2,560 research outputs found
Survey of Inter-satellite Communication for Small Satellite Systems: Physical Layer to Network Layer View
Small satellite systems enable whole new class of missions for navigation,
communications, remote sensing and scientific research for both civilian and
military purposes. As individual spacecraft are limited by the size, mass and
power constraints, mass-produced small satellites in large constellations or
clusters could be useful in many science missions such as gravity mapping,
tracking of forest fires, finding water resources, etc. Constellation of
satellites provide improved spatial and temporal resolution of the target.
Small satellite constellations contribute innovative applications by replacing
a single asset with several very capable spacecraft which opens the door to new
applications. With increasing levels of autonomy, there will be a need for
remote communication networks to enable communication between spacecraft. These
space based networks will need to configure and maintain dynamic routes, manage
intermediate nodes, and reconfigure themselves to achieve mission objectives.
Hence, inter-satellite communication is a key aspect when satellites fly in
formation. In this paper, we present the various researches being conducted in
the small satellite community for implementing inter-satellite communications
based on the Open System Interconnection (OSI) model. This paper also reviews
the various design parameters applicable to the first three layers of the OSI
model, i.e., physical, data link and network layer. Based on the survey, we
also present a comprehensive list of design parameters useful for achieving
inter-satellite communications for multiple small satellite missions. Specific
topics include proposed solutions for some of the challenges faced by small
satellite systems, enabling operations using a network of small satellites, and
some examples of small satellite missions involving formation flying aspects.Comment: 51 pages, 21 Figures, 11 Tables, accepted in IEEE Communications
Surveys and Tutorial
Pathfinder autonomous rendezvous and docking project
Capabilities are being developed and demonstrated to support manned and unmanned vehicle operations in lunar and planetary orbits. In this initial phase, primary emphasis is placed on definition of the system requirements for candidate Pathfinder mission applications and correlation of these system-level requirements with specific requirements. The FY-89 activities detailed are best characterized as foundation building. The majority of the efforts were dedicated to assessing the current state of the art, identifying desired elaborations and expansions to this level of development and charting a course that will realize the desired objectives in the future. Efforts are detailed across all work packages in developing those requirements and tools needed to test, refine, and validate basic autonomous rendezvous and docking elements
Digital Twin for Non-Terrestrial Networks: Vision, Challenges, and Enabling Technologies
This paper explores the transformative potential of digital twin (DT)
technology in the context of non-terrestrial networks (NTNs). NTNs,
encompassing both airborne and space-borne elements, present unique challenges
in network control, management, and optimization. DT is a novel approach to
design and manage complicated cyber-physical systems with a high degree of
automation, intelligence, and resilience. The adoption of DTs within NTNs
offers a dynamic and detailed virtual representation of the entire ecosystem,
enabling real-time monitoring, simulations, and data-driven decision-making.
This paper delves into the envisioned integration of DTs in NTNs, discussing
the technical challenges and highlighting key enabling technologies. Emphasis
is placed on technologies such as Internet of things (IoT), artificial
intelligence (AI), space-based cloud computing, quantum computing, and others,
providing a comprehensive overview of their potentials in empowering DT
development for NTNs. In closing, we present a case study involving the
implementation of a data-driven DT model to facilitate dynamic and
service-oriented network slicing within an open radio access network (O-RAN)
architecture for NTNs. This work contributes to shaping the future of network
control and management in the dynamic and evolving landscape of non-terrestrial
communication systems
Technology for the Future: In-Space Technology Experiments Program, part 2
The purpose of the Office of Aeronautics and Space Technology (OAST) In-Space Technology Experiments Program In-STEP 1988 Workshop was to identify and prioritize technologies that are critical for future national space programs and require validation in the space environment, and review current NASA (In-Reach) and industry/ university (Out-Reach) experiments. A prioritized list of the critical technology needs was developed for the following eight disciplines: structures; environmental effects; power systems and thermal management; fluid management and propulsion systems; automation and robotics; sensors and information systems; in-space systems; and humans in space. This is part two of two parts and contains the critical technology presentations for the eight theme elements and a summary listing of critical space technology needs for each theme
Advanced adaptive compensation system for free-space optical communications
Massive amounts of information are created daily in commercial fields like earth observation, that must be downloaded to earth ground stations in the short time of a satellite pass. Today, much of the collected information must be dropped due to lack of bandwidth, and laser downlinks can offer tenths of gigabits throughput solving this bottleneck limitation. In a down-link scenario, the performance of laser satellite communications is limited due to atmospheric turbulence, which causes fluctuations in the intensity and the phase of the received signal leading to an increase in bit error probability. In principle, a single-aperture phase-compensated receiver, based on adaptive optics, can overcome atmospheric limitations by adaptive tracking and correction of atmospherically induced aberrations. However, under strong-turbulence situations, the effectiveness of traditional adaptive optics systems is severely compromised. In such scenarios, sensor-less techniques offer robustness, hardware simplicity, and easiness of implementation and integration at a reduced cost, but the state-of-the-art approaches still require too many iterations to perform the correction, exceeding the temporal coherence of the field and thus falling behind the field evolution.
