step rate in the rotation process,the space rotation torque was calculated.According to the torque margin requirements,the starting and running duty ratios were reasonably configured.A control method that can effectively reduce the influence of the return error on the accuracy of the scanning step angle is proposed.The experimental data of the motion performance test of the scanning drive system shows that the average step angle of the system in the target imaging interval is within 21.6 "± 1 ",the maximum deviation is less than 5 ",and the standard deviation is less than 2 ",which meets the index requirements.In the design process of the CCD imaging system,the FPGA logic driver is written to complete the driving of the detector and the peripheral chip,so as to realize the collection and upload of the image signal.Different from the continuous imaging mode of the low-orbit imaging spectrometer,the imaging detection system uses trigger imaging to achieve the purpose of real-time control of the imaging process.The relevant logic timing is designed.The timing simulation and circuit testing verify the design of the CCD imaging system.The pendulum imaging integrated control system is responsible for coordinating the workflow of the scanning system and the imaging detection system.According to the requirements of the spatial resolution and the observed signal-to-noise ratio in different observation modes,the number of frame overlays and the number of pixel merges are set reasonably.In order to achieve the goal of reducing the time of the scanning imaging process,the optimal cooperation between the imaging circuit and the driving circuit during the scanning imaging process is designed to meet the process time requirements in each detection mode.The scanning imaging control system has passed the acceptance of the technical pre-research stage,and can provide a reference for the design of the next engineering prototype and the final spaceborne equipment.