Space Situational Awareness System Research Articles

Design of an optical system for a Multi-CubeSats debris surveillance mission

The detection and observation of space debris in Low Earth Orbit is generally carried out through the use of ground based radars and telescopes. These instruments allow for a precise reconstruction of the space debris trajectories, and therefore represent a key asset for planning avoidance maneuvers when threats of collisions are predicted.The recent deployment of mega-constellations, with the consequent increase of the number of satellites, imposes new challenges in terms of simultaneous tracking capability and readiness of the current space situational awareness systems. This adds to the current need to track small and dull objects to further mitigate the probability of triggering cascade collisions. However, ground based observations are limited due to their intrinsic sensibility to atmospheric refraction, their diurnal inoperability and their dependence on meteorological hazards.This paper proposes to study the feasibility and the benefits of a potential deployment of a constellation of CubeSats in Low Earth Orbit, to acquire optical observations of space debris with enhanced accuracy, as part of the ORCA mission: Orbit Refinement for Collision Avoidance. Here, the focus is on the optical design of the payload instrument to be integrated onboard of the orbiting platforms.The study trades-off the current state-of-art of optical detection technologies, by assessing their performance against a set of specific requirements: (a) the minimization of the uncertainty associated to the image resolution; (b) a field of view that maximizes the extent of the monitored area; (c) an optimal exposure time to avoid under or overexposure of the image; (d) minimization of the effects of light diffraction and above all, (e) the maximization of the signal to noise ratio to detect the smallest and dullest objects possible.Several configurations of optical systems are then chosen as suitable for the ORCA constellation, also considering the system design implications of its integration into a CubeSat, such as size requirements. Commercial Off-The-Shelf hardware are explored and performances of the optical system are evaluated through numerical simulations in order to estimate the detectable sizes of space debris while taking into account their potential distances from the sensor. This paper concludes with estimates of the impact of the ORCA mission on space situational awareness for decades to come.

Localization and classification of space objects using EfficientDet detector for space situational awareness

Space situational awareness (SSA) systems play a significant role in space navigation missions. One of the most essential tasks of this system is to recognize space objects such as spacecrafts and debris for various purposes including active debris removal, on-orbit servicing, and satellite formation. The complexity of object recognition in space is due to several sensing conditions, including the variety of object sizes with high contrast, low signal-to-noise ratio, noisy backgrounds, and several orbital scenarios. Existing methods have targeted the classification of images containing space objects with complex backgrounds using various convolutional neural networks. These methods sometimes lose attention on the objects in these images, which leads to misclassification and low accuracy. This paper proposes a decision fusion method that involves training an EfficientDet model with an EfficientNet-v2 backbone to detect space objects. Furthermore, the detected objects were augmented by blurring and by adding noise, and were then passed into the EfficientNet-B4 model for training. The decisions from both models were fused to find the final category among 11 categories. The experiments were conducted by utilizing a recently developed space object dataset (SPARK) generated from realistic space simulation environments. The dataset consists of 11 categories of objects with 150,000 RGB images and 150,000 depth images. The proposed object detection solution yielded superior performance and its feasibility for use in real-world SSA systems was demonstrated. Results show significant improvement in accuracy (94%), and performance metric (1.9223%) for object classification and in mean precision (78.45%) and mean recall (92.00%) for object detection.

