E. A. Titenko, E. A. Schilenkov, S. N. Frolov, V. P. Soglaev · 6 authors
The purpose of the research is to find ways to increase the efficiency of the nanosatellite constellation (network) in the conditions of replenishment and retirement of spacecraft during operation in orbit based on a self-organizing mesh network, in which routing is carried out dynamically based on the connectivity of network elements. Methods are based on decision-making techniques, systems analysis, and decentralized control principles, enabling a nanosatellite network to independently reconfigure itself to meet changing operating conditions and task requirements. Using the properties of self-organization and adaptive control methods (distribution and responsiveness to change), the nanosatellite constellation maintains a configuration of satellites capable of exchanging data and service information. A two-level network reconfiguration method has been developed, enabling proactive changes to the composition of nanosatellites based on historical assessments of the quality and strength of transmitted signals. Algorithms for route list generation and route analysis have been developed, which can be executed autonomously on each nanosatellite in the constellation. Results . The developed reconfiguration method enables asynchronous addition and deletion of satellites from the network based on received or discovered information about their status and connections between satellites. It is shown that the decentralized approach has linear time complexity for the most critical algorithms for updating and constructing network routes. Conclusion . The developed reconfiguration method and algorithms for managing a nanosatellite constellation form the basis for developing network software that allows each satellite to autonomously make decisions about modifying its status and route list.
Thomas Sandholm, Sayandev Mukherjee, John Feland, Bernardo A. Huberman
Frequent handovers between satellites, and the lack of a central (on-board) state database, challenge the delivery of communication services from Low-Earth-Orbit (LEO) satellite constellations. Traditional blockchain protocols to maintain distributed state are unsuitable for on-board deployment as they do not take the moving dynamics and inter-satellite links of constellation orbits into account. In this paper, we propose LeoDist, a distributed ledger for LEO constellations. We introduce novel concepts, such as leader-handover, neighbor synchronization, and service area gossiping to meet the challenges of this dynamic environment. To the best of our knowledge, LeoDist is the first distributed ledger on board LEO satellites to support the core routing, state synchronization and consensus blockchain protocols while accounting for orbital dynamics and coverage area. We show using a lab testbed with the NASA core Flight System (cFS) that LeoDist is able to route, gossip, reach consensus, synchronize state and process transactions efficiently, offering 3-4 orders of magnitude faster leader failover and handover compared to Raft, up to 171 distributed transactions per second, and broadcasting across a constellation of 95 satellites in less than 50 ms on standard UDP/IP links.
The emerging Web3 has great potential to provide worldwide decentralized services powered by global-range data-driven networks in the future. To ensure the security of Web3 services among diverse user entities, a decentralized identity (DID) system is essential. Especially, a user's access request to Web3 services can be treated as a DID transaction within the blockchain, executed through a consensus mechanism. However, a critical implementation issue arises in the current Web3, i.e., how to deploy network nodes to serve users on a global scale. To address this issue, emerging Low Earth Orbit (LEO) satellite communication systems, such as Starlink, offer a promising solution. With their global coverage and high reliability, these communication satellites can complement terrestrial networks as Web3 deployment infrastructures. In this case, this paper develops three hybrid satellite-ground modes to deploy the blockchain-enabled DID system for Web3 users. Three modes integrate ground nodes and satellites to provide flexible and continuous DID services for worldwide users. Meanwhile, to evaluate the effectiveness of the present hybrid deployment modes, we analyze the complete DID consensus performance of blockchain on three hybrid satellite-ground modes. Moreover, we conduct numerical and simulation experiments to verify the effectiveness of three hybrid satellite-ground modes. The impacts of various system parameters are thoroughly analyzed, providing valuable insights for implementing the worldwide Web3 DID system in real-world network environments.
Paul-Cristian VASILE, Alexandru Georgescu, Daniela Munteanu
Space systems have become key components in a wide variety of critical infrastructures and some would say that they are critical infrastructures in themselves.They provide data gathering, communications, navigation, positioning and timing services that enable an important variety of critical services affecting billions of users.Increasingly, distributed ledger technology has begun to be integrated into the functioning of space systems, both in support of their roles and also to enable new roles.This article traces the main applications, discusses the issues inherent in blockchain use for space systems and underscores the potential that the technology provides across the space sector.
This paper aims to discuss the function of software in satellite system and the reliability analysis of satellite software. Firstly, the overview of satellite system and the importance of software in it are introduced. Then, the concept of reliability, reliability evaluation method and factors affecting reliability of satellite software are expounded in detail. Then, the strategy to improve the reliability of satellite software is discussed. Finally, the article looks forward to the future development trend of satellite software reliability, including the application of artificial intelligence, machine learning, and distributed ledger technology. These new technologies are expected to further improve the reliability of satellite pieces and provide a solid guarantee for the safety of satellite communication.
