Large Satellite Constellations Research Articles

Expected Impact of Glints from Space Debris in the LSST

We examine the simple model put forth in a recent note by Loeb regarding the brightness of space debris in the size range of 1–10 cm and their impact on the Rubin Observatory Legacy Survey of Space and Time (LSST) transient object searches. Their main conclusion was that “image contamination by untracked space debris might pose a bigger challenge [than large commercial satellite constellations in Low-Earth orbit].” Following corrections and improvements to this model, we calculate the apparent brightness of tumbling low-Earth orbit (LEO) debris of various sizes, and we briefly discuss the likely impact and potential mitigations of glints from space debris in LSST. We find the majority of the difference in predicted signal-to-noise ratio (S/N), about a factor of 6, arises from the defocus of LEO objects due to the large Simonyi Survey Telescope primary mirror and finite range of the debris. The largest change from the Loeb estimates is that 1–10 cm debris in LEO pose no threat to LSST transient object alert generation because their S/N for detection will be much lower than estimated by Loeb due to defocus. We find that only tumbling LEO debris larger than 10 cm or with significantly greater reflectivity, which give 1 ms glints, might be detected with high confidence (S/N > 5). We estimate that only one in five LSST exposures low on the sky during twilight might be affected. More slowly tumbling objects of larger size can give flares in brightness that are easily detected; however, these will not be cataloged by the LSST Science Pipelines because of the resulting long streak.

Anti-satellite weapon tests to disrupt large satellite constellations

Anti-satellite weapon tests to disrupt large satellite constellations

Metals from spacecraft reentry in stratospheric aerosol particles

Large increases in the number of low earth orbit satellites are projected in the coming decades [L. Schulz, K.-H. Glassmeier, Adv. Space Res. 67, 1002-1025 (2021)] with perhaps 50,000 additional satellites in orbit by 2030 [GAO, Large constellations of satellites: Mitigating environmental and other effects (2022)]. When spent rocket bodies and defunct satellites reenter the atmosphere, they produce metal vapors that condense into aerosol particles that descend into the stratosphere. So far, models of spacecraft reentry have focused on understanding the hazard presented by objects that survive to the surface rather than on the fate of the metals that vaporize. Here, we show that metals that vaporized during spacecraft reentries can be clearly measured in stratospheric sulfuric acid particles. Over 20 elements from reentry were detected and were present in ratios consistent with alloys used in spacecraft. The mass of lithium, aluminum, copper, and lead from the reentry of spacecraft was found to exceed the cosmic dust influx of those metals. About 10% of stratospheric sulfuric acid particles larger than 120 nm in diameter contain aluminum and other elements from spacecraft reentry. Planned increases in the number of low earth orbit satellites within the next few decades could cause up to half of stratospheric sulfuric acid particles to contain metals from reentry. The influence of this level of metallic content on the properties of stratospheric aerosol is unknown.

The high optical brightness of the BlueWalker 3 satellite

Large constellations of bright artificial satellites in low Earth orbit pose significant challenges to ground-based astronomy1. Current orbiting constellation satellites have brightnesses between apparent magnitudes 4 and 6, whereas in the near-infrared Ks band, they can reach magnitude 2 (ref. 2). Satellite operators, astronomers and other users of the night sky are working on brightness mitigation strategies3,4. Radio emissions induce further potential risk to ground-based radio telescopes that also need to be evaluated. Here we report the outcome of an international optical observation campaign of a prototype constellation satellite, AST SpaceMobile’s BlueWalker 3. BlueWalker 3 features a 64.3 m2 phased-array antenna as well as a launch vehicle adaptor (LVA)5. The peak brightness of the satellite reached an apparent magnitude of 0.4. This made the new satellite one of the brightest objects in the night sky. Additionally, the LVA reached an apparent V-band magnitude of 5.5, four times brighter than the current International Astronomical Union recommendation of magnitude 7 (refs. 3,6); it jettisoned on 10 November 2022 (Universal Time), and its orbital ephemeris was not publicly released until 4 days later. The expected build-out of constellations with hundreds of thousands of new bright objects1 will make active satellite tracking and avoidance strategies a necessity for ground-based telescopes.

Red Light or Green Light?: Legal Considerations for Regulating Traffic in Orbit

The number of functional and non-functional satellites, and other pieces of orbital debris, is constantly increasing due to new space activities, including use of large constellations of small satellites, and the growth of commercial space missions. Congestion in space challenges the ongoing safety, security and sustainability of space activities and space assets. There are now more than one million debris items larger than 1cm orbiting the Earth, and this number may grow exponentially as more than 100,000 additional satellites are planned for launch over the next ten years. These will only add to the increasing risk of damage and destruction to any satellite involved in case of a collision in space. In this context, there is a necessity to develop a Space Traffic Management (STM) regime that encompasses the means and the rules to safely access, conduct activities in, and return from outer space. It would also aim to protect the Long-Term Sustainability (LTS) of space activities by ensuring that space remains a secure environment, even as global society relies ever more on space-based applications such as communications, navigation and Earth observation. This article examines those rules present in the current space legal framework that are relevant to the regulation of space traffic and analyses two key concepts for establishing a comprehensive STM regime, namely the monitoring of space activities through data access and information sharing, and appropriate coordination mechanisms between states, Space Agencies and private operators. space law, regulation, traffic in orbit, space debris, space situational awareness, information sharing, coordination, international cooperation

Optimized Controller Provisioning in Software-Defined LEO Satellite Networks

The controller provisioning, which adjusts the number, locations, and members of satellite controllers adaptive to the dynamic network load and topology, fundamentally impacts the performance of software-defined satellite networks (SDSNs). An ideal provisioning strategy should achieve a low total control overhead throughout the entire satellite operation period, which is extremely challenging since the network load can only be predicted in a short time scale. Existing methods can hardly achieve this goal for they greedily configure controllers in each time slot, where switches have to frequently migrate from one controller to another. In this paper, we focus on achieving globally optimized strategies with only current network load information. We firstly propose a comprehensive control overhead model and formulate the Controller Provisioning Problem (CPP) in SDSNs as a non-convex integer programming problem. To solve the problem, we propose an approximate algorithm named AROA by introducing a regularization framework and based on randomized rounding. We theoretically derive its competitive ratio. To produce strategies in time for future large satellite constellations, we further propose a more efficient heuristic algorithm HROA. Evaluations on our built simulation system show that our proposed methods significantly outperform related schemes in control overhead, latency, and scalability.

Can Regulating Large Satellite Constellations as Monopolies Improve Sustainability Standards While Providing Effective and Equitable Internet Access?

Large satellite constellations (LSC) in Low Earth Orbit (LEO) provide the means to deliver internet to previously underserved populations. The LSC’s economic potential combined with a growing demand for internet access has led to multiple companies pledging their own internet LSCs in hopes of capitalizing on this need. This, in addition to growing interest in LEO, risks destabilizing the LEO environment if not regulated properly. The current U.S. Orbital Debris Standard Mitigation Practices (USODSMP) are woefully outdated and only sporadically followed by operators. Furthermore, there are no licensing regulations for other key sustainability requirements, such as propulsion and tracking. Accelerated growth of internet LSCs without proper regulation will lead to an unsafe and unsustainable LEO environment. There needs to be a change in how governments regulate private and public LSCs, in particular those providing internet telecommunications. Internet LSCs are the fastest growing population in LEO, often directly competing for orbits and broadband frequencies. In this thesis I investigate whether the U.S. could apply aspects of terrestrial utility infrastructure to better regulate satellite internet. In particular, I question whether the U.S. government could regulate internet LSCs as monopolies. Such regulatory control would allow the U.S. to better enforce and revise sustainability regulations and ensure fair access to internet services. Viewing internet as a utility, as a necessity of modern life to which all citizens deserve access, this thesis proposes the U.S. license a single internet LSC from within its borders. I explored two potential regulatory approaches: one based on the U.S.’s public utility system and one based on European internet infrastructure. I then presented these approaches to five experts in the field of space sustainability and solicited their feedback. From these results, I determined that both of my regulatory approaches are not feasible in their current forms within the U.S.; however, both approaches produce potential partial applications and variations of their initial design that may find traction. This thesis concludes that adopting an interoperability framework in LEO would allow for precise and targeted sustainability, technology, and capacity standards for each orbital corridor, empower regulatory bodies to enforce these standards, and preserve competition among Commerical Satellite Operators (CSOs). Finally, a government internet LSC competing against commercial internet LSCs, akin to terrestrial municipal internet, would demonstrate technological feasibility, satisfy equity requirements, and provide a baseline LSC for CSOs to compete against. To see the complete thesis, please visit https://scholar.colorado.edu/concern/undergraduate_honors_theses/5138jg42t.

