Commercial Satellite Communications Research Articles

Hollow cathode discharge instability onset in electric thrusters

Hollow cathodes are an integral part of ion, and Hall thrusters are used for electric propulsion in deep space missions and in commercial communications satellites. Hollow cathodes are known to operate in a quiescent “spot mode” and in a noisy “plume mode” in which plasma instabilities generate erosive energetic ions. The onset of the plume mode in hollow cathodes has been defined historically as when the keeper voltage oscillation values exceed 5 Vpp (peak-to-peak). Using a LaB6 hollow cathode in a vacuum chamber setup that simulates operation in ion and Hall thrusters, a set of emissive and Langmuir probes have been used to investigate the plasma properties associated with plume mode onset as a function of discharge current and gas flow rate. We find that the plume mode onset occurs at even less than 2 Vpp of the keeper voltage for the 5–75 A hollow cathode investigated here and starts at higher gas flow rates than expected from the traditional 5 Vpp metric used by those in the field. Mode competition and coupling between three different instabilities observed in the near-cathode plume affect the overall plasma oscillation levels that are correlated to energetic ion production. We find that the plasma oscillation levels measured by in situ plasma diagnostics are more indicative of the presence of oscillations and the generation of energetic ions than indirect keeper voltage measurements.

A Review of SATis5: Perspectives on Commercial and Defense 5G SATCOM Integration

This review provides a comprehensive review of past and existing works on 5G systems with a laser focus on 5G Satellite Integration (SATis5) for commercial and defense applications. The holistic survey approach is used to gain an in-depth understanding of 5G-Terrestrial Network (5G-TN), 5G-Non-Terrestrial Network (5G-NTN), SATis5 testbeds, and projects along with related SATis5 architectures. Based on the survey results, the review provides (i) outlook perspectives on potential SATis5 architectures for current and future integrated defense and commercial satellite communication (SATCOM) with 5G systems, and (ii) a thorough understanding of problems associated with anticipated outlooks and corresponding studies addressing these problems. The commercial SATis5 architectures discussed here can be extended to civilian SATCOM applications.

Assessing China's commercial satellite communications sector as a potential case of disruptive innovation

China's space industry has made exponential advancements since its creation in 1956, and has recently witnessed a rapid growth of commercial companies. At the same time, certain Chinese industries have found success in disruptive innovation, which have displaced established competitors in both domestic and international markets. We examine whether Chinese commercial space companies might follow the footsteps of these other industries and generate cost, application, and business model innovations that disrupt the satellite communications sector. Our findings draw from in-person interviews with commercial space companies in China, and a review of news articles and investment data. Results indicate that while emerging commercial space companies are not very technologically mature compared to their Western counterparts, they exhibit many of the attributes of disruptive innovation in the global space sector.

Research of flexible terminal

In recent years, with the rapid development of high-low Earth Orbit Commercial Satellite Communication Technologies and products, and the increasing demand of aviation, navigation and space trunking communication, satellite Communication has entered the stage of satellite Internet development with hybrid application of GEO Satellite and NGSO Constellation. Based on the characteristics of GEO satellite and NGSO satellite, this paper studies the flexible terminal which can access the GEO and NGSO Constellation, designs and analyzes the key technologies such as low cost phased array antenna and flexible waveform, providing some insights and ideas around the development for the mixed application of the terminal in GEO and NGSO satellites.

Global‐Scale Observations of the Limb and Disk Mission Implementation: 1. Instrument Design and Early Flight Performance

AbstractThe Global‐scale Observations of the Limb and Disk (GOLD) is a National Aeronautics and Space Administration mission of opportunity designed to study how the Earth's ionosphere‐thermosphere system responds to geomagnetic storms, solar radiation, and upward propagating atmospheric tides and waves. GOLD employs an instrument with two identical ultraviolet spectrographs that make observations of the Earth's thermosphere and ionosphere from a commercial communications satellite owned and operated by Société Européenne des Satellites (SES) and located in geostationary orbit at 47.5° west longitude (near the mouth of the Amazon River). They make images of atomic oxygen 135.6 nm and N2 Lyman‐Birge‐Hopfield (LBH) 137–162 nm radiances of the entire disk that is observable from geostationary orbit and on the near‐equatorial limb. They also observe occultations of stars to measure molecular oxygen column densities on the limb. Here, we provide an overview of the instrument and compare its prelaunch and early flight measurement performance. Direct comparison of LBH spectra of an electron lamp taken before launch with spectra on orbit provides evidence that both cascade and direct excitation are important sources of thermospheric LBH emission.

