High Precision Relative Position Measurement Of Mutual Approximation Between An Asteroid And Its Nearby Star

In recent years,the observation of near-earth asteroids has become a hot topic in astronomy.The precise astrometry of asteroids can not only improve the accuracy of the asteroid ephemeris and the theory of the asteroid orbit,but also provide a service for the study of the formation and evolution of the solar system.The accuracy of traditional astrometry is largely dependent on the number of reference stars in the field of view.When the number of reference stars in the field of view is insufficient and the speed of the asteroid is fast,the measurement precision of the traditional astrometry method is not accurate enough.In order to improve the position measurement accuracy of asteroids with insufficient reference stars in the field of view,this paper extend application of mutual approximation to the position measurement of asteroids for the first time in order to obtain higher position measurement accuracy.The observation data used in this experiment were obtained from the2.4m telescope in Lijiang,Yunnan province,which tracked the asteroid Apophis for several consecutive nights from February 4 to 7,2013.We used Gaia DR2 as the reference catalogue and performed image processing operations such as cropping,flat field correction,star search,centering and matching on these multi-night observation data.Then we used the traditional method based on the plate constant model and the mutual approximation method to respectively calculate the position of the asteroid and compare the measurement accuracy of the two methods.The experimental results show that when the reference stars in the field of view are insufficient,the accuracy of the asteroid position measurement obtained by the method of mutual approximation is obviously higher than that of the traditional method.At the same time,when we use the method of mutual approximation to solve the problem,we find that the method of solving speed parameters can be further improved by analyzing the parameters that affect the final solution precision of the method.Therefore,we proposed a new method for solving the velocity of the asteroid.The velocity of the method is very consistent with the theoretical velocity of the IMCEE ephemeris in France,and it's obviously improved compared with the traditional method.We found that the advantage of using our speed solution became more apparent when the asteroid was moving faster.In addition,it will be one of the future research is to explore different weighting schemes to obtain more accurate motion model,so as to further improve the measurement accuracy of the mutual approximation method.