Juan A. Fraire

Researcher in Space Networking and Informatics

Inria CONICET Saarland University

Publications Conference paper · Mega-constellations · 2021

On the automation, optimization, and in-orbit validation of intelligent satellite constellation operations

Gregory Stock, Juan A. Fraire, Holger Hermanns, Eduardo Cruz, Alastair Isaacs, and Zhana Imbrosh

AIAA/USU Conference on Small Satellites (SmallSat), 2021

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Abstract

Recent breakthroughs in technology have led to a thriving"new space"culture in low-Earth orbit (LEO) in which performance and cost considerations dominate over resilience and reliability as mission goals. These advances create a manifold of opportunities for new research and business models but come with a number of striking new challenges. In particular, the size and weight limitations of low-Earth orbit small satellites make their successful operation rest on a fine balance between solar power infeed and the power demands of the mission payload and supporting platform technologies, buffered by on-board battery storage. At the same time, these satellites are being rolled out as part of ever-larger constellations and mega-constellations. Altogether, this induces a number of challenging computational problems related to the recurring need to make decisions about which task each satellite is to effectuate next. Against this background, GomSpace and Saarland University have joined forces to develop highly sophisticated software-based automated solutions rooted in optimal algorithmic and self-improving learning techniques, all this validated in modern nanosatellite networked missions operating in orbit.

Cite

BibTeX
@inproceedings{stock2022automation,
  author    = {Stock, Gregory and Fraire, Juan A. and Hermanns, Holger and Cruz, Eduardo and Isaacs, Alastair and Imbrosh, Zhana},
  title     = {On the automation, optimization, and in-orbit validation of intelligent satellite constellation operations},
  booktitle = {AIAA/USU Conference on Small Satellites (SmallSat)},
  year      = {2021},
  url       = {https://digitalcommons.usu.edu/smallsat/2021/all2021/168/}
}

More on mega-constellations

  1. Distributed On-Demand Routing for LEO Mega-Constellations: A Starlink Case Study Gregory Stock, Juan A. Fraire, and Holger Hermanns Advanced Satellite Multimedia Systems Conference and Signal Processing for Space Communications Workshop (ASMS/SPSC), 2022
    Abstract

    The design and launch of large-scale satellite networks create an imminent demand for efficient and delay-minimising routing methods. With the rising number of satellites in such constellations, pre-computing all shortest routes between all satellites and for all times becomes more and more infeasible due to space and time limitations. Even though distributed on-demand routing methods were developed for specific LEO satellite network configurations, they are not suited for increasingly popular mega-constellations based on Walker Delta formations.The contributions of this paper are twofold. First, we introduce a formal model that mathematically captures the time-evolving locations of satellites in a Walker Delta constellation and use it to establish a formula to compute the minimum number of ISL hops between two given satellites. In the second part, we present an on-demand hop-count-based routing algorithm that approximates the optimal path while achieving superior performance compared to classical shortest-path algorithms like Dijkstra.

  2. Managing Fleets of LEO Satellites: Nonlinear, Optimal, Efficient, Scalable, Usable, and Robust Gregory Stock, Juan A. Fraire, Tobias Mömke, Holger Hermanns, Fakhri Babayev, and Eduardo Cruz IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, 2020
    Abstract

    Size and weight limitations of low-earth orbit (LEO) small satellites make their operation rest on a fine balance between solar power infeed and power demands of communication technologies on board, buffered by on-board battery storage. As a result, the problem of planning battery-powered payload utilization together with intersatellite communication is extremely intricate. Nevertheless, there is a growing trend toward constellations and megaconstellations that are to be managed using sophisticated software support. Earlier work has leveraged cost-optimal reachability in priced timed automata for deriving near-optimal finite-horizon schedules to operate a single LEO satellite in orbit. This article harvests that work and improves it in several dimensions, all needed for true in-orbit applicability: 1) the battery representation is no longer bound to be linear, but can be kinetic, which means that the optimization problem includes nonlinearities; 2) the management is perpetuated by a receding horizon scheduling strategy; 3) the model is continuously improved with the latest telemetry received from orbit; 4) a tandem of satellites equipped with state-of-the-art intersatellite link transponders is considered; 5) the core optimization problem is now solved using dynamic programming with antichain-based pruning, which is proven to be optimal and despite all the additional features outperforms the earlier approach by orders of magnitude; 6) the entire approach is grounded in the concrete requirements of the GOM X–4 LEO mission; 7) care is taken to make the approach usable by the space engineers, and robust against failures of parts of the toolchain; and 8) an extensive test campaign validates accuracy, efficiency, scalability, and robustness with respect to the operational requirements and constraints of LEO constellations.

  3. On the Use of Mega Constellation Services in Space: Integrating LEO Platforms Into 6G Non-Terrestrial Networks Gabriel Maiolini Capez, Mauricio A. Cáceres, Roberto Armellin, Christopher P. Bridges, Juan A. Fraire, Stefan Frey, and Roberto Garello IEEE Journal on Selected Areas in Communications, 2024
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    This paper presents a framework for integrating Low-Earth Orbit (LEO) platforms with Non-Terrestrial Networks (NTNs) in the emerging 6G communication landscape. Our work applies the Mega-Constellation Services in Space (MCSS) paradigm, leveraging LEO mega-constellations’ expansive coverage and capacity, designed initially for terrestrial devices, to serve platforms in lower LEO orbits. Results show that this approach overcomes the limitation of sporadic and time-bound satellite communication links, a challenge not fully resolved by available Ground Station Networks and Data Relay Systems. We contribute three key elements: (i) a detailed MCSS evaluation framework employing Monte Carlo simulations to assess space user links and distributions; (ii) a novel Space User Terminal (SUT) design optimized for MCSS, using different configurations and 5G New Radio Adaptive Coding and Modulation; (iii) extensive results demonstrating MCSS’s substantial improvement over existing Ground Station Networks and Data Relay Systems, motivating its role in the upcoming 6G NTNs. The space terminal, incorporating a multi-system, multi-orbit, and software-defined architecture, can handle Terabit-scale daily data volumes and minute-scale latencies. It offers a compact, power-efficient solution for properly integrating LEO platforms as space internet nodes.