Non-geostationary Satellite Research Articles

Generation and Evaluation of LAI and FPAR Products from Himawari-8 Advanced Himawari Imager (AHI) Data

Leaf area index (LAI) and fraction of photosynthetically active radiation (FPAR) absorbed by vegetation are two of the essential biophysical variables used in most global models of climate, hydrology, biogeochemistry, and ecology. Most LAI/FPAR products are retrieved from non-geostationary satellite observations. Long revisit times and cloud/cloud shadow contamination lead to temporal and spatial gaps in such LAI/FPAR products. For more effective use in monitoring of vegetation phenology, climate change impacts, disaster trend etc., in a timely manner, it is critical to generate LAI/FPAR with less cloud/cloud shadow contamination and at higher temporal resolution—something that is feasible with geostationary satellite data. In this paper, we estimate the geostationary Himawari-8 Advanced Himawari Imager (AHI) LAI/FPAR fields by training artificial neural networks (ANNs) with Himawari-8 normalized difference vegetation index (NDVI) and moderate resolution imaging spectroradiometer (MODIS) LAI/FPAR products for each biome type. Daily cycles of the estimated AHI LAI/FPAR products indicate that these are stable at 10-min frequency during the day. Comprehensive evaluations were carried out for the different biome types at different spatial and temporal scales by utilizing the MODIS LAI/FPAR products and the available field measurements. These suggest that the generated Himawari-8 AHI LAI/FPAR fields were spatially and temporally consistent with the benchmark MODIS LAI/FPAR products. We also evaluated the AHI LAI/FPAR products for their potential to accurately monitor the vegetation phenology—the results show that AHI LAI/FPAR products closely match the phenological development captured by the MODIS products.

Design and analysis of multibeam communication satellite links operated at Ka Band Frequency in Indonesia

In this paper, we design the link budget of communication satellite. This communication satellite is designed for Ka-Band Frequency for broadband communication in Non-Geostationary Orbit (NGSO) with altitude of 1200 km. The ability of this communication satellite depends on the strength of the signal and the amount of thermal noise. Ka-Band has wider bandwidth and higher data capacity but the drawback of this frequency is it is susceptible to rain attenuation in which Indonesia is an equatorial area that has high rainfall rate, so that the design of communication satellite in Ka-Band needs more consideration to determine satellite system parameter to keep the signal strength great. Indonesia is a wide archipelago country and satellite link design requires beam that can cover all Indonesia with great signal strength and multibeam antenna technology is one of solutions to overcome it. In this research, design and analysis of communication satellite is done using multibeam antenna. The main challenge of the design is to generate the link budget’s result to meet determined parameter. Iterative calculation in design must be used to find an effective link margin and bit rate of this communication satellite. The main result of this research is multi beam satellite provide better performance than single beam satellite in Ka band frequency. The use of BPSK modulation in multi beam satellite shows better performance than other modulation types.

Spectrum Sensing and Recognition in Satellite Systems

In the scenario of frequency coexistence between the geostationary (GEO) and non-geostationary (NGEO) satellite networks, the NGEO system should not incur harmful interference to the GEO system according to the policy of the Radio Regulations. Therefore, spectrum sensing as a promising solution is applied widely in this scenario. With the increasing number of NGEO satellites in the space, one NGEO system could be affected by other NGEO systems while sensing the signal from the GEO system. Given these preconditions, the cognitive radio scenario considered in this paper is that: the GEO system is regarded as the primary user, one NGEO system is regarded as the secondary user, and another NGEO system is regarded as the interfering user. Meanwhile, all the satellite systems are supposed to operate with more than one discrete transmit power levels, which is practical and fits the concept of adaptive power control. In our context, we propose a spectrum strategy using hypothesis testing as well as maximum a posteriori to differentiate the GEO signal from the interfering NGEO and noise, and then identify the specific power level utilized by the GEO system. Moreover, we derive the closed-form expressions for threshold of verifying the status of the GEO and for decision regions to determine its power level. Finally, extensive simulations are provided to verify the proposed studies.