WRC-23 on the Horizon: Large Satellite Constellations, ITU Issues, and Industry Perspective

Although the previous World Radiocommunications Conference (WRC-19) attempted to resolve spectrum-sharing issues among the disparate new satellite constellations, issues have multiplied as these constellations are coming into use before all the rules have been created. The upcoming WRC, to be held at the end of 2023, will grapple with spectrum and situational sharing issues among constellations that are larger than ever before, and that are disrupting national regimes designed for licensing more traditional, one-at-a-time geostationary satellites. The agenda for WRC-27 will surely include multiple areas of study related to constellations, and the International Telecommunication Union (ITU) will need to work closely with the UN’s Office of Outer Space Affairs (UNOOSA) to resolve situational issues such as traffic management, debris, and the sustainability of the outer space environment. The emergence of operational constellations is disrupting legal regimes for states and industrial players, and future Agenda Items (AIs) should be added to WRC-27 or future Committee on the Peaceful Uses of Outer Space (COPUOS) sessions. constellations, LEO, ITU, spectrum, WRC

Investigating the Risks of Debris-Generating ASAT Tests in the Presence of Megaconstellations

The development of large constellations of satellites (i.e., so-called megaconstellations or satcons) is poised to increase the number of LEO satellites by more than an order of magnitude in the coming decades. Such a rapid growth of satellite numbers makes the consequences of major fragmentation events ever more problematic. In this study, we investigate the collisional risk to on-orbit infrastructure from kinetic anti-satellite (ASAT) weapon tests, using the 2019 Indian test as a model. We find that the probability of one or more collisions occurring over the lifetime of ASAT fragments increases significantly in a satcon environment compared with the orbital environment in 2019. For the case of 65,000 satellites in LEO, we find that the chance of one or more satellites being struck by ASAT fragments of size 1 cm or larger is more than 25% for a single test. Including sizes down to 3 mm in our models suggests that impacts will occur for any such event. Finally, we apply our methods to examine the November 2021 Russian ASAT test, also finding a significant collision probability over the lifetime of the fragments. The heavy commercialization of LEO demands a commitment to avoiding debris-generating ASAT tests.

Satellite Constellation Avoidance with the Rubin Observatory Legacy Survey of Space and Time

We investigate a novel satellite avoidance strategy to mitigate the impact of large commercial satellite constellations in low-Earth orbit on the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). We simulate the orbits of currently planned Starlink and OneWeb constellations (∼40,000 satellites) to test how effectively an upgraded Rubin scheduler algorithm can avoid them, and assess how the overall survey is affected. Given a reasonably accurate satellite orbit forecast, we find it is possible to adjust the scheduler algorithm to effectively avoid some satellites. Overall, sacrificing 10% of LSST observing time to avoid satellites reduces the fraction of LSST visits with streaks by a factor of 2. Whether such a mitigation will be required depends on the overall impact of streaks on science, which is not yet well quantified. This is due to a lack of adequate information about satellite brightness distributions as well as the impact of glints and low surface brightness residuals on alert purity and systematic errors in cosmological parameter estimation. A significant increase in the number of satellites or their brightness during Rubin Operations may make implementing this satellite avoidance strategy worthwhile.

