MEO Satellites Research Articles

Thales alenia space 6 th generation digital transparent processor (DTP6G) - a multi-mission, multi-mode versatile product at the heart of telecom solutions

Flexibility and in-flight reconfigurability offered by digital processing have become key features in today's telecom satellite payloads. In recent years, Thales Alenia Space has developed several generations of on-board digital transparent processors (DTP) by introducing the most advanced and disruptive technologies. Thales Alenia Space DTPs are state-of-the-art sub-systems at the heart of payloads using analogue-to-digital (ADC) and digital-to-analogue (DAC) channelizers on their input and output RF accesses and making extensive use of digital processing to support channel routing with fine bandwidth granularity. After several payloads based on 5th generation processors, Space Inspire (INstant SPace In-orbit REconfiguration)) solution uses a 6th generation processors offering another step in flexibility through Digital Beam Forming (DBFN). This latest processor generation leverages DTP3G and 5G assets as well as in-flight heritage and provides many more features. Developped with support of CNES & DGA (French DoD), DTP6G covers Civil but also MilsatCom/GovSatCom missions thanks to high performances and small routing granularity. Its main current usecases are GEO but it is compatible with LEO to MEO orbits. Although DBFN is a key addition of DTP6G, it can still be operated with fixed-beam antennas or with an analog BFN. Another new feature is the embedded High Speed Command/Control link (HiLink) providing high TMTC throughput over several waveforms (Full CCSDS or CCSDS over DVBS2). Internal encryption is proposed (AES) but access to an external encryption unit (NSA-type) is also possible. This C&C link combined with a high-performance/large-storage-capacity processing board ensures fast operability and a high-level of observability. DTP6G processor is also ready for future implementations of a Regenerative companion, Beamhopping and Multi-user scenarios. The paper will present Thales Alenia Space transparent processor roadmap leading to DTP6G, its mission coverage, main features and a status of development & production.

Quantum Advantage of Binary Discrete Modulations for Space Channels

We assume information is discrete-modulated over coherent states of the single-mode electromagnetic field and transmitted over space quantum channels. In this work, we provide a comparison of quantum detection with classical detection for communication using on-off keying (OOK) and binary phase shift keying (BPSK) for illustrative system parameters for LEO, MEO and GEO satellites. To do so, we assume an attenuation-only (pure-loss) channel and compute the Shannon capacities for the following detection methods: classical (shot-noise limited) single-photon and coherent detectors as well as optimal quantum hypothesis-testing (Helstrom) detection. As in classical system engineering design, we also obtain theoretical references for comparison, namely, Shannon capacities and Holevo bounds for the ideal Gaussian optical channel. Our results show the ranges of transmitted power and orbital heights for which either classical or quantum detection is optimal, thus providing useful insights into design guidelines and operations of future space communication systems. We also obtain the remarkable result that the BPSK Holevo bound achieves the ultimate quantum capacity of the considered channel.

Performance analysis of cross-frequency Doppler-assisted carrier phase tracking

Using the Doppler frequency obtained from tracking a GNSS pilot signal to aid in tracking another signal modulated with higher rate navigation messages in a different frequency band can improve tacking robustness and lower the message demodulation threshold. Based on an analysis of received signal frequency coherence, a linearized mathematical model of the cross-frequency Doppler-assisted carrier phase tracking loop is built, a thermal noise jitter calculation equation for the assisted tracking loop is derived, and its dynamic stress response characteristics are examined. The loop design requirements for eliminating the influence of inter-frequency frequency bias are clarified, as are the cross-frequency assist signal selection criteria. Monte Carlo simulations and preliminary field tests validate the theoretical results using the B1C pilot signal-aided tracking B2b signal of the MEO satellite in the BeiDou satellite navigation system (BDS). Experimental results show that the carrier phase tracking threshold of the B2b signal can be reduced by about 4 dB.

