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As small satellites are finding increased applicability in a number of space missions, the community is actively exploring the feasibility of missions employing active instruments on small spacecraft. In particular, synthetic aperture radars are of interest as they prove to be versatile tools for Earth Observation purposes. This paper proposes a trade space exploration model to identify designs for space-borne satellite synthetic aperture radars that address the desired instrument requirements. Two trade space analysis approaches are proposed, based on a multivariate analysis with two evaluation metrics and using parallel coordinate plots. The paper demonstrates the utility of the trade space model by considering two case studies. The first study looks at radar instruments on a broad range of small satellite platforms. This study narrows down a trade space of 1265 feasible radar designs to less than 44 Pareto optimal designs at different center frequencies (C- and X-band), elicits conditions for L-band SARs feasibility, and discusses the feasibility bounds and technical constraints on associated instrument and spacecraft requirements. The second study considers radars for 3U CubeSat platforms. The study identifies 44 Pareto optimal designs within 12,928 feasible designs and sheds light on the operational constraints required for the development of such innovative miniaturized radars.

A renewed interest in lunar exploration with the focus on establishing a constant human presence on the Moon calls for developing new lunar human landing systems (HLS) which would deliver the crew from the prospective Lunar Gateway station to the surface of the Moon and back. Over the years, different human lunar lander architectures were proposed and multiple architecture studies were performed. However, those studies are relevant to the specific assumptions and lunar architectures proposed at the time of conducting the study. Since the current vision for lunar exploration includes new features, such as having the Lunar Gateway and switching to reusable systems, there is a need for a new HLS architecture study. Such studies are being performed by private companies; however, those are rarely publicly available. The goal of this paper is to address this gap and provide a publicly available architectural analysis within the current views on the future human lunar exploration. We assume the Lunar Gateway in an L2 near rectilinear halo orbit and a landing site at the lunar South Pole; the number of HLS crew of 4; the surface stay time of ~7 days, the payload mass delivered to the surface of 500 kg, and the payload mass returned from the surface of 250 kg. A set of parametric models including an HLS model and an HLS program cost model is developed for the analysis. 39 architectures with varying number of stages (1, 2, and 3 stages) and propellant combinations (LOX/LH2, LOX/CH4, and MMH/NTO) are explored. The Pareto analysis shows that there is a difference between typical performance trends for expendable and reusable architectures. For expendable architectures, the 2-stage option seems to be the most advantageous while, for reusable architectures, the 1- and 3-stage options are either comparable or win over the 2-stage option even for the number of system uses as low as 3. In terms of the propellant combinations, pure LOX/LH2 or combined LOX/LH2/LOX/CH4 architectures dominate the tradespace. Assuming that the inter-stage propellant compatibility is a preferred option for systems refueling from the Gateway, 1-stage and 3-stage all LOX/LH2 architectures are identified as the likeliest candidates to have lowest HLS-related production and launch costs. Further cost analysis of those two architectures shows that the 1-stage HLS wins over the 3-stage system in terms of the overall HLS program cost if a long-term exploration program (on the order of tens of missions) is assumed.

This paper proposes the concept of experiential systems engineering (ESE) as a hands-on education approach for teaching systems engineering (SE) tools and methods in postgraduate university courses, following the conceive, design, implement, and operate (CDIO) approach to modern engineering education. It describes ESE as implemented by the author and his research team in the Space Systems Engineering courses at Skoltech over the course of Fall 2014–Spring 2017. It describes the experience of student cohorts in applying SE to stratospheric balloon missions for education purposes, simulating real-life project experience including customer interface management, and operating projects designing and implementing an SE management plan. It describes the proposed approach and provides lessons learnt to generalize ESE to any specific engineering discipline of interest. A mapping between the learning objectives of ESE and the CDIO education framework is proposed. It extends the concept of hands-on SE education. It will be useful to educators interested in novel approaches to SE education and to experiment new ways to deliver a subject that is traditionally believed difficult to teach in university.

This 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.

This chapter overviews the key mission concepts associated with distributed CubeSat missions and outlines technical challenges entailed for key-related technical domains. Distributed CubeSat systems are mission architectures enabling new functionalities for CubeSat systems and providing design strategies to complement or enhance missions employing larger satellite platforms through interoperability. The chapter provides a brief description of the concepts of clusters, constellations, fractions, federations, series, swarms, and trains. It provides an overview of enabling technologies associated to distributed CubeSat systems. While most of these concepts have not yet been demonstrated in orbit with CubeSat systems, they are certainly an area of interest for further consideration in the development of future CubeSat platforms. This chapter aims at providing a broad overview and understanding of opportunities and key technical challenges associated with distributed CubeSat systems.

