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.
Beth Probert, Ruaridh Clark, Erik Blasch, M MacDonald
The proliferation of satellite constellations in Low Earth Orbit necessitates a shift away from centralised control, and towards autonomous, decentralised systems for Space Situational Awareness. Crucially, this transition requires establishing trust between satellites in a zero-trust environment, independent of a central authority. Distributed Ledger Technologies offer a resilient foundation for decentralised operations. However, in the domain of space systems, a unified framework that securely integrates consensus-based validation with cooperative Orbital Determination remains unexplored. To address this gap, the Autonomous Cooperative Consensus Orbit Determination framework is introduced, designed for on-board, peer-to-peer validation of orbital data. A novel consensus mechanism, Proof of Inter-Satellite Evaluation, is at the framework's core, and is tailored for resource-constrained systems. Measurement quality is evaluated by using a two-sided chi-squared test on the Normalised Innovation Squared, which is derived from the statistical output of an Extended Kalman Filter. This test is employed to provide a defence against both sensor faults and sophisticated spoofing attacks by penalising data that is either excessively noisy or unnaturally perfect. This statistical evaluation is weighted by a dynamic, long-term reputation score that rewards consistent, high-quality data contributions and penalises untrustworthy behaviour. Simulation results demonstrate that the framework effectively secures the network's distributed ledger by confirming valid transactions and robustly rejecting those from faulty or malicious nodes. The resulting architecture is presented as a viable solution for enabling resilient and autonomous cooperative space systems.
This paper introduces SAT-IOTA, a lightweight and AI-driven cybersecurity framework designed for blockchain-powered satellite infrastructures. Unlike traditional detection approaches, SAT-IOTA employs predictive anomaly analytics combined with a Sliding Window (SW) machine learning mechanism to proactively identify and mitigate security threats in space-air-ground integrated networks (SAGINs). The proposed framework integrates IOTA distributed ledger technology (DLT) for secure, decentralized telemetry data management, tokenized satellite components, and resilience against cyber-physical attacks. Through a custom-built testbed with Hornet nodes, we evaluate the frameworks performance under denial-of-service (DoS) scenarios, achieving 97% prediction accuracy and an F-measure of 80%. The results confirm that SAT-IOTA enhances space system security by combining blockchain-driven trust with AI-based anomaly prediction, offering a scalable and resource-efficient solution for next-generation satellite communications.
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 work develops a novel two-phase control framework that enables a swarm of compact spacecraft (agents), such as CubeSats and Nanosats, to autonomously capture tumbling and uncooperative targets. By leveraging decentralized, bio-inspired swarm behavior control and distributed coordination strategies, the proposed system enables fully interchangeable agents to achieve robust, leaderless self-organization. During the capture, flocking behavior guides agents towards the target, while anti-flocking behavior enforces uniform dispersion of agents around it to provide full surface coverage and effective encapsulation prior to capture. A consensus-based protocol synchronizes the capture action among agents by allowing all agents to agree on a common action time. In this process, each agent autonomously identifies available capture points and participates in an auction-based allocation algorithm to collectively allocate optimal capture positions among agents. Simulation results validate the effectiveness of the proposed framework in autonomously capturing targets of various shapes, sizes and motion patterns, and demonstrate scalability across different swarm sizes. Overall, the proposed approach shows significant potential for coordinated, efficient, and robust swarm-based capture of uncooperative targets in space, offering benefits in scalability, adaptability, robustness, and cost-effectiveness.
Modern space vehicles capture a wealth of sensor data that is in high-demand by a wide range of commercial and nation-state beneficiaries. This data can be used to monitor our planet, monitor space traffic and manage collision avoidance, among other use cases. While there is ongoing investment into cross-linking satellite constellations and building an ‘on-orbit internet’, it remains unclear how the integral requesting and delivery of this data will be facilitated. We propose a distributed marketplace for space domain awareness that engages smart contracts and a distributed ledger to manage the engagement of satellites across an untrusted ecosystem. Furthermore, this work implements a simulated on-orbit marketplace consisting of independent nodes able to efficiently and securely exchange data and services under a series of representative scenarios. The marketplace software payload was designed to conform to the power and compute constraints of a modern space vehicle while implementing secure smart contracting and format-preserving validation techniques, demonstrating the practical viability of the on-orbit marketplace as a concept.
Blockchain technology is a collective, distributed, and unalterable ledger (i.e. block of data), which is linked securely. The blocks are connected and form a chain in which each block contains information about its previous block. In this chapter, the influence of artificial intelligence on blockchain technology is discussed elaborately in different areas like healthcare, agriculture, IoT, and so on. The various optimization algorithms used to enhance performance are also discussed and recorded. The open research issues and challenges, along with the future directions to be concentrated on in the blockchain network, are deeply analyzed and presented.