This thesis proposes a new iterative AO technique for strong turbulence compensation that reduces the correction time, bridging the limitation of similar systems in lasercom applications. It is based on the standard sensor-less system design, but it additionally uses a short-exposure focal intensity image to accelerate the correction. The technique combines basic principles of Fourier optics, image processing, and quadratic signal optimization to correct the wave-front. This novel approach directly updates the phases of the most intense focal-plane speckles, maximizing the power coupled into a single-mode fiber convexly.
Numerical analyses show that this method has a robust and excellent performance under very strong turbulence. Laboratory results confirm that a focal speckle pattern can be used to accelerate the iterative compensation. This technique delivers nearly twofold bandwidth reduction compared with standard methods, and sufficient signal gain and stability to allow high throughput data transmission with nearly error-free performance in emulated satellite downlink scenarios. A property highlight is the in-advance knowledge of the required number of iterations, allowing on-demand management of the loop bandwidth in different turbulent regimes. Besides remaining conceptually and technically simple, it opens a new insight to iterative solutions that may lead to the development of new methods. With further refinement, this technique can surely contribute to making possible the use of iterative solutions in laser communicationsSatélites de observación de la tierra diariamente generan gigantescas cantidades de datos que deben ser enviados a estaciones terrenas. La mayorÃa de la información recolectada debe desecharse debido al reducido tiempo visible de un satélite en movimiento y el limitado ancho de banda de transmisión. Enlaces ópticos pueden solucionar esta limitación ofreciendo multi-gigabit de ancho de banda. Sin embargo, el desempeño de un downlink laser está limitado por la turbulencia atmosférica, la cual induce variaciones en la intensidad y la fase de la señal recibida incrementando la probabilidad de error en los datos recibidos. En principio, un receptor basado en una apertura simple utilizando óptica adaptativa puede corregir las aberraciones de fase inducidas por la atmósfera, mejorando el canal de transmisión. Sin embargo, la eficiencia de los sistemas de óptica adaptativa tradicionales se ve seriamente reducida en situaciones de turbulencia fuerte. En tales escenarios, técnicas iterativas ofrecen mayor robustez, simplicidad de diseño e implementación, asà como también facilidad de integración a un costo reducido. Desafortunadamente, dicha tecnologÃa aún requiere demasiadas iteraciones para corregir la fase distorsionada, excediendo el tiempo de coherencia del frente de onda. Esta tesis propone una nueva técnica iterativa de óptica adaptativa capaz de reducir el tiempo de convergencia en escenarios de turbulencia fuerte. La técnica utiliza el diseño tradicional de los sistemas de corrección iterativos, agregando el uso de una imagen focal de intensidad para acelerar el proceso de corrección del campo distorsionado. En dicha técnica se combinan principios básicos de óptica de Fourier, procesamiento de imagen, y optimización cuadrática de la señal para corregir el frente de onda. De esta forma, la fase de los puntos focales de mayor intensidad (speckles) puede modificarse directamente y con ello maximizar de forma convexa la potencia acoplada en fibra. Los análisis numéricos demuestran robustez y un excelente desempeño en escenarios de turbulencia fuerte. Los resultados de laboratorio confirman que el moteado de intensidad puede utilizarse para acelerar la corrección iterativa. Esta técnica utiliza la mitad del ancho de banda requerido con la técnica tradicional, al mismo tiempo que ofrece suficiente ganancia y estabilidad de la señal para lograr enlaces ópticos con muy baja probabilidad de error. Al mismo tiempo, la técnica propuesta permite conocer con anticipación el número total de iteraciones y posibilita la administración bajo demanda del ancho de banda requerido en diferentes escenarios de turbulencia. Esta tesis ofrece una mirada diferente a los métodos iterativos, posibilitando el desarrollo de nuevos conceptos y contribuyendo al uso de soluciones iterativas en comunicaciones laser por espacio libre.Postprint (published version
