近地小行星极短弧定轨的进化算法研究
STUDY ON EVOLUTIONARY ALGORITHMS FOR INITIAL ORBIT DETERMINATION OF NEAR-EARTH ASTEROIDS WITH TOO-SHORT-ARC
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摘要: 近地小行星的巡天项目不断涌现, 得到了海量的观测数据.而巡天观测方式使获得的数据弧段过短, 传统方法在定轨和识别上存在极大困难,加之短弧定轨问题本身的病态性,如何有效利用这些短弧数据对于发现、监测和评估小行星的威胁具有重要意义.在进化算法下构建极短弧定轨的计算框架, 选用三变量的(a,e,M)优选法,保持维数较低的同时, 使优化结果不再依赖观测量.采用参数较少、操作简便的差分进化算法,利用不同偏心率小行星的轨道模拟数据进行试验,对获得的最优解及其分布聚集区域进行分析, 大偏心率轨道由于其本身的复杂性,会对算法搜索的灵敏度产生影响, 需缩小搜索空间以提高搜索能力.结果表明算法在小偏心率问题中表现较好,可以得到有效结果为后续工作提供参考信息, 大偏心率问题在传统方法失效的情况下,虽然最优解在整体分布中并不明显, 但分布仍包含真实解,可结合分布密度和适值大小进行分析. 未来需要对大偏心率问题作进一步研究,考虑其观测位置和观测时刻对算法产生的影响, 分类计算.Abstract: Surveying projects of near-earth asteroids continue to emerge, and obtain massive observation data. However, this pattern makes the obtained arc too short, and the traditional methods have great difficulty in orbit determination and identification with ill-posed problem in itself when the arc is short. Then how to effectively use these short arc is of great significance for discovering, monitoring and evaluating the threat of asteroids. Under the evolutionary algorithms, a calculation framework for too-short-arc is constructed with three-variable (a,e,M) optimization, which keeps the dimensionality low while makes the optimization results no longer rely on observational measurements. The differential evolution algorithm with fewer parameters and simple operation is used to conduct experiments using orbital simulation data of asteroids with different eccentricity, then the optimal solutions and their aggregation regions are analyzed. The large eccentricity orbits will have an impact on the sensitivity of the algorithm search due to its complexity, it is need to reduce the search space to improve the search ability. The results show that the algorithm performs well in small eccentricity problem, and can obtain valid results to provide information for subsequent work. And for large eccentricity problem, while the traditional method fails, the distribution of the algorithm still contains the real solution. For the phenomenon that the optimal solution is not obvious in the global distribution, it can be analyzed by combining the distribution density and fitness value. Further research on the issue of large eccentricity is needed in the future, the influence of different observation positions and observation time on the algorithm should be considered, and calculate by classification.