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The rapid development of Low Earth Orbit (LEO) mega constellations has significantly contributed to several aspects of human scientific progress, such as communication, navigation, and remote sensing. However, unrestrained deployment of constellations has also strained orbital resources and increased spacecraft congestion in LEO, which seriously af...
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... Events, such as the 2007 Fengyun-1C Chinese anti-satellite test alone, increased the number of trackable debris by 25% a . Additionally, the emerging NewSpace era is also directly increasing the occupation of low-Earth orbit (LEO) [3], which will in turn boost the number of debris in space in the near future. For example, SpaceX, through their Starlink mega-constellation, has the objective of placing more than 40,000 satellites in orbit around Earth, providing a large satellite Internet-access coverage, largely contributing to space pollution. ...
Ensuring the sustainability of future space missions requires addressing the space-debris issue proactively. Space debris threatens future space missions, making the need for collision avoidance manoeuvres essential. This research explores robust methods to perform such manoeuvres, focusing on guidance and control systems, using the Starlink constellation as a reference. A robust guidance system integrating convex optimisation enables autonomous, fuel-efficient collision avoidance of space debris. Testing across diverse conditions shows suitability for various satellite characteristics. Attitude-control requirements are analysed with a linear quadratic regulator controller. Low-thrust manoeuvres with constant capabilities are optimal for this specific mission, minimising fuel usage and achieving desired miss distances. The outcomes of this research represent a significant advancement in space-debris mitigation and contribute to enhancing space sustainability.
... Additionally, countries around the world have plans for LEO mega constellations; it is expected in the next decade, that nearly 100,000 constellation satellites will be launched (J. Zhang et al., 2022), a number which exceeds the total of satellites launched in the first half century of the space age by over a factor of 16. While these satellites have important societal benefits, including increasing access to high-speed internet in remote areas, the increase in LEO satellites has exponentially increased the number of close encounters between satellites, which in-turn increases the chances of collisions. ...
Atmospheric neutral density is a crucial component to accurately predict and track the motion of satellites. During periods of elevated solar and geomagnetic activity atmospheric neutral density becomes highly variable and dynamic. This variability and enhanced dynamics make it difficult to accurately model neutral density leading to increased errors which propagate from neutral density models through to orbit propagation models. In this paper we investigate the dynamics of neutral density during geomagnetic storms. We use a combination of solar and geomagnetic variables to develop three Random Forest machine learning models of neutral density. These models are based on (a) slow solar indices, (b) high cadence solar irradiance, and (c) combined high‐cadence solar irradiance and geomagnetic indices. Each model is validated using an out‐of‐sample data set using analysis of residuals and typical metrics. During quiet‐times, all three models perform well; however, during geomagnetic storms, the combined high cadence solar iradiance/geomagnetic model performs significantly better than the models based solely on solar activity. The combined model capturing an additional 10% in the variability of density and having an error up to six times smaller during geomagnetic storms then the solar models. Overall, this work demonstrates the importance of including geomagnetic activity in the modeling of atmospheric density and serves as a proof of concept for using machine learning algorithms to model, and in the future forecast atmospheric density for operational use.
... Space debris, with its continuously increasing quantity, not only occupies precious orbital resources, but also threatens the safety of spacecraft. Therefore, active debris removal (ADR) is an inevitable demand for the sustainable development of the space industry [2], [3], [4]. Compared with many popular ADR technologies, the tethered system has broad application prospects due to its unique advantages, such as its light weight, small space occupation, and long operating distance et al. ...
This paper investigates the librational motion control problem of the tethered space-tug (TST) system in the process of deorbiting space debris. By analyzing the dynamic equations of the TST system, the librational motion control problem of the system in 3-dimensional space can be transcribed to librational motion control problems inside and outside the orbital plane. The motion of the TST system inside or outside the orbital plane can be properly characterized through a highly simplified ring-string (R-S) model, which can be properly analyzed using the finite time-domain wave equation. An absorbing excitation method is proposed to suppress the librational motion of the R-S model, where the librational motion suppression control is achieved by offsetting the equivalent excitation obtained through motion analysis. Different from wave-based controls which ignore the mass of execution structure, the effect of the mass of the tug and target on the control rate is compared through numerical simulations of four control rates based on the absorbing excitation method.
... In recent years, with the rapid deployment and development of large-scale satellite constellations, satellite communication has emerged as an exceptional supplementary solution to ground-based communication systems, demonstrating remarkable application potential [1][2][3]. The successful commercialization of Starlink constellation has spurred the advancement of satellite internet, OneWeb, Project Kuiper, and the China's GW constellation are all accelerating their deployment [4][5][6]. ...
... Define n φ is the actual phase feeding value of n-th element, n δφ is the phase error of n-th element, n u ∆ is the beam pointing error generated by the n-th element and n u δ is beam pointing error generated by the n-th element and all elements before it. The procedure of the SCCPFM is: 1) For the 1-st element, 1 1 ...
