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Satellite density distribution in LEO with the Starlink and OneWeb mega-constellations as filed (and amended) with the FCC. Provided that the orbits are nearly circular, the number densities in those shells will exceed 10–6 km⁻³. Because the collisional cross-section in those shells is also high, they represent regions that have a high collision risk whenever debris is too small to be tracked or collision avoidance manoeuvres are impossible for other reasons.
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The rapid development of mega-constellations risks multiple tragedies of the commons, including tragedies to ground-based astronomy, Earth orbit, and Earth’s upper atmosphere. Moreover, the connections between the Earth and space environments are inadequately taken into account by the adoption of a consumer electronic model applied to space assets....
Citations
... There is very little data on the environmental impact of deorbiting on atmospheric chemistry and in-situ data collection is practically impossible. The few existing studies agree that while the current impact of deorbiting is likely negligible, the projected exponential growth of satellites in LEO (Ciocca et al., 2021) and the ensuing need to deorbit these objects could exacerbate the risks of damaging the ozone layer (Pultarova, 2021), as well as lead to a runaway, uncontrolled solar radiation management experiment on a planetary scale (Boley and Byers, 2021). While there are currently around 9000 satellites in orbit (ESA 2023b), the United Nations Office for Outer Space Affairs (UNOOSA, 2023a) reports that '35 per cent of all satellites launched over the past three years' (p. 3) and that there is the potential of 100,000 satellites being launched over the next decade. ...
... Both studies find 'that the atmospheric impact of spacecraft reentries is relatively low, there are still high-level uncertainties on aerothermodynamics and atmospheric chemistry-transport modelling and a lack of observational (in-situ) data to evaluate assumptions and models' (ESA, 2022). Some other studies conclude that '[t]he predicted strong increase in anthropogenic injection [of deorbited space derbis] will make it significant in comparison to the natural injection [meteoroids] which can have yet unknown effects on Earth's atmosphere and the terrestrial habitat' (Schulz and Glassmeier, 2021), that satellites could soon become the dominant source of high-altitude alumina (Boley and Byers, 2021), and that 'radiative forcing from space debris aluminium, interactions with high altitude cloud formation and possible consequences on measurement techniques of the middle atmosphere appear to be feasible consequences of space debris re-entries' (Jain and Hastings, 2022). Recently, a study by Murphy et al. (2023) revealed that '[a]bout 10% of stratospheric sulfuric acid particles larger than 120 nm in diameter contain aluminium and other elements from spacecraft reentry'. ...
Space debris is a major issue for space safety as any collision of a space object with even a small piece of debris can have catastrophic consequences. The most recent dramatic increase of the number of satellites in Earth’s orbit is clearly exacerbating the risks. In this context there is a growing norm of disposal of orbital debris through atmospheric re-entry: space debris is to ‘burn up harmlessly in the atmosphere’, in order to provide for a ‘clean space’. Unfortunately, there is very little data on the environmental impact of deorbiting on atmospheric chemistry and in-situ data collection is practically impossible. The few existing studies – our own modelling included – agree that while the current impact of deorbiting is likely negligible, the projected exponential growth of satellites in LEO could exacerbate the risks. In consequence, space sustainability may come at the expense of damaging the health of the middle and upper atmosphere, with potentially unforeseeable consequences. Against this backdrop, we argue that in order to manage LEO sustainably, we must overcome this – what we call – ‘atmosphere-blindness’: our limited understanding of space-Earth system links through orbital disposal practices and their atmospheric impacts. While there is growing environmental consciousness with regard to outer space, we need to acknowledge that space sustainability is embedded in a wider context of outer space geopolitics, where the benefits and risks of the space infrastructure are distributed highly unequally. In our view it is thus crucially important to undertake more interdisciplinary research on the issue of de-orbiting, as it is not merely a technical environmental problem to be fixed but also an inherently political matter of planetary scale environmental justice.
... The Hubble Telescope and the International Space Station are wellknown objects in LEO. Companies site the satellites into orbit in an unparalleled frequency to build a mega constellations of communication satellites in LEO [3]. Constellations LEO objects orbit around the planet have high speeds. ...
