Federated Satellite Systems Research Articles

FSSCat: The Federated Satellite Systems 3Cat Mission: Demonstrating the capabilities of CubeSats to monitor essential climate variables of the water cycle [Instruments and Missions

The Federated Satellite Systems/ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Cat-5 (FSSCat) mission was the winner of the European Space Agency (ESA) Sentinel Small Satellite (S <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ) Challenge and overall winner of the 2017 Copernicus Masters competition. It consisted of two six-unit CubeSats. The Earth observation payloads were 1) the Flexible Microwave Payload 2 (FMPL-2) onboard <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Cat-5/A, an L-band microwave radiometer and GNSS reflectometer (GNSS-R) implemented using a software-defined radio (SDR), and 2) the HyperScout-2 onboard <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Cat-5/B, a hyperspectral camera, with the first experiment using artificial intelligence to discard cloudy images. FSSCat was launched on 3 September 2020 and injected into a 535-km synchronous orbit. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Cat-5/A was operated for three months until the payload was probably damaged by a solar flare and coronal mass ejection. During this time, all scientific requirements were met, including the generation of coarse-resolution and downscaled soil moisture (SM) maps, sea ice extent (SIE) maps, concentration and thickness maps, and even wind speed (WS) and sea surface salinity (SSS) maps, which were not originally foreseen. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Cat-5/B was operated a few more months until the number of images acquired met the requirements. This article briefly describes the FSSCat mission and the FMPL-2 payload and summarizes the main scientific results.

Federated Space Systems’ Trade-Space Exploration for Strategic Robustness

Motivated by the growth of the commercial space economy and renewed focus on the disaggregation of military space systems, this work develops a method for conceptual design of federated satellite systems as a collaborative system of systems (SOS). Objectives seek to improve the likelihood of successful SOS formation and pursue constituent system utility robustness. The proposed metaheuristic optimization trade-space exploration method accounts for technical and economic design variables and multi-decision-maker strategy dynamics. Constituent system designs are ranked on their simulated net present value. A game-theoretic measure of risk dominance is used in concert with the net present value to assess the robustness and utility of candidate SOS designs. The method is validated with a notional application case that assesses potential collaboration between Earth-observing and telecommunications systems. The proposed methodology reduces the threshold probability of partner collaboration for which SOS participation is economically rational by up to 18% for the most efficient designs as compared to a typical conceptual design method, thereby increasing the likelihood of successful SOS formation. The results highlight the importance of accounting for strategy dynamics when designing systems for collaboration.

Towards Federated Satellite Systems and Internet of Satellites: The Federation Deployment Control Protocol

Presently, the Earth Observation community is demanding applications that provide low latency and high downlink capabilities. An increase in downlink contacts becomes essential to meet these new requirements. The Federated Satellite Systems concept addresses this demand by promoting satellite collaborations to share unused downlink opportunities. These collaborations are established opportunistically and temporarily, posing multiple technology challenges to be implemented in-orbit. This work contributes to the definition of the Federation Deployment Control Protocol which formalizes a mechanism to fairly establish and manage these collaborations by employing a negotiation process between the satellites. Moreover, this manuscript presents the results of a validation campaign of this protocol with three stratospheric balloons. In summary, more than 27 federations with 63.0% of throughput were established during the field campaign. Some of these federations were used to download data to the ground, and others were established to balance data storage between balloons. These federations allowed also the extension of the coverage of a ground station with a federation that relayed data through a balloon, and the achievement of a hybrid scenario with one balloon forwarding data from a ground device. The results demonstrate that the proposed protocol is functional and ready to be embedded in a CubeSat mission.

A Novel Dissemination Protocol to Deploy Opportunistic Services in Federated Satellite Systems

Earth Observation applications are demanding higher spatial resolution and shorter revisit times than existing systems, which can be met by ad-hoc constellations of Federated Satellite Systems. These systems are distributed satellite architectures which rely on the collaboration between satellites that share unused resources, such as memory storage, computing capabilities, or downlink opportunities. In the same context, the Internet of Satellites paradigm expands the federation concept to a multi-hop scenario, without predefining a particular satellite system architecture, and deploying temporal satellite networks. The basis of both concepts is the offer of unused satellite resources as services. Therefore, it is necessary that satellites notify their availability to the other satellites that compose the system. This work presents a novel Opportunistic Service Availability Dissemination Protocol, which allows a satellite to publish an available service to be consumed by others. Details of the protocol behavior, and packet formats are presented as part of the protocol definition. The protocol has been verified in a realistic scenario composed of Earth Observation satellites, and the Telesat mega-constellation as network backbone. The achieved results demonstrate the benefits of using a protocol as the proposed one, which in some cases even doubles the amount of data that can be downloaded. To the best of our knowledge, this proposal is the first protocol that allows deploying opportunistic services for Federated Satellite Systems.

