Stray Light Analysis And Correction For Low Light Level Imager Of Twilight Orbit Satellite

The wavebands of space detectors are mostly visible and infrared.Visible band of the detector often works during the day.Due to the sensitivity of the sensor,the detector is difficult to observe the visible light in the night.With the development of low light level imager,space-borne low light level imager has begun to appear.Low light remote sensing images have been used in many fields.The demand for the low light level imager for twilight area becomes more and more obvious.Although the designers conduct stray light analysis and design stray light suppression equipment during the design phase,stray light may still be present when the satellite is on orbit.The space-borne low light detection is easily affected by the stray light.This will affect the observed data.In response to this problem,this paper studies the stray light removal algorithm of the low light level imager.Firstly,based on the orbit characteristics of the twilight orbit satellite,this paper analyzes the causes of the stray light.The twilight orbit satellite orbit system is established by the SGP4 model and geographic location method.By analyzing the characteristics of stray light obtained from the data of NPP polar orbiting satellite and comparing with the data of twilight orbit satellite,the characteristics of stray light are analyzed.Secondly,According to the analysis of the stray light,this paper designed the corresponding twilight orbit satellite Low light detector stray light removal algorithm.In order to obtain the true stray light data,we preprocessed the data.An automatic region division method is designed to finding the specific area affected by stray light,getting the start and cut-off boundary of the data,and using least square based polynomial curve fitting method to get the characterization of stray light mathematical model.We establish the entire data stray light look-up table by the cubic spline interpolation method.Finally,we use stray light lookup table to modify data affected by stray light.And two kinds of non-stray light standard data with the same lunar phases,different time and different zenith angle are used to compare with the revised results.The results show that the stray light correction algorithm in this paper can effectively remove stray light and restrain the surface information while preserving the radiation information.