Research On Autonomous Orbit Determination Of Navigation Constellation Based On Laser/Microwave Fusing Inter-satellite Observations

With the development of inter-satellite links' technology,laser inter-satellite link survey system is an ideal alternative to microwave system because of its high precision of measure and high bit rate.Due to the inevitability of development and the steps in the development process,the fusion of microwave and laser inter-satellite links is inevitable.In this paper,we'll do the study and analyze on the only microwave inter-satellite links and laser/microwave fusing inter-satellite links,and the autonomous orbit determination of navigation constellation which is based on the two inter-satellite link modes.The main works are as follows:(1)Research and design on the inter-satellite links.Firstly the ranging principles and main deviation source of microwave and laser are studied,as well as the visibility conditions of inter-satellite links.Then considering the advantages and disadvantages of the two kinds of links,a method that let the laser to be the static links which the two satellites are in the same trajectory,and the microwave to be the dynamic links which the two satellites are in the different trajectory is proposed,then we can obtain the laser/microwave fusing inter-satellite observation model.In this paper,we simulate and analyze the topological structure and determination accuracy factor of the Walker24/6/1 and Walker24/3/2 constellation which are based on the microwave links and laser/microwave fusing links.The results show that the fusion laser/microwave inter-satellite link is better than the microwave inter-satellite link for the constellation structure and the overall observation error accuracy.(2)The process of satellite orbit determination is studied,which divided into two parts.The first part is to set up the differential equation according to the satellite dynamic model and obtain the approximate states of the satellites by solving the equations.The second part is to set up the observation equation based on the different observations and correct the approximate states by orbit determinations which are based on least square method and kalman filter method.(3)The sequential centralized and sequential distributed autonomous orbit determination are studied.In this paper,we simulate the two constellations' sequential orbit determinations based on different inter-satellite links modes.The results of determination based on laser/microwave fusing links are better than the results of determination based on microwave links,which the average deviations of Walker24/6/1 constellation's sequential centralized and distributed determination based on laser/microwave fusing links reduce by 36.6% and10.7% compared to the way based on only microwave,and Walker24/3/2 constellation's deviation reduce by30.6% and 7.9%.The robustness of kalman filter which use the laser/microwave fusing links gets better,especially under the situation of bad initial covariance matrix.(4)An autonomous orbit determination algorithm combining the short-term dynamics technique and the pseudo-inverse adjustment is proposed.This algorithm set up the state transition between epoch steps using the orbit dynamics to solve the problem of velocity calculation,at the same time,solve the problem of rank defect because of the lack of start information of position calculation by pseudo-inverse adjustment.In this paper,we give the detailed solution procedure and flow-process diagram of short-term orbit determination,and select the most suitable length of term by deviation analysis.In this length of term,run the algorithm under situations of the two constellations based on the different observation modes,than compare the deviations.The data and graph show,algorithm using the inter-satellite link of laser/microwave fusion but unweighted,can only better than the results using the link of microwave a little,which Walker24/6/1 and Walker24/3/2 constellation's average deviation reduce by 8.2% and 20.6% compared to the algorithm only using microwave While when the algorithm use the link of laser/microwave fusion and also weighted by their observation noise,the results of algorithm will become much better,which Walker24/3/2 and Walker 24/3/2 reduce by 72.3% and 75.0% compared to the results using microwave.