Identifying Retrofitting Opportunities for Federated Satellite Systems

This paper aims at identifying retrofitting possibilities to incorporate existing spacecraft into a network of federated satellite systems. The paper presents a systematic review of possible retrofitting options, such as direct modifications including replacement and addition of interfaces, and indirect modifications through the addition of intermediary federated negotiators. The paper considers existing frequency regulations for the analysis in the technical domain, but does not take into consideration how complex or time-consuming any legislative changes might be. Although the paper concludes that direct modifications of existing satellites are nonfeasible from a technical point of view, it identifies a possible scenario of retrofitting by adding intermediary negotiator satellites. The link budget for the intersatellite link between an existing satellite mission, such as SPOT-6, and a conceptual satellite negotiator was estimated. The work concludes that from a link budget point of view and existing technology, such a configuration can provide a slant range from several hundred to thousands of kilometers. The work defines models for trade-off analysis identifying correlations between satellite negotiator parameters and the number of covered satellites. The paper concludes proposing several possible satellite negotiator architectures and high-level technical requirements based on analysis of characteristics of existing and planned satellites.

Mechanism Design for Exchanging Resources in Federated Networks

This paper introduces a mechanism for pricing and exchanging resources in federated networks of task-processing elements. An operational model is developed to allocate processing, storage and communication resources to computational demands. This model finds an efficient and stable solution to combinatorial routing and allocating resources among networked elements with technical constraints. Using mixed-integer linear programming (MILP) formulation, we find optimal solution to processing tasks, allocating links, storing and delivering data to destination. A trusted auctioneer uses a mechanism to allocate resources to computational tasks and suggests prices for exchanging resources across a federation using minimum number of MILP solutions to a network topology. The proposed mechanism maximizes the collective value for a federation and ensures an expected value for each federate and minimizes the computational cost associated with the operational runs. The auctioneer doesn’t have access to utility functions and private information on resources a priori while assumes a federation with self-centric and rational participants. An application of federated satellite systems is developed with endogenous components such as adaptive bidding and opportunity cost of using resources. Numerical results show that the proposed mechanism improves the collective and expected values in a federation with strategic federates.

Architecting federations of systems: A framework for capturing synergy

AbstractThis paper defines Federations of Systems, introduces a tailored architecting framework, and demonstrates it in a satellite design case study. While certainly not being new concepts in the literature, federations are a class of Systems of Systems (SoS) that have not been extensively explored due to the scarcity of applied examples and still few practitioners facing their specific design challenges. This is expected to change with the advent of the Internet of Things, Machine to Machine applications, collaborative consumption, and Federated Satellite Systems. It has become henceforth necessary to develop approaches in design and architecting capable of addressing such interconnected sets of systems.Federations are SoS characterized by the absence of global goals and stakeholders, and cooperation enabled only on an opportunistic basis. Systems engage in federations when the perceived benefit exceeds the costs of the necessary interfaces. The proposed framework quantifies the upper limits to the net benefits of cooperation between systems through the concept of synergy. Using synergy as a heuristic to navigate federated design spaces, the framework predicts the appearance and evolution of federations.The demonstration of the framework in a six‐satellite federation shows that advantages of federating emerge with the collaboration between just two systems. Interface costs, architectural cost preferences, and network topology drive the achievable benefits. Specifically, when considering communication architectures under 80 MUSD for satellite systems, federating is advantageous when the interface lifecycle costs are below 15 MUSD. This demonstration case exemplifies how federating can assist systems in achieving design points that dominate the solutions of their local tradespace.

Data authentication, integrity and confidentiality mechanisms for federated satellite systems

This work addresses a critical topic in federated satellites development: the lack of trust between stakeholders that would prevent any stakeholder joining a satellite federation owned and operated by multiple parties. A characterisation of security needs for federated satellite systems is proposed, showing that in order for a federation to offer an environment for a beneficial cooperation, a notion of identity, both user identity and data authentication, has to be introduced, and stakeholders' security requirements have to be satisfied. This paper presents a public key infrastructure (PKI) based protocol for addressing stakeholders' security requirements and ensuring data authentication, integrity and confidentiality in data transfer operations within satellite federations. The performance and cost overheads of the proposed security protocol are first characterised with an experimental implementation on a Raspberry Pi 2 platform, used as a representative proxy testbed of commercial off-the-shelf avionics for small satellites, and then with a benchmark on a range of CPUs to analyse which platforms achieve set performance goals with radio-based and laser-based communications. Recommendations for implementing security mechanisms in federated satellite systems are thus derived.

