Satellite Services Research Articles

Synthesis‐Style Auto‐Correlation‐Based Transformer: A Learner on Ionospheric TEC Series Forecasting

AbstractAccurate 1‐day global total electron content (TEC) forecasting is essential for ionospheric monitoring and satellite communications. However, it faces challenges due to limited data and difficulty in modeling long‐term dependencies. This study develops a highly accurate model for 1‐day global TEC forecasting. We utilized generative TEC data augmentation based on the International Global Navigation Satellite Service (IGS) data set from 1998 to 2017 to enhance the model's prediction ability. Our model takes the TEC sequence of the previous 2 days as input and predicts the global TEC value for each hourly step of the next day. We compared the performance of our model with 1‐day predicted ionospheric products provided by both the Center for Orbit Determination in Europe (C1PG) and Beihang University (B1PG). We proposed a two‐step framework: (a) a time series generative model to produce realistic synthetic TEC data for training, and (b) an auto‐correlation‐based transformer model designed to capture long‐range dependencies in the TEC sequence. Experiments demonstrate that our model significantly improves 1‐day forecast accuracy over prior approaches. On the 2018 benchmark data set, the global root mean squared error (RMSE) of our model is reduced to 1.17 TEC units (TECU), while the RMSE of the C1PG model is 2.07 TECU. Reliability is higher in middle and high latitudes but lower in low latitudes (RMSE < 2.5 TECU), indicating room for improvement. This study highlights the potential of using data augmentation and auto‐correlation‐based transformer models trained on synthetic data to achieve high‐quality 1‐day global TEC forecasting.

Suitability of Dual-Band, Dual-Polarized Patch Antennas with a Superstrate for the Miniaturization of Ku-Band Antenna Arrays for Automotive Applications

The extension of low-earth orbit (LEO) services to non-terrestrial mobile communications has huge potential for eliminating network white spots and providing high-speed, low-latency links with worldwide geographic coverage. State-of-the-art user terminals for mobile platforms are too large for integration into a passenger vehicle. Antenna elements loaded with a dielectric superstrate could potentially lead to a considerable miniaturization of the user terminal. As per link budget calculations, an array with a gain of 27 dBi is necessary to ensure a throughput of 25 Mbps in the downlink at the Ku-band. A conventional array with a gain of 6 dBi per element, assuming a 12 × 12 arrangement with half-wavelength spacing, would require a footprint of 36 λ2 at 10 GHz to achieve this target and appears unsuitable for automotive integration. This paper proposes a low-profile, dual-band, dual-polarized, vertically stacked patch antenna with superstrate loading and shows that the inclusion of the superstrate improves the antenna’s gain by at least 3 dB. Therefore, compared to a conventional array, a superstrate-loaded array would need only half of the number of elements to meet the target gain, thus occupying only half of the surface area, and offers better integration for automotive applications. Requiring half of the number of elements also implies considerably reduced design complexity and cost.

After Sales Services as Determinant of Customers’ Patronage of Satellite Products and Services: A Study of South-South Nigeria

In this study, we examined whether after sales services serve as determinants of customers’ patronage among selected satellite products/services companies in South-South Nigeria. To offer a novel view on the research theme, three (3) after sales service dimensions were employed, namely; product warranty, installation and delivery. Questionnaire was the major instrument of data collection, which was administered on four hundred respondents out of which three hundred and seventy-three were completely retrieved. Data obtained in were analysed using descriptive, diagnostic and inferential statistical techniques. Findings indicated that there is a significant relationship between the after sales services dimensions (product delivery, installation and warranty)and customer’s patronage of satellite products. The implication of the finding is that after sales services serve as determinants of customers’ patronage. In view of the findings, it is recommended that management of satellite products and services need to enhance their strategic plans aimed at further improving product delivery, installation and warranty by ensuring that their transmissions are more effective than ever before so as to attract more customers, increase profitability and market share. Again, the study recommends that management of satellite products and services need to improve on their product warranty, delivery and installation policies so as to further assure customers of improved and quality products as well as attracting more customers.