Earth rotation parameters from BDS, GPS, and Galileo data: An accuracy analysis

The Earth Rotation Parameters (ERPs) are estimated with the BeiDou Navigation Satellite System (BDS), GPS, and Galileo observations from approximately 100 selected International Global Navigation Satellite System (GNSS) Service (IGS) tracking stations around the world. The results are compared with the IGS final products (IGSF) and the International Earth Rotation and Reference Systems Service (IERS) series 14C04 at 12 UTC. The accuracy of the ERPs derived from the GPS-only reaches the IGS accuracy level. The standard deviations of the differences in the X-pole, Y-pole, and Length of Day (LOD), compared with the IGSF, are 23 μas, 20 μas, and 7 μs/day, respectively. Meanwhile, the standard deviations of the differences in the X-pole, Y-pole, and LOD, in contrast with IERS 14C04, are 28 μas, 25 μas, and 9 μs/day, respectively. Similarly, the ERPs are estimated using BDS-only and Galileo-only observations from approximately 100 selected IGS stations. For ERPs derived from BDS Medium Earth Orbit (MEO-only) satellites, the standard deviations of the differences in the X-pole, Y-pole, and LOD, compared with the IGSF, are 76 μas, 53 μas, and 19 μs/day, respectively, and 75 μas, 55 μas, and 19 μs/day, respectively, compared with IERS 14C04. Likewise, for the ERPs derived from Galileo-only observations, the standard deviations of the differences in the X-pole, Y-pole, and LOD, compared with the IGSF, are 48 μas, 31 μas, and 12 μs/day, respectively, and 48 μas, 30 μas, and 14 μs/day, respectively, in contrast with IERS 14C04. Despite the three orbital planes, tracking station distribution, and unoptimized models for the BDS MEO satellites, these results are close to the IGS accuracy level. The impact of spurious system-specific signals on these solutions is investigated using spectral analysis, a notable spurious signal appears for the 3-plane BDS MEO and Galileo constellations. The pronounced peaks at the frequencies of 2.97 cycles per year (cpy) for Polar Motion and Polar Motion rate, 1.98 cpy for LOD are significantly larger than those from GPS.

Relativistic effects in BDS-3 high-accuracy intersatellite time synchronization

The Global Navigation Satellite Systems (GNSSs) apply conventional relativistic corrections to correct apparent clock offsets. However, with the continuous improvements made to time synchronization approaches and onboard atomic clocks, this model has obviously limits the accuracy improvements of BDS-3 intersatellite time synchronization, and also limited the apparent performance of BDS-3 onboard atomic clocks. This study demonstrates that the amplitude of GNSS conventional relativistic periodic errors can reach 0.08 ns for BDS-3 MEO and IGSO satellites within a day, and 0.40 ns within a month. The frequency stability of the errors’ signal can reach 1.33E-14 (approximately10000 s) and 1.78E-15 (approximately1 day), and the absolute influences on the predicted clock offset accuracy can reach 0.05 ns (1 h), 1.08 ns (1 day). Notably, the above signals caused by the model errors are found in the results of current high-accuracy intersatellite time synchronization based on BDS-3 intersatellite links (ISLs). After adopting a higher-accuracy relativistic correction model, the frequency instability of BDS-3 intersatellite clock offsets is obviously reduced, and the RMS of 24 h fitting residual can be reduced by approximately 60% from 0.12 ns to 0.05 ns. The average 2 h 95% predicted error decreases by approximately 17% from 0.38 ns to 0.32 ns. These results indicate that this high-accuracy relativistic correction model can improve both the BDS-3 satellites’ time synchronization accuracy and the BDS-3 apparent clock offset prediction capability. This study, thus contributes to time synchronization research and signal-in-space accuracy improvements for BDS-3.

Geocenter Motions Derived from BDS Observations: Effects of the Solar Radiation Pressure Model and Constellation Configuration

As the first hybrid-constellation global navigation system, China’s BeiDou navigation satellite system (BDS) has been fully constructed since July 2020 and provides open services for worldwide users. Due to the natural sensitivity of satellite tracking techniques to geocenter motion, BDS has the capability to determine the geocenter coordinates (GCC). This study aims to improve the precision of geocenter coordinates derived from BDS. To that end, 3-year sets of daily geocenter coordinates have been determined with BDS observations. Different solar radiation pressure (SRP) models, including the empirical CODE orbit model (ECOM), the extended ECOM model (ECOM2), and the a priori box-wing along with the ECOM model (BW + ECOM), have been applied for the BDS geocenter estimation. We show that the BW + ECOM model is beneficial in recovering the geocenter motion. Compared to the ECOM, the BW + ECOM model appears to mitigate the draconitic signal of BDS, which reduces the annual amplitude of the GCC-Z by a factor of 2.9. On the other hand, the amplitude of the 3 cpy signal is also reduced by a factor of 2.9. Furthermore, we studied the impact of BDS constellation configuration on the geocenter estimation. The results indicate that the inclusion of IGSO satellites significantly mitigates the spurious signals in the spectra of the GCC-Z. The amplitudes of the annual signal and 3 cpy signal are reduced by (28%, 14%), (33%, 61%), and (31%, 9%) for ECOM, ECOM2, and BW + ECOM cases, respectively. Meanwhile, the amplitude of the 7-day signal related to the orbital period of MEO satellites is also reduced by 32–45%. Thus, the BW + ECOM model and the MEO+IGSO hybrid configuration are recommended for BDS to determine the geocenter coordinates. However, despite these improvements, a significant annual signal with an amplitude of 20.2 mm and a visible 3 cpy signal with an amplitude of 6.1 mm still exist when compared to the Satellite Laser Ranging (SLR) solution.