Benefits of Using Mobile Ad-Hoc Network Protocols in Federated Satellite Systems for Polar Satellite Missions

The operational network of individual observation nodes project evaluated the benefits of applying distributed satellite system (DSS) architectures to Earth observation. One of its outcomes is the identification of Arctic services as top priority current user needs that require near-real-time observations. Using inter-satellite communications (ISC) capabilities, a federated satellite system (FSS) can establish a win-win collaboration between two spacecrafts to provide these services. However, as a FSS is established during the contact between two satellites, the service duration is limited. Therefore, the Internet of satellites (IoSat) paradigm promotes the use of multi-hop sporadic networks to deploy FSS. In this paper, the routing protocol (which identifies routes between a source-destination pair) becomes crucial. One of the most extended networks is the mobile ad-hoc network (MANET), in which nodes are constantly moving and changing the network topology. In principle, applying MANET technologies in the IoSat context would provide self-organization, self-configuration, and flexibility to satellite systems. The optimized link-state routing (OLSR) protocol is the predominant solution in MANET, because it quickly reacts against topology changes. This paper aims at studying the benefits of using satellite networks with MANET solutions (e.g. OLSR) for polar satellite missions. The results presented in this article demonstrate that the access time is significantly improved, and thus these new Arctic services can be achieved.

Design and Optimization of a Polar Satellite Mission to Complement the Copernicus System

The space industry is currently witnessing two concurrent trends: the increased modularity and miniaturization of technologies and the deployment of constellations of distributed satellite systems. As a consequence of the first trend, the relevance of small satellites in line with the “cheaper and faster” philosophy is increasing. The second one opens up completely new horizons by enabling the design of architectures aimed at improving the performance, reliability, and efficiency of current and future space missions. The EU H2020 ONION project (“Operational Network of Individual Observation Nodes”) has leveraged on the concept of fractionated and federated satellite systems (FFSS) to develop and design innovative mission architectures resulting in a competitive advantage for European earth observation (EO) systems. Starting from the analysis of emerging needs in the European EO market, the solutions to meet these needs are identified and characterized by exploring FFSS. In analogy with terrestrial networks, these systems envision the distribution of satellite functionalities amongst multiple cooperating spacecrafts (nodes of a network), possibly independent, and flying on different orbits. FFSS are considered by many as the future of space-based infrastructures, as they offer a pragmatic, progressive, and scalable approach to improve existing and future space missions. This paper summarizes the main results of the ONION project and the high-level design of the marine weather forecast mission for polar regions.

Sealed‐Bid Reverse Auction Pricing Mechanisms for Federated Satellite Systems

ABSTRACTThis paper develops a framework to simulate and evaluate pricing policies of spacecraft trading commodities, such as data routing, in a federated satellite network. Federated satellite systems allow the reallocation of underutilized assets, enabling their use as services between owners and third parties. The paper, by means of game theory, focuses on sealed‐bid reverse auction pricing schemes, benchmarks first‐price and second‐price auction strategies, and evaluates the associated trade‐offs in terms of performance and cost, and losses in Pareto efficiency introduced by system‐level operation constraints. The analysis considers an application case study for federated satellite systems operating in Low Earth Orbit for commercial purposes. Satellite federations are a novel paradigm envisioning on‐orbit opportunistic sharing of resources through an ad hoc mobile satellite network. The architecture creates the basis for the realization of a commercial cloud computing environment in orbit, with spacecraft establishing communications links between each other leveraging on system design margins. The results of the case study in space provide new insights on the design of federated satellites and their operations while characterizing emergent behaviors and efficient trade‐offs on the Pareto front of the cost–performance curve.

Architecting Information Security Services for Federated Satellite Systems

This paper investigates the provision of information security services in federated satellite systems. The discussion is initiated by describing possible threats that the system faces, as well as the specific security services that have to be provided in order to mitigate them. Next, a set of five primal security functions that a federated satellite system has to implement is defined, and an interaction state model is propose to characterize the security state when two federates are interacting with each other. Differences in these security states are then used to define the interaction state machine, which is a transition state diagram that can be used to rapidly identify which security functionality has to be provided in order to securitize an unreliable interaction. Finally, the interaction state model and interaction state machine are applied in a multihop setting where information is relayed through multiple federated satellite system participants. Based on this discussion, the concept of best-effort versus guaranteed services is defined as applied to the context of federated satellite systems and information security services. Their usefulness in architecting information security services is finally demonstrated through an illustrative example.

