The Starlink satellites launched on 3 February 2022 were lost before they fully arrived in their designated orbits. The loss was attributed to two moderate geomagnetic storms that occurred ...consecutively on February 3-4. We investigate the thermospheric neutral mass density variation during these storms with the Multiscale Atmosphere-Geospace Environment (MAGE) model, a first-principles, fully coupled geospace model. Simulated neutral density enhancements are validated by Swarm satellite measurements at the altitude of 400-500 km. Comparison with standalone TIEGCM and empirical NRLMSIS 2.0 and DTM-2012 models suggests better performance by MAGE in predicting the maximum density enhancement and resolving the gradual recovery process. Along the Starlink satellite orbit in the middle thermosphere (∼ 200 km altitude), MAGE predicts up to 150% density enhancement near the second storm peak while standalone TIEGCM, NRLMSIS 2.0 and DTM-2012 suggest only ∼ 50% increase. MAGE also suggests altitudinal, longitudinal, and latitudinal variability of storm-time percentage density enhancement due to height dependent Joule heating deposition per unit mass, thermospheric circulation changes, and travelling atmospheric disturbances. This study demonstrates that a moderate storm can cause substantial density enhancement in the middle thermosphere. Thermospheric mass density strongly depends on the strength, timing, and location of high-latitude energy input, which cannot be fully reproduced with empirical models. A physics-based, fully coupled geospace model that can accurately resolve the high-latitude energy input and its variability is critical to modeling the dynamic response of thermospheric neutral density during storm time.
Summary
This paper presents low Earth orbit (LEO) satellite constellation configuration based on the performance of Doppler effect in laser intersatellite links (LISLs). It studies the impact of the ...LEO constellation's parameters on the performance of the Doppler effect in LISLs. The paper aims to develop LEO satellite constellation configurations that evolve LISLs with minimal Doppler shift. It evaluates the impact of the variation of the relative distance, the inclination angle of the LEO constellation orbital planes, the orbital planes number in the LEO constellation, and the altitude on the performance of Doppler wavelength shift (DWS) in LISLs, for different operating laser wavelengths (OLWs) with respect to two possible intersatellite links (ISL) connection modes within the constellation, straight ISL (n‐to‐n) and inclined ISL (n‐to‐n − 1). n is the order of the satellite in the orbital plane. Simulations are conducted to evaluate the performance of these configurations in terms of altitude, OLW, inclination angle, and the number of orbital planes. In addition, both OneWeb and Starlink constellations are studied to evaluate DWS performance. The study demonstrates that DWS decreases either with the diminution of the relative distance between linked LEO satellites, the inclination of LEO constellation, and the OLW, or with the augmentation of the orbital planes number and altitude. Moreover, the overall DWS between two LEO satellites in the proposed constellation is at least 50% lower than the constellation configuration in other literature. The paper proposes the LEO constellation's configurations that perform LISLs with less possible Doppler effect by optimizing the LEO constellation parameters that impact the Doppler effect. The result of this study helps in the early stage of LEO satellite constellation designing in terms of payload simplicity and cost.
This letter presents an observability analysis for terrestrial receiver localization via pseudorange measurements extracted from a single low Earth orbit (LEO) satellite. It is shown that a ...stationary receiver with an unknown state (position and time) can theoretically localize itself with a LEO satellite with a known state (position, velocity, and time). In addition, bounds on the determinant of the <inline-formula> <tex-math notation="LaTeX">l </tex-math></inline-formula>-step observability matrix are derived and geometric interpretations are presented indicating directions of poor observability. The implications of the analysis on observability-aided LEO satellite selection are discussed. Experimental results are presented showcasing the conclusions of the observability analysis for a receiver localizing itself with a single Starlink satellite or a single Orbcomm satellite.
Democratizing LEO Satellite Network Measurement Izhikevich, Liz; Tran, Manda; Izhikevich, Katherine ...
Proceedings of the ACM on measurement and analysis of computing systems,
02/2024, Letnik:
8, Številka:
1
Journal Article
Recenzirano
Low Earth Orbit (LEO) satellite networks are quickly gaining traction with promises of impressively low latency, high bandwidth, and global reach. However, the research community knows relatively ...little about their operation and performance in practice. The obscurity is largely due to the high barrier of entry for measuring LEO networks, which requires deploying specialized hardware or recruiting large numbers of satellite Internet customers. In this paper, we introduce HitchHiking, a methodology that democratizes global visibility into LEO satellite networks. HitchHiking builds on the observation that Internet-exposed services that use LEO Internet can reveal satellite network architecture and performance, bypassing the need for specialized hardware. We evaluate HitchHiking against ground truth measurements and prior methods, showing that it provides more coverage and accuracy. With HitchHiking, we complete the largest study to date of Starlink network latency, measuring over 2,400 users across 27 countries. We uncover unexpected patterns in latency that surface how LEO routing is more complex than previously understood. Finally, we conclude with recommendations for future research on LEO networks.