Swarm and Location-Based QoS Routing Algorithm in MEO/LEO Double-Layered Satellite Networks

In this paper, we mainly research on the QoS (Quality of Service) routing algorithms for MEO/LEO (medium Earth orbit/low Earth orbit) double-layered satellite networks. In this type of networks, the rapidly changing network topology due to relative motion of satellites is one of the main challenges when designing an efficient routing algorithm. Specifically, the issues of high rerouting overhead and traffic routing with diverse QoS requirements remain to be resolved. This paper proposed a M-BMDP (modified bandwidth constrained minimum delay path) routing algorithm based on swarm and location for MEO/LEO double-layered satellite networks. This algorithm forms a set of LEO groups according to the footprint of MEO satellites and chooses the relative MEO satellites as its group manager. For delay sensitive traffic, the algorithm can improve the QoS as the cost of packet loss based on hop limit. And for users located in reversed crevice zone, the traffic can route through one MEO satellite to reduce the time delay. The simulation results show that the M-BMDP algorithm performs better in rerouting delay, overhead and pack loss rate compared with existing solutions.

Preliminary Analysis of BDS-3 Performance for ARAIM

<h3>Abstract</h3> To support the operation of advanced receiver autonomous integrity monitoring (ARAIM), an integrity support message indicating a minimum performance level of satellite constellation is required for aircraft navigation. With BDS-3 providing worldwide service since July 2020, it is desirable to undertake a detailed study on its signal-in-space range error characteristics and prior fault probabilities for ARAIM. The latest accuracy criteria released by the China Satellite Navigation Office in May 2021 is validated by the 27 MEO and IGSO satellites in orbit from July 2020 to June 2021, in which 10 single satellite faults were identified and analyzed in detail with no constellation fault found. Based on this one-year data, the probability of single satellite faults and constellation faults can be initially set as 8 × 10⁻⁵ and 1 × 10⁻³, respectively, for BDS-3 in ARAIM.

Theory and Experiment Analysis on the Influence of Floods on a GNSS Pseudo-Range Multipath and CNR Signal Based on Two Cases Study in China

The surrounding environment of a GNSS observation station is changed during a flood, and this results in a more serious multipath than in a normal environment. Considering that the multipath error is largely related to the pseudo-range multipath and CNR (Carrier-to-noise ratio) of the GNSS signal, the influence of floods on a pseudo-range multipath and CNR is analyzed in theory and through experiment. To ensure the accuracy of the analysis results, the ground track repeat period of GPS, GLONASS, and BDS satellites is investigated from the perspective of theory and skyplots. Two real cases study collected in Zhengzhou and Xinxiang, China, in 2021, are used to demonstrate the influence of floods on a pseudo-range multipath and CNR in detail. Experimental results show that the pseudo-range multipath of a GPS satellite performs more seriously during a flood. The maximum RMS increase rate is approximately 17.85%, and the average of all other satellites with a whole arc is approximately 6.55%. In addition, the CNR of three GNSS systems performs a decrease during a flood. For GPS and GLONASS satellites, the decrease performs more seriously at a high elevation angle than that at a low elevation angle. The maximum decrease is approximately 5 dB-Hz for the GPS satellite and approximately 7 dB-Hz for the GLONASS satellite. In terms of the BDS system, the CNR of all three orbital type satellites decreases during a flood. The average decrease is approximately 2 dB-Hz for BDS MEO and GEO satellites, and about 1 dB-Hz for the BDS IGSO satellite.

BDS-3 Broadcast Ephemeris Orbit Correction Model Based on Improved PSO Combined with BP Neural Network.

During the operation of navigation satellites, errors in the broadcast ephemeris orbits are caused by the influence of ingress factors and other factors. To address this phenomenon, this paper examines the use of the computational intelligence (CI) methods to implement track correction and to develop an optimized BP neural network model based on an improved particle swarm algorithm. The model improves the inertia weights and learning factor parameters of the particle swarm optimization (PSO) algorithm to improve the global optimization capability and accelerate the convergence speed. The improved PSO (IPSO) algorithm is used to perform a global optimization search for the hyperparameters of the BP neural network, and then the neural network model is trained by broadcast ephemeris Keplerian root number and regression parameters. The model is validated using the broadcast ephemeris data of the BDS-3 MEO and IGSO satellites, and the mean square error correction rate of multiple satellites with different correction models shows that the error correction rate of the IPSO-BPNN model can reach 70.2–84% and the error correction rate can be improved by 14.2–56.8% compared with the PSO-BPNN model. The proposed algorithm provides an important reference for BDS-3 and other global navigation satellite systems for improving the accuracy of satellite orbit determination.

Creating Efficient Integrated Satellite-Terrestrial Networks in the 6G Era

With the increasing communication demands, extending the connectivity to the rest areas has become imperative for future 6G networks. The integrated satellite-terrestrial network is promising to provide global broadband access for all types of users, which has drawn much attention from both the academia and industry. In this article, we investigate the integrated satellite-terrestