Cosmic-ray Rejection And Restoration For Single Spectroscopic Ccd Images In LAMOST

Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST) is located at Xinglong Observing Station of National Astronomical Observatories, Chinese Academy of Sciences. As a large fiber spectroscopy telescope, it can possess the highest spectrum acquiring rate in the world. LAMOST is a milestone in the history of Chinese astronomical researching.In nature, LAMOST is a complex set of imaging system. Hence, plenty of image processing algorithms are suitable here to be used to process the spectroscopic CCD images. There are many problems may occurred during observing. All these should be processed properly after that. This paper will focus on the inevitable problem of cosmic-ray hits in spectroscopic CCD images.After introducing the spectroscopic CCD images and cosmic-ray hits in detail, we propose a novel method to reject and restore cosmic-ray hits based on template matching algorithm. Then the idea of general purpose computation on graphic hardware is applied to speed up our algorithm. Radial basis function interpolation is also introduced here to achieve better restoring results. In summary, the main works are described as follows,1. Based on the different profile between spectrum and cosmic-ray hits, we provide a new idea to identify cosmic-ray hits. Instead of searching for cosmic-ray hits directly, we confirm those pixels belonged to normal spectrum first. Then the left pixels are affected by cosmic-ray hits.2. Using the Improved template matching, we introduce the procedure of rejecting cosmic-ray hits step by step. The experiments show that our method has impressive performs.3. By introducing the popular idea of GPU computing, we use GPU to do the work of matching. Final result shows that the cost time is shorted greatly.4. As the extension of template matching, templates are used to repair the pixels affected by cosmic-ray hits. With the help of RBF interpolation, we can obtain better restoring results.