The Application Of Different Image Denoising Algorithms In High Precision Astrometry

As an important branch of astronomy,astrometry is of great significance to the study of the solar system,space exploration missions and the study and improvement of planetary satellite dynamics models.All kinds of noise interference in the imaging process of celestial object observartion images is a source that affects high-precision astrometry.The noise changes the information of the original pixel and causes the digital centering of star to be shifted.Therefore,it is significant to reduce the interference of image noise to high-precision astrometry.Up to now,the smoothing denoising algorithm is seldom used in the research of high-precision astrometry.This paper mainly studies the application of three image denoising algorithms in high-precision astrometry.The algorithm includes Least-Squares Smooth Filter Algorithm,Bilateral Filter Algorithm and Binomial Filter Algorithm.In order to realize the above three algorithms,we generated a large number of artificial star images,and successfully selected the optimal parameters of each algorithm through simulation experiments.Then,based on the CCD image of NGC1664 cluster taken by the 2.4m telescope of Yunnan Observatory,the above three denoising algorithms were used for experimental research.After the above three methods were processed separately,the newly released Gaia DR2^[1](Data Release 2)was further adopted as the reference catalog to verify the accuracy of position measurement.Finally,our results indicate that the three algorithms can improve the position measurement accuracy of the bright star in different degrees,and the Least-Squares smoothing algorithm is the most effective method.In addition,using the three algorithms can search more stars,and the maximum number of stars can be increased by about 18%.Finally,based on the Cassini ISS image,Enceladus's position can be measured with high-precision.And then,by comparing the difference of position measurement accuracy of the observed objects before and after bilateral filtering smoothing,we can verify that whether the bilateral filtering smoothing is advantageous over the edge detection,thus improving the position measurement accuracy of the observed objects.Finally our results indicate that the effect of bilateral filtering smoothing on the edge detection of the large disk was quite limited for the Cassini ISS image.However,this algorithm can effectively reduce image noise,reduce false star search and improve work efficiency.On the other hand,the use of bilateral filter can improve the signal-to-noise ratio and then find the faint reference star that could not be found before.So that we can successfully calculate the measured position of the observed object and improve the image utilization rate of Cassini ISS.