Global‐Scale Observations of the Limb and Disk Mission Implementation: 2. Observations, Data Pipeline, and Level 1 Data Products

AbstractThe Global‐scale Observations of the Limb and Disk (GOLD) is a National Aeronautics and Space Administration mission of opportunity designed to study how the Earth's ionosphere‐thermosphere system responds to geomagnetic storms, solar radiation, and upward propagating atmospheric tides and waves. GOLD employs two identical ultraviolet spectrographs that make observations of the Earth's thermosphere and ionosphere from a commercial communications satellite owned and operated by Société Européenne des Satellites (SES) and located in geostationary orbit at 47.5° west longitude (near the mouth of the Amazon River). They make images of atomic oxygen 135.6 nm and N2 Lyman‐Birge‐Hopfield radiances from the entire disk that is observable from geostationary orbit and on the near‐equatorial limb. They also observe occultations of stars to measure molecular oxygen column densities on the limb. Here we describe the algorithms and science data processing that convert downlinked data to spectral‐spatial image cubes and occultation spectra, calibrated in geophysical units. These Level 1 data products include disk and near‐equatorial limb images of spectra acquired on a 30‐min cadence beginning at 06:10 Coordinated Universal Time and ending at 23:10. Nighttime images of the disk, covering regions east of the terminator, begin at 20:10 Coordinated Universal Time and also continue until 00:40 the next day. During the day, some limb images are replaced by time series of stellar spectra that exhibit absorption by molecular oxygen as the star is occulted by the Earth's atmosphere. Instrumental artifacts that occasionally appear in the released data are discussed.

A New Data Set of Thermospheric Molecular Oxygen From the Global‐scale Observations of the Limb and Disk (GOLD) Mission

AbstractThe Global‐scale Observations of the Limb and Disk (GOLD) instrument was launched on 25 January 2018 onboard the SES‐14 commercial communications satellite and began nominal science operations in October 2018. Operating from geostationary orbit at 47.5°W longitude, GOLD images the Earth's thermosphere and ionosphere in the far‐ultraviolet (132–162 nm), measuring critical geophysical parameters by continuously scanning the Earth's disk and limb 18 hours per day. GOLD also performs stellar occultation measurements using bright type O and B stars. Up to 10 occultations per day are obtained at latitudes ranging from 60°S to 45°N and two fixed longitudes, ~33°E and ~128°W. The occultation data provide a direct measurement of atmospheric absorption in the O2 Schumann Runge continuum, which is used to retrieve the O2 density profile from 130‐ to 200‐km altitude. This paper describes the GOLD occultation measurement technique and the operational retrieval algorithm used to derive the Level 2 O2DEN data product. The spatial, temporal, and local time sampling of the GOLD O2 data product is summarized, and the data quality, retrieval errors, and validation plans are discussed. Occultations are observed under both daytime and nighttime conditions, providing the O2 density over a complete range of local times. GOLD retrievals have an estimated precision of 10% and a vertical resolution of 5–10 km, depending on altitude. The data have sufficient accuracy and resolution to provide scientifically useful constraints on the O2 abundance and variability. Initial comparisons show qualitative agreement, but also notable differences, between the GOLD O2 data and the Naval Research Laboratory Mass Spectrometer Incoherent Scatter Radar (NRLMSISE‐00) empirical model predictions.

Secure Satellite Communication Digital IF CMOS $Q$ -Band Transmitter and $K$ -Band Receiver

