Study On Photometric Of Space Target

As the armament competition about outer space of the earth among various countries in the world, especially the number of artificial space target is increasing year by year, using ground-based optoelectronic observation equipment for photometric measurement become one of the main method to determine target state.Photometric measurement equipment is high precision measuring equipment to determine the target material and posture movement way through the observation of space target luminosity changes using ground-based optoelectronic observation equipment. Space target is obtained by photoelectric observation equipment location information, gray level information of target is obtained by high sensitivity detector,the actual need light curve is obtained by photometric measurement software, to determine state information like target posture、physical properties.Based on large photoelectric observation equipment platform, research object is the photometric measurement system, for the purpose of improve the rapidity and accuracy of measurement space target photometric information, in view of the defects of the existing measuring methods, design and research the model at aspect of designed system, image processing and measuring way. The main work summarized as follows:Mathematical model of detection ability of photometric measurement system was deduced, system detection ability was simulation, provide theoretical basis for system design and implementation; Coordinate transformation model was deduced among the image coordinate system, celestial coordinate system and the horizontalcoordinate system, provide theoretical basis for target location information in various coordinates transformation; The position vector relationship among the sun, space target and observation equipment was deduced; Set up the phase angle data for photometric curve of the horizontal axis, provide the basis for photometric data normalization.Refractive and reflective optical system which apply to photometric was designed,achieved the 1 m diameter, view Angle is 1.328 °, lage invariant is 5.792, based on the classic Newton type optical system and audition and reasonable use of field lens.Not only the view of expanding at the same time get better image quality, and shorten the tube length, suppresses the ghost, improve the detection ability of faint magnitude.To solve the problem of trailing target real-time processing, this paper proposes a adaptive threshold measurement method based on location information. According to the target location information with reference star, open a window to the appropriate area for operation, using the fast iterative between-cluster variance threshold algorithm to split window range, to avoid the other star of the target area, the influence of threshold value compared with the traditional segmentation method,reduces the algorithm complexity and improves the operation speed.For high-precision extraction photometric values, an improved active contour method is proposed. According to the structure of the flow direction scalar field(FDS), select the appropriate threshold to seed selection, and the initial segmentation by an improved region growing method, according to the region adjacency graph of region merging. Compared with the traditional snake model, this algorithm has strong noise resistance, improves the operation speed.To combination with the engineering practice, adopts the wide spectrum measurement and filter measurement, the wide spectrum measurement way’s signal-to-noise ratio is high, the detectable limit magnitude is 16 magnitude in the 19 magnitude skylight background, measurement precision can reach 0.15 magnitude,the filter measurement way under the same SNR detectable limit magnitude is 14 magnitude at 19 magnitude skylight background, measurement precision can reach0.02 magnitude.In conclusion, this paper has set up a platform with meters level caliber and user-oriented measurement software, calibration the parameters of the system, verify the algorithm, this paper have been applied in actual engineering.