Spacecraft conjunction assessment optimisation using deep learning algorithms applied to conjunction data messages (CDMs)

The lack of global regulations on space debris management during the early days of the space era until the last few decades of the 20th century resulted in a consistent increase in space debris. Spacecraft collisions in orbit and the industry's growing interest in launching constellations of satellites are now exacerbating the problem. To address those concerns, multiple space organisations worldwide have implemented Situational Space Awareness programmes with integrated Conjunction Assessment systems that allow the detection of spacecraft conjunctions with an estimated collision risk probability. While this approach has proved effective in the last two decades, the foreseen increment of artificial space objects in orbit in the coming years will put any existing system under severe stress if the technology does not evolve to match the new demands. The objective of this research is two-fold: it evaluates different architectures used in the field of Deep Learning to increase the accuracy of on-orbit Conjunction Events forecasting. It provides a multi-purpose modular, Machine Learning based Python library to support Conjunction Assessment activities. The results of this study show that simpler cell architectures used in the Recurrent Neural Networks outperform the corresponding Vanilla versions in terms of accuracy for the problem at hand. It also demonstrates that the attention mechanism provides the best performance with up to 40% more accuracy

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.This work has been (partially) funded by “CommSensLab” Excellence Research Unit Maria de Maeztu (MINECO grant MDM-2016-0600), the Spanish Ministerio MICINN and EU ERDF project “SPOT: Sensing with pioneering opportunistic techniques” (grant RTI2018-099008-BC21/AEI/10.13039/501100011033), by the grant PID2019-106808RA-I00/AEI/FEDER/UE from the EDRF and the Spanish Government, and by the Secretaria d’Universitats i Recerca del Departament d’Empresa i Coneixement de la Generalitat de Catalunya (2017 SGR 376, and 2017 SGR 219).Peer ReviewedPostprint (published version

Enhancing 5G global connectivity via satellite constellations: preliminary sizing of phased array antennas using a heuristic solver with genetic algorithms

Satellite 5G connectivity to handheld devices is a critical technology that has significant benefits in various areas, such as remote healthcare, emergency response, and global connectivity. Achieving this requires state-of-the-art satellite constellations that can provide high-speed, reliable, and low-latency connections. Phased array antennas are a key component of these constellations, providing directional, high-gain signals, and beamforming capabilities to enable the delivery of high-speed and reliable data transfer. In this paper, we propose an approach to preliminary sizing of phased array antennas for 5G satellite connectivity accounting for stakeholders’ requirements and use cases constraints. To optimize the configuration of phased array antennas, we explore the tradespace of feasible design configurations using a heuristic solver approach leveraging genetic algorithms. The tradespace exploration has been constrained with link budget limit, launcher mass and volume, launch capacity, and minimum system performance. Building on this information, the solver identifies the near-optimal configurations that meet design specifications while maximizing satellite throughput. The results stemming from the application of the method and related tool, demonstrate the potential of our approach to build systems that deliver high-speed and reliable connectivity to handheld devices from space, enabling remote healthcare, emergency response, and global connectivity. Overall, this paper presents a novel and efficient approach to optimizing the configuration of phased array antennas for satellite 5G connectivity, and our findings offer opportunities to enhance the design and performance of satellite constellations by quickly converging to a preliminary sizing of a viable option eventually refined in later stages of design and development of the spacecraft system