Operators of low-Earth-orbit (LEO) non-geostationary satellite networks, also known as mega-constellations, are required by current regulations to share all available satellite spectrum. This paper proposes a consensus mechanism to facilitate spectrum sharing with accountability by multiple operators, a subset of which may even be adversarial. A distributed ledger is used to securely record and track the state of consensus on spectrum usage, including interference incidents and the corresponding responsible parties. A key challenge is that operators generally do not have initial agreement due to noise in their analog measurements. To address this, two categories of spectrum-sharing solutions are studied in detail. The first category employs an exact Byzantine fault tolerant (BFT) agreement model; the second category utilizes an approximate BFT agreement model. Practical considerations were taken into account regarding the BFT agreements, substantiated by numerical findings on the feasibility of the proposed solutions within the context of non-geostationary orbit satellite networks (NGSO).
Ramakrishnan Raman, Kodipaka Rajeshwar Rao, S. John Justin Thangaraj, S. Praveen Kumar · 6 authors
The fusion of terrestrial radio and satellite communications will result in a world completely connected with sixth-generation (6G) networks. But there is a limitation of power and space available on satellites due to low computing power, limited storage space, and insufficient security occur. It is critical to utilize information storage and access protection in satellite networks efficiently to prevent data tampering and alteration. Satellite communications play an increasing role in global communication networks, creating security problems. Based on the Quantum Key Distribution (QKD) protocol, this proposal suggests a security and authentication method for satellite communication networks. A wireless and heterogeneous network architecture utilizes both open-source and commercial hardware to enable communication. The three stages of registration, authentication, and cancellation facilitate communication. As data is transmitted to satellites from ground stations, all measurements of significance are then logged on a decentralized blockchain. All certifications generated by rogue nodes are subsequently cleared from the blockchain by ground stations. It has been suggested that the technology be used with upcoming 6G networks, as well as the Internet of Things, self-driving cars, and other rapidly expanding applications.
Blockchain has found many applications, apart from Bitcoin, in different fields and it has the potential to be very useful in the satellite communications and space industries. Decentralized and secure protocols for processing and manipulating space transactions of satellite swarms in the form of Space Digital Tokens (SDT) can be built using blockchain technology. Tokenizing space transactions using SDTs will open the door to different new blockchain-based solutions for the advancement of constellation-based satellite communications in the space industry. Developing blockchain solutions using smart contracts could be used in securely authenticating various P2P satellite communications and transactions within/between satellite swarms. To manage and secure these transactions, using the proposed SDT concept, this paper suggested a blockchain-based protocol called Proof of Space Transactions (PoST). This protocol was adopted to manage and authenticate the transactions of satellite constellations in a P2P connection. The PoST protocol was prototyped using the Ethereum blockchain and experimented with to evaluate its performance using four metrics: read latency, read throughput, transaction latency, and transaction throughput. The simulation results clarified the efficiency of the proposed PoST protocol in processing and verifying satellite transactions in a short time according to read and transaction latency results. Moreover, the security results showed that the proposed PoST protocol is secure and efficient in verifying satellite transactions according to true positive rate (TPR), true negative rate (TNR), and accuracy metrics. These findings may shape a real attempt to develop a new generation of Blockchain-based satellite constellation systems.
Aboul Ella Hassanien, Mohamed Torky, Essam Goda, Václav Snåšel · 5 authors
<title>Abstract</title> Blockchain technology can play a vital role in the space industry and satellite communication. This disruptive technology can build decentralized and secure protocols for processing and manipulating space transactions in the form of space digital tokens (SDTs). Tokenizing space transactions in the form of SDTs will enable various blockchain-based applications in the space industry. Moreover, blockchain protocols based on smart contracts can be utilized to authenticate many space transactions and P2P communications in a transparent, verifiable, and secure manner. This paper proposes a new blockchain-based solution for managing and securing satellite transactions using a novel concept called SDT. SDT is then used to develop a new blockchain protocol called proof of space transactions (PoST), which is then used in proposing a new blockchain-based protocol for authenticating satellite transactions. The proposed PoST protocol is implemented and simulated using the Ethereum blockchain. Five metrics are used to evaluate the protocol's performance: Ethereum GAZ, read latency, transaction latency, read throughput, and transaction throughput. The performance evaluation results proved the efficiency and reliability of PoST in managing and securing satellite transactions.
David Hyland-Wood, Peter Robinson, Roberto Saltini, Sandra Johnson · 5 authors
Integration of space-based communications infrastructure within 5G networks presents specific challenges for spacecraft, namely a necessary rationalization of currently patchy communications security and the assurance of identity when conducting high-level spacecraft tasking and control operations. This chapter presents approaches to addressing both issues via the deployment of an enterprise Ethereum blockchain modified with a consensus algorithm appropriate for access by spacecraft. We discuss the applicability of enterprise Ethereum blockchains to the problem of spacecraft communication security, analyze the properties of blockchain consensus algorithms suitable for use with spacecraft, and suggest information architectures to allow secure spacecraft integration into 5G networks.