Performance Analysis of Algorithms for Coordination of Earth Observation by CubeSat Constellations

Two algorithms that coordinate activities across a resource-constrained, Earth-observing CubeSat constellation are presented. The Resource-Aware SmallSat Planner algorithm performs online planning of activities for a satellite while keeping the satellite’s resources within constraints. The Limited Communication Constellation Coordinator algorithm performs coordination of observations across the constellation to reduce average revisit times for a set of targets. The algorithms are simulated for 24 h with an 18 satellite Low Earth Orbit constellation. Three orbital geometries are examined, with different configurations of intersatellite and satellite-to-ground communications links to share planning information. Results indicate that coordination through Resource-Aware SmallSat Planner/Limited Communication Constellation Coordinator and a background communications constellation improves observation performance, with sensor-averaged revisit times of 197, 203, and 225 min (over three orbital geometries) versus 204, 211, and 240 min for a baseline random sensor selection method. The results also reveal that the constellations studied perform poorly at sharing planning information via only downlinks and crosslinks and point to the need for a method of calculating the information sharing utility of such links in a coordinated constellation. These findings are relevant for Federated Satellite Systems because they provide guidance on next steps toward integrating large networks of heterogeneous small satellites into large-scale, coordinated, Earth-observing systems.

An implementation of Software Defined Radios for federated aerospace networks: Informing satellite implementations using an inter-balloon communications experiment

Novel space mission concepts such as Federated Satellite Systems promise to enhance sustainability, robustness, and reliability of current missions by means of in-orbit sharing of space assets. This new paradigm requires the utilization of several technologies in order to confer flexibility and re-configurability to communications systems among heterogeneous spacecrafts. This paper illustrates the results of the experimental demonstration of the value proposition of federated satellites through two stratospheric balloons interoperating with a tracking ground station through Commercial Off-The-Shelf Software Defined Radios (SDRs). The paper reports telemetry analysis and characterizes the communications network that was realized in-flight. Furthermore, it provides details on an in-flight anomaly experienced by one of the balloons, which was recovered through the use of the federated technology that has been developed. The anomaly experienced led to the early loss of the directional link from the ground station to the affected stratospheric balloon node after 15min in flight. Nevertheless, thanks to the federated approach among the systems, the ground station was still able to retrieve the balloon׳s data in real time through the network system, for which the other balloon operated as a federated relay for 45min in flight, uninterrupted. In other words, the federated approach to the system allowed triplicating the useful lifetime of the defective system, which would have not been possible to realize otherwise. Such anomaly coincidentally demonstrated the value of the federated approach to space systems design. The paper paves the way for future tests on space assets.

Design Implications for Missions Participating in Federated Satellite Systems

This paper analyzes the design implications for space missions participating in opportunistic satellite federations. Satellite federations are a novel instance of distributed satellite systems implementing the concept of opportunistic collaboration in space among heterogeneous missions; trading resources, such as data relay; storage; and computing power among participant missions. The ability of a spacecraft to join a federation is mainly constrained by bus power availability and spacecraft attitude. The paper quantifies design implications for missions to participate in satellite federations. In particular, the paper quantifies the overall spacecraft mass impacts associated with operations on margins within a federation. A systems-level spacecraft model is developed to show that overall system mass impacts for typical-use low-Earth-orbit spacecraft participating in a satellite federation are 12, 1.1, and 0.6% for small-, medium-, and large-class platforms, respectively. It is shown that up to per orbit federated satellite system connectivity is achievable for more then 70% lifetime on low-Earth-orbit platforms. The paper also addresses orbital geometry considerations by formulating a satellite-to-satellite coverage-optimization problem. This research work allows designers to identify optimal federation engagement levels for different satellite missions and helps to identify beneficial orbital geometries for federates seeking to act as resource suppliers.

The Federated Satellite Systems paradigm: Concept and business case evaluation

This paper defines the paradigm of Federated Satellite Systems (FSS) as a novel distributed space systems architecture. FSS are networks of spacecraft trading previously inefficiently allocated and unused resources such as downlink bandwidth, storage, processing power, and instrument time. FSS holds the promise to enhance cost-effectiveness, performance and reliability of existing and future space missions, by networking different missions and effectively creating a pool of resources to exchange between participants in the federation. This paper introduces and describes the FSS paradigm, and develops an approach integrating mission analysis and economic assessments to evaluate the feasibility of the business case of FSS. The approach is demonstrated on a case study on opportunities enabled by FSS to enhance space exploration programs, with particular reference to the International Space Station. The application of the proposed methodology shows that the FSS concept is potentially able to create large commercial markets of in-space resources, by providing the technical platform to offer the opportunity for spacecraft to share or make use of unused resources within their orbital neighborhood. It is shown how the concept is beneficial to satellite operators, space agencies, and other stakeholders of the space industry to more flexibly interoperate space systems as a portfolio of assets, allowing unprecedented collaboration among heterogeneous types of missions.