A Comprehensive Survey on Orbital Edge Computing: Systems, Applications, and Algorithms
The number of satellites, especially those operating in low-earth orbit
(LEO), is exploding in recent years. Additionally, the use of COTS hardware
into those satellites enables a new paradigm of computing: orbital edge
computing (OEC). OEC entails more technically advanced steps compared to
single-satellite computing. This feature allows for vast design spaces with
multiple parameters, rendering several novel approaches feasible. The mobility
of LEO satellites in the network and limited resources of communication,
computation, and storage make it challenging to design an appropriate
scheduling algorithm for specific tasks in comparison to traditional
ground-based edge computing. This article comprehensively surveys the
significant areas of focus in orbital edge computing, which include protocol
optimization, mobility management, and resource allocation. This article
provides the first comprehensive survey of OEC. Previous survey papers have
only concentrated on ground-based edge computing or the integration of space
and ground technologies. This article presents a review of recent research from
2000 to 2023 on orbital edge computing that covers network design, computation
offloading, resource allocation, performance analysis, and optimization.
Moreover, having discussed several related works, both technological challenges
and future directions are highlighted in the field.Comment: 18 pages, 9 figures and 5 table
EO-ALERT: A Novel Architecture for the Next Generation of Earth Observation Satellites Supporting Rapid Civil Alerts
Satellite Earth Observation (EO) data is ubiquitously used in many applications, providing basic services to
society, such as environment monitoring, emergency management and civilian security. Due to the increasing request
of EO products by the market, the classical EO data chain generates a severe bottleneck problem, further exacerbated
in constellations. A huge amount of EO raw data generated on-board the satellite must be transferred to ground,
slowing down the EO product availability, increasing latency, and hampering the growth of applications in
accordance with the increased user demand.
This paper provides an overview of the results achieved by the EO-ALERT project (http://eo-alert-h2020.eu/), an
H2020 European Union research activity led by DEIMOS Space. EO-ALERT proposes the definition and
development of the next-generation EO data processing chain, based on a novel flight segment architecture that
moves optimised key EO data processing elements from the ground segment to on-board the satellite, with the aim of
delivering the EO products to the end user with very low latency (quasi-real-time). EO-ALERT achieves, globally,
latencies below five minutes for EO products delivery, reaching latencies below 1 minute in some scenarios.
The proposed architecture solves the above challenges through a combination of innovations in the on-board
elements of the data chain and the communications. Namely, the architecture introduces innovative technological
solutions, including on-board reconfigurable data handling, on-board image generation and processing for the
generation of alerts (EO products) using Artificial Intelligence (AI), on-board data compression and encryption using
AI, high-speed on-board avionics, and reconfigurable high data rate communication links to ground, including a
separate chain for alerts with minimum latency and global coverage.
The paper presents the proposed architecture, its performance and hardware, considering two different user
scenarios; ship detection and extreme weather observation/nowcasting. The results show that, when implemented
using COTS components and available communication links, the proposed architecture can deliver alerts to ground
with latency lower than five minutes, for both SAR and Optical missions, demonstrating the viability of the EOALERT
concept and architecture. The paper also discusses the implementation on an avionics test bench for
testing the architecture with real EO data, with the aim of demonstrating that it can meet the requirements of the
considered scenarios in terms of detection performance and provides technologies at a high TRL (4-5). When
proven, this will open unprecedented opportunities for the exploitation of civil EO products, especially in latency
sensitive scenarios, such as disaster management
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