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
Mason J. Molesky, Elizabeth A. Cameron, Jerry Jones, Michael Esposito · 6 authors
This paper proposes a solution to facilitate on-orbit satellite communication data integrity and security by utilizing blockchain technology. A proliferating demand has created a growing reliance on satellites for communications, GPS, imagery, and other uses. The decreased cost of entry into the space industry has increased the number of entrants and also the number of satellites and the amount of space debris. These orbital debris pose a serious threat to spacecraft. Therefore, tracking these objects is crucial. Blockchain technology offers a unique solution to this problem by utilizing functions, processes, and information already incorporated into satellites while maintaining a maximum of forty-eight hours of data. The use of blockchain provides a high level of trusted positional data that can be used to predict and avoid collisions which will save billions of dollars and valuable time. This paper provides a technological design, rational, and risk analysis of this proposal.
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.
In recent years, formation flying has been recognized as an enabling technology for a variety of mission concepts in both the scientific and defense arenas. Examples of developing missions at NASA include magnetospheric multiscale (MMS), solar imaging radio array (SIRA), and terrestrial planet finder (TPF). For each of these missions, a multiple satellite approach is required in order to accomplish the large-scale geometries imposed by the science objectives. In addition, the paradigm shift of using a multiple satellite cluster rather than a large, monolithic spacecraft has also been motivated by the expected benefits of increased robustness, greater flexibility, and reduced cost. However, the operational costs of monitoring and commanding a fleet of close-orbiting satellites is likely to be unreasonable unless the onboard software is sufficiently autonomous, robust, and scalable to large clusters. This paper presents the prototype of a system that addresses these objectives-a decentralized guidance and control system that is distributed across spacecraft using a multiple team framework. The objective is to divide large clusters into teams of "manageable" size, so that the communication and computation demands driven by N decentralized units are related to the number of satellites in a team rather than the entire cluster. The system is designed to provide a high level of autonomy, to support clusters with large numbers of satellites, to enable the number of spacecraft in the cluster to change post-launch, and to provide for on-orbit software modification. The distributed guidance and control system will be implemented in an object-oriented style using a messaging architecture for networking and threaded applications (MANTA). In this architecture, tasks may be remotely added, removed, or replaced post launch to increase mission flexibility and robustness. This built-in adaptability will allow software modifications to be made on-orbit in a robust manner. The prototype system, which is implemented in Matlab, emulates the object-oriented and message-passing features of the MANTA software. In this paper, the multiple team organization of the cluster is described, and the modular software architecture is presented. The relative dynamics in eccentric reference orbits is reviewed, and families of periodic, relative trajectories are identified, expressed as sets of static geometric parameters. The guidance law design is presented, and an example reconfiguration scenario is used to illustrate the distributed process of assigning geometric goals to the cluster. Next, a decentralized maneuver planning approach is presented that utilizes linear-programming methods to enact reconfiguration and coarse formation keeping maneuvers. Finally, a method for performing online collision avoidance is discussed, and an example is provided to gauge its performance.
In recent years, formation flying has become an enabling technology for several mission concepts at both NASA and the Department of Defense. In most cases, a multiple-satellite approach is required in order to accomplish the large-scale geometries imposed by the sensing objectives. In general, the paradigm shift of using a multiple-satellite cluster rather than a large, monolithic spacecraft has also been fueled by the objectives of increased robustness, greater flexibility, and reduced cost. However, the operational costs of monitoring and commanding a large fleet of close-orbiting satellites is likely to be unreasonable unless the onboard software is sufficiently autonomous, robust, and reconfigurable. This paper presents the prototype of a system that addresses these objectives – a decentralized guidance and control system that is distributed across spacecraft using a multipleteam framework. The system is designed to provide a high-level of autonomy, to support clusters with large numbers of satellites, to enable the number of spacecraft in the cluster to change post-launch, and to provide for on-orbit software modification. The real-time distributed system will be implemented in C++ using the MANTA environment (Messaging Architecture for Networking and Threaded Applications). In this architecture, tasks may be remotely added, removed or replaced post-launch to increase mission flexibility and robustness. This built-in adaptability will allow significant or simple software modifications to be made on-orbit in a robust manner. The prototype system, which is implemented in Matlab, emulates the task-based and message-passing features of the MANTA software. In this paper, the multiple-team organization of the cluster is described, and the relative dynamics in circular and eccentric reference orbits is reviewed. Families of periodic, relative trajectories are identified and represented with static geometric parameters. An analytic solution for impulsive maneuvering is used for whole orbit-period control in circular orbits, and linear programming techniques are used to find time-weighted, minimum-fuel control solutions. Finally, the decentralized guidance law design is presented, with a comparison between the optimal and a sub-optimal assignment algorithm.
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.>