Measuring Data Loss Resulting from Interference

This paper presents an observing methodology for calibrated measurements of radio interference levels and compares these with threshold interference limits that have been established for interference entering the bands allocated to the Radio Astronomy Service. The measurement time and bandwidth intervals for these observations may be commensurate with the time and frequency variability characteristic of the interfering signals and the threshold levels may be appropriately scaled from the values presented in ITU-R RA.769 using a 2000[Formula: see text]s reference time interval. The data loss for astronomical instruments may be measured as a percentage of occupancy in the time–frequency domain both for short and long measurement intervals. The observed time–frequency occupancy characteristics for non-geostationary satellite systems and earth stations in the mobile–satellite service may be incorporated into an effective power flux density simulation to obtain the effective data loss and sky blockage due to these services.

Secure Communication in Non-Geostationary Orbit Satellite Systems: A Physical Layer Security Perspective

Satellite communication systems serve as an indispensable component of wireless heterogeneous networks in 5G era for providing various critical civil and military applications. However, due to the broadcast nature and full accessibility of wireless medium, serious security threats exist from such systems. As an effort to address this issue, this paper, for the first time, investigates the secure communication in a non-geostationary orbit (NGSO) satellite system from a physical layer security perspective. Specifically, we focus on the downlink of an NGSO satellite which provides services to a fixed earth station and is wiretapped by a fixed eavesdropper. We first apply three types of orbiting models to characterize the movement state of the satellite. Based on the orbiting models, we then provide theoretical analysis for the secure communication performance of such a system. The expressions of two fundamental performance metrics, secrecy capacity and secrecy outage probability, are derived in a closed form for any system time. Finally, we conduct extensive simulations to validate our theoretical performance analysis and illustrate the security performance in a practical NGSO satellite communication system.

Regulatory Best Practices to Bridge the Digital Divide and Make Internet Access Available and Affordable for Everyone Using Non-Geostationary Satellite Constellations

Regulatory Best Practices to Bridge the Digital Divide and Make Internet Access Available and Affordable for Everyone Using Non-Geostationary Satellite Constellations

Occurrence probability of co-frequency interference and system availability of non-geostationary satellite system in global dynamic scene

Occurrence probability of co-frequency interference and system availability of non-geostationary satellite system in global dynamic scene

NewSpace Spectrum Sharing: Assessing Interference Risk and Mitigations for New Satellite Constellations

The number of satellites in non-geostationary orbits (NGSOs) is planned to grow dramatically, from about a thousand in orbit today to more than 15,000. Most of the new constellations will provide broadband communications, sharing spectrum in Ku/Ka-band and V-band. While not all the constellations will be launched, the potential for harmful interference is obvious. However, the actual risk of interference is not known. We perform a quantitative risk assessment for NGSO-NGSO interference to inform regulatory and operational decision making. To our knowledge, this is the first publicly available probabilistic NGSO-NGSO risk assessment for multi-constellation configurations. Unlike previous studies that only consider RF signal levels, we characterize interference impacts by the degradation in data throughput. We use Monte Carlo modeling to calculate the risk of co-channel interference between four planned NGSO constellations operating in Ka-band (LeoSat, O3b, OneWeb’s MEO, and Telesat) and three in V-band (OneWeb’s MEO, SpaceX’s LEO, and Telesat). We consider the interference risk to communication between an NGSO satellite and a user terminal. (The interference risk is greater for user terminals than gateways.) Engineering risk is the combination of likelihood and consequence. Our consequence metric is the percentage degradation in throughput relative to a fixed reference value (%DTp). Our baseline condition excludes interference hazards but includes poor atmospheric transmission so that %DTp can be non-zero even for baseline. Our primary result is that NGSO-NGSO interference risk in Ka-band and V-band is low, even without mitigation. Under reasonable assumptions, we find that the mean value of %DTp for the baseline condition can be up to 12 percentage points (pp); interference increases this by 3pp or less. In our most conservative scenario (all satellites in an interfering constellation form co-channel, co-polarization links with earth stations in a small area), the increase in mean %DTp due to interference can reach 18pp. The large constellations—OneWeb and SpaceX—are most likely to cause interference to others. Our results suggest that the need for interference mitigation will be limited. In cases where mitigation is needed, we find that look-aside mitigation based on ephemeris information—which does not require coordination between operators—can benefit large constellations but can harm small constellations. We believe that mitigation will have to include coordination. This raises questions about how to achieve coordination using operational information, e.g., which satellite is serving a particular earth station on which channel.