The rapid deployment of satellite constellations has propelled the swift development of the satellite industry. Low-cost solutions spanning the entire industry chain will significantly accelerate the improvement of satellite internet. On the user side, phased array antenna terminals are gradually replacing reflector antennas, yet the ensuing challenges of hardware architecture and costs. Lowering the resolution of phase shifter is one solution, but this may result in a loss of beam pointing accuracy. A novel two-stage phase shifter phased array architecture is proposed, coupling subarray division with mixed-resolution phase shifters to reduce costs while ensuring the beam performance. The architecture boasts low complexity and ease of implementation. Simulation results demonstrate the balanced performance of this architecture in scanning accuracy and beam sidelobes, marking a promising path for industrial applications.
... Besides, a novel passive cancellation technique was presented based on multipath effect and a novel digital cancellation method considering nonlinearity factor in full-duplex system. Zhang et al. [ 3 ] focused on a pre-coded inter-satellite routing algorithm with load balancing for balanced satellite communication links. As well, a space-based spectrum situational awareness method was designed with spectrum situational maps. ...
... This method ensures continuous communication even in the most remote areas where VHF and HF might be less effective. While mega constellations are designed to enhance coverage and redundancy (Long & Zhang, 2024;Zhang et al., 2022), marking a significant shift in SATCOM systems, individual satellites within these constellations may still experience signal degradation during space weather events. First, as an electromagnetic wave-based communication system, SATCOM is influenced by changes in ionospheric conditions (Goodman, 2005). ...
Aviation communication is significant for the safe, efficient, and orderly operation of air traffic. The aviation industry relies on a sophisticated network to maintain air‐ground communications. However, space weather events can disrupt the ionosphere conditions and damage satellites, leading to High‐Frequency (HF) communication blackouts and satellite communication failures. These disruptions can jeopardize flight safety, especially for flights over polar regions. In response, strategies such as cancellations, rescheduling, or rerouting to lower latitudes may be necessary, despite the low flight efficiency and substantial financial losses. With the background of the anticipated solar maximum in 2025 and a growing number of polar flights, it is indispensable to have a comprehensive understanding of the space weather effects on aviation communication and develop constructive strategies from an Air Traffic Management (ATM) perspective. Hence, we simulate scenarios with different durations of communication failures and assess the corresponding economic losses. Based on the data derived from historical polar flights in 2019, there are daily 18 polar flights with trajectories crossing the north polar region higher than 82°N. Simulation results show that the economic losses associated with these polar flights can range from €0.03 million to €1.32 million, depending on both the duration of communication failures and the adopted air traffic management strategies. We believe that this study can shed light on the effects of space weather‐induced communication failures on polar flight operations and provide guidance for mitigating these effects in the aviation industry.
... Hence, in the LEO satellite category, particular focus is given to the Starlink constellation of satellites, and it was taken as our case study. The key reason is because Starlink represents the world's largest low Earth orbit (LEO) internet constellation, slated to encompass a total of 42,000 satellites [57]. The next-largest commercial con- ...
... Hence, in the LEO satellite category, particular focus is given Starlink constellation of satellites, and it was taken as our case study. The key rea because Starlink represents the world's largest low Earth orbit (LEO) internet con tion, slated to encompass a total of 42,000 satellites [57]. The next-largest commerci stellation planned in LEO is by OneWeb, with 7000 satellites [58]. ...
... Hence, in the LEO satellite category, particular focus is given to the Starlink constellation of satellites, and it was taken as our case study. The key reason is because Starlink represents the world's largest low Earth orbit (LEO) internet constellation, slated to encompass a total of 42,000 satellites [57]. The next-largest commercial constellation planned in LEO is by OneWeb, with 7000 satellites [58]. ...
The growing amount of space debris in the low Earth orbit poses a danger to manned as well as uncrewed missions. Additionally, the new business model of providing internet from space is emerging among new space players, making low Earth orbit more crowded. These factors have encouraged the space community to focus on sustainability in space. Satellite manufacturers typically have the capability to perform complete life cycle analysis (LCA) on their own products based on the manufacturing data. However, there is a lack of a method for non-manufacturers such as environmentalists and the general public to predict the carbon footprint of satellite manufacturing using a subsystem-level mass budget. Hence, this paper presents a method to quantify environmental pollution caused by the production of satellite constellations. Starlink is taken as a case study in this paper, and mass budget is predicted based on space systems engineering budget estimation techniques, the parametric method, and Federal Communication Commission orbital data. With the budget table used as an input, space-specific life cycle assessment is performed based on European Space Agency's life cycle inventory database. Finally, the single score for Starlink constellation version 1 was found to be 76 kilo points. This signifies the annual environmental load. These results could be helpful in obtaining an overview of the environmental effects of the production phase of satellite constellations. Further, the results could act as a foundation for further research on implementing more circular approach practices on Earth as well as in space.
