彗星311P天基-地基光学联合定轨及精度分析

Orbit determination and accuracy analysis for comet 311P based on space-based and ground-based optical data

  • 摘要: 我国计划于2034年左右对彗星311P/PANSTARRS(311P/PANSTARRS,原名P/2013 P5)进行近距离探测,获取其精密轨道是保证任务成功的前提。本文以我国小天体探测任务为背景,采用武汉大学行星射电科学团队自主研发的小天体精密定轨软件SPOT(Small Body Precise Orbit Determination Toolkit),利用2005年10月17日至2021年01月18日发布的地基天基望远镜光学观测数据,对彗星311P进行了精密轨道确定的研究。SPOT解算的彗星311P三维位置与速度不确定度分别为约130 km和5.034 × 10-3 m/s,与国际知名小行星定轨软件OrbFit解算的彗星311P的三维位置和速度不确定度(135.8 km和5.270 × 10-3 m/s)近乎一致。这一实验结果验证了SPOT软件光学定轨模块的可靠性,同时也指出了当前彗星311P轨道位置不确定度在百公里量级。此外,分析了轨道确定中所用力学模型对解算结果的影响,结果表明:当前311P轨道确定过程中可以忽略16个大主带小行星的引力摄动、广义相对论摄动以及太阳光压摄动。最后,探讨了任务之前潜在的地基光学观测对彗星311P轨道确定的贡献,发现潜在的地基光学观测可以降低彗星311P的轨道不确定度,但是在任务开始时轨道位置不确定度依然高达几十公里。

     

    Abstract: Objectives: China has formulated plans to undertake a proximity exploration of comet 311P/PANSTARRS (previously known as P/2013 P5) around 2034. However, the successful execution of this mission is contingent upon obtaining an accurate determination of the orbit of comet 311P. Methods: In this paper, the SPOT (Small Body Precise Orbit Determination Toolkit) developed by the Planetary Radio Science Team of Wuhan University is used to perform a study of the precise orbit determination for comet 311P in the context of China’s small body exploration mission. We used the optical observations of ground-based and space-based telescopes released from 17 October 2005 to 18 January 2021. Results: The position and velocity uncertainties of comet 311P obtained by SPOT are about 130 km and 5.034 × 10-3 m/s respectively, which are in close agreement with the position and velocity uncertainties (135.8 km and 5.270 × 10-3 m/s) calculated by the well-known OrbFit. Conclusions: This experimental outcome not only validated the dependability of the optical data-based orbit determination module of the SPOT software, but also highlighted that the current positional uncertainty of comet 311P’s orbit is on the order of hundreds of meters. Furthermore, this study investigates the influence of the mechanical model utilized in the orbit determination process on the calculation results. The findings indicate that the gravitational field of the 16 large main belt asteroids, as well as the perturbations caused by general relativity and solar light pressure, can be neglected in the current orbit determination process of 311P. Additionally, the paper evaluates the potential impact of ground-based optical observations conducted before the mission on the orbit determination of Comet 311P. Conclusions: The results suggest that such observations have the potential to reduce the orbital uncertainty of the comet, but the uncertainty in the position of the orbit still remains significant, with values reaching tens of kilometers.

     

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