This paper reports the first CMOS RF integrated chipset for secure commercial and military satellite communication enabling next-generation low size, weight, and power (SWaP) terminals. This chipset is a significant departure from current terminals relying on individually qualified IC components by taking advantage of advanced CMOS integration. The transmitter and receiver designs are digital IF architectures that rely on the higher sampling rate capability of CMOS, and precise digital filtering, quadrature frequency translation, and frequency hopping/de-hopping. The CMOS transmitter is a fully integrated system-on-chip (SoC) design, while the receiver consists of a co-designed RF and digital IF receiver. The Tx/Rx uses a 200-/300-MHz double data rate (DDR) interface driving/receiving a complex frequency translator with sub-hertz frequency hopping resolution via on-chip numerically controlled oscillators (NCO). The transmitter includes two 12-b return-to-zero (RZ) digital-to-analog converters (DACs) and quadrature modulator to form a single-sideband (SSB) upconverter achieving >30-dB spur rejection. An RF upconverter with an X2 multiplier drives a 24-dBm $Q$ -band CMOS stacked power amplifier (PA). The RF receiver implements a matched inverter amplifier (IA) followed by a complementary active balun that current drives a passive mixer with a trans-impedance active combiner. The digital IF receiver includes a high-linearity variable gain amplifier (VGA) that drives an 8 $\times $ time-interleaved 1.2-GS/s analog-to-digital converter (ADC) with dc offset and gain calibration with an embedded digital receiver. Both the transmitter and receiver use a 1.5-GHz IF signal. The combined CMOS chipset was demonstrated with a current military satcom modulation and protocol and achieves 5 $\times $ lower power consumption and size versus the current configuration.

Method of common-view time transfer using communication satellites

Chinese area position system (CAPS) can provide positioning, time and velocity service to China region users by renting several commercial communication satellites. We studied a real-time common-view time transfer method in this paper using communication satellites of CAPS. This method can fully use CAPS resources of the communication satellites and orbit determination stations to broadcast the information of timing bias mode parameters from the ground base stations. The timing bias data information can be demodulated and calculated by users from the navigation message by receiving the satellite signal in one-way, so the common-view time transfer process are implemented. This method can provide time service with the accuracy better than 5 ns, which is a kind of high accuracy time transfer method at present. Users can obtain this kind of time services in real-time and only need to receive CAPS time service signal in one-way reception way and without the process of past-data exchange. This paper provides detailed information on the principle of the common-view time transfer method based on communication satellites. Moreover, the experiment platform has been set up to test the performance of this new method. The long baseline experimental results of Xi’an-Kashi and Xi’an-Sanya indicated that the accuracy of CAPS single-satellite is better than that of GPS single-satellite common-view time transfer. The common-view time transfer based on communication satellite can provide time service to users with the accuracy better than 5 ns.

Using Commercial Communication Satellites to Attain Information Superiority and Improve Troop and Weapon Control

Using Commercial Communication Satellites to Attain Information Superiority and Improve Troop and Weapon Control

Preparing for the Worst: The Space Insurance Market's Realistic Disaster Scenarios

Abstract Approximately 30 satellite launches are insured each year, and insurance coverage is provided for about 200 in-orbit satellites. The total insured exposure for these risks is currently in excess of US$25 billion. Commercial communications satellites in geostationary Earth orbit represent the majority of these, although a larger number of commercial imaging satellites, as well as the second-generation communication constellations, will see the insurance exposure in low Earth orbit start to increase in the years ahead, from its current level of US$1.5 billion. Regulations covering Lloyd's of London syndicates require that each syndicate reserves funds to cover potential losses and to remain solvent. New regulations under the European Union's Solvency II directive now require each syndicate to develop models for the classes of insurance provided to determine their own solvency capital requirements. Solvency II is expected to come into force in 2016 to ensure improved consumer protection, modernized ...

Fractal Bandpass Filter Using Y-shaped Dual-Mode Resonator for C-Band Receiver (Research Note)

In this study, a fractal, Y-shaped dual-mode resonator bandpass filter (BPF) with input-output cross-coupling is introduced. A parallel-coupling feed structure with a cross coupling has been used to generate two transmission zeroes (TZs) near the lower and upper cutoff frequency that can effectively improve the passband edge selectivity. Also, a fractal shaped based on conventional diamond and square is located. Current density and equivalent model is also given depending on the odd/even excitation resonance condition. The demonstrated filter with a compact size of 0.5*18.3mm2 exhibits a fractal bandwidth of 67% centred as 6GHz(f0) within the 4 to 8GHz bandwidth and minimum insertion loss of 0.3 dB, maximum return loss of 13,15.7dB and flat group delay around 0.3ns that is candidate for use in commercial communications satellites(C-Band).

