Research On High-dynamic Small Star Sensor

Star Sensor is an optical attitude sensor based on observing star. It is themost widely used and highest accuracy optical attitude sensor. For therestrictions by generation and process of star map, dynamic performance oftraditional star sensor is not well, resulting in limited application. With therapid development of spaceflight technology, spacecraft requires higherdynamic performance of star sensor. Besides, lighter and smaller product isdesired.This paper focuses on the study of improving the dynamic performanceof star sensor. There are three main areas, namely, photoelectric detection,signal processing, high dynamic pattern recognition technology. Among, thehardware platform of photoelectric detection and signal processingdetermines target characteristics and data processing speed of dynamic starmap. It is the main aspect that influences dynamic performance. Highaccuracy photoelectric detection system and rapid signal processing system isthe basis of star sensor to achieve high dynamic performance, which is thefocus of this paper.Firstly, the characteristics and application of star sensor are reviewed. Inview of the high dynamic requirement, this paper presents the general schemeof high dynamic start sensor based on absorption of domestic andinternational advanced technical solution. This scheme researchcharacteristics of ghosting and motion of star on high dynamic condition. Itreduces the impact of object extraction from ghosting of star, improves theabilities of recognition of fast moving star, effectively make star sensor adaptto high dynamic situation. In view of smear of high dynamic star map, this paper presents a methodbased on CCD weak light detection and realized it. This method adopts largeaperture optical system and high sensitivity detector, through increasing lightenergy input and expanding the dynamic range of photoelectric detection,reduces noise of circuit system, solves the problem of energy dispersion ofstar in high dynamic condition. The experiment results show that this methodhas high detecting sensitivity, large detection range and other features, whichcan effectively improve the photoelectric detection system's ability andreduce the influence to star from the stray light and circuit noise.Aim at the influence to star map recognition from signal processingspeed, design and realize a high speed signal processing system, acquireparallel process of image and signal, control the time of signal processing inone exposure period, solve the problem of low signal processing speed andlow data update rate existed in traditional star sensor, resulting in star maprecognition unaffected by signal processing time. The test results show thatthe signal processing speed of this signal processing system meets therequirements of high dynamic index.In this paper, according to the characteristic of star map moving fast,improve operation mode of star map recognition, propose an adaptivetracking algorithm based on fast centroid tracking, effectively solve theproblem that the influence to star tracking from the motion of star map andsmear of star, improve the ability of stably tracking star of star sensor.Finally, using optical star simulator and on-ground measurementengineering prototype was tested. Test results show that the indexes ofproducts meet the goal, prove that research is effective. The result of thisresearch has been applied in actual project with good results, greatly narrowthe gap between domestic high dynamic and international star sensor.