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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.

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 review paper analyzes technology trends observed in New Space missions, using a patent analytics approach. The analysis is complemented with a literature review of the subjects identified. The main objective of this review is to draw a comprehensive picture of technology trends in New Space and to discuss potential scenarios for further development of this novel type of missions. Building on the existing scientific literature, we survey alternative definitions and then propose our own definition of New Space missions as synthesis of the ongoing debate in the field. We identified more than two hundred organizations active in the development of both upstream and downstream products and services for New Space missions. Using a commercially available patent analytics tool, we collected 933 patents protecting technologies disclosed by those organizations. We used the Latent Dirichlet Allocation (LDA), a topic modeling algorithm, to analyze patents' data and to identify the underlying structures in New Space's technology trends. Ten major topics have been identified respectively named “Remote sensing & image acquisition”, “Flying/launch systems”, “Telecommunication systems”, “Constellation management”, “Digital Processing Architectures”, “Image analysis”, “Manufacturing process & materials”, “Feature recognition and extraction”, “Antenna systems”, and “Space platforms”. A deeper analysis of patents' claims revealed a core cluster defined as “data cluster” including data analysis topics (Remote sensing & image acquisition, Image analysis, and Feature recognition and extraction), data transmission topics (Telecommunication systems and Antenna systems from both hardware and software perspective) and related enabling technologies such as constellation management. Based on this analysis, the evolution of data cluster related technologies is surveyed in order to review the current technology state of the art as well as identifying potential areas that will benefit the most from further technology developments to improve New Space missions’ performance. Lastly, we identify technology trends for future New Space development based on the insights obtained by the synthesis of our literature and patent survey. We discuss the key directions for future development emerging from our review, such as the use of commercial off the shelf components, the increasing use of miniaturized technology, and software defined technology.

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.

We present the preliminary results of our investigation on the effectiveness of the Serum methodology for Agile development of space hardware. We analyze the development process of a hardware payload that is part of a host nanosatellite mission composed of two 6U CubeSats (30cm x 20cm x 10cm). The host mission is a collaboration with several partners including academia and small and medium enterprises. Scrum is a product development process created as a faster, more effective way of developing software. The goal of our investigation is to understand whether and by how much the same Scrum principles that proved successful in software can be adopted vis-a-vis in hardware projects. We also intend to identify the fundamental challenges in such an approach for space missions. In the host mission, Scrum has been adopted for the development of the payload subject to the investigation. The paper introduces the ongoing development process and identifies Scrum-related challenges internal to the payload development and challenges related to the coordination of the process with partners adopting established development processes. The paper identifies opportunities of future work for the fine tuning of Agile development methodologies in space projects and illustrates key statistics that have been collected throughout the development so far.

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.

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 15 min 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 45 min 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.

Both startups and traditional space industry are exploring new business opportunities and new engineering approaches in what is becoming known now as New Space.

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.

Satellite architectures where networked, heterogeneous observation nodes capture data in a distributed manner are seen as feasible solutions to address the needs of next-generation Earth observation services (i.e. higher spatial, spectral and temporal resolutions at viable costs). Nevertheless, the problems that designers face when approaching these systems-of-systems are still eclipsed by the heterogeneity, dimensionality and multi-level complexity of those. In spite of the many underlying technological challenges, how to optimally architect distributed satellite systems, remains an open source of debate. In this context, this paper presents a design-oriented methodology that is aimed at providing high-level design solutions for this type of architectures in generic EO use-cases. In order to find optimal solutions, the methodology detailed in this paper is grounded on an aggregated architectural figure-of-merit that compresses: (a) system-level performance metrics; (b) use-case requirements; (c) development and launch costs; and (d) a set of architectural quality attributes. The latter contributing term models, assesses and weights several of the so-called 'ilities' of an architecture and allows to select designs that exhibit some desired qualities. With a dimensionality of more than five thousand architectural alternatives, the study has been illustrated with a marine weather forecast use-case. Both the exploration of design alternatives and the analysis of the results have shown the benefits of medium and small satellite platforms and have stressed their potential in the design of distributed satellite systems. Finally, this paper concludes by suggesting that this very optimization framework and methodology could also be used for a quantitative gap analysis aiming at deriving the technological road map for future engineering teams.

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.

Earth observation satellite programs are currently facing, for some applications, the need to deliver hourly revisit times, subkilometric spatial resolutions, and near-real-time data access times. These stringent 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. In this context, this paper presents partial results from ONION, a research project devoted to studying distributed satellite systems and their architecting characteristics. A design-oriented framework that allows selecting optimal architectures for the given user needs is presented in this paper. The framework has been used in the study of a strategic use-case and its results are hereby presented. From an initial design space of 5586 potential architectures, the framework has been able to preselect 28 candidate designs by an exhaustive analysis of their performance and by quantifying their quality attributes. This very exploration of architectures and the characteristics of the solution space are presented in this paper along with the selected solution and the results of a detailed performance analysis.