Operators’ Requirements for SSA Services

The space data association (SDA), an association of global satellite operators working to ensure a controlled, reliable, and efficient space environment, has run a survey among its members to gather data on their Conjunction Assessment concept of operations. These include collision avoidance Go/No-Go metrics, collision avoidance targets, and operational constraints. This paper assesses the various positional accuracy requirements of space situational awareness (SSA) data associated with each of these diverse "Go/No-Go" metrics as employed in the conjunction mitigation processes used for space traffic coordination and spaced traffic management. These metrics include miss distance at the time of closest approach (TCA), componentized miss distance (e.g., TCA radial separation to preclude collision even when in-track or cross-track separations or uncertainties are unknown), and maximum collision probability and estimated actual probability. A common practice is to approximate a spacecraft’s hardbody with an encapsulating sphere. This one-shape-fits-all approach eliminates the need to determine orientation, but results in an overestimated object volume and an overinflated probability unless both satellites are actually spheres. The dependence of collision probability on orientation and configuration/shape of the satellites at TCA is examined in contrast to the use of an encapsulating spheres to produce more representative probabilities. To overcome the lack of knowledge of the enveloping box's orientation a spectrum of collision probability values corresponding to a range of box orientations, from which the interrelationship between attitudinal knowledge and position accuracy required for a given collision probability threshold can be determined. It was found that such an approach can typically reduce probability by a factor of 3 or more. The interrelationships between SSA positional accuracy, the operator-selected Go/No-Go metric and its threshold, timeliness, and resulting maneuver frequency is also explored. For example, the necessity to perform a collision avoidance maneuver adhere to a squared relationship on the adopted miss-distance threshold. The miss distance threshold adopted by the operator should, if done properly, be a function of the estimated accuracy of the primary and secondary objects as a function of time. This paper concludes by comparing the accuracy requirements derived for each metric above with estimates of positional accuracy observed in actual SSA data fusion experiments conducted this past year. In many situations, the accuracy of legacy and commercial SSA systems is insufficient to support the adopted Go/No-Go metric without using comprehensive data fusion techniques. Recommendations for operators are provided.

The Need for Establishing a New United Nations Body to Protect Earth from Back Contamination and Outer Space from Forward Contamination

The purpose of the article is to explore the necessity to establish a new United Nations body, which is authorised to monitor and protect Earth and its organisms from biological contamination from extra-terrestrial sources and to protect outer space from forwarding contamination. Recent studies show that these contaminations could potentially have an extremely detrimental effecton life on Earth and for the safety of future outer space exploration. The study is doctrinal research and primary and secondary legal sources of international space law and environmental law are analysed. The research also applies a theoretical approach to determine what sets of principles should be applied and what intuitional innovation is needed to achieve optimally the goals of improving safety standards. This article presents a proposal for establishing a specialized UN organ to monitor an international agreement for the international planetary quarantine protocol of Earth. The need of establishing a new body in the system of the UN for protection of the Earth’s environment from harmful contamination caused by activities in outer space is quite distinguished. This publication aims also to increase awareness about the need for institutional innovation of the present UN system, particularly concerning global challenges like contamination from outer space and contamination of outer space. One of the major global challenges of today is the absence of safeguards for the protection of Earth from back contamination, an extra-terrestrial source of infection and destruction of space debris on the surface. The proposed new legal instrument would create guarantees for the protection of Earth and the outer space environment, support the adoption of a common space situational awareness system for monitoring and disclosing information about what is happening in outer space.

RGB-D based multi-modal deep learning for spacecraft and debris recognition

Recognition of space objects including spacecraft and debris is one of the main components in the space situational awareness (SSA) system. Various tasks such as satellite formation, on-orbit servicing, and active debris removal require object recognition to be done perfectly. The recognition task in actual space imagery is highly complex because the sensing conditions are largely diverse. The conditions include various backgrounds affected by noise, several orbital scenarios, high contrast, low signal-to-noise ratio, and various object sizes. To address the problem of space recognition, this paper proposes a multi-modal learning solution using various deep learning models. To extract features from RGB images that have spacecraft and debris, various convolutional neural network (CNN) based models such as ResNet, EfficientNet, and DenseNet were explored. Furthermore, RGB based vision transformer was demonstrated. Additionally, End-to-End CNN was used for classification of depth images. The final decision of the proposed solution combines the two decisions from RGB based and Depth-based models. The experiments were carried out using a novel dataset called SPARK which was generated under a realistic space simulation environment. The dataset includes various images with eleven categories, and it is divided into 150 k of RGB images and 150 k of depth images. The proposed combination of RGB based vision transformer and Depth-based End-to-End CNN showed higher performance and better results in terms of accuracy (85%), precision (86%), recall (85%), and F1 score (84%). Therefore, the proposed multi-modal deep learning is a good feasible solution to be utilized in real tasks of SSA system.