Employee Training, Service Quality and Customers’ Patronage of Satellite Products and Services: Evidence from South-South, Nigeria

This study investigated whether employee training and service quality influence customers’ patronage of satellite products/services companies in the South-South region of Nigeria. To do this, 400 questionnaires were administered, out of which 373 were completely retrieved and found usable. Data obtained in the survey were analysed using descriptive and inferential statistical tools. Findings indicated that there is a significant relationship between employee training, service quality and customer patronage of satellite products. The implication is that employee training and service quality serve as means of improving or enhancing the patronage of customers. Given that service quality positively affects customers’ patronage, there is a need for the management of satellite products/services to sustain their service quality mechanisms in order to attract more customers further. As a matter of fact, they should further strengthen their product by seeking more outlets or well-trained individuals who are capable of installing and repairing their products (decoders) when customers seek their attention. This study contributes to knowledge by using hybrid theories to describe employee training and service quality effects on customers’ patronage of satellite products/ services in Nigeria.

Robust integrated planning for LEO satellite network design and service operations

We try to understand Low Earth Orbit (LEO) satellites from an operations research perspective. We propose an integrated model to support the strategic designing of ground stations, as well as the operational planning of traffic routes. A Mixed-Integer Nonlinear Program is proposed to solve the integrated model. Through a case study using satellite simulation platforms, we find that the responsiveness of key satellites is more sensitive to system design parameters compared with that of non-key satellites.

Coexistence of terrestrial and non‐terrestrial networks on adjacent frequency bands

SummaryThis paper presents the latest achievements concerning 3GPP Release‐17 adjacent band coexistence simulation work on 5G new radio non‐terrestrial networks (NTNs) for satellite communications. For the first time, 3GPP considered the introduction of mobile satellite service (MSS) frequency bands for 3GPP user equipment (UE) direct connectivity with satellites and had to consider the coexistence in adjacent bands with terrestrial networks (TNs). This paper will further explain the most challenging and the main surprising outcomes of this work, which opened new market opportunities for both terrestrial and non‐terrestrial stakeholders. The main conclusions can be summarized as follows: (1) NTN UE can reuse the current requirements of the TN UE, (2) the satellite connectivity does not require a dedicated satellite waveform, and (3) TN can co‐exist with NTN on adjacent channels with relaxed ACIR requirements for the tested simulation scenario.

Investigating Spectrum Allocation Policies to Accommodate New Entrants in the Market: A Case Study of South Africa

One of the goals of the telecommunications industry is to provide universal connectivity to its consumers. Achieving this goal is highly dependent on the allocation of radio frequency (RF) spectrum. The RF spectrum refers to the frequencies assigned to diverse services such as mobile, fixed, and satellite services. These allocations are regulated by international, regional, and local authorities. Countries across the globe have embarked on the journey to transform their RF spectrum allocation policies to be more inclusive and hybrid in nature. Such changes in some countries, have enabled new entrants and incumbent operators to provide low-cost connectivity into small rural communities, bridging the digital divide gap. Due to current policies by some regulators and perceived anti-competitive laws, new entrants and small operators find it difficult to penetrate the telecommunications market in South Africa. To address this challenge, the overall and ongoing study, proposes an alternative and inclusive framework for universal coverage and low-cost connectivity that accommodates both incumbent and new entrant operators in South Africa. To achieve this aim, a qualitative desktop research approach was used to analyze publicly available information, including journal articles, RF spectrum policy documents from various countries, International Telecommunication Union (ITU) documents and other academic sources. The objective of this paper is to contribute to the ongoing discussions regarding the policy on the allocation of RF spectrum. As this is an ongoing study, preliminary findings indicated that auctions remain a popular RF spectrum allocation model of choice, despite being perceived by some scholars as less competitive and inflexible. The final study findings, which would be in a subsequent research paper, aim to develop a new RF spectrum framework that may help achieve universal coverage and low-cost connectivity in South Africa.

Interference Analysis of Coexisting 5G Networks and NGSO FSS Receivers in the 12-GHz Band

Despite the promising attributes of the 12 GHz band for expanding terrestrial 5G network’s capacity and coverage, interference between coexisting networks remains a major issue. This paper develops a simulation-based evaluation framework and investigates the harmful interference between the 5G radio links and incumbent fixed non-geostationary satellite orbit (NGSO) fixed satellite services (FSS) receivers of the 12 GHz band. A variety of features including actual deployment locations of 5G base stations (BSs) and fixed NGSO FSS receivers, industry-standardized beamforming at BSs, directional signal reception at FSS receivers, realistic propagation channels with obstruction from buildings, and channel scheduling at 5G BSs are incorporated in the interference study. Simulation results conducted in a realistic urban-micro deployment scenario confirm that the terrestrial 5G networks with directional BSs can coexist in the 12GHz band by suitably selecting exclusion zone’s radius around the FSS receiver. Simulation results also show that interference in the coexisting network can be notably reduced by appropriately activating BSs in the 12 GHz band based on their locations and surroundings.

