Astrodynamics

Abstract Understanding the internal composition of a celestial body is fundamental for formulating theories regarding its origin. Deep knowledge of the distribution of mass under the body’s crust can be achieved by analyzing its moments of inertia and gravity field. In this regard, the two moons of the Martian system have not yet been closely studied and continue to pose questions regarding their origin to the space community; thus, they deserve further characterization. The Martian Moons eXploration mission will be the first of its kind to sample and study Phobos over a prolonged period. This study aims to demonstrate that the adoption of periodic and quasi-periodic retrograde trajectories would be beneficial for the scientific value of the mission. Here, a covariance analysis was implemented to compare the estimation of high-order gravitational field coefficients from different orbital geometries and for different sets of processed observables. It was shown that the adoption of low-altitude non-planar quasi-satellite orbits would help to refine the knowledge of the moon’s libration angle and gravitational field.

Edoardo Ciccarelli

Nicola Baresi

Covariance analysis of periodic and quasi-periodic orbits around Phobos with applications to the Martian Moons eXploration mission

火卫一周期和准周期轨道协方差分析及其在火星卫星探测任务中的应用

Sébastien Henry

Roberto Armellin

Thibault Gateau

Safe-event pruning in spacecraft conjunction management

航天器交会管理中的安全事件剪枝

Wei Zhang

Xiuhong Wang

Wen Cui

Zhi Zhao

Sirui Chen

Self-induced collision risk of the Starlink constellation based on long-term orbital evolution analysis

基于长期轨道演化分析的Starlink星座自诱导碰撞风险

Abstract As an emerging approach to space situational awareness and space imaging, the practical use of an event-based camera (EBC) in space imaging for precise source analysis is still in its infancy. The nature of event-based space imaging and data collection needs to be further explored to develop more effective event-based space imaging systems and advance the capabilities of event-based tracking systems with improved target measurement models. Moreover, for event measurements to be meaningful, a framework must be investigated for EBC calibration to project events from pixel array coordinates in the image plane to coordinates in a target resident space object’s reference frame. In this paper, the traditional techniques of conventional astronomy are reconsidered to properly utilise the EBC for space imaging and space situational awareness. This paper presents the techniques and systems used for calibrating an EBC for reliable and accurate measurement acquisition. These techniques are vital in building event-based space imaging systems capable of real-world space situational awareness tasks. By calibrating sources detected using the EBC, the spatiotemporal characteristics of detected sources or “event sources” can be related to the photometric characteristics of the underlying astrophysical objects. Finally, these characteristics are analysed to establish a foundation for principled processing and observing techniques which appropriately exploit the capabilities of the EBC.

Nicholas Owen Ralph

Alexandre Marcireau

Saeed Afshar

Nicholas Tothill

André van Schaik

Gregory Cohen

Astrometric calibration and source characterisation of the latest generation neuromorphic event-based cameras for space imaging

Yongjie Liu

Yu Jiang

Hengnian Li

Zongbo Huyan

Hongchao Wang

Determining origins of satellite breakup events in LEO region

确定低地球轨道区域卫星解体事件的起源

Abstract Future missions to the Moon and beyond are likely to involve low-thrust propulsion technologies due to their propellant efficiency. However, these still present a difficult trajectory design problem, owing to the near continuous thrust, lack of control authority and chaotic dynamics. Lyapunov control laws can generate sub-optimal trajectories for such missions with minimal computational cost and are suitable for feasibility studies and as initial guesses for optimisation methods. In this work a Reinforced Lyapunov Controller is used to design optimal low-thrust transfers from geostationary transfer orbit towards lunar polar orbit. Within the reinforcement learning (RL) framework, a dual-actor network setup is used, one in each of the Earth- and Moon-centred inertial frames respectively. A key contribution of this paper is the demonstration of a forwards propagated trajectory, removing the need to define a patch point a priori. This is enabled by an adaptive patch distance and extensive initial geometry exploration during the RL training. Results for both time- and fuel-optimal transfers are presented, along with a Monte Carlo analysis of the robustness to disturbances for such transfers. Phasing is introduced where necessary to aid rendezvous with the Moon. The results demonstrate the potential for such techniques to provide a basis for the design and guidance of low-thrust lunar transfers.

Harry Holt

Reinforced Lyapunov controllers for low-thrust lunar transfers

用于低推力月球转移的强化李雅普诺夫控制器

Abstract Scientific interest in asteroids and their physical characteristics is growing. These bodies provide insights into the primordial solar system and represent a valuable source of metals, silicates, and water. Several missions over the past few years have aimed to improve and better identify the main properties of these poorly known celestial bodies. However, these missions relied on touchdown(s) on the target asteroid to gather samples, which is complicated owing to the difficulty of accurately reaching and rendezvousing with the body. This study aims to assess the feasibility of an in-orbit asteroid sample collection mission. Such a strategy could prevent complex operations related to landing and touchdown maneuvers and avoid the dead times present in a mission requiring several landings. The presented collection scenario, which focuses on the asteroid Ryugu, proposes gathering samples using a spacecraft injected into a halo orbit around the second libration point, L 2 . For this purpose, the orbits in the neck region of the zero velocity curves are analyzed. A novel methodology to characterize bouncing behavior is introduced. An interpolation-based approach was used to recover the appropriate restitution coefficients for each collision occurring at a specific impact angle. This was applied to both the rigid body model and the point mass approximation studied for two different sites on the asteroid. Furthermore, the study enlarged the region of interest from only L 2 to its neighboring zones to return a more global and realistic point of view. Considering the solar radiation pressure and asteroid aspherical potential, particles of different sizes ejected from different longitudes and with different ejection angles were classified according to their trajectories to finally build a database. Based on this analysis, an aerogel-based collection strategy inspired by that used in the Stardust-NExT (NASA) mission was investigated to assess its possible applicability to the analyzed scenario.

Carlo Burattini

Camilla Colombo

Mirko Trisolini

Aerogel-based collection of ejecta material from asteroids from libration point orbits: Dynamics and capture design

基于气凝胶的从拉格朗日点轨道收集小行星喷射物材料：动力学与捕获设计

Yin Chu

Shengping Gong

Minimum-time rendezvous for Sun-facing diffractive solar sails with diverse deflection angles

面向太阳的衍射太阳帆在不同偏转角度下的最短时间会合

Mohammadmehdi Seddighi

Mahdi Jafari-Nadoushan

Designing a concurrent detumbling and redirection mission for asteroid mining purposes via optimization

通过优化设计用于小行星采矿的并发消旋与偏转任务

Wenxue Chen

Yudong Hu

Changsheng Gao

Wuxing Jing

Luring cooperative capture guidance strategy for the pursuit—evasion game under incomplete target information

不完全目标信息下追逃博弈的诱导协同捕获制导策略

Abbreviation	Astrodyn
Journal Impact	2.54
Quartiles(Global)	ENGINEERING, AEROSPACE(Q1)

ISSN	2522-008X, 2522-0098
h-index	19

Publication Information	Publisher: Tsinghua University Press，Publishing cycle: ，Journal Type: journal，Open Access Journals: No
Basic data	Year of publication: 2017，Proportion of original research papers: ，Self Citation Rate:， Gold OA Rate:

Astrodynamics

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