New satellite systems such as Starlink have arisen as promising illumination sources for passive radar applications due to their high power and wide-band signal (transmission channels up to 250 MHz), ...and their almost ubiquitous presence. In this work, an acquisition system based on Radio Frequency System-on-Chip (RFSoC) with an instantaneous bandwidth of 256 MHz was employed to record complete Starlink signals at different carrier frequencies. The Starlink users' downlink was selected as the source of illumination due to its transmission characteristics. A measurement campaign was carried out at Warsaw University of Technology facilities to acquire transmitted signals at different transmission channels. A detailed analysis in time and frequency domains is carried out to identify Starlink's capabilities for passive radar purposes. Results show similar behavior of Starlink signals at different channels, with an under-demand pulse kind transmission for the users' data as well as continuous transmission of pilot carriers for synchronization purposes. The pulsed data signal was employed to compute the first ambiguity function of a Starlink signal to determine the performance of a future Starlink-based passive radar.
In this paper, the possibility to exploit Starlink satellites as illuminators of opportunity for passive inverse synthetic aperture radar is investigated. Specifically, the always on beacon signals ...transmitted by Starlink satellites are considered as a reliable source of illumination. Although these signals are inherently narrow-band, their potential reception over long times (e.g. few minutes), and the corresponding significant variations of the aspect angle to a target during such times, allow the exploitation of beacon signals for Doppler radar tomography, following an approach similar to the one described in 1. To this end, the slow-time K-space signal occupancy of Starlink beacon signals is derived and it is shown how the K-space can be filled in. The possibility to utilise simultaneously multiple beacon signals originating from multiple Starlink satellites is also investigated.
Megaconstellation networks, represented by Starlink and OneWeb, have become a promising solution for the wide-area Internet of Things (IoT). IoT messages collected by the satellite can be routed to ...the ground gateway via multiple intersatellite link (ISL) relays and then access the ground network. Compared to traditional constellations, megaconstellations with massive satellites require more ISL relays that are greatly affected by the number and location of ground gateways. In this article, we focus on the ISL usage for connecting satellites and gateways and propose a novel method with low computation cost to evaluate the ISL usage metric. Then, we formulate a mixed-integer optimization model for the gateway site optimization (GSO) problem with minimizing the overall ISL usage, which is then simplified through model transformation. An IBD-PSO algorithm is proposed to solve the transformed GSO problem. Based on the Starlink constellation, simulation results have verified the proposed method by comparisons with previous studies. We further investigate how the gateway placement is affected by the gateway number and traffic demand pattern. The relations between gateway placement and ISL hop count of different satellites are also studied.
Low Earth Orbit Satellite Networks such as Starlink promise to provide world-wide Internet access. While traditionally designed for stationary use, a new dish, released in April 2023 in Europe, ...provides mobile Internet access including in-motion usage, e.g., while mounted on a car. In this paper, we design and build a mobile measurement setup. Our goal is to fully autonomously conduct continuous Starlink measurements while the car is in motion. We share our practical experiences, including challenges regarding the permanent power supply. We measure the Starlink performance over the span of two months from mid-January to mid-March 2024 when the car is in motion. The measurements consist of all relevant network parameters, such as the download and upload throughput, the RTT, and packet loss, as well as detailed power consumption data. We analyze our dataset to assess Starlink's mobile performance in Central Europe, Germany, and compare it to stationary measurements in proximity. We find that the mobile performance is significantly worse than stationary performance. The power consumption of the new dish is higher, but seems to be more correlated to the heating function of the dish than to the speed of the vehicle.
In this paper, we begin by describing the Starlink constellation’s configuration plan, treating each satellite as a network node, naming and numbering the various nodes, and then classifying the ...laser interstellar links (LISLs) according to their orbital alignment and whether they are permanently visible. Whereupon, the method for calculating the respective theoretical interstellar distances required for establishing LISLs under two distinct orbital scenarios, co-orbital and hetero-orbital are analyzed, and the optimal phasing factors are proposed by solving an optimization algorithm for the shortest distance. The OneWeb and Starlink constellations, as well as the constellation states of various phasing factors are simulated, respectively. The Starlink constellation with F = 11 obtains the best coverage between 60° north and south latitudes predicated upon the analysis of the constellation N Asset Coverage. Following that, the first phase of the Starlink constellation deployment was modeled in order to analyze and count the number of permanent LISLs in orbit, adjacent to, and nearby. Subsequently, the characteristics of azimuthal, elevation, and range (AER) were subsequently analyzed to ascertain their variation law and to compile the number of permanent and temporary LISLs that could be established at various inter-distance ranges. Finally, predicated on the simulation results, the optimal LISLs connection strategy for the Starlink constellation is evaluated and a static topology for the constellation is constructed.
There has been a great interest in deploying large-scale Low-Earth Orbit (LEO) satellite constellations for wireless communications. This paper shows that LEO satellite constellations developed for ...communication purposes can be exploited for ground target imaging applications, where a unique advantage is to achieve super-high imaging resolutions that are not achievable via other imaging techniques. A new imaging algorithm is developed for this novel integrated sensing and communication (ISAC) application based on delay-sensitive signal processing and irregular sensing data exploitation. Imaging performance is analyzed. Simulations with the practical SpaceX Starlink satellite orbital data are conducted to verify both the new algorithm and the analysis results. This paper demonstrates that while the resolution of conventional satellite imaging is limited to sub-meters, the new method can potentially use only a small set of LEO satellites to achieve sub-centimeter resolution.