Research Advancements in Key Technologies for Space-Based Situational Awareness

The space environment has become highly congested due to the increasing space debris, seriously threatening the safety of orbiting spacecraft. Space-based situational awareness, as a comprehensive capability of threat knowledge, analysis, and decision-making, is of significant importance to ensure space security and maintain normal order. Various space situational awareness systems have been designed and launched. Data acquisition, target recognition, and monitoring constituting key technologies make major contributions, and various advanced algorithms are explored as technical supports. However, comprehensive reviews of these technologies and specific algorithms rarely emerge. It disadvantages the future development of space situational awareness. Therefore, this paper further reviews and analyzes research advancements in key technologies for space situational awareness, emphasizing target recognition and monitoring. Many mature and emerging methods are presented for these technologies while discussing application advantages and limitations. Specially, the research prospects of multiagent and synergetic constellation technologies are expected for future situational awareness. This paper indicates the future directions of the key technologies, aiming to provide references for space-based situational awareness to realize space sustainability.

A Modern Space Situational Awareness System

We, Tuparev AstroTech in partnership with Astro Syteme Austria, present a next-generation Space Situational Awareness (SSA) system currently being created for the tracking and characterisation of satellites and space debris in the age of big-data astronomy. Our SSA system will be based on the image processing of white-light images to detect streaks produced by satellites and space debris. These images will be obtained by a network of 20-30 custom and in-house built SSA observatory stations, which will be made operational worldwide over the coming decade. The system will use machine learning algorithms to choose the optimal part of the sky to observe at any given moment, analyse the incoming data on-site and in real-time, and deliver various standardised data packages and science-quality images to be stored on a bespoke central archive capable of storing petabytes of data. With this system, we aim to cover a greater geographical and celestial area than any previous SSA system, to create a scalable system that is both fast and efficient, and to enable access to orders of magnitude more storage capacity and information than any other system currently available, commercial or governmental.

우주상황인식을 위한 인공우주물체 추락 예측 소프트웨어 개발

The high-level Space Situational Awareness (SSA) objective is to provide to the users dependable, accurate and timely information in order to support risk management on orbit and during re-entry and support safe and secure operation of space assets and related services. Therefore the risk assessment for the re-entry of space objects should be managed nationally. In this research, the Software for Re-Entry Prediction of space objects (SREP) was developed for national SSA system. In particular, the rate of change of the drag coefficient is estimated through a newly proposed Drag Scale Factor Estimation (DSFE), and is used for high-precision orbit propagator (HPOP) up to an altitude of 100 km to predict the re-entry time and position of the space object. The effectiveness of this re-entry prediction is shown through the re-entry time window and ground track of space objects falling in real events, Grace-1, Grace-2, Tiangong-1, and Chang Zheng-5B Rocket body. As a result, through analysis 12 hours before the final re-entry time, it is shown that the re-entry time window and crash time can be accurately predicted with an error of less than 20 minutes.

Task Planning for Multiple-Satellite Space-Situational-Awareness Systems

Space situational awareness (SSA) plays an important role in maintaining space advantages. Task planning is one of the key technologies in SSA to allocate multiple tasks to multiple satellites, so that a satellite may be allocated to supervise multiple space objects, and a space object may be supervised by multiple satellites. This paper proposes a hierarchical and distributed task-planning framework for SSA systems with focus on fast and effective task planning customized for SSA. In the framework, a global task-planner layer performs satellite and object clustering, so that satellites are clustered into multiple unique clusters on the basis of their positions, while objects are clustered into multiple possibly intersecting clusters, hence allowing for a single object to be supervised by multiple satellites. In each satellite cluster, a local task planner performs distributed task planning using the contract-net protocol (CNP) on the basis of the position and velocity of satellites and objects. In addition, a customized discrete particle swarm optimization (DPSO) algorithm was developed to search for the optimal task-planning result in the CNP. Simulation results showed that the proposed framework can effectively achieve task planning among multiple satellites and space objects. The efficiency and scalability of the proposed framework are demonstrated through static and dynamic orbital simulations.