Nowadays, constellations and distributed networks of satellites are emerging as clear development trends in the space system market to enable augmentation, enhancement, and possibilities of new applications for future Earth Observation (EO) missions. While the adoption of these satellite architectures is gaining momentum for the attaining of ever more stringent application requirements and stakeholder needs, the efforts to analyze their benefits and suitability, and to assess their impact for future programmes remains as an open challenge to the EO community. In this context, this paper presents the mission and system architecture conceived during the Horizon 2020 ONION project, a European Union research activity that proposes a systematic approach to the optimization of EO space infrastructures. In particular, ONION addressed the design of complementary assets that progressively supplement current programs and took part in the exploration of needs and implementation of architectures for the Copernicus Space Component for EO. Among several use cases considered, the ONION project focused on proposing system architectures to provide improved revisit time, data latency and image resolution for a demanding application scenario of interest: Marine Weather Forecast (MWF). A set of promising system architectures has been subject of a comprehensive assessment, based on mission analysis expertise and detailed simulation for evaluating several key parameters such as revisit time and data latency of each measurement of interest, on-board memory evolution and power budget of each satellite of the constellation, ground station contacts and inter-satellite links. The architectures are built with several heterogeneous satellite nodes distributed in different orbital planes. Each platform can embark different instrument sets, which provide the required measurements for each use case. A detailed mission analysis has then been performed to the selected architecture for the MWF use case, including a refined data flow analysis to optimize system resources; a refined power budget analysis; a delta-V and a fuel budget analysis considering all the possible phases of the mission. This includes from the correction of launcher injection errors and acquisition of nominal satellite position inside the constellation, orbit maintenance to control altitude, collision avoidance to avoid collision with space debris objects and end-of-life (EOL) disposal to comply with EOL guidelines. The relevance of the system architecture selected for the MWF has been evaluated for three use cases of interest (Arctic sea-ice monitoring, maritime fishery pressure and aquaculture, agricultural hydric stress) to show the versatility and the feasibility of the chosen architecture to be adapted for other EO applications., This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 687490.

This work presents a method and a tool for conducting conceptual design studies for projects such as a space exploration mission and a satellite constellation in a concurrent manner in both time and space, while taking into account the structure of the system to design and the dependencies between the system’s constituting elements. Design work is parallelized to reduce the time required to converge to a solution for a preliminary design, which includes the system architecture, its detailed requirements, and its costs. The multidisciplinary team of designers works in colocation to leverage effective direct human interaction for discussing design trade-offs quickly. While this is practice in space agencies for mission feasibility studies, a common methodology was not described so far. Our work proposes a method for the coordination of discipline experts and the sequence of activities performed during conceptual design studies, which use integrated parametric system models. Our method reduces the number of design iterations by applying a design structure matrix clustering algorithm to the system model and deriving a schedule for the design session. We also describe the tool Concurrent Engineering Data Exchange Skoltech we developed for collaborative work on the parametric system models and serve as an instrument for research on complex system design methodologies. The tool features a fast synchronization mechanism for the concurrent work of multiple design experts, and it supports our coordination method for concurrent design studies. The tool was published as open-source software, so other researchers can use it and build upon it. We used our tool and applied the method to two case studies of preliminary satellite designs and tested them with groups of students of a satellite engineering class and researchers from our institute. Throughout the experiments, we recorded information about user interactions and collected user feedback for the evaluation of the coordination method and the collaboration tool. Both method and tool demonstrated their validity in our experimental setting.