Heterogeneously Integrated Filtering Power Amplifier for Radio Determination Satellite Service

Heterogeneously Integrated Filtering Power Amplifier for Radio Determination Satellite Service

Cognitive Radio Strategy Combined with MODCOD Technique to Mitigate Interference on Low-Orbit Satellite Downlinks.

The concept of cognitive radio (CR) as a tool to optimize the obstacle of spectral coexistence has promoted the development of shared satellite-terrestrial wireless networks. Nevertheless, in some applications like Earth Exploration Satellite Services, which demand high spectral efficiency (bps/Hz) for downlink transmissions, spectral coexistence amidst interferences from cellular Base Stations is still challenging. Our research aims to mitigate these interferences on low-orbit satellite downlinks carrying imaging data received from a ground station. In order to fulfill this, we present cognitive radio approaches to enhance spectrum exploitation and introduce the adaptive modulation and coding (MODCOD) technique to increase RF power and spectral efficiencies. Therefore, we propose a combined methodology using CR and adaptive MODCOD (ACM) techniques. Afterwards, we applied the solution by monitoring the signal to interference plus noise ratio and the MODCOD strategy. Finally, we provide a real in situ case study at the Cuiabá ground station located in Brazil's central area, which receives images from an Earth observation satellite (EOS). In addition to demonstrating the strategy effectiveness in this scenario, we conducted a bench test emulating the interfering wireless communication system. In this sense, we demonstrated the proposed approach, successfully mitigating the harmful effects on the received EOS images.

To What Extent Will Space Debris Impact the Economy?

With the expansion of the space industry, debris congestion has become a serious problem. When space debris collides with satellites in orbit, it may damage the satellites or, in the worst case, cause an explosion. While economic activity influences debris congestion, debris can also influence the economy. To what extent does debris affect the economy? Furthermore, what would be the optimal path of debris emission considering the economy and space environment? This study aims to quantify the severity of the problem. We simulate the damage caused by the environmental problem of orbital debris using a standard economic growth model in macroeconomics, augmented with a satellite sector and collision possibility. In the model, launching satellites means two things: more factors of production and more orbital objects. A newly launched satellite provides satellite services to the economy and increases production capacity. At the same time, by being placed in orbit, a satellite increases the risk of collisions. Our results show that debris will cause negative damage of approximately 1.95% of global Gross Domestic Product (GDP) in the long term if no debris is remediated at all.

Beam Steering 3D Printed Dielectric Lens Antennas for Millimeter-Wave and 5G Applications.

Two types of cost-efficient antennas based on dielectric gradient index dielectric lens have been designed for 5G applications at 28 GHz. The first is a linearly polarized flat lens antenna (LP-FLA) for terrestrial 5G communications. The second is a novel circularly polarized stepped lens antenna (CP-SLA) for 5G satellite services. An efficient design method is presented to optimize and conform the lens topology to the radiation pattern coming from the antenna feeder. The LP-FLA is fed by a traditional linearly polarized pyramidal horn antenna (PHA). The CP-SLA is fed by an open-ended bow-tie waveguide cavity (BCA) antenna. This cavity feeder (BCA), using cross-sections with bow-tie shapes, allows having circular polarization at the desired frequency bandwidth. The two types of presented antennas have been manufactured in order to verify their performance by an easy, low-cost, three-dimensional (3D) printing technique based on stereolithography. The peak realized gain value for the flat (LP-FLA) and stepped (CP-SLA) lens antennas have been increased at 28 GHz to 25.2 and 24.8 dBi, respectively, by disposing the lens structures at the appropriated distance from the feeders. Likewise, using an array of horns (PHA) or open-ended bow-tie waveguide cavity (BCA) antenna feeders, it is possible to obtain a maximum steering angle range of 20° and 35°, for a directivity over 15 dBi and 10 dBi, in the planar and stepped lens antennas, respectively.