Integrated Space Situational Awareness Systems: SDA and SSA – Advantages and Limitations

SDA (Space Domain Awareness) and SSA (Space Situational Awareness – SSA) have been defined as comprehensive knowledge of space objects and the ability to track, understand, and predict their future location. The purpose of the article is to present SSA initiatives to protect space systems, which are now recognized as fundamental assets of the sustainable development of each country. The destruction of even a part of the space infrastructure can have severe consequences for the security of citizens and economic activity. These systems assume the combination of all data obtained by various entities operating in space and Earth to create a common database. The SSA system was created based on the US military programme SDA (Space Domain Awareness); SSA and SDA are almost similar, but SDA is a new term replacing SSA, which existed previously. SDA is a better and improved SSA. Increasingly, the SSA programme is part of national and EU space strategies, but it is not yet possible to include it in international space law.

Space Situational Awareness (SSA) for Providing Safety and Security in Outer Space: Implementation Challenges for Europe

The main goals of the article are to describe space situational awareness (SSA) for safety and security purposes and to place SSA in the context of national and regional security law and policy. Building national or regional SSA systems should guarantee the security of people and infrastructure in outer space and on Earth from threats from space. Military aspects are also considered in the SSA system, because they reflect sensitive and fundamental security and defence issues. The SSA system is crucial for human security, and it is the responsibility of the states to understand the need to implement it correctly into national policy and law. SSA and its systems will evolve, building on already existing state activities and taking into account international cooperation frameworks. The practical example of the international use of SSA is the creation of the EU Consortium (with Poland on board), which will require internal and external cooperation from their member states for security purposes.

Safety and Security law: Space Situational Awareness System (SSA) in Transatlantic Relations. Europe vis a vis the US

This article undertakes a very sensitive issue such as space security and its implementation urgency into national law. There are a number of challenges to the security of space infrastructure, such as unintentional threats (space debris), intentional threats (space weapons, malicious interference, cyber-attacks) or threats related to the weather in space (geomagnetic storms, solar storms, etc.) Space is increasingly congested and various prevention and protection measures need to be implemented. On the other hand, there is a growing dependence on the space of some countries, including European ones. There is therefore an urgent need to speed up this work on security and international cooperation, e.g. between the European Union and the US – the “space leader”. The transatlantic cooperation between European states and the US is crucial in the area or space security. The US has necessary knowledge in its long history of experience of making space strategy, policy and security law and may be a good example for Europe in building the safety and security structures in space.

Applicability of Civil and Defense Dual Use to Space Situational Awareness System in Japan

This article deals with the possibilities and challenges of Japan's dual-use space situational awareness (SSA) systems. Japan is unique in a way that military use of outer space was completely prohibited for almost 40 years until the Basic Space Act (2008) became effective. The change in its space policy was decided because of the rapidly worsening security environment in East Asia, accompanied by preeminent threats to the safety, stability and sustainable use of outer space that constitutes a prerequisite for the safety and welfare of any country. This has led Japan to begin developing a full-scale SSA operation. However, Japan's long-standing non-military practice forces it to design and develop its SSA systems in a different manner than other advanced spacefaring nations. Given such conditions/restrictions, this article first identifies a Japanese means of constructing full-scale dual-use SSA systems, particularly taking into account the functions and capabilities of the Japan Aerospace Exploration Agency (JAXA), the significance of the Japan-U.S. Alliance and a series of recent governmental decisions. The merits and challenges of Japan's whole-of-government construction of the dual-use SSA will then be explored; this involves difficult processes to coordinate different defense and civil mission requirements. The conclusion envisions a balance between the Japan Air Self Defense Force's superior air defense capability and JAXA's accumulated technical capabilities, which together would enable full-fledged defense space utilization starting with the SSA.