For many researchers, defense against DDoS attacks has always been a major subject of attention. Within the LEO Satellite-Terrestrial (LSTN) network field, distributed denial of service (DDoS) attacks is considered to be one of the most potentially harmful attack techniques. For the facilitation of network protection by the detection of DDoS malicious traces inside a network of satellite devices, machine learning algorithms plays a significant role. This paper uses modern machine learning approaches on a novel benchmark Satellite dataset. The STIN and NSL-KDD datasets has been used to detect network anomalies. The pre-processing of data has been performed effectively and a host of ML methods have been applied to classify the outputs into normal, regular node or untrustable /malicious node. We have evaluated the analysis results in presence of attacks as well as without presence of attacks, supervised machine learning techniques basic measurements like accuracy, True positive, False positive etc. Our proposed trust model shows better accuracy, nearby 98% and we have shown that our proposed machine learning based security model performs better to get rid of DDoS attacks on integrated LEO satellite-terrestrial networks without compromising on the packet routing efficiency. We are able to improve routing speed and improve network security against distributed denial of service (DDoS) attacks by integrating an ensemble-based trust model trained on NSL-KDD+STIN+Exata Simulated resultant dataset with ACO for routing decisions. In dynamic network scenarios, as trustworthiness is an essential criterion in route decision-making, this proposed approach signifies resilient and adaptable routing.
... The syndrome predicts the denial of protected space regions through space debris build-up and its onset can already be observed in Fig. 1. However, recent trends have intensified the problem as thousands of satellites are launched to form mega-constellations in LEO [4]. ...
As artificial objects in Low Earth Orbit (LEO) become more numerous, the risk for breakup events threatening space-based services increases rapidly. Laser ablation methods have previously been proposed for the removal of small-size (1 - 10
cm) debris fragments, but a mission-level feasibility study is yet to be performed. This work investigates the mission concept and spacecraft design feasibility of a space-based laser aiming to de-orbit 50% of the debris generated by an on-orbit catastrophic event, using an agent-based modelling approach applied to the 2009 Cosmos-Iridium collision example. Several parameters were varied to generate a feasibility envelope on the payload performance, showing that the necessary capabilities for mission feasibility are within ranges achievable with current or near-term technology. Additionally, the financial challenges of the mission are discussed. A cost estimate for a single-flight mission of 550 M€ was generated based on the conceptual design developed for this study and is in agreement with previous
research. This work shows that a laser ablation concept for the removal of small-size debris in LEO is feasible both technically and financially. It further provides a modelling base for future research on similar concepts for different mission scenarios.
... Resident space objects refer to both active and inactive satellites, spacecraft, debris or any human-made object in space. The number of satellites being launched into orbit is rapidly increasing due to mega constellations developed by companies including SpaceX, OneWeb, Amazon, Telesat and GW [8]. Space debris in particular poses a significant risk to the operation of global positioning systems, telecommunications and weather forecasting because the debris can deorbit, explode or cause collisions creating even more debris [9]. ...
The large quantity of resident space objects orbiting Earth poses a threat to safety and efficient operations in space. Radar sensors are well suited to detecting objects in space including decommissioned satellites and debris, whereas the more commonly used optical sensors are limited by daylight and weather conditions. Observations of three non-operational satellites using a VHF radar system are presented in this paper in the form of micro Doppler signatures associated with rotational motion. Micro Doppler signatures are particularly useful for characterising resident space objects at VHF given the limited bandwidth resulting in poor range resolution. Electromagnetic simulations of the micro Doppler signatures of the defunct satellites are also presented using simple computer-aided design (CAD) models to assist with interpretation of the radar observations. The simulated micro Doppler results are verified using the VHF radar data and provide insight into the attitude and spin axis of the three resident space objects. As future work, this approach will be extended to a larger number of resident space objects which requires a automated processing.