This paper analyzes the Execution Tickets proposal on Ethereum Research, unveiling its potential to revolutionize the Ethereum blockchain's economic model. At the core of this proposal lies a novel ticketing mechanism poised to redefine how the Ethereum protocol distributes the value associated with proposing execution payloads. This innovative approach enables the Ethereum protocol to directly broker Maximal Extractable Value (MEV), traditionally an external revenue stream for validators. The implementation of Execution Tickets goes beyond optimizing validator compensation; it also introduces a new Ethereum native asset with a market capitalization expected to correlate closely with the present value of all value associated with future block production. The analysis demonstrates that the Execution Ticket system can facilitate a more equitable distribution of value within the Ethereum ecosystem, and pave the way for a more secure and economically robust blockchain network.
With the rising demands from customers and users and the development of ever advanced technologies, many space missions nowadays require more than one satellite to fulfill their mission objectives. Although replacing single satellite systems (SSSs) by multiple satellite systems (MSSs) offers advantages, such as enhanced spatial and temporal coverage as well as high robustness and multifunctional purposes, it also introduces new challenges. There is no doubt that as the number of satellites in a mission grows, the complexity and operation cost of controlling and coordinating these satellites only by human (or ground based) operators will increase dramatically. In addition, for some deep space missions or complex operational tasks, due to the long signal transmission time between the spacecraft and ground-based antennas or short communication windows, there will not be enough time or resources for operators to sufficiently and efficiently control all of the required onboard functions from mission control centers. Therefore, to enhance the efficiency of operating an MSS, and to reduce the cost of human resources and ground infrastructure, an onboard autonomous system (OAS) for MSS is a promising solution. For specific missions, the use of an OAS may even be a mission enabler. One important function of an OAS is to provide planning and re-planning services based on different mission requirements. The objective of this research is to develop and characterize onboard autonomous mission planning and re-planning approaches for MSSs. Traditional planning approaches have been reviewed and proven to be inappropriate and inefficient for complex planning problems in the harsh space environment when severe system constraints are enforced and a large number of vehicles constitutes the MSS. % Artificial intelligence (AI) approaches, in contrast, are more suitable for complex problems due to their broad adaptability and their ability to cope with large-scale variables. To overcome these deficiencies, engineers and researchers have started to develop OAS with the help of Artificial Intelligence (AI) techniques to allow for more complex space missions. Based on the relevance of this problem, the following research questions (RQs) have been formulated and will be answered in this thesis. % and a review of the state-of-the-art scientific literature \\textbf{RQ1: What are the strengths of using AI in space missions? How to use a centralized AI algorithm in a multi-satellite system to decompose mission objectives and perform mission planning for the entire system?} \\textbf{RQ2: How to define emergency situations which may occur during mission operations? How to use AI algorithms to handle mission re-planning and re-scheduling problems?} \\textbf{RQ3: How to design cooperation and negotiation approaches for an MSS to reach an agreement? How to improve AI algorithms for distributed onboard mission planning problems?} To define potential scenarios, a reference mission is introduced in this thesis, called \\textit{Discovering the Sky at the Longest Wavelength (DSL)}. The mission is assumed to comprise one Mother Satellite (MS) and eight Daughter Satellites (DSs) in a lunar orbit. Its scientific objective is to observe the universe in the hitherto-unexplored very low frequency (below 30 MHz) electromagnetic spectrum. The DSs collect scientific data only in those parts of the orbit which is shielded from radio frequencies emitted by the Earth. These DSs can only transmit collected data to the MS when they are outside of this shielded orbit sections, to prevent interferences caused by communication. % The DSs collect scientific data and transmit those to the MS with the constraints what scientific data collection may only occur in the part of the orbit. This part of the orbit is shielded from radio frequencies emitted by the Earth and no other DSs are transmitting data to the MS. This renders mission operations of DSL very complex. The existing body of knowledge on mission planning problems for multi-satellite systems is reviewed. It comprises three categories: classical approaches, heuristic approaches, and advanced techniques (e.g., team negotiation mechanisms, evaluation algorithms). Targeting the complexity of foreseeable DSL planning problems, nine representative optimization algorithms are applied to fourteen test functions. The results indicate that Evolutionary Algorithms (EAs) have a broader adaptability than classical approaches. They are also more efficient than other heuristic approaches. Therefore, EAs family is selected as suitable candidate for the reference MSS. % fourteen test functions are used to test nine representative algorithms to provide a preliminary selection for the reference MSS.