Multi-objective optimization using parallel simulation for space situational awareness

Improving space situational awareness (SSA) remains one of the Department of Defense’s (DoD) top priorities. Current research has shown that the modeling of geosynchronous orbit (GEO) SSA architectures can help identify optimal combinations of ground- and space-based sensors. This paper extends previous research by expanding design boundaries and refining the methodology. A multi-objective genetic algorithm was used to examine this increased trade-space containing 1022 possible design combinations. The results of the optimizer clearly favor 1.0 m aperture ground telescopes combined with 0.15 m aperture sensors in a 12-satellite geosynchronous polar orbit (GPO) constellation. The GPO regime offers increased access to GEO resident space objects (RSO) since other orbits are restricted by a 40° solar exclusion angle. When performance is held constant, a GPO satellite constellation offers a 22.4% reduction in total system cost when compared to Sun synchronous orbit (SSO), equatorial low earth orbit (LEO), and near-GEO constellations. Parallel high-performance computing provides the possibility of solving an entirely new class of complex problems of interest to the DoD. The results of this research can educate national policy makers on the benefits of proposed upgrades to current and future SSA systems.

Strategic Implications of the Proliferation of Space Situational Awareness Technology and Information: Lessons Learned from the Remote Sensing Sector

Space situational awareness (SSA) refers to the ability to monitor and understand the state of the space environment, including the ability to track, understand, and predict the location of human-generated and natural objects in orbit around the Earth. This capability is a critical element in attributing and deterring attacks against space assets and in avoiding unintentional collisions. Historically, the United States Department of Defense has operated the most extensive SSA system in the world. Although, in recent years, it has shared data with commercial and foreign users on an ad hoc basis to help avoid collisions, access to the full database is highly restricted. Other nations, including Russia and Europe, have begun to develop or expand independent SSA systems. A number of commercial entities have also begun operating in this area, selling or planning to sell SSA services to satellite operators and governments. There are concerns in the United States about whether this proliferation of SSA technology and information will adversely affect national security, and questions about how the United States should respond to this situation. This article uses the example of remote sensing satellite technology and information, which experienced a similar transition from U.S. and Soviet dominance to participation by a wider range of nations and commercial entities, to identify the key strategic risks and opportunities posed by this trend. I discuss the extent to which these strategic risks and opportunities apply to the proliferation of SSA technology and information, finding that while the same strategic concerns are relevant in this case, typically the risks are lower. There are significant opportunities for the United States to benefit from this proliferation of technology. The article discusses the implications of these findings and offers recommendations that will allow the United States to further decrease the strategic risks associated with this trend, while increasing the benefits.

Performance Analysis of Sensor Systems for Space Situational Awareness

With increased human activity in space, the risk of re-entry and collision between space objects is constantly increasing. Hence, the need for space situational awareness (SSA) programs has been acknowledged by many experienced space agencies. Optical and radar sensors, which enable the surveillance and tracking of space objects, are the most important technical components of SSA systems. In particular, combinations of radar systems and optical sensor networks play an outstanding role in SSA programs. At present, Korea operates the optical wide field patrol network (OWL-Net), the only optical system for tracking space objects. However, due to their dependence on weather conditions and observation time, it is not reasonable to use optical systems alone for SSA initiatives, as they have limited operational availability. Therefore, the strategies for developing radar systems should be considered for an efficient SSA system using currently available technology. The purpose of this paper is to analyze the performance of a radar system in detecting and tracking space objects. With the radar system investigated, the minimum sensitivity is defined as detection of a 1-m2 radar cross section (RCS) at an altitude of 2,000 km, with operating frequencies in the L, S, C, X or Ku-band. The results of power budget analysis showed that the maximum detection range of 2,000 km, which includes the low earth orbit (LEO) environment, can be achieved with a transmission power of 900 kW, transmit and receive antenna gains of 40 dB and 43 dB, respectively, a pulse width of 2 ms, and a signal processing gain of 13.3 dB, at a frequency of 1.3 GHz. We defined the key parameters of the radar following a performance analysis of the system. This research can thus provide guidelines for the conceptual design of radar systems for national SSA initiatives.