Safety Assessment for Full Flight between Beidou Radio Determination Satellite Service Airborne Equipment and 5G System

The Beidou Radio Determination Satellite Service (RDSS) is an advantageous service of the Beidou system. However, due to the weak landing power of Beidou RDSS signals and an operating frequency close to the 5G frequency, the system is vulnerable to interference from ground signals. In this paper, from the perspective of civil aviation safety, different evaluation indicators are used for the takeoff and cruise phases, respectively, to study the impact caused by adjacent frequency interference on airborne Beidou RDSS equipment. In the takeoff phase, accurate aircraft position information is obtained by processing real trajectory files. Deterministic analysis methods are used to determine the safety distance for the coexistence of the two systems. During the cruise phase, ground-based 5G base stations have less influence on the airborne RDSS receiver due to the high flight altitude, so the main consideration is electromagnetic compatibility between the airborne Beidou RDSS system and the 5G ATG system. By establishing a Boeing 737–800 simulation model, the antenna isolation degree is used as the evaluation index, and a reasonable antenna layout is given according to the evaluation results. In this study, the theoretical simulation and real flight data are combined to summarise the exact range of adjacent frequency influence during the takeoff phase and a reasonable antenna layout during the cruise phase.

Design and dynamics simulation of axial radial double locking satellite docking mechanism

Aiming at the docking requirements of small satellites in orbit service, an axial, radial double-locking satellite docking mechanism was designed to realize the docking and separation of small satellites. Capture docking using the butt bar and the groove. The mechanism possesses multiple advantages, such as simple structure and fast response. A dynamic model considering contact, collision, buffering, and friction was established, and ADAMS software simulated the docking process. Apart from that, the dynamics and motion data of the mechanism were obtained. As revealed by the results, under the initial conditions of the general light and small docking mechanism, the mechanism can achieve the set task and complete the docking with a small collision force. What’s more, the buffer device can absorb 85.5% of the energy of the satellite, and the mechanism has a certain attitude correction ability. Altogether, this exploration can provide a reference for designing satellite docking mechanisms and formulating a docking strategy in the future.

A miniaturized quintuple-band frequency selective surface based on enclosed cross slots

Abstract This article presents a low-profile quintuple-band frequency selective surface (FSS) that is designed as a sub-reflector for applications including satellite systems (C band), EPR (electron paramagnetic resonance) spectrometers, motion and traffic light crossing detectors (X band), Direct Broadcast Satellite and broadcasting satellite service (Ku band), and shortrange applications (K band). The dimensions of the miniaturized unit cell 0.08λ0×0.08λ0×0.012λ0, where, λ0 is the free-space wavelength corresponding to the lower cut-off frequency. There are five stop bands, and frequencies at which they resonate are 6.3, 7.06, 9.30, 11.2, 14.0, and 18.64 GHz. The fractional bandwidths (FBW) of these bands are 62.6, 7.5, 9.2, 11, and 11.69%, respectively. Additionally, as a result of the structure’s four-fold symmetry, it exhibits a good polarization-insensitive response as well as a stable response in both the TE and TM modes. Full-wave simulation is performed on the structure, after which an equivalent circuit model is constructed.

Application of predictive control for manipulator mounted on a satellite

Specific conditions of on-orbit environment are taken into account in the design of all devices intended to be used in space. Despite this fact malfunctions of satellites occur and sometimes lead to shortening of the satellite operational lifetime. It is considered to use unmanned servicing satellite, that could perform repairs of other satellites. Such satellites equipped with a manipulator, could be used to capture and remove from orbit large space debris. The critical part of planned missions is the capture manoeuvre. In this paper a concept of the control system for the manipulator mounted on the satellite is presented. This control system is composed of the trajectory planning module and model predictive controller (the latter is responsible for ensuring precise realization of the planned trajectory). Numerical simulations performed for the simplified planar case with a 2 DoF manipulator show that the results obtained with the predictive control are better than the results obtained with adaptive control method.

Compliant robotic behaviors for satellite servicing.