In the last years, the need to access Earth Observation high spatial resolution data with very low latency, ideally in near-real-time, has increased. Distributed Satellite Systems have emerged as an effective and efficient architecture to deal with these tight requirements. One of these systems is the Federated Satellite Systems which explore the benefits of sharing unused and available resources between satellites, such as memory storage or downlink opportunities. This interaction is known as satellite federations. Additional downlink contacts may enable low-latency communications and increase the downlink capacity. Therefore, the deployment of federations would allow satisfying current Earth Observation community demands. This work contributes to establish this promising paradigm by presenting a proof-of-concept of a federated system, called FSS Experiment payload. This payload is boarded into three stratospheric balloons, and it provides them communications means to create federations. The design of the payload, and the flight campaign results are presented in this work. These results demonstrate the feasibility of deploying federations, as well as the benefits of deploying them in future EO missions. This work has been funded by “CommSensLab” Excellence Research Unit Maria de Maeztu (MINECO grant MDM-2016-0600), and the Spanish Ministerio MICINN and EU ERDF project (RTI2018-099008-B-C21) “Sensing with pioneering opportunistic techniques” by the grant FI-DGR 2015 of AGAUR - Generalitat de Catalunya (FEDER). The authors would like to acknowledge Skoltech and all the students that with their passion have made possible this balloon campaign.

THIS Special Section of the Journal on Spacecraft and Rockets was created based on the 5th International Workshop on Federated and Fractionated Satellite Systems (FSS Workshop) that has taken place in at ISAE-SUPAERO, Toulouse, France, on 2 and 3 November 2017. The Fifth edition of the Workshop came after four events that had previously taken place at MIT (Boston) in 2012, at the Skolkovo Institute of Science and Technology (Moscow) in 2014, at Cornell University (Ithaca) in 2015, and at La Sapienza University (Rome) in 2016. The workshop aimed at forging links to create a multidisciplinary and international research and industrial community that will follow novel approaches to innovate the way in which spacecraft missions are conceived, designed, implemented, and operated. During the two-day workshop in Toulouse, a keynote address was delivered by Grazia Vittadini, at that time Head of Engineering at Airbus Defence and Space, and a keynote address was delivered by Giancarlo Filippazzo, Copernicus Programme Coordinator of the European Space Agency (ESA). In addition, 10 scientific contributions were made by a variety of contributors from all over the world. For this Special Section, 4 of those contributions have been further developed into full journal papers, that have then been reviewed and handled according to AIAA’s Journal of Spacecraft and Rockets (JSR) standards. Federated Satellite Systems (FSS) is a new concept in space systems design aiming at creating a commercial cloud-computing environment enabling sharing and trading of in-space resources between spacecraft. FSS is an instance of distributed satellite systems; DSS encompass concepts such as fractionated spacecraft, satellite constellations, and other systems architectures looking at distributing decision-making, functionality and ownership across multiple flying units. Federated satellites exchange resources such as link capacity, downlink capacity, processing capability and storage capacity. This exchange improves the efficiency utilization of spacecraft resources and makes use of unallocated resource margins of participating missions. The research community started to explore benefits and costs of a federated approach to spacecraft design, and several research avenues have just started opening in this field. From a commercial perspective, the federated satellite systems concept allows the creation of new markets of in-space resources, among other benefits in spacecraft cost, performance, and reliability. The commercial viability of federated satellite system concepts started to emerge in 2017–2018, when we started seeing important investments in space startups developing distributed systems for commercial data relay and cloud data storage, implementing some of the ideas that were originally envisioned in the federated satellite system paradigm. It seems clear that the time is ripe for the exploitation of federative concepts in space. To do so, several technical questions on space systems design and architecture, connectivity, and related research areas need to be solved. This special section addresses some of the abovementioned technical issues, looking at both technology and system layers of federated systems in space. The first paper, “Architectural optimization results for a network of Earth-observing satellite nodes” by Carles Araguz et al., describes part of the results of the ONION project, a European research project devoted to study distributed satellite systems and their architecting characteristics. The paper in particular addresses the challenge of designing novel space systems. Very strict requirements, combined with the consolidation of small-satellite platforms and novel distributed architecture approaches, are stressing the need to study the design of new, heterogeneous and heavily networked satellite systems that can potentially replace or complement traditional space assets. This paper presents a design-oriented framework that allows selecting optimal architectures for a given user needs. The second paper, “Cluster-keeping Algorithms for the Satellite Swarm Sensor Network Project” by Eviatar Edlerman and Pini Gurfil, looks into cluster control algorithms for the satellite swarms, illustrated by the Satellite Swarm Sensor Network (S3Net) project. A methodological development of orbit control algorithms is presented, with emphasis on outlining the algorithms structure, information flow, and software implementation. The methodology enables operation of multiple satellites in coordination, to enable fractionation of space sensors and augmentation of data provided therefrom. In the paper “Identifying retrofitting opportunities for Federated Satellite Systems” by Rustam Akhtyamov et al. the authors address the possibilities of including FSS-like capabilities in existing satellite structures. Such retrofitting possibilities, for this particular case or in general, are important items for industry today. In this paper, a systematic review of possible retrofitting options such as direct modifications, which include replacement and addition of interfaces, and indirect modifications with adding an intermediary (FSS Negotiator) are addressed. And finally, in the paper “Impact of Delayed Acknowledgment on TCP performance over LEO satellite constellations” by Bastien Tauran et al., the authors aim at quantifying the impact of a default TCP option, Delayed Acknowledgment (DelAck), in the context of LEO satellite constellations. To cope with high channel impairment that may affect such satellite constellations, physical and link layer reliability schemes have been introduced, at the price of an increase of the end-to-end delay seen by the transport layer (e.g. TCP). Although DelAck is used to decrease the feedback path load and for overall system performance, the use of this option conjointly with satellite link layer recovery schemes might increase the delay and might be counterproductive. The Guest Editors would like to thank all the reviewers that helped to evaluate the papers and, indeed, bring them to a higher level. Their constructive support was very much appreciated. A. Golkar and R. Vingerhoeds Toulouse, April 2019