Economic Critiques of National and International Ngso Spectrum Regulations Concerning the Ku-And Ka-Bands

Recently, the Federal Communications Commission (FCC) granted OneWeb permission to use certain portions in Ku-/Ka- spectrum bands on new non-geostationary satellite orbit (NGSO) technology to offer Fixed Satellite Services (FSS) broadband services in the United States. Before the grant was awarded, twelve other applicants applied to the FCC hoping to deploy NGSO-like networks in the same spectrum bands to offer the same services. Such a surge in the number of applications - what has been called a “gold rush” mentality - to gain access to Ku-/Ka-band frequencies raised questions to the spectrum management process used to allocate and assign these frequencies: whether the national and international regulations applied to FSS-NGSO provide sufficient incentives for license holders to be selected based upon their placing the highest value on the spectrum, or whether there may be sufficient market failures justifying the use of a non-market-based spectrum management approach to accessing these resources? This paper seeks answers to these questions by providing a critique of the FSS-NGSO spectrum allocation and assignment processes consistent with modern spectrum management best practices; it uses OneWeb as a case study. A techno-economic framework to conduct a qualitative analysis of the applicable FCC and International Telecommunication Union (ITU) spectrum management regulations was developed to answer these research questions. The three key analytical factors to this framework are: (1) the extent of the spectrum use flexibility offered to the FSS-NGSO players, (2) the quality of the spectrum property rights offered to the FSS-NGSO users, and (3) the potential transaction costs associated with the oversight from the ITU, FCC, and other international regulatory authorities. The results of using these factors to evaluate the FSS-NGSO processes show that FSS-NGSO players have limited ability to move Ku-/Ka-band spectrum resources to higher-valued uses if needed. Such limitation results from inflexible, uncertain, hard to achieve, and lengthy national and international spectrum regulations. Moreover, the regulatory processes do not incentivize the most efficient use of spectrum resources, nor establish sufficient property rights that provide stability and reduce risk to investment.

Blind Spot of Spectrum Awareness Techniques in Non-geostationary Satellite Systems

Spectrum awareness techniques have been proposed as a promising solution to improve the utilization of available spectrum bands. However, few works have discussed the feasibility of spectrum awareness techniques in satellite systems. In the scenario of spectrum coexistence between geostationary (GEO) and nongeostationary (NGEO) satellite systems, this paper investigates the issue of blind spot where the spectrum awareness techniques may fail to identify the spectrum holes. Both the uplink and downlink transmissions are analyzed and three key parameters, i.e., altitude of NGEO satellite and antenna diameters of NGEO and GEO earth stations, are considered. Simulation results show that in the uplink, when the NGEO satellite approaches to the GEO satellite with a certain heights, there exists the situation of blind spot. In addition, this paper also provides a specific method to eliminate or reduce the range of blind spot.

Supporting location/identity separation in mobility-enhanced satellite networks by virtual attachment point

Location/identity separation can be used to enhance mobility in satellite networks. However, given the high mobility of non-geostationary satellite networks, usage of conventional binding update schemes will inevitably result in a large number of binding updates. In this work, a novel virtual attachment point based indirect binding scheme is proposed to address this issue. Moreover, a multi-layer service area based vertical update scheme is further investigated to eliminate the ping-pong effect. A random walk model based analysis and a Monte carlo method based simulation are conducted to evaluate our schemes. And the evaluation results demonstrate the validity and efficiency of our schemes comparing to conventional scheme, i.e. mobile IP.

Database-Assisted Spectrum Sharing in Satellite Communications: A Survey

This survey paper discusses the feasibility of sharing the spectrum between satellite telecommunication networks and terrestrial and other satellite networks on the basis of a comprehensive study carried out as part of the European Space Agency’s Advanced Research in Telecommunications Systems programme. The main area of investigation is the use of spectrum databases to enable a controlled sharing environment. Future satellite systems can largely benefit from the ability to access spectrum bands other than the dedicated licensed spectrum band. Potential spectrum sharing scenarios are classified as: a) secondary use of the satellite spectrum by terrestrial systems, b) satellite system as a secondary user of spectrum c) extension of a terrestrial network by using the satellite network; and d) two satellite systems sharing the same spectrum. We define practical use cases for each scenario and identify suitable techniques. The proposed scenarios and use cases cover several frequency bands and satellite orbits. Out of all the scenarios reviewed, owing to the announcement of many different mega-constellation satellite networks, we focus on analyzing the feasibility of spectrum sharing between geostationary orbit (GSO) and non-geostationary orbit (NGSO) satellite systems. The performance is primarily analyzed on the basis of widely accepted recommendations of the Radiocommunications Sector of the International Telecommunications Union. Finally, future research directions are identified.

Special Issue: Smart Satellite Systems

Special Issue: Smart Satellite Systems

Hybrid Structure and Fuzzy Logic High Precision Control for Non-Geostationary Satellite Antenna Tracking

In recent years, the accurate control of the antenna pointing system faced an increasing development. New model and control scheme are here proposed to optimize the stability of a tracking platform for non-geostationary satellite antenna. Two different control schemes are compared to control the antenna; a conventional linear PI control scheme, and a FLC (Fuzzy Logic Controller)-based non-linear control scheme. Moreover, in this paper we consider the antenna tracking based on traditional actuator using only DC motor compared to a hybrid linear actuator consisting of a DC motor and a lead screw in series with a piezoelectric stack. The performances of these strategies and their characteristics are analyzed and discussed. The proposed schemes are modeled in Matlab/Simulink environment in order to validate their practical applications by computer simulations.

A Global Internet: The Next Four Billion Users

New SpaceVol. 3, No. 3 Economist's CornerA Global Internet: The Next Four Billion UsersWard HansonWard HansonSearch for more papers by this authorPublished Online:14 Sep 2015https://doi.org/10.1089/space.2015.0033AboutSectionsView articleView Full TextPDF/EPUB ToolsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View articleFiguresReferencesRelatedDetailsCited byA Beam Search-Based Channel Allocation Method for Interference Mitigation of NGSO Satellites with Multi-Beam Antennas23 March 2022 | Aerospace, Vol. 9, No. 4A Hotspot Information Extraction Hybrid Solution of Online Posts’ Textual DataScientific Programming, Vol. 2021Performance Analysis of Large-Scale NGSO Satellite-Based Radio Astronomy SystemsIEEE Access, Vol. 9Low-Complexity Algorithm for Radio Astronomy Observation Data Transport in an Integrated NGSO Satellite Communication and Radio Astronomy SystemIEEE Open Journal of the Communications Society, Vol. 2Impacts of Large-Scale NGSO Satellites: RFI and A New Paradigm for Satellite Communications and Radio Astronomy SystemsIEEE Transactions on Communications, Vol. 67, No. 11A New Paradigm for Non-Geostationary Satellite Communications and Radio Astronomy SystemIntroduction to the Center of Excellence for Commercial Space Transportation Issue of the New Space Journal Ken Davidian1 March 2018 | New Space, Vol. 6, No. 1Distributed Earth Satellite Systems: What Is Needed to Move Forward?Journal of Aerospace Information Systems, Vol. 14, No. 8 Volume 3Issue 3Sep 2015 InformationCopyright 2015, Mary Ann Liebert, Inc.To cite this article:Ward Hanson.A Global Internet: The Next Four Billion Users.New Space.Sep 2015.204-207.http://doi.org/10.1089/space.2015.0033Published in Volume: 3 Issue 3: September 14, 2015PDF download

