In order to solve the estimation problem in nonlinear systems, particle filtering algorithm is selected to improve the accuracy of observation. However, the classical Kalman filtering is only applicable to linear systems. In addition, in order to improve the accuracy of observation and positioning, filtering algorithm can be used for estimation. Although there have been some research achievements, more research is based on single satellite orbit determination algorithm. Since the motion process of the active section is more complicated than the other two sections, this paper focuses on the study of the orbit estimation in the ascent phase of the spacecraft.Ĭurrently, several studies have been conducted on certain aspects of satellite positioning, including the single-satellite direction of arrival (DOA) locating methods based on the WGS-84 model, single-satellite locating and tracking algorithms for synchronous orbiting satellites with bearing-only measurements, passive satellite locating and tracking methods by single satellite, multisatellite coordinated locating methods, single-satellite orbit determination methods for navigation satellites, and autonomous orbit determination method for navigation satellites.
Generally, the orbit of a spacecraft is divided into three sections: the ascent phase propelled by rockets, the inertial flight period in the outer space of the Earth, and the attack period after reentry into the atmosphere. Based on the movement model and observation model of the observation satellite and the spacecraft, the mathematical inference is made on the orbital parameters of the spacecraft (including the orbit position, initial value of velocity, and other model parameters), providing information to judge the spacecraft types and flight intentions.
When the observation satellite flies for a period of time, the detector measures the observation data of the target relative to the moving satellite. Specifically, inferences are made based on observational data and through mathematical models and calculation methods. The purpose of detection is to infer the orbital parameters of the spacecraft. Passive detectors passively receive target radiation. Active detectors use active methods (such as radar and laser) to search for targets. The detectors installed on satellites can be divided into active and passive ones. Currently, satellites are an important platform for detecting the launch and orbit parameters of the spacecraft.
Discovery of launch and detection of its orbital parameters is the first step to realize monitoring and responding. Therefore, it is of great strategic significance to monitor and quickly respond to hostile spacecraft launched by other countries to maintain national security. Some countries launch spacecraft with special purposes, such as ballistic missiles and reconnaissance satellites. Finally, the effectiveness of the two-satellite point-by-point intersection positioning algorithm and the single-satellite positioning algorithm is verified through the experiment simulation on the real data. Besides, by combining the results of the proposed satellite positioning algorithms with mathematic models of the spacecraft orbit, the particle filtering based on the Monte Carlo algorithm is applied to filtering of the final results of the spacecraft. Meanwhile, two mathematic models of the spacecraft orbit are presented based on the kinematics characteristic and the least square method. To estimate and analyze the orbit of a spacecraft in the ascent phase, three algorithms are proposed in this paper: a two-satellite point-by-point intersection positioning algorithm, single-satellite positioning algorithm, and multiple-point intersection collaborative positioning algorithm.
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