23 research outputs found

    A GMSK VHF-uplink/UHF-downlink transceiver for the CubeSat missions: Thermo-functional performance

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    © 2018, CEAS. Functional and thermal performance characteristics of a very high frequency/ultra high frequency (VHF/UHF) transceiver based on Gaussian minimum shift keying (GMSK) modulation are presented. The transceiver has been designed for CubeSats telemetry and commanding needs or low rate data download. The design is validated at 27 dBm, 30 dBm and 33 dBm transmitting powers over −20 ∘C to +51 ∘C. Under these thermal conditions, the transmitter spurious dynamic response shows little if any change and the average sensitivity of receiver at the 12 dB signal noise and distortion (SINAD) is −116.7 dBm at 140 MHz and −116.78 dBm at 149.98 MHz. The transmitter and receiver frequencies are stable and the current consumption as well the output RF levels are steady. The design has been verified against a simulation model which allows system tradeoff analysis. The measurements demonstrate the transceiver made with commercial grade parts has dependable performance at the low earth altitudes and orbital heating conditions

    Performance of GMSK for telemetry and PN ranging under realistic conditions

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    In the frame of CCSDS activities, a system capable of simultaneously transmitting high rate telemetry and ranging has been studied in the last years. In this system the telemetry is transmitted through a GMSK modulator with the PN (Pseudo Noise) ranging sequence included as an additional phase shift. The receiver first estimates the transmitted telemetry bits, regenerates and removes the estimated GMSK signal from the received signal, and then estimates the ranging chips and, through a bank of correlators, the round trip delay of the received ranging signal. Ranging is an interfering signal which degrades the performance of the telemetry subsystem, while errors in the estimation of telemetry bits compromise the correct detection of the ranging chips. The first simulation results obtained by ESOC were presented at TTC 2010 in the paper “Analysis of GMSK for Simultaneous Transmission of Ranging and Telemetry” and were limited to ideal synchronization and to the case of a telemetry bit rate equal to the ranging chip rate. In this new paper we describe additional results obtained from the simulation of the complete system, including realistic synchronization, and for telemetry rates which are different from the chip rate. The paper will: 1) consider the effects of the receiver telemetry clock jitter on the regenerated GMSK signal and on the subsequent ranging receiver: it will be shown that regeneration through the Laurent OQPSK approximation or through a look-up table, which directly stores the GMSK phase for each combination of input bits, achieve good performance with low complexity; 2) discuss the effects of perfect synchronization between the transmitted telemetry and ranging signals: in this case, depending on the relative delay between the two signals, the recovered ranging clock may suffer from a bias, which corresponds to an error in the range estimation (lack of accuracy); 3) estimate the system losses when the telemetry bit rate is different from the ranging chip rate; 4) estimate the loss due to phase noise. The analysis will be limited to the case of GMSK with BTb=0.5 and ranging code T2B, which is the suggested scheme for deep space missions with demanding acquisition time requirements

    ソフトウェア無線プラットフォームの実装戦略を用いた超小型衛星通信システムの最適化

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    In nano-satellite missions, Software Defined Radios (SDR) have been widely used in the implementation of communication subsystems in order to increase the flexibilization both in the space segment and on the ground stations. Also, Commercial Off-The-Shelf components (COTS) are widely used to develop subsystems for nano-satellite missions in order to reduce development costs and because those are relatively easy to purchase especially for developing countries. However, COTS components are not space-certified and it becomes a problem when satellites are wanted to be used in high reliability missions. An example of that is Ten-Koh, a Low Earth Orbit (LEO) environment observation satellite developed in the Kyushu Institute of Technology in Japan, in which one of the top-level mission requirements was to re-use as much as possible the components utilized on a previous successful mission (Shinen-2) in order to mitigate the failure risks by using non-certified/non-space heritage components and to decrease the development time following the lean satellite design methodology. In this research, an SDR implementation for the space segment is proposed in order to optimize the communication system designed for Ten-Koh satellite. The proposed implementation consists of the integration of two COTS modules (a single-board computer with a radio frequency module) using embedded Linux, Python and GNU radio developing tools. The purpose is to demonstrate that the proposed system can be used safely in future satellite missions overcoming the design constraints, limitations and issues experimented during the Ten-Koh design and operation phases showing the improvements in terms of performance, flexibility, cost and development time. In addition to above, this research shows the on-orbit issues presented in the Ten-Koh mission due to the radiation effects and describes the facilities, equipment, methodology and results of a radiation test performed for the main processor used in the Ten-Koh mission and for the single-board computer used in the proposed SDR system in order to find the possible causes of the failures presented on-orbit and to compare the results for verifying if the proposed system can be used safely in the radiation environment on LEO orbit.九州工業大学博士学位論文 学位記番号:工博甲第498号 学位授与年月日:令和2年3月25日1 - INTRODUCTION|2 - TEN-KOH MISSION OVERVIEW|3 - TEN-KOH COMMUNICATION SYSTEM ARCHITECTURE|4 - PROPOSED SDR IMPLEMENTATION|5 - RESULTS AND DISCUSSION|6 - RADIATION TEST|7 - CONCLUSION九州工業大学令和元年