Special issue: Shining a light on future broadband satellite systems: optical and quantum space communications systems and technologies

Optical space communications have moved from the Research & Development (R&D) stage and are now ready to be applied in commercial satellite communication systems, bringing with them significant advantages such as much higher data rates, low probability of intercept, no restriction for frequency use, lower payload volume and mass, and less power consumption requirements. The European Space Agency has demonstrated laser communications from an airborne platform to ground stations, further establishing that high-throughput laser communications are feasible and ready for commercial service, and the European Data Relay System is relying on optical inter satellite links for its commercial data relay service. The US fundedTransformational Satellite Communications System program, developed and partially validated highly successful inter-satellite laser optical links, proving the efficacy and efficiency of laser communications. In Japan, there is a lot of activity on optical communications by satellite, and China has declared an intention to develop a quantum satellite. Researchers in Austria and Spain are working on applications of quantum communications, and the UK has recently announced an investment to convert quantum-physics research into commercial products. A new generation of proposed satellite constellations has intent to develop a service addressing the high bandwidth data and next-generation service needs of carriers, enterprises, and government agencies around the world, based entirely on optical wave technology. We would like to invite papers addressing these and other related topics:

Technology Trends and Challenges of Antennas for Satellite Communication Systems

Communication is one of the most essential activities of mankind and there is no doubt that satellite communications have made a tremendous stride in this matter. The goal has been to create uninterrupted, seamless, high throughput connectivity no matter where. The fact that this is all possible is because of the existence of electromagnetic waves: Antennas play a pivotal role in advanced functionality, efficient usage of the bandwidth, and cost effective deployment of this technology. The trends of the technological development of antennas for a wide range of commercial satellite communication services and the challenges faced in their development are chronologically reviewed. Various antenna concepts are summarized and future challenges are projected. A rather comprehensive list of references is included to assist the reader with further reading beyond this paper.

A plan to clear energetic protons from the radiation belt

The Earth's radiation belts have been a known hazard to satellites since at least 1962, when an American high‐altitude nuclear weapons test named Starfish Prime produced an artificial belt that disabled the first commercial communications satellite, TelStar 1. In the years since the Cold War, thousands of satellites have been put into orbit, and surface charging, high‐energy protons, high‐energy electrons known as “killer electrons,” and other hazards of the inner magnetosphere have continued to take their toll. Satellites can be hardened against these radiation hazards, but some researchers have recently floated a more radical idea: If specially designed transmitters are put into space and set to emit tightly tuned waves, known as electromagnetic ion cyclotron (EMIC) waves, they could potentially push the highly energetic protons out of the Earth's inner radiation belt, clearing the satellite's path.

On-orbit servicing system assessment and optimization methods based on lifecycle simulation under mixed aleatory and epistemic uncertainties

To assess the on-orbit servicing (OOS) paradigm and optimize its utilities by taking advantage of its inherent flexibility and responsiveness, the OOS system assessment and optimization methods based on lifecycle simulation under uncertainties are studied. The uncertainty sources considered in this paper include both the aleatory (random launch/OOS operation failure and on-orbit component failure) and the epistemic (the unknown trend of the end-used market price) types. Firstly, the lifecycle simulation under uncertainties is discussed. The chronological flowchart is presented. The cost and benefit models are established, and the uncertainties thereof are modeled. The dynamic programming method to make optimal decision in face of the uncertain events is introduced. Secondly, the method to analyze the propagation effects of the uncertainties on the OOS utilities is studied. With combined probability and evidence theory, a Monte Carlo lifecycle Simulation based Unified Uncertainty Analysis (MCS-UUA) approach is proposed, based on which the OOS utility assessment tool under mixed uncertainties is developed. Thirdly, to further optimize the OOS system under mixed uncertainties, the reliability-based optimization (RBO) method is studied. To alleviate the computational burden of the traditional RBO method which involves nested optimum search and uncertainty analysis, the framework of Sequential Optimization and Mixed Uncertainty Analysis (SOMUA) is employed to integrate MCS-UUA, and the RBO algorithm SOMUA-MCS is developed. Fourthly, a case study on the OOS system for a hypothetical GEO commercial communication satellite is investigated with the proposed assessment tool. Furthermore, the OOS system is optimized with SOMUA-MCS. Lastly, some conclusions are given and future research prospects are highlighted.

Cost impact of automated acceptance testing of electrical ground support equipment for spacecraft testing

In today's environment, building a reliable and cost effective spacecraft is perhaps emphasized more than ever before. Sponsors are looking for the same high quality products but at lower costs and with shorter schedules. Whether it is a spacecraft for the Department of Defense (DoD), a research observatory for the National Aeronautics and Space Administration (NASA), or a commercial communications satellite, total cost is a significant factor.