Design of a Compact Dual Band Microstrip Antenna for Ku-Band Applications

ABSTRACT A new design of dual band compact microstrip antenna is proposed for Ku-band applications.Dual band is achieved using three pairs of thin slits from the sides of a rectangular patch and feeding with a microstrip feed line.The result shows that a return loss of -32.9dB is achieved at the first resonant frequency of 12.72GHz, and -14.4dB is obtained at the second resonant frequency of 14.4GHz frequency with VSWR ≤ 2indicating improved matching conditions. The results ofsimulation are return loss, radiation pattern, VSWR, and band widtharepresented. The design is performed by using Ready-madeSoftware package Zeland- IE3D. The antenna is fabricated using thin film and photolithographic technique and measured using the Vector Network Analyzer. The final result shows that good agreement between the simulated and measured results. Keywords Microstrip antenna,Ku-band, Dual band 1. INTRODUCTION Microstrip antennas have been one of the most innovative topics in antenna theory and design in recent years, and are increasingly finding application in a wide range of modern microwave systems [1]. Inherently they have numerous advantages like easy to fabricate using standard integrated circuit techniques, have microstrip lines [1low profile, are conformal, and can be easily integrated in arrays with electronic components. Nevertheless, microstrip antennas typically suffer from narrowband radiation (a few percent of center frequency), low gain, poor polarization purity, tolerance problem and limited power capacity. However, applications such as frequency tuning take advantage of the inherent narrow bandwidth of the microstrip antenna. Systems such as satellites, global position system(GPS) are required to operate at two different frequenciesthat are very far from each other. Microstrip antennas canavoid the use of two different single band antennas. A variety of methods has been proposed to obtain dual frequency operation. Such as loading slits [2], using slots in the patch [3], [4], loading the patch with shorting pins [5], [6] and [7], using stacked patches [8], [9], [10] and[11] or using two feeding ports [12] are the most exploited ones. In addition, there are planar antennas of special geometries fto achieve dual-bandoperation [13]. The Federal Communication Commission adopted a First Report and Order (First R&O) to permit non-geostationary satellite orbit (NGSO) and fixed-satellite service (FSS) providersto operate in various segments of the Ku-band, and adopted rules and policies to govern these operations. NGSO FSS can provide a variety of new services to the public, such as high-speed Internet access, other types of high-speed data, video and telephony services. Because of its ability to serve large portions of the earth’s surface, NGSO FSS can bring advanced services to rural areas. The Commission also adopted technical criteria so that NGSO FSS operations can share spectrum with incumbent services on a co-primary basis without causing unacceptable interference to them andwithout unduly constraining future growth of incumbent services or NGSO FSS system flexibility [14]. In this paper, a simple new compact design of single layer single patch element with microstrip feed line is proposed for dual frequency operation in Ku-band. The design and optimization resulted in a downlink frequency of 12.72GHz and uplink frequency of 14.4GHz. The most obvious application in the Ku-band is aircraft, spacecraft and satellite based communication system.

First-Order Statistics Prediction for a Propagation Channel of Arbitrary Non-Geostationary Satellite Orbits

First-Order Statistics Prediction for a Propagation Channel of Arbitrary Non-Geostationary Satellite Orbits

Seasonal Variations of Polarization Diversity Gain in a Vegetated Area considering High Elevation Angles and a Nomadic User

Seasonal variations of the polarization diversity gain are addressed for a nomadic user in a vegetated area taking high elevation angles and nongeostationary satellites into consideration. Corresponding experimental data were obtained at a frequency of 2.0 GHz at Stromovka Park in Prague, the Czech Republic, within the full in-leaf and out-of-leaf periods of 2013 and 2014, respectively. By detecting copolarized and cross-polarized components of the transmitted left- and right-handed circularly polarized signals, the corresponding diversity gain was obtained for multiple-input single-output (MISO), single-input multiple-output (SIMO), and combined MISO/SIMO cases. It was found that tree defoliation results in a significant decrease of the polarization diversity gain achieved for low time percentages in particular scenarios.

Hop-Limited Adaptive Routing in Packet-Switched Non-Geostationary Satellite Networks

Hop-Limited Adaptive Routing in Packet-Switched Non-Geostationary Satellite Networks

In‐line interference mitigation techniques for spectral coexistence of GEO and NGEO satellites

SummaryThe interest towards the deployment of Low Earth Orbit (LEO)/Medium Earth Orbit (MEO) satellite systems in several frequency bands is increasing due to the requirement of low latency for real‐time systems and high demand of broadband data. When the number of usable Non‐Geostationary (NGEO) satellites, that is, LEO/MEO in space, increases, the frequency coexistence between the NGEO satellite systems with the already existing geostationary (GEO) satellite networks becomes a requisite. In this context, it is crucial to explore interference mitigation techniques between GEO and NGEO systems in order to allow their spectral coexistence. More specifically, in the coexistence scenario of GEO and NGEO satellite networks, in‐line interference may be a serious problem, especially in the equatorial region. In this paper, we provide several frequency sharing studies in the context of the coexistence of an NGEO satellite link with another NGEO/GEO satellite link. Furthermore, we carry out interference analysis between GEO and MEO satellite systems considering the case of the O3b satellite system and propose an adaptive power control technique for both the uplink and downlink scenarios in order to mitigate the in‐line interference. Moreover, we suggest several cognitive solutions for mitigating the in‐line interference and provide future research issues. Copyright © 2014 John Wiley & Sons, Ltd.