    AIS message extraction from overlapped AIS signals for SAT-AIS applications

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    The AIS (Automatic Identification System) is a communication standard for ships traveling the seas and oceans. It serves as a collision avoidance system by identifying nearby ships, thus assisting in safe navigation. The SAT-AIS (Satellite based Automatic Identification System) is a communication technology for ship traffic surveillance from space and is under active research and development worldwide. The basic principle of the SAT-AIS system is to monitor AIS channels. The motivation for using terrestrial AIS technologies with space applications is of great interest to safety organizations that monitor ship traffic in high seas and oceans. These regions far away from coastal zones are unreachable from the terrestrial antennas, which have a usual range of 40 kilometres. Successful application of the SAT-AIS could provide AIS data to coast guards and other agencies, with an hourly ship location update from every place on the planet. The first trials of SAT-AIS in 2006 suffered from some serious difficulties. As AIS was initially designed to be a terrestrial traffic avoidance application for ships, with the traffic participants communicating among their neighbours and the nearby coast guard, it was developed without resistivity against effects which arise when applied for space applications. Apart from signal strength and Doppler shift effects, which could be constructively handled, the demodulation of overlapped AIS messages proved to be a great challenge. This work analyses the problem of overlapping AIS signals and proposes innovative approaches for reconstructing these based on L^2 norm orthogonalization and projections. Moreover, the work showcases results of demodulation efficiency analysis for simulated real world application of satellite passes over a dedicated shipping region based on AIS channel simulation in noisy environment For more reliable AIS data reception in space, new dedicated frequencies are allocated for channels AIS3 and AIS4, which are being affirmed for all AIS transceiver installations from 2013. These new frequency channels carry dedicated messages with a ship position report, encapsulated into smaller data packets at lower report rates, which promises to partly eliminate the packet overlapping problem. Since the new Space-AIS format does not completely solve the packet collision problem and as the steady growth of interest on terrestrial-AIS message content received from space continues to persist, the topic of solving overlapped AIS signals remains vital for SAT-AIS applications

    Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

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    Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression

    OPTIMIZATION OF INTER-CUBESAT COMMUNICATION LINKS

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    Cubesat constellations may become the next generation of communication backbone architecture to provide future worldwide communication services. In this thesis, we investigate the feasibility of deploying Cubesat constellations with inter-satellite links (ISL) for the delivery of continuous global communication. Cubesat constellation designs for various mission scenarios are proposed and verified using a simulation toolkit commonly used by space engineers. Link optimization to improve the overall theoretical data rate is also discussed. The results obtained affirm that a Cubesat constellation at an orbital height of 450 km can achieve a data rate of 11.46 kbps and requires the least number of satellites in the constellation. We ascertained that using ISL as the communication backbone in a network architecture, complete with space and globally distributed ground nodes, is achievable. In the near future, there is a high potential for the implementation of ISL with optical communication links, whereby there is assurance of a significantly higher data rate and lower power requirements.Civilian, Singapore Technologies ElectronicsApproved for public release; distribution is unlimited

    Proceedings of the Third International Mobile Satellite Conference (IMSC 1993)

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    Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial cellular communications services. While the first and second International Mobile Satellite Conferences (IMSC) mostly concentrated on technical advances, this Third IMSC also focuses on the increasing worldwide commercial activities in Mobile Satellite Services. Because of the large service areas provided by such systems, it is important to consider political and regulatory issues in addition to technical and user requirements issues. Topics covered include: the direct broadcast of audio programming from satellites; spacecraft technology; regulatory and policy considerations; advanced system concepts and analysis; propagation; and user requirements and applications

    衛星受信機のための動的部分再構成型復調器の設計と実装

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    九州工業大学博士学位論文 学位記番号:工博甲第461号 学位授与年月日:平成30年9月21日1: Introduction|2: Background and Literature Review|3: Dynamic Partial Reconfigurable Demodulation System – Classification|4: DPRDS – DPR|5: ICAP Multiple Access by DPRDS and SEU Mitigation Systems|6: Conclusion and Future Perspective九州工業大学平成30年
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