Development priorities for in-space propulsion technologies

During the summer of 2010, NASA's Office of Chief Technologist assembled 15 civil service teams to support the creation of a NASA integrated technology roadmap. The Aero-Space Technology Area Roadmap is an integrated set of technology area roadmaps recommending the overall technology investment strategy and prioritization for NASA's technology programs. The integrated set of roadmaps will provide technology paths needed to meet NASA's strategic goals. The roadmaps have been reviewed by senior NASA management and the National Research Council.With the exception of electric propulsion systems used for commercial communications satellite station-keeping and a handful of deep space science missions, almost all of the rocket engines in use today are chemical rockets; that is, they obtain the energy needed to generate thrust by combining reactive chemicals to create a hot gas that is expanded to produce thrust. A significant limitation of chemical propulsion is that it has a relatively low specific impulse. Numerous concepts for advanced propulsion technologies with significantly higher values of specific impulse have been developed over the past 50 years.Advanced in-space propulsion technologies will enable much more effective exploration of our solar system, near and far, and will permit mission designers to plan missions to “fly anytime, anywhere, and complete a host of science objectives at the destinations” with greater reliability and safety. With a wide range of possible missions and candidate propulsion technologies with very diverse characteristics, the question of which technologies are ‘best’ for future missions is a difficult one. A portfolio of technologies to allow optimum propulsion solutions for a diverse set of missions and destinations are described in the roadmap and herein.

Development of a GPU-Based Two-Way Time Transfer Modem

We have developed a new two-way time transfer modem to improve the time transfer precision of remote clock comparison. As a timing signal, we apply a binary offset carrier, which is similar to those signals used for the next-generation Global Navigation Satellite Systems. We took advantage of versatile A/D and D/A converters, and most of the digital signal processing stages were realized by software, running on an off-the-shelf PC. This enabled us to realize the complete system with cheaper equipment, leading to an affordable low-cost modem. For the real-time digital signal processing stages implemented in software, we relied on a graphics processing unit (GPU) developed for computer game enthusiast. The developed modem can receive four channels at the same time with a single GPU card. We performed two-way satellite time transfer experiments using these modems between Japan and Taiwan. The obtained results are consistent within 200 ps with respect to the results of GPS carrier phase time transfer. As a consequence, we improved the time transfer precision by nearly one order of magnitude as compared to a conventional two-way modem without increasing the connection fees caused by commercial communication satellites.

Current wideband MILSATCOM infrastructure and the future of bandwidth availability

The military satellite communications (MILSATCOM) infrastructure is typically broken into three categories: wideband, protected, and narrowband. Wideband systems emphasize high capacity, protected systems prioritize anti-jam features and covertness, and narrowband systems emphasize support to the disadvantaged user by providing low data rate communications to small / mobile users. This focuses on the existing wideband MILSATCOM infrastructure (namely the Defense Satellite Communications System and Global Broadcast Service), because the architecture that exists is aging technology that lacks the ability to provide the required bandwidth to the warfighters without relying on commercial satellites. Bandwidth is limited and expensive to purchase, resulting in the DoD leasing transponders on commercial communications satellites - a solution that may not always be an option. This also illustrates various technologies and future programs currently being investigated by the Department of Defense (DoD) in order to augment and/or replace existing systems, and the resulting capability and benefits provided to the warfighter. These programs include the Wideband Global SATCOM (WGS) (previously known as Wideband Gapflller Satellite System), and the Advanced Wideband System (AWS) / Transformational Satellite Communications System (TSAT). Both WGS and AWSITSAT will significantly increase the bandwidth capacity of the wideband MILSATCOM architecture. These military initiatives take advantage of nascent technology such as IP router technology and laser cross-links to maximize performance. Finally, thia describes several techniques to augment these MILSATCOM programs and increase their capacity and effectiveness, including: use of a network-style approach (vice point-to-point), combining space and terrestrial systems, use of near-space communication platforms (e.g., high-altitude. UAVs or balloons), operating at higher frequencies, use of multiple satellites and re-use frequencies, and use of IP accelerators. These techniques increase the bandwidth capacity and improve its effectiveness by providing diversity, better quality of service via multiple relays, improved link performance via network architecture, and increase the amount of effective bandwidth available by including airborne platforms as additional communications relays.