A Study on Re-entry Predictions of Uncontrolled Space Objects for Space Situational Awareness

The key risk analysis technologies for the re-entry of space objects into Earth’s atmosphere are divided into four categories: cataloguing and databases of the re-entry of space objects, lifetime and re-entry trajectory predictions, break-up models after re-entry and multiple debris distribution predictions, and ground impact probability models. In this study, we focused on reentry prediction, including orbital lifetime assessments, for space situational awareness systems. Re-entry predictions are very difficult and are affected by various sources of uncertainty. In particular, during uncontrolled re-entry, large spacecraft may break into several pieces of debris, and the surviving fragments can be a significant hazard for persons and properties on the ground. In recent years, specific methods and procedures have been developed to provide clear information for predicting and analyzing the re-entry of space objects and for ground-risk assessments. Representative tools include object reentry survival analysis tool (ORSAT) and debris assessment software (DAS) developed by National Aeronautics and Space Administration (NASA), spacecraft atmospheric re-entry and aerothermal break-up (SCARAB) and debris risk assessment and mitigation analysis (DRAMA) developed by European Space Agency (ESA), and semi-analytic tool for end of life analysis (STELA) developed by Centre National d’Etudes Spatiales (CNES). In this study, various surveys of existing re-entry space objects are reviewed, and an efficient re-entry prediction technique is suggested based on STELA, the life-cycle analysis tool for satellites, and DRAMA, a re-entry analysis tool. To verify the proposed method, the re-entry of the Tiangong-1 Space Lab, which is expected to re-enter Earth’s atmosphere shortly, was simulated. Eventually, these results will provide a basis for space situational awareness risk analyses of the re-entry of space objects.

Security in space: Should space traffic management also concern payloads management?

Significant initiatives on space traffic management have been recently taken, essentially by developing principles of outer space transparency and confidence building measures (TCBM) beneficial to a safer conduct of space activities. The need for improved practices in space traffic management is a consequence of the increasing number of space-faring nations allowing for more types of missions, growing number of space debris, new private entrants, and rising space content in running critical national infrastructures, to name a few. These expanding space activities underscore the society's dependency on space systems and its vulnerability, calling for an improved long-term sustainability of outer space activities. But the lack of information on the nature of some space payloads and their associated missions introduce a persistent flaw in succeeding to achieve a long thought stable and safer space environment. Indeed this noticeable weakness in the mentioned initiatives is not taken into account at this stage. To overcome this difficulty, a space situational awareness system (SSAS) based on a multinational organization, or under the purview of a UN steered agency, is proposed. It could be implemented promptly, provided there is a shared political will and a recognized urgent need to do so by major space-faring nations gauging their long-term interest while there is still time. The space deterrence postures by dominant space powers that have been identified during the past ten years, or so, argues in favour of broadening as soon as possible the scope of the current TCBM.

Modeling and Simulation of Space Situation Awareness System Based on Parallel Control Theory

The basic components and complex property of SSA (space situational awareness) system is introduced. It is elaborated that the reason and method of researching SSA system based on parallel control theory. Specific idea and steps of modeling and simulation are proposed through ACP method of parallel control theory, and a simple simulated instance was used as a prototype of achieving artificial system of SSA.

Space debris tracking needs improvements, report states

With more and more space debris littering the skies above Earth, the U.S. Air Force Space Command (AFSPC) needs to keep up with demands to track the debris and prevent collisions with satellites by improving the U.S. Strategic Command's Joint Space Operations Center (JSpOC) infrastructure, modernizing software, and increasing the ability to more easily incorporate new algorithms and sensor data into its system, according to a 6 September report by a U.S. National Research Council committee. “If there is a single message of this study, it is that the Air Force needs to encourage a change in culture to emphasize openness—in transparency of its algorithms, in the interaction of its people with the user community and the scientific community, and in its providing of a reasonable amount of sensor tracking data to the scientific community for testing algorithms,” according to the report, entitled Continuing Kepler's Quest: Assessing Air Force Command's Astrodynamics Standards. “The Air Force needs to position the JSpOC—and its overall space situational awareness system—to rapidly evaluate, adapt, and adopt evolving technologies to meet community needs proactively.”