Architecting CubeSat constellations for messaging service, Part I

In today's modern and globalized world, connectivity is a key factor for businesses, production facilities, sensor networks, and ordinary people. However, there are still populated areas which are not covered by ground-based telecommunications infrastructure. This is where telecommunication satellite constellations come in, as they can provide coverage to remote and uninhabited regions and fill existing connectivity gaps to ensure data transfer. LoRa is one of the technologies designed for data transmissions over long distances with low power consumption. Alongside with other technologies of the Low-Power Wide Area Network family, it is widely used for Internet of Things applications. LoRa chirp spread spectrum modulation is robust against the Doppler frequency shifts encountered in low earth orbits, and it has already been used in IoT satellite communications. Due to the low transmitted signal power, the achieved data rate is not high, making it a suitable technology for telecommunications payloads on CubeSat platforms for messaging services. As compared to existing traditional communication satellite systems, CubeSat constellations are low-cost and may offer an affordable connectivity service to developing regions. This study is divided in two parts. In Part I the demand model is built based on the population distribution not covered by cell towers. The LoRa link performance is analyzed, considering the impact of LoRa channel parameters variation, such as spreading factor and channel bandwidth, while satellite orbital height, transmission antenna beamwidth, and transmitter peak power have a direct impact on the payload mass. Among thousands of possible configurations, 73 feasible payload designs have been downselected. In Part II of the study, the satellite mass and the total system cost are estimated based on the payload parameters obtained. Messages transmission simulation via a constellation is conducted in order to identify optimal constellation architectures for messaging service, as well as the main drivers of the system economic profitability. The presented analysis results provide a deeper understanding of LoRa connectivity advantages and limitations together with the performance drivers, which will support the optimization of future LoRa-based satellite communication systems and other IoT satellite constellations.European Commission, Government of CataloniaThis has been supported by the predoctoral program AGAUR-FI ajuts (2023 FI-1 00477) Joan Oró of the Secretariat of Universities and Research of the Department of Research and Universities of the Generalitat of Catalonia and the European Social Plus Fund.This project was also sponsored in part by the project “GENESIS: GNSS Environmental and Societal Missions – Subproject UPC”, Grant PID2021-126436OB-C21, sponsored by MCIN/AEI/10.13039/ 501100011033/ and EU ERDF “A way to do Europe”.This study would also not have been possible without the support of the Skolkovo Institute of Science and Technology, whose funding enabled the international collaboration through its Academic Mobility program.Acta Astronautic

System design study of a constellation of small spacecraft to deliver seamless 5G connectivity to unmodified cell phones through an end-to-end non-terrestrial network

The increasing demand for high-speed mobile data services has led to the development of 5G and 6G technology, which promises to revolutionize the way people access and use the internet. However, the full exploitation of 5G network potential is often limited by the challenges related to the deployment of the physical infrastructure required to support these networks. In order to address these limitations, a new approach is needed to bring 5G services to areas that are currently underserved. This paper presents the results of a system design study that explores the use of a constellation of small spacecraft to deliver seam-less 5G connectivity to unmodified cell phones, through an endto-end non-terrestrial network. Within the study, several use cases have been considered including offering enhanced service to cities and connecting areas not served by traditional mobile services such as remote regions, ships and offshore platforms, regions hit by natural disasters and contested battlefields. A trade space exploration approach was undertaken to identify the optimal solution for meeting stakeholders’ requirements associated with the different use cases. The analysis explores the effects of key architectural decisions on overall system performance and lifecycle cost, benchmarking them against foreseen customers’ needs and market demand. A variety of alternatives were evaluated including the number of satellites, types of orbits, number of orbital planes, satellite size, weight and power, antenna technologies, inter-satellite links technologies and routing schemes among others. As a result, it was proposed the use of a constellation of about 3000 satellites in a sun-synchronous Low Earth Orbit (LEO) orbit, with a satellite lifetime of 5 years. Each satellite is equipped with a phased array antenna in 5G non-terrestrial band frequency n256 for direct connectivity to unmodified user cell phones and free space optical telecommunication terminals for on-orbit backhauling. Commercial Off-The-Shelf (COTS) components for spacecraft subsystems and sensors were considered when available. With more than 95% of Earth coverage and high system scalability, the mission represents a promising solution for providing global 5G connectivity paving the way for a more connected world

Additive Manufacturing Evaluation Tool for Design Studies

In recent years, the engineering community realized the potential for additive manufacturing (AM) to be a gamechanger 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

Lunar human landing system architecture tradespace modeling

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

FSSCat: the Federated Satellite Systems 3 Cat Mission: demonstrating the capabilities of CubeSats to monitor essential climate variables of the water cycle

The Federated Satellite Systems/ 3 Cat-5 (FSSCat) mission was the winner of the European Space Agency (ESA) Sentinel Small Satellite (S 3 ) 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 3 Cat-5/A, an L-band microwave radiometer and GNSS reflectometer (GNSS-R) implemented using a softwaredefined radio (SDR), and 2) the HyperScout-2 onboard 3 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. 3 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. 3 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

Demonstration of the federated satellite systems concept for future earth observation satellite missions

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.Peer ReviewedPostprint (published version