... However, pervasive cloud cover poses challenges to systematic monitoring, necessitating more robust CD systems in satellite-based RS applications [2]. Advancements in aerospace technology, particularly low-earth orbit (LEO) satellite constellations [3], enhance data collection capabilities for near real-time high-resolution imaging. ...
The space sector is a fast-growing market, boosting the historical institutional space exploration economy with new industries emerging as it becomes more open for business. Despite a promising outlook arising from the surging competition, the rise in the number of satellites launched into space could be more sustainable. Space overcrowding is a pressing threat that could render future space endeavours more difficult, if not impossible. This work investigates how effective deep learning (DL) methods are for increasing the accuracy of cloud detection (CD) models in remote sensing (RS) satellite images to make intelligent decisions while in orbit without any human intervention. Synthetic satellite images were created by training a Deep Convolutional Generative Adversarial Network or DCGAN on Sentinel-2 Level 1C and Landsat 8-9 satellite data. Then, a Convolutional Neural Network or CNN was trained on these artificial images for automatic CD and classification. The study shows DCGAN can produce realistically-looking satellite images with 98.17% confidence and when synthesized with real satellite images to train a CNN, clouds can be detected with 88.70% accuracy. High accuracy of onboard-CD satellites is vital for Earth Observation (EO) missions because it enhances the quality and efficiency of satellite image data processing and applications, reducing the transmission and storage costs by sending only the cloud-free images to ground stations. By having the existing satellites more capable and independent, the need for launching new satellites or increasing the satellite communication frequency can be reduced, thereby helping to mitigate the overcrowding of satellites in space.
... The key policy issues to consider range from spectrum allocation and coordination (especially as 6G shifts to more of a 3D network structure) (Polese et al., 2023b), through to collision and space debris risks for drones and mega-constellations. Environmental impact assessment will also be important to avoid negative environmental externalities, including light pollution and emissions (Boley and Byers, 2021;Guyot et al., 2023;Osoro et al., 2023;Wilson, 2022). ...
With the arrival of the peak smartphone era, users are upgrading their smartphones less frequently, and data growth is decelerating. To ensure effective spectrum management decisions, policy makers require a thorough understanding of prospective wireless broadband technologies, current trends and emerging issues. Here, we review the sixth cellular generation (‘6G’), in comparison to two new Wi-Fi standards, including IEEE 802.11be (‘Wi-Fi 7’) and IEEE 802.11bn (‘Wi-Fi 8’). We identify three emerging issues necessary for successful telecommunication policy. Firstly, evidenced-based policy making needs to be able to measure effectively how much demand takes place where and how. Thus, new datasets are needed reflecting real usage by different wireless broadband technologies, for indoor and outdoor users. Secondly, with data consumption growth slowing, there needs to be an urgent reassessment of spectrum demand versus allocation. Past forecasts do not reflect recent data and regulators urgently need to re-evaluate the implications for spectrum management. Finally, regulators need new and improved Lifecycle Impact Assessment metrics of cellular versus Wi-Fi architectures, to support successful policy decisions which mitigate energy and emissions impacts.
... There is increasing interest in space domain awareness (SDA) worldwide due to the increasing number of resident space objects (RSOs) [1]. This number has expanded rapidly in recent years due to the advent of mega-constellations such as the SpaceX Starlink constellation [2]. ...
