Star map recognition refers to matching the star map observed in the star tracker and the star map composed of the navigation star in the star list according to geometric features to determine the corresponding relationship between the observation star and the navigation star.Star map recognition is one of the core tasks of star tracker,and it is also an important difference between star tracker and traditional imaging system such as star camera.
Star map recognition algorithms are divided into star tracking algorithm and autonomous recognition algorithm according to the recognition autonomy,non-autonomous recognition algorithm and autonomous recognition algorithm according to the presence or lack of initial attitude,and local star map recognition algorithm and all-sky autonomous star map recognition algorithm according to the recognition region.
Non-autonomous recognition requires other sensors to provide coarse precision attitude information,and according to this information,the local sky area corresponding to the star map can be calculated,which greatly reduces the number of navigation star matching in recognition,so the recognition time is short.
When no rough attitude information is provided,all-day autonomous recognition is needed,which mainly occurs in the initial capture or sudden loss of attitude information.The recognition process does not require other sensor devices to provide the initial rough attitude,which plays an important role in satellite autonomy,reliability and microminiaturization,and has become the mainstream of current star tracker development.
At present,the on-orbit operation of star tracker usually includes two working modes,namely initial attitude acquisition mode and tracking mode,and the corresponding recognition algorithm is mainly all-sky autonomous recognition algorithm and tracking algorithm.In the initial moment when the machine starts to work or when the attitude is lost due to interference,the star tracker has no prior information and can only rely on the star map for all-day autonomous recognition.The recognition of all-sky star map generally requires a long time of star point extraction and star map recognition,and has a fairly high and accurate recognition rate.The tracking mode of the star tracker is introduced based on the results of all-sky autonomous recognition and attitude calculation.
Therefore,star map recognition is essentially to find the closest navigation star to the observed star pattern in the navigation star catalog.The most representative of these algorithms is the raster algorithm.Compared with other algorithms,the raster algorithm has a higher recognition rate and a smaller size of the navigation catalog.
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