The demands of traditional industrial robotics differ significantly from those of space robotics. While industry requires robots that can perform repetitive tasks with precision and speed, the space environment needs robots to cope with uncertainties, dynamics, and communication delays or interruptions, similar to human astronauts. These demands make a well-suited application for compliant robotics and behavior-based programming. Pose Target Wrench Limiting (PTWL) is a compliant behavior paradigm developed specifically to meet these demands. PTWL controls a robot by moving a virtual attractor to a target pose. The attractor applies virtual forces, based on stiffness and damping presets, to an underlying admittance controller. Guided by virtual forces, the robot will follow the attractor until safety conditions are violated or success criteria are met. We tested PTWL on a variety of quasi-static tasks that may be useful for future space operations. Our results demonstrate that PTWL is an extremely powerful tool. It makes teleoperation easy and safe for a wide range of quasi-static tasks. It also facilitates the creation of semi-autonomous state machines that can reliably complete complex tasks with minimal human intervention.

Accuracy of trained technicians in screening orbital and adnexal diseases at rural vision centers in South India.

To assess the agreement between the diagnosis made by trained technicians at vision centers (VC) and oculoplasty specialists at the base hospital, in patients referred from VC to the orbit and oculoplasty clinic of a tertiary eye care hospital in south India. This was a retrospective study that compared the findings of VC technicians and the specialists of the orbit and oculoplasty services in a base hospital. A total of 384 patients referred from 17 VCs between May 2021 and May 2022 were included. The diseases were categorized according to the site of involvement as diseases of the eyelids (43%), diseases of the lacrimal system (37.3%), orbital diseases (15.6), and others (4.1%). The mean age of the patients was 35.9 years and 50.6% were females. Medical records of all referred patients who attended the orbit clinic were analyzed. Of the 384 patients, 378 (98.67%) were confirmed to have o. bital and adnexal diseases. There was an overall 80% agreement between the diagnosis made by trained VC technicians and oculoplasty specialists; the kappa coefficient was 0.78 (95% confidence interval [CI]: 0.76 to 0.80), with a P value < 0.001. The agreement was the highest for diseases of the lacrimal system (90.9%, kappa coefficient 0.87), followed by eyelid pathologies (80%, kappa coefficient: 0.77). Of these, 54.8% of patients were managed with surgical procedures. There is good agreement between the findings of VC technicians and oculoplasty specialists. Trained technicians can help in the early detection and referral to higher centers. They also help to make sure adherence to treatment and periodic evaluation, especially in resource-constraint settings.

Out-of-Band Fibre-Optic Time and Frequency Transfer Using Asymmetric and Symmetric Opto-Electronic Repeaters.

Signal repeaters for fibre-optic communication can be realized with back-to-back connected transceivers. This configuration can provide high gain (≈30 dB) at low cost, and the needed semiconductor lasers and modulators can be realized for practically any relevant wavelength. Unfortunately, for time and frequency transfer the uncorrelated wavelength drifts in the transceiver lasers can compromise transfer stability, and device replacement due to failure may result in large time offsets that have to be measured via global navigation satellite services. This work demonstrates that good results can nevertheless be obtained with standard telecom DWDM tranceivers over long time periods (years). More importantly, a simple wavelength-symmetric repeater is proposed that can be used to cancel the detrimental effects of wavelength drifts and which lessens the need for link re-calibrations after transceiver replacements. In a proof-of-concept test setup, timing drift due to wavelength drift of a repeater laser is reduced by approximately two orders of magnitude.

Development of bandwidth‐enhanced X–Ku band reflectarray antenna using a novel design strategy

SummaryThis paper reports the development of a reflectarray (RA) antenna using overlapping tri‐resonance phase distribution to produce enhanced bandwidth performance in X/Ku band frequencies. The RA with square aperture (24 cm) operating from 11 to 15.8 GHz is constructed using unit cells with concentric Malta cross and square ring developed on Diclad substrate isolated from the ground through a 2.5‐mm air layer. Variation in the concentric element's size along with the length of the delay line connected to the square ring offers a 518° phase range. The distribution of the 529 RA elements is done using the phase variations observed at 12, 13, and 14 GHz. The optimized design of the proposed antenna offers a simulated peak gain of 27.43 dBi at 12 GHz and a 1‐dB gain bandwidth of 38%. The experimental validation of the fabricated prototype exhibits a peak gain of 27.4 dBi at 12 GHz with a sidelobe level (SLL), and cross‐polarization level less than −15.6 dB, and −28 dB respectively, and a 1‐dB gain bandwidth of 37%. The enhanced performance characteristics of the proposed X/Ku wideband reflectarray antenna befit the uplink and downlink operations of fixed satellite services (FSS).