=-098 % The fourteen test functions we used contain different types of objective functions and constraints to guarantee the diversity of the preliminary selection. % The goal of this selection is to identify a suitable approach for an MSS to handle different types of optimization problems. Eight constrained and six unconstrained test functions are employed as benchmarks. The operations concept of the DSL mission foresees that the initial mission planning is performed by the MS, while the eight DSs are preliminary executing data collection and transmission tasks. % Considering the scientific design of the DSL mission, the initial mission planning procedures are all performed by the Mother Satellite (MS), while the rest eight Daughter Satellites (DSs) are just participating satellites which response for gathering and transmitting data. During this phase, the MSS implements a centralized architecture and the MS conducts a centralized planning approach. By comparing basic Genetic Algorithm (GA) with several state-of-the-art improved GAs, its weaknesses are revealed. In this thesis, to overcome early and slow convergence problems, the need to develop a new mutation strategy for GA is motivated. % By revealing the weaknesses of the basic Genetic Algorithm (GA), along with a comparison with several other improved GAs, The proposed novel mutation strategy is called Hybrid Dynamic Mutation (HDM), which contains a standard mutation operator and an escape mutation operator. While the standard mutation operator uses a small mutation rate for approaching the global optimum, the escape mutation operator uses a larger mutation rate to allow an escape from local optima. The simulation results indicate that the proposed HDM can improve the basic GA (which turns into the HDMGA) leading to a superior performance on correctness and effectiveness as compared to alternative GAs. Based on these findings, AI related methods are considered a promising category as compared to classical methods due to their flexibility and effectiveness to support the onboard planning for an MSS. In addition, the proposed HDMGA also provides a satisfying result for the considered initial mission planning problems. Internal or external causes, e.g. an actuator failure or the challenging space environment, can lead to a satellite malfunction during mission operations. This thesis considers the two most important behaviors of the DSL mission, observation and communication, and proposes potential emergency scenarios to handle possible system failures on DSs. Two re-planning methods, one called the Cyclically Re-planning Method (CRM), the other one the Near Real-time Re-planning Method (NRRM), are established and compared. The CRM performs re-planning at the beginning of each orbit and only re-plans for one orbit. The NRRM performs re-planning in a near real-time setting when the emergency occurs. Its re-planning covers for the rest of the mission. Three simulation study cases are formulated based on assumed emergency scenarios. % Each case is designed to represent a different level of failures on multiple DSs. The proposed two methods are compared on three aspects: the total number of data observed from all DSs within a certain time frame, the total number of data the MS received from all DSs within a certain time frame, and the average computation time needed for re-planning. The results indicate that: (1) The NRRM allows to observe and transmit more data than the CRM within a specific operational lifetime. (2) The NRRM requires more computational time than the CRM for emergency situations, while it requires less time than the CRM for nominal situations. % For emergency situations, the CRM can therefore provide re-planning sequences faster than the NRRM, while for nominal operations, the NRRM is much faster than the CRM. This research also covers a much more severe scenario, namely that the MS becomes fully non-functional in an emergency situation. This would render the MS unable to provide mission planning and re-planning services for the MSS. Without its main controller on the MS, all DSs now need to cooperate to jointly solve the mission planning problems. Due to the loss of the MS, both distributed and decentralized architectures, which the MSS could then use are introduced. In a distributed architecture, each DS is connected with all other DSs directly or through DS which acts as retranslator. In a decentralized architecture, each DS can only communicate with its neighbors. Considering that the mission allocation problems in different organizational architectures are similar to information games in game theory, a game-theoretical model of the Multi-Satellite Mission Allocation (MSMA) problem is formulated. % Three new negotiation mechanisms are introduced, compared and analyzed in theoretical terms. The Utility-based Regret Play (URP) negotiation mechanism is proposed for an MSMA problem using a distributed architecture. It inherits the ability to evaluate individual utility at each negotiation step from the Utility-based Fictitious Play, and the ability to regret the current choice and for not proposing particular choices in the past negotiation steps from the Regret Matching
Rohit Mital, Jack de La Beaujardiere, Rohan Mital, Marge Cole · 5 authors
With the thrust towards multi-sensor satellite architectures for earth and space exploration, such as constellations and swarms, new technologies are required to enable the transition to this future capability. One of the areas of interest is establishing secure, efficient and prioritized data and command communication pathways among ground and space-based sources for such systems. This paper presents early research results on the potential role, capabilities and value of blockchain usage within constellation and swarm satellite architectures. It demonstrates the use of blockchain's smart contract and distributed ledger capabilities for secure and prioritized multi-sensor satellite collaborative data exchanges, as well as the logging and tracking of command and control events. Adapting and utilizing this emerging technology will aid in addressing technology gaps expected from future constellation flight architectures, such as managing collective computational operations (correlation), dynamic and autonomous observation planning, time-critical events, and provenance tied to ground and space-based autonomous operations and control recordkeeping. In this scenario blockchain is applied in encrypted command transmittal to multiple, yet specific, entities enabling acknowledgement transmittals, performance scalability, and automatic event-based triggering.
The avionics system of Hermes is called spacionics. Spacionics is defined as a set of onboard items which treat, exchange, or store information in electrical form, and provide and distribute electrical power. The main drivers for spacionics design are mass and safety. The spacionics organization depends on the priorities assigned to different criteria. These priorities can lead to either a centralized or a decentralized data processing architecture. It has been necessary to centralize the widest part of the data processing, which is split into two pools of computers, one dedicated to guidance, navigation and control and one dedicated to mission and vehicle management. The first one, made of 4 computers and 4 data busses, is able to perform its functions autonomously and automatically even after 2 failures. The second one, including only 2 strings, requires the implementation of safety protection activated, if necessary, either by the crew or by the control.>