... The last few decades have seen an explosion in space exploration, with a rapid increase in the number of satellite launches, with several private companies creating their megaconstellations with an expected number topping more than ∼42,000 satellites (J. Zhang et al. 2022). As we write, there are over 6000 satellites, including more than 5000 constellation satellites in orbit (UCS 6 ; UNOOSA 7 ; J. Mc Dowell 8 ), and these numbers are expected to increase dramatically in the next decade. ...
Orbiting space objects have become in the last decade a major nuisance impacting ground astronomy and orbiting space assets, from observatories to satellites and space stations. In particular with the rise of the satellite population in Low Earth Orbits, space objects are becoming an even bigger threat and a strong problem to astronomical observations. To tackle these threats, several coordinated surveillance networks composed of dedicated sensors (telescopes, radars, and laser ranging facilities) track and survey space objects, from debris to active satellites. As part of the European Space Surveillance & Tracking network, Portugal is developing the Pampilhosa da Serra Space Observatory, with both radio and optical telescopes dedicated to the Space Situational Awareness domain, deployed at a Dark Sky destination. To optimize telescope survey time, we developed CLOud Watcher at Night (CLOWN), an application interface that automatically monitors clouds in real time. This software can correctly trace cloud positions in the sky and provide accurate pointing information to the observation planning of the optical telescope to avoid cloudy areas. CLOWN only requires the use of an all-sky camera, which is already a norm in observatories with optical telescopes and can be used with any camera, including those for which no information about its model specification do exist. CLOWN does not require great computing power, and it does not require the installation of additional equipment. CLOWN results are very promising and confirm that the app can correctly identify clouds in a variety of different conditions and cloud types.
... Because of the increased use of other orbits closer to Earth, like LEO, it has been suggested that they may soon need coordination, although this is not currently performed, especially since satellites in LEO do not have a fixed location. The ITU and WRC have engaged in efforts through discussions and proposals to develop frameworks for coordination amidst the growing number of constellations [57,58]. During the World Radio Communication Conference (WRC-23), a proposal to review the equivalent power flux density (EPFD) limits was approved in order to address the unfavorable limits placed on LEO users, especially in spectrum utilization [59,60]. ...
In the 21st century, mega-constellations and interconnected satellite constellations deployed at various orbital altitudes, such as LEO, MEO, and GEO, with low Earth orbits (LEOs) being the most commonly used, have emerged as a trend, aiming to enhance the productivity and reduce the costs in space service delivery. The UNOOSA has noted the uncertainty in the exact number of satellites but conducted simulations based on a substantial sample, projecting a significant increase from the 2075 satellites recorded in orbit in 2018. This surge in the launch of mega-constellations poses profound challenges to existing international space laws, originally formulated with limited consideration for private space actors, who are increasingly engaging in space activities, particularly with the cost-effective utilization of mega-constellations. This study critically analyzes the compatibility of mega-constellations with the current international space laws by examining the applicability of mega-constellations concerning equitable access and the non-appropriation principle, addressing their potential occupation of substantial orbital spaces during activities, and analyzing whether the acquisition of orbital slot licenses violates these two principles. Following an in-depth analysis, this study proposes recommendations to amend the existing laws, aiming to resolve ambiguities and address emerging challenges. Recognizing the time-consuming process of amending international space laws, this study suggests practical recommendations for supplementary rules of the road, prompting reflection on the potential obsolescence of the current international space laws in the face of evolving space activities.
... The last few decades have seen an explosion in space exploration, with a rapid increase in the number of satellite launches, with several private companies creating their mega-constellations with an expected number topping more than ∼ 42000 satellites (Zhang et al. 2022). As we write, there are over 6000 satellites including more than 5000 constellations satellites in orbit (Mc Dowell 2023;UNOOSA 2022;UCS 2022), and these numbers are expected to dramatically increase in the next decade. ...
Orbiting space objects have become in the last decade a major nuisance impacting ground astronomy and orbiting space assets, from observatories to satellites and space stations. In particular with the rise of the satellite population in Low Earth Orbits (LEOs), space objects are becoming an even bigger threat and a strong problem to astronomical observations. To tackle these threats several coordinated surveillance networks composed of dedicated sensors (telescopes, radars and laser ranging facilities) track and survey space objects, from debris to active satellites. As part of the European Space Surveillance \& Tracking (EU-SST) network, Portugal is developing the PAmpilhosa da Serra Space Observatory (PASO), with both radio and optical telescopes dedicated to the Space Situational Awareness (SSA) domain, deployed at a Dark Sky destination. To optimize telescope survey time, we developed {\tt{CLOWN}} (CLOud Watcher at Night), an application interface that automatically monitors clouds in real time. This software can correctly trace clouds positions in the sky, provides accurate pointing information to the observation planning of the optical telescope to avoid cloudy areas. {\tt{CLOWN}} only requires the use of an all-sky camera, which is already a norm in observatories with optical telescopes and can be used with any camera, including those for which no information about its model specification do exist. {\tt{CLOWN}} does not require great computing power and it does not require the installation of additional equipment. {\tt{CLOWN}} results are very promising and confirm that the app can correctly identify clouds in a variety of different conditions and cloud types.