This work aims to facilitate deployment of novel distributed space systems architectures such as Federated Satellite Systems (FSS). In particular, the purpose of the work is to identify retrofitting possibilities to incorporate existing satellites into a network. For the satellite case, the paper presents a systematic review of possible retrofitting options such as direct modifications, which include replacement and addition of interfaces, and indirect modifications with adding an intermediary (FSS Negotiator). While the paper concludes that direct modifications of existing satellites are non-feasible from the technical point of view, it also identifies a possible scenario of retrofitting by adding as an intermediary a Negotiator satellite. The link budget for the inter-satellite link between an existing satellite mission such as SPOT-6 and FSS Negotiator was estimated. The work concludes that from the link budget point of view with the existing communication technologies such configuration can provide a slant range limited from several hundred to thousands kilometers. Through analysis of open data of satellite characteristics, including ITU information concerning planned or existing space stations, the work comes up with several models for the further trade-off analysis, identifying how parameters of FSS Negotiator such as an operated bandwidth and frequency, types of supported modulations and cumulative throughput correlate with the covered number of satellites. These results might be used for the tradeoff analysis for the FSS Negotiator mission design. Eventually paper proposes several possible FSS Negotiator architectures and its high-level technical requirements based on analysis of characteristics of existed and planned satellites.

Traditionally, the space industry produced large and sophisticated spacecraft handcrafted by large teams of engineers and budgets within the reach of only a few large government-backed institutions. However, over the last decade, the space industry experienced an increased interest towards smaller missions and recent advances in commercial-off-the-shelf (COTS) technology miniaturization spurred the development of small spacecraft missions based on the CubeSat standard. CubeSats were initially envisioned primarily as educational tools or low cost technology demonstration platforms that could be developed and launched within one or two years. Recently, however, more advanced CubeSat missions have been developed and proposed, indicating that CubeSats clearly started to transition from being solely educational and technology demonstration platforms to offer opportunities for low-cost real science missions with potential high value in terms of science return and commercial revenue. Despite the significant progress made in CubeSat research and development over the last decade, some fundamental questions still habitually arise about the CubeSat capabilities, limitations, and ultimately about their scientific and commercial value. The main objective of this review is to evaluate the state of the art CubeSat capabilities with a special focus on advanced scientific missions and a goal of assessing the potential of CubeSat platforms as capable spacecraft. A total of over 1200 launched and proposed missions have been analyzed from various sources including peer-reviewed journal publications, conference proceedings, mission webpages as well as other publicly available satellite databases and about 130 relatively high performance missions were downselected and categorized into six groups based on the primary mission objectives including “Earth Science and Spaceborne Applications”, “Deep Space Exploration”, “Heliophysics: Space Weather”, “Astrophysics”, “Spaceborne In Situ Laboratory”, and “Technology Demonstration” for in-detail analysis. Additionally, the evolution of CubeSat enabling technologies are surveyed for evaluating the current technology state of the art as well as identifying potential areas that will benefit the most from further technology developments for enabling high performance science missions based on CubeSat platforms.