There is increasing interest in space domain awareness worldwide, motivating investigation of the use of non-traditional sensors for space surveillance. One such class of sensor is VHF wind profiling radars, which have a low cost relative to other radars typically applied to this task. These radars are ubiquitous throughout the world and may potentially offer complementary space surveillance capabilities to the Space Surveillance Network. This paper updates an initial investigation on the use of Buckland Park VHF wind profiling radars for observing resident space objects in low Earth orbit to further investigate the space surveillance capabilities of the sensor class. The radar was operated during the Australian Defence “SpaceFest” 2019 activity, incorporating new beam scheduling and signal processing functionality that extend upon the capabilities described in the initial investigation. The beam scheduling capability used two-line element propagations to determine the appropriate beam direction to use to observe transiting satellites. The signal processing capabilities used a technique based on the Keystone transform to correct for range migration, allowing the development of new signal processing modes that allow the coherent integration time to be increased to improve the SNR of the observed targets, thereby increasing the detection rate. The results reveal that 5874 objects were detected over 10 days, with 2202 unique objects detected, representing a three-fold increase in detection rate over previous single-beam direction observations. The maximum detection height was 2975.4 km, indicating a capability to detect objects in medium Earth orbit. A minimum detectable RCS at 1000 km of −10.97 dBm² (0.09 m²) was observed. The effects of Faraday rotation resulting from the use of linearly polarised antennae are demonstrated. The radar’s utility for providing total electron content (TEC) measurements is investigated using a high-range resolution mode and high-precision ephemeris data. The short-term Fourier transform is applied to demonstrate the radar’s ability to investigate satellite rotation characteristics and monitor ionospheric plasma waves and instabilities.
... The CW model has been exploited for numerous rendezvous and formation flying applications [18][19][20][21][22][23][24][25] in circular orbits in near-Earth space, and subsequently used for modeling orbital dynamics in this work. Furthermore, the application of the CW equations is suitable for a large number of artificial objects in nearly circular LEOs [26]. The CW equations accommodate additional control variables that enable us to describe the dynamics of controllable objects, such as active satellites, and non-controllable objects, such as defunct satellites and debris. ...
CubeSats have become versatile platforms for various space missions (e.g., on-orbit servicing and debris removal) owing to their low cost and flexibility. Many space tasks involve proximity operations that require precise guidance, navigation, and control (GNC) algorithms. Vision-based navigation is attracting interest for such operations. However, extreme lighting conditions in space challenge optical techniques. The on-ground validation of such navigation systems for orbital GNC becomes crucial to ensure their reliability during space operations. These systems undergo rigorous testing within their anticipated operational parameters, including the exploration of potential edge cases. The ability of GNC algorithms to function effectively under extreme space conditions that exceed anticipated scenarios is crucial, particularly in space missions where the scope of errors is negligible. This paper presents the ground validation of a GNC algorithm designed for autonomous satellite rendezvous by leveraging hardware-in-the-loop experiments. This study focuses on two key areas. First, the rationale underlying the augmentation of the robot workspace (six-degree-of-freedom UR10e robot + linear rail) is investigated to emulate relatively longer trajectories with complete position and orientation states. Second, the control algorithm is assessed in response to uncertain pose observations from a vision-based navigation system. The results indicate increased control costs with uncertain navigation and exemplify the importance of on-ground testing for system validation before launch, particularly in extreme cases that are typically difficult to assess using software-based testing.
... The uncontrolled re-entry of thousands of satellites into Earth's atmosphere could also pose a hazard to people and property on the ground and to airplanes in flight 2 . Re-entries could also alter Earth's upper atmosphere chemistry in non-trivial ways, owing to ablation products that are wildly different from the background flux of meteoroids [3][4][5] . ...
... Satellite re-entries from mega-constellations are likely to become the dominant source of high-altitude alumina in the near future, with presently unknown effects. 175 The prediction of nitric oxide due to entering debris or re-useable components is relatively easy as the high temperature air chemistry is well understood. On the contrary, the effect and amount of soot and black carbon emissions are principally unknown, and no validated predictive tools exist. ...
This paper presents a review of current aerothermal design and analysis methodologies for spacecraft. It briefly introduces the most important system architectures, including rockets, gliders, and capsule-based configurations, and gives an overview of the specific aerothermal and thermo-chemical effects that are encountered during their different flight phases and trajectories. Numerical and experimental design tools of different fidelity levels are reviewed and discussed, with a specific focus placed on the present limitations and uncertainty sources of models for the wide range of physical phenomena that are encountered in the analyses. This includes high temperature thermodynamics, chemical effects, turbulence, radiation, and gasdynamic effects. This is followed by a summary of current predictive capabilities and research foci, with missing capabilities identified. Finally, a future strategy toward an efficient and predictive aerothermal design of re-useable space transportation systems is proposed.
