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1. Novel Source–Sink Model for Space Environment Evolution with Orbit Capacity Assessment

   https://doi.org/10.2514/1.A35579  

   D’Ambrosio, Andrea; Servadio, Simone; Mun Siew, Peng; Linares, Richard (July 2023, Journal of Spacecraft and Rockets)

   The increasing number of anthropogenic space objects (ASOs) in low Earth orbit (LEO) poses a threat to the safety and sustainability of the space environment. Multiple companies are planning to launch large constellations of hundreds to thousands of satellites in the near future, increasing the probability of collisions and debris generation. This paper analyzes the long-term evolution of the LEO ASO population with the goal of estimating LEO orbital capacity. This is carried out by introducing a new probabilistic source–sink model. The developed source–sink model is a multishell multispecies model, which includes different object species, such as active and derelict satellites, and debris. Furthermore, debris are divided into the following two subgroups: trackable and nontrackable debris, the last ones representing a significant hazard for active satellites. In addition, the proposed model accounts for collision events and atmospheric drag effects, which include the influence of solar activity. Indeed, the Jacchia–Bowman 2008 thermospheric density model is exploited. The results prove that considering untracked debris within the model produces more collisions, and therefore a smaller population of active satellites affecting the safety of LEO and its orbital capacity. 

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2. Detection of Denial-of-Service Attacks in a Software-Defined LEO Constellation Network

   Agnew, Dennis; McNair, Janise (March 2023, Government Microcircuit Applications and Critical Technology Conference (GOMAC Tech))

   Satellite communication (SATCOM) is a critical infrastructure for tactical networks--especially for the intermittent communication of submarines. To ensure data reliability, recent SATCOM research has begun to embrace several advances, such as low earth orbit (LEO) satellite networks to reduce latency and increase throughput compared to long-distance geostationary (GEO) satellites, and software-defined networking (SDN) to increase network control and security. This paper proposes an SD-LEO constellation for submarines in communication networks. An SD-LEO architecture is proposed, to Denial-of-Service (DoS) attack detection and classification using the extreme gradient boosting (XGBoost) algorithm. Numerical results demonstrate greater than ninety-eight percent in accuracy, precision, recall, and F1-scores. 

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3. A Characterization of Route Variability in LEO Satellite Networks

   https://doi.org/10.1007/978-3-031-28486-1_14  

   Bhosale, Vaibhav; Saeed, Ahmed; Bhardwaj, Ketan; Gavrilovska, Ada (January 2023, Passive and Active Measurement (PAM 2023))

   LEO satellite networks possess highly dynamic topologies, with satellites moving at 27,000 km/hour to maintain their orbit. As satellites move, the characteristics of the satellite network routes change, triggering rerouting events. Frequent rerouting can cause poor performance for path-adaptive algorithms (e.g., congestion control). In this paper, we provide a thorough characterization of route variability in LEO satellite networks, focusing on route churn and RTT variability. We show that high route churn is common, with most paths used for less than half of their lifetime. With some paths used for just a few seconds. This churn is also unnecessary with rerouting leading to marginal gains in most cases (e.g., less than a 15% reduction in RTT). Moreover, we show that the high route churn is harmful to network utilization and congestion control performance. By examining RTT variability, we find that the smallest achievable RTT between two ground stations can increase by 2.5x as satellites move in their orbits. We show that the magnitude of RTT variability depends on the location of the communicating ground stations, exhibiting a spatial structure. Finally, we show that adding more satellites, and providing more routes between stations, does not necessarily reduce route variability. Rather, constellation configuration (i.e., the number of orbits and their inclination) plays a more significant role. We hope that the findings of this study will help with designing more robust routing algorithms for LEO satellite networks. 

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4. S-Band Low Earth Orbit Reconfigurable Small Satellite System for Space Environment Sensing

   Noemi Miguelez-Gomez, Carlos R. (January 2021, 2021 IEEE Space Hardware and Radio Conference (SHaRC2021))

   null (Ed.)

   The applications of additive manufacturing (AM) techniques have rapidly increased in industry sectors in recent years. In combination with the ever-increasing number of new constellations of communications satellites in Low-Earth Orbit (LEO), the innovative technology presents promising qualities for space industry applications, particularly for radio frequency (RF) systems. This paper presents a S-band telemetry and data backup system for space radiation experiments for LEO to analyze the effects of long-term exposure of materials to the harsh space environment. The design presented in this paper is based on Commercial Off-The-Shelf (COTS) components, presenting approximately an average and peak power consumption of 0.8 W, and 1 W, respectively, while transmitting the peak configurable RF output power of 20 dBm. Including an AM radiation shielding, the system can be accommodated in 76 mm x 76 mm x 46 mm. Its modular design makes this system fully configurable, allowing a wide variety of applications. In this work, all the on-board measurements are backed up on an on-board memory card with error correction capabilities, as well as downlinked, enabling the possibility to monitor the total absorbed radiation during the experiment, as well as the communications link impact of the degradation of the on-board RF materials and circuit components. The system can be commanded while in orbit to reconfigure on-board sensor measurements and transceiver parameters. 

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5. Energetic Electron Precipitation Observed by FIREBIRD‐II Potentially Driven by EMIC Waves: Location, Extent, and Energy Range From a Multievent Analysis

   https://doi.org/10.1029/2020GL091564  

   Capannolo, L.; Li, W.; Spence, H.; Johnson, A. T.; Shumko, M.; Sample, J.; Klumpar, D. (March 2021, Geophysical Research Letters)

   Abstract We evaluate the location, extent, and energy range of electron precipitation driven by ElectroMagnetic Ion Cyclotron (EMIC) waves using coordinated multisatellite observations from near‐equatorial and Low‐Earth‐Orbit (LEO) missions. Electron precipitation was analyzed using the Focused Investigations of Relativistic Electron Burst Intensity, Range and Dynamics (FIREBIRD‐II) CubeSats, in conjunction either with typical EMIC‐driven precipitation signatures observed by Polar Orbiting Environmental Satellites (POES) or with in situ EMIC wave observations from Van Allen Probes. The multievent analysis shows that electron precipitation occurred in a broad region near dusk (16–23 MLT), mostly confined to 3.5–7.5 L‐shells. Each precipitation event occurred on localized radial scales, on average ∼0.3 L. Most importantly, FIREBIRD‐II recorded electron precipitation from ∼200 to 300 keV to the expected ∼MeV energies for most cases, suggesting that EMIC waves can efficiently scatter a wide energy range of electrons. 

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