In recent years, the engineering community realized the potential for additive manufacturing (AM) to be a game-changer in product development. Nevertheless, it is not yet possible to fully take advantage of this technology because it implies a different approach to engineering design. The dependencies of AM on related technologies, such as material modeling, design tools, computing, and process design represent a challenge for engineers. A comprehensive system engineering approach is needed to address the introduction of AM in new design projects. This article proposes a systems design approach to evaluate the use of AM in the development of new systems at the early stage of design. The methodology aims to provide a preliminary estimation of performance, cost, and time of parts manufactured using additive techniques. The article introduces a set of design drivers and criteria to standardize the design process and support the manufacturing technique decision-making process. The methodology is experimentally tested and validated by evaluating tradeoffs for two different case studies considering different engineering parameters. The analysis of the results shows a good consistency between framework predictions and experimental evidence, with an uncertainty level lower than 5%. The reliability of obtained results is discussed.

During these years, novel Distributed Satellite Systems (DSS) have addressed the new Earth Observation (EO) requirements (e.g. near-real time access to data, or multi-point observations). One of the DSS proposals is the concept of Federated Satellite System (FSS) which has explored the benefits of sharing available and unused resources between satellite to maximize the system utility. The possibility to use additional downlink opportunities thanks to federations is a resource that could improve current EO missions, and thus achieving the required performance. For that reason, the FSS Experiment payload has been implemented as a FSS proof-of-concept between 6-Unit CubeSats in the FSSCAT mission. This article presents the design, and the test results of this payload demonstrating its feasibility for future EO missions.

International audience; Due to accelerating technological progress any engineered system eventually becomes obsolete and the question arises as to its modernization. Disciplines such as change and configuration management propose methods to maintain system at operational level by incorporating relatively small changes. When major rebuild is required to the system, existing literature proposes to follow the same System Engineering processes as during new system design and development. Systems Engineering, traditionally focused on design and development of new systems, paying limited attention to modernization of existing ones and its processes need to be specially tailored to the modernization of existing system. In the case of straightforward application of Systems Engineering processes, the step of new system formulation is often neglected and considered as something already granted. This paper gives an overview of approaches and methods in the field of system modernization. It proposes a metrics for classification of different types of system modernization. To facilitate system modernization this work introduces a framework based on proposed metrics, Design Structure Matrixes and functional analysis. The framework consists of decomposition and synthesis phases and aims to define new (modified) system, by providing a set of alternatives. The proposed framework anticipates application of traditional System Engineering approach. The paper is illustrated with an example in the field of car retrofitting.

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 500 s−1 pe...

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.

As small and nanosatellites become increasingly relevant in the aerospace industry1, 2, the need of efficient, lightweight and cost-effective networking solutions drives the need for the development of lightweight and low cost networking and communication terminals. In this paper we propose the design and prototype results of a hybrid optical and radio communication architecture developed to fit the coarse pointing capabilities of nanosatellites, tested through a proxy flight experiment on stratospheric balloons. This system takes advantage of the higher data-rate offered by optical communication channels while relying on the more mature and stable technology of conventional radio systems for link negotiation and low-speed data exchange. Such architecture allows the user to overcome the licensing requirements and scarce availability of high data-rate radio frequency channels in the commonly used bands. Outlined are the architecture, development and test of the mentioned terminal, with focus on the communication part and supporting technologies, including the navigation algorithm, the developed fail-safe approach, and the evolution of the pointing system continuing previous work done in 3. The system has been built with commercial-off-the-shelf components and demonstrated on a stratospheric balloon launch campaign. The paper outlines the results of an in-flight demonstration, where the two platforms successfully established an optical link at stratospheric altitudes. The results are then analyzed and contextualized in plans of future work for nanosatellite implementations.

Federated satellite systems (FSS) are a new class of space-based systems which emphasize a distributed architecture. New information exchanging functions among FSS members enable data transportation, storage, and processing as on-orbit services. As a system-of-systems, however there are significant technical and social barriers to designing a FSS. To mitigate these challenges, this paper develops a multi-stakeholder interactive simulation for use in future design activities. An FSS simulation interface is defined using the High Level Architecture to include orbital and surface assets and associated transmitters, receivers, and signals for communication. Sample simulators (federates) using World Wind and Orekit open source libraries are applied in a prototype simulation (federation). The application case studies a conceptual FSS using the International Space Station (ISS) as a service platform to serve Earth-observing customers in sun-synchronous orbits (SSO). Results identify emergent effects between FSS members including favorable ISS power conditions and potential service bottlenecks to serving SSO customers.