Review on strategies of space-based optical space situational awareness

Space-based optical(SBO)space surveillance has attracted widespread interest in the last two decades due to its considerable value in space situation awareness(SSA).SBO observation strategy,which is related to the performance of space surveillance,is the top-level design in SSA missions reviewed.The recognized real programs about SBO SAA proposed by the institutions in the U.S.,Canada,Europe,etc.,are summarized firstly,from which an insight of the development trend of SBO SAA can be obtained.According to the aim of the SBO SSA,the missions can be divided into general surveillance and space object tracking.Thus,there are two major categories for SBO SSA strategies.Existing general surveillance strategies for observing low earth orbit(LEO)objects and beyond-LEO objects are summarized and compared in terms of coverage rate,revisit time,visibility period,and image processing.Then,the SBO space object tracking strategies,which has experienced from tracking an object with a single satellite to tracking an object with multiple satellites cooperatively,are also summarized.Finally,this paper looks into the development trend in the future and points out several problems that challenges the SBO SSA.

Jamming Monitoring Technology of the Space Situational Awareness Facilities:A Comprehensive Survey

Complicated electromagnetic environments of the space situational awareness facilities(i.e.,satellite navigation systems,radar)would significantly impact normal operations.Effective monitoring and the corresponding diagnosis of the jamming signals are essential to normal opera-tions and the innovations in anti-jamming equipment.This paper demonstrates a comprehensive survey on jamming monitoring algorithms and applications.The methods in dealing with jamming signals are summarized primarily.Subsequently,the jamming detection,identification,and direc-tion finding techniques are addressed separately.Based on the established studies,we also provide some potential trends of the demonstrated jamming monitoring issues.

Safe-event pruning in spacecraft conjunction management

Spacecraft conjunction management plays a crucial role in the mitigation of space collisions.When a conjunction event occurs,resources and time are spent analyzing,planning,and potentially maneuvering the spacecraft.This work contributes to a subpart of the problem:Confidently identifying events that will not lead to a high collision probability,and therefore do not require further investigation.The method reduces the dimensionality of the data via principal component analysis(PCA)on a subset of features.High-risk regions are then determined by clustering the projected data,and events that do not belong to a high-risk cluster are pruned.A genetic algorithm(GA)is developed to optimize the number of clusters and feature selection of the model.Furthermore,an ensemble learning framework is proposed to combine the suboptimal models for better generalization.The results show that the first set of parameters pruned approximately 50%of the events in the testing set with no false negatives,whereas the second set of parameters pruned 70%of the events and maintained a near-perfect recall.These results could benefit the optimization of operational resources and allow operators to focus better on the events of interest.

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

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.

情境主义国际评述与城市空间再解读

该文首先简要介绍情境主义国际的景观社会与日常生活批判思想及其建构情境的主要策略,并通过剖析其思想和实践中所蕴含的批判潜力和不足,揭示出隐藏在空间背后知识、资本和权力的意识形态运作。然后从知识、资本、权力互为表征的视角重新审视城市空间,并针对空间知识的生产,空间生产中的资本积累方向和权力运作方式中存在的不足提出相应解决策略。最后,根据文中的分析结论,提出情境主义思想对我国城市空间生产的现实意义。

建筑边缘空间的情景主义特征及其营造方法研究

建筑边缘空间产生于内部功能与外部环境的矛盾中,兼有两者性质的同时创造新的内容,因而成为建筑设计的主体与视觉秩序的关键.首先,文章通过阐述情景主义理论内容及其空间观,分析其与建筑边缘空间特征的一致性,揭示建筑边缘空间所具备的情景主义特征,以为通过情节营造构建其内在秩序与场所意象奠定理论基础.基于此,文章结合实际案例,进一步总结归纳建筑边缘空间的情景营造方法,探讨提高边缘空间认同感、体验感与场所感的途径,以期实现人、建筑及自然的对话与融合,为建筑边缘空间的情景化设计提供理论基础与思路策略.

建筑和电影中的居住空间

本文讨论了电影建筑,即电影中所表现的建筑影像。建筑与城市的精神任务是营造我们的现世感.完美地衔接自我和世界体验的层面,而电影建筑关注于电影如何在脑海中构建和创造精神空间从而反映人类精神、思想和感情中内在的短暂的建筑形象。真正的建筑是在由物质建造的空间和主体精神空间之间的经验感觉和意义的交流。一次积极的建筑体验基本上是对自我的强化经验.这种经验确凿和舒适地将人置于文化整体之中。很显然,电影艺术能够使建筑行业本身对这种交流的微妙性的体察更加敏锐。

A review of space-object collision probability computation methods

The collision probability computation of space objects plays an important role in space situational awareness,particularly for conjunction assessment and collision avoidance.Early works mainly relied on Monte Carlo simulations to predict collision probabilities.Although such simulations are accurate when a large number of samples are used,these methods are perceived as computationally intensive,which limits their application in practice.To overcome this limitation,many approximation methods have been developed over the past three decades.This paper presents a comprehensive review of existing space-object collision probability computation methods.The advantages and limitations of different methods are analyzed and a systematic comparison is presented.Advice regarding how to select a suitable method for different short-term encounter scenarios is then provided.Additionally,potential future research avenues are discussed.

作为社会学视角的空间:空间解释的面向与限度

尽管空间的社会性已经比较明确,但关于空间的社会学性——空间如何作为一个社会学分析视角——还未被深入讨论。因此,本研究试图回答空间视角具备哪些理论分析的潜力或面向,其所具备的理论特点与分析限度为何。研究表明,空间视角具有四个面向:就社会结构面向而言,空间的占有状态构成了社会阶层分化的动力;就社会变迁面向而言,空间的生产是影响社会变迁速度和方向的重要机制;就社会控制面向而言,空间的"场所化"成了权力运作的主要技艺;就社会行动面向而言,空间的权利诉求构成了都市运动的重要逻辑。在此基础上,研究揭示了空间解释所具备的情境性和基于实践的复合性两个特点,在肯定了这两个特点所具备的优势之后,研究进一步讨论了其具备的分析限度。