In Search of the Most Appropriate Mechanism for Resolving the Disputes Arising from Large Satellite Constellations

In Search of the Most Appropriate Mechanism for Resolving the Disputes Arising from Large Satellite Constellations

Environmental sustainability of future proposed space activities

As actors in the space sector are proposing ever more ambitious plans for the future, it is important to evaluate their consequences on the Earth's environment, which are yet poorly known. To address this gap, this study presents a streamlined Life Cycle Assessment of future space activities over the period from 2022 to 2050 based on plans that would likely drive the environmental impacts of the space sector if they were realised. Large constellations of satellites, space tourism, Moon missions, and space-based solar power were considered in a first scenario, while rocket-based point-to-point travel on Earth and Mars colonisation were also included in two other scenarios. To this aim, the model is based on data from companies' declarations and actual space systems and uses life cycle inventory and impact assessment data from the Strathclyde Space Systems Database. In the first scenario, the study finds that by 2050 proposed plans would lead to an unprecedented surge in the impacts of the space sector (×9 on climate change) and in the number of satellites in orbit (∼112,000, all from large constellations). Ozone depletion from launch events could reach significant levels (6% of annual global impacts), while in a decade emissions of black carbon and aluminium oxide from rockets may alter the radiative balance of the atmosphere as much as present-day global aviation, although these effects are uncertain and poorly understood yet. Moreover, the mass injected into the atmosphere by re-entering artificial objects would become significant (∼27× the natural level for aluminium), while its environmental consequences remain largely unquantified. In the two other scenarios, results indicate that speculative plans of rocket-based point-to-point travel on Earth and Mars colonisation could deplete ozone several times as much as all other human activities combined, while air acidification and climate change could reach several percent of annual global impacts and planetary boundaries. The mitigation of these impacts using low carbon fuels would be limited by supply availability and by the emission of non-CO2 climate forcers and ozone-destroying compounds during launch and re-entry. Consequently, environmental sustainability is identified as a potential limiting factor to the development of intense space activities and to making humanity a multi-planetary species. Furthermore, political and social acceptability could play a major role in the development of recreational space travel since it exacerbates environmental inequalities due to an unparalleled combination of economic inaccessibility and high environmental footprints per passenger. Overall, results strongly suggest that there is a pressing need to include environmental considerations in addition to technical and economic analyses in space projects definition and space systems design.

Analytical model for collision probability assessments with large satellite constellations

At a time when space debris are already a growing issue in the space sector, the deployment of large constellations, made of hundreds to thousands of satellites, is of concern from an environmental point of view. In the next decade, the space sector will undergo a considerable change as the population of active satellites is about to quintuple. This scenario will pose new challenges regarding space traffic management, generating the demand for more powerful and efficient tools.In this study, an analytical model for collision probability assessments between de-orbiting or injecting space objects and satellite constellations is presented. Considering the first to be subjected to a continuous tangential acceleration, its spiraling motion would result in a series of close approaches in the proximity of a constellation. The mathematical description of the crossing dynamics relies on the assumptions of circular orbits and independent collision probabilities, but does not require to propagate the satellites’ orbit. The statistical model presented in the current work constitutes an efficient tool for the evaluation of the mean collision probability related to this type of events. A comparison with a propagation method has been performed for validation purposes, showing that the model is capable of delivering accurate results, also in case of elliptical crossing orbits.The statistical model has been used to assess the risk connected to constellation’s satellites replacement, once they have reached their programmed End-of-Life. The environmental impact of the full replacement of 12 approved constellations is analysed by means of average collision probability. In particular, it is shown that the key features for space exploitation sustainability are the maximum thruster acceleration, the size of the satellites and the true anomaly phases between constellations’ and crossing satellites. The consequences of an in-orbit collision are also investigated by assessing the collision risk generated by the formation of a debris cloud.The results corroborate the need for international standards for space traffic management as an exponentially increasing satellite population could trigger a chain reaction of collisions, making Low Earth Orbit inaccessible for decades.

Improving international governance of space debris in the era of large constellations of small satellites and China’s response

The rapid development of large constellations of small satellites will inevitably lead to a sharp increase of space debris, and thus brings about great threat to space safety and space environment. This poses severe challenges to the current international governance of space debris. The existing space debris mitigation guidelines are neither adaptive nor effective in dealing with the space debris problem in the era of large constellations of small satellites. Under such background, it is indispensable to establish an innovative space debris governance mechanism combining rules both concerning space debris mitigation, prevention, and more importantly, space debris active removal. In this regard, China has been improving its domestic space legislation regarding space debris management at the domestic level. On the other hand, China shall continue to promote the innovative development of space debris governance mechanism at the international level, so as to cope with the conundrums resulting from the development of large constellations of small satellites.

An Evaluation of the General Public’s Perception of the Commercialization of Space

In the past decade, commercial companies have rapidly expanded their presence in the space industry. Notably, SpaceX comprises the entirety of NASA's crewed launch capacity as of 2020 and approximately splits uncrewed launches with the United Launch Alliance. As interests in space quickly grow, the power of these companies has the potential to grow troublesome. The purpose of this study was to evaluate the public opinion of these private space companies, as the implications of their operations could change life for the human race significantly. Changes such as satellite constellations, space tourism, asteroid mining, and colonies on the Moon and Mars will alter life for our species; future operations, legislation, and regulation must be created with the views of all humanity considered. Previous research has concluded that Americans generally support space exploration, but this work lacks specificity in increasingly relevant fields, such as satellite constellations. This study reinforced previous findings while drawing conclusions on new topics, utilizing a survey where participants were asked questions evaluating six Topics of Inquiry. Using a combination of descriptive and inferential analysis, the researcher found that most people support space exploration and would like to see more funding and resources put towards it. Broadly, most participants have a positive perception of these private space companies and believe in a need for moderate government oversight. Large satellite constellations were widely supported, suggesting an overall positive attitude towards the utilization of space, given that participants were informed of particular risks imposed by constellations such as SpaceX's Starlink.

Analytical simulations of the effect of satellite constellations on optical and near-infrared observations

Context. The number of satellites in low-Earth orbit is increasing rapidly and many tens of thousands of satellites are expected to be launched in the coming years. There is a strong concern among the astronomical community about the contamination of optical and near-infrared observations by satellite trails, what has led to several initial investigations of the impact of large satellite constellations. Aims. We expand the impact analysis of such constellations on ground-based optical and near-infrared astronomical observations in a more rigorous and quantitative way, using updated constellation information and considering imagers and spectrographs and their very different characteristics. Methods. We introduce an analytical method that allows us to rapidly and accurately evaluate the effect of a very large number of satellites, accounting for their magnitudes and the effect of trailing of the satellite image during the exposure. We use this to evaluate the impact on a series of representative instruments, including imagers (traditional narrow field instruments, wide-field survey cameras, and astro-photographic cameras) and spectrographs (long-slit and fibre-fed), taking their limiting magnitude into account. Results. Confirming earlier findings, the effect of satellite trails is more damaging for high-altitude satellites, on wide-field instruments, or essentially during the first and last hours of the night. Thanks to their brighter limiting magnitudes, low- and mid-resolution spectrographs will be less affected, but the contamination will be at about the same level as that of the science signal, introducing additional challenges. High-resolution spectrographs will essentially be immune. We propose a series of mitigating measures, including one that uses the described simulation method to optimise the scheduling of the observations. We conclude that no single mitigation measure will solve the problem of satellite trails for all instruments and all science cases.

Management of Celestial Systems under Spatial Grasp Model

Many governmental agencies and private companies of different countries are now rushing into space around Earth in hope to provide smart communication, industrial, security, and defense solutions. This often involves massive launches of cheap small satellites which are also contributing to the growth of space debris. The current paper discusses how the developed high-level system philosophy and model can effectively organize distributed space-based systems on different stages of their development and growth. The briefed Spatial Grasp Technology, based on parallel pattern-matching of distributed environments with high-level recursive mobile code, can effectively provide any networking protocols and important applications of large satellite constellations, especially those on Low Earth Orbits. The paper contains examples of technology-based solutions for establishing basic communications between satellites, starting from their initial, often chaotic, launches and distributing and collecting data in the growing constellations with even unstable and rapidly changing connections between satellites. It describes how to organize and register networking topologies in case of predictable distances between satellites, and how the fixed networking structures can help in solving complex problems. The latter including those related to the new Space Development Agency multiple-satellite defense-oriented architecture and allowing for effective integration of its continuous earth custody observation and cooperative missile tracking and elimination layers, based on self-spreading mobile intelligence. Earlier versions of the technology, described in many papers, six books including, were prototyped and used in different countries, with the current one quickly implementable too, even in university-based environments.

A tethered plate satellite as a sweeper of small space debris

Removing space debris is an urgent task to ensure sustainable space activity. Towards this end, we propose herein a tethered plate satellite that can remove many items of small space debris successively by collisions alone without capturing them or performing major orbital manoeuvres. The strategy involves a tethered plate that moves more slowly than the space debris at the same altitude so that the speed difference in the collision causes re-entry of the space debris. Numerical verification using an on-orbit object database indicates that, for the requisite number of collisions, this strategy would require a reasonable amount of orbital manoeuvres. The results indicate that six such spacecraft operating for one decade would suffice to reduce the amount of removable space debris in a certain altitude range by 96.10%. Based on these results, a mission concept is proposed in which debris-removal systems would remove almost all the removable space debris in a given altitude range, thereby allowing for the operation of large satellite constellations.

Risk-aware sensor scheduling and tracking of large constellations

Commercial proposals for large constellations of satellites present a major problem in the field of Space Situational Awareness (SSA). Space traffic management systems must produce accurate and timely predictions of potential collisions for operators to perform evasive maneuvers. This requires precise orbit determination solutions, but limitations on sensor resources can impair tracker performance. This work presents an integrated tasking and tracking system that can autonomously task a network of ground sensors to track large constellations with the goal of identifying hazardous conjunctions. The sensor scheduling approach combines information gain maximization with predicted probability of collision to produce a single reward function for tasking. The labeled multi-Bernoulli filter, a multi-target filter capable of resolving data ambiguity, processes the data and the resulting catalog estimate drives another round of scheduling. A tracking simulation involving 4,545 satellites in low-Earth orbit and a network of twelve ground-based sensors demonstrates how this scheduling method can focus on high-risk targets while maintaining custody of the entire constellation. A conjunction assessment is performed using the estimated catalog at the end of the tracking phase, and the accuracy of the analysis is used to evaluate the scheduling method’s efficacy.

The UN COPUOS Guidelines for the Long-term Sustainability of Outer Space Activities

The United Nations has addressed the concept of sustainable development on Earth in a number of global summits and fora for the past 40 years. Extending the concept of sustainability to outer space is a much more recent development, arising from the realization that the Earth's orbital space environment constitutes a finite resource that is being used by an increasing number of space actors that include States, commercial actors and other non-governmental entities. The proliferation of space debris, the increasing complexity of space operations, the emergence of large constellations of satellites, and the increased risks of collisions and interference with the operation of satellites raise concerns about the safety of space operations and the long-term sustainability (LTS) of space activities. Addressing these developments and risks requires international cooperation. The leading international forum to discuss questions of international cooperation in space activities is the United Nations Committee on the Peaceful Uses of Outer Space (UN COPUOS). In 2010, the Committee began its consideration of this topic with a view to producing a set of internationally agreed guidelines that States could follow to ensure that their space activities would not cause harm to the space environment or the safety of space operations. Following a broad international process conducted under the aegis of COPUOS, in June 2019 the Committee adopted a set of 21 voluntary, non-binding UN COPUOS Guidelines for the Long-term Sustainability of Outer Space Activities (‘COPUOS LTS Guidelines’). This paper provides a brief overview of the development of these guidelines, summarizes the salient features of the guidelines and discusses the implementation of these guidelines from the perspectives of government, industry and civil society. In adopting this set of LTS Guidelines, COPUOS acknowledged that more work needs to be done on this topic and it agreed to establish a follow-up LTS working group with a five-year mandate to continue the work. The main themes and challenges facing the next phase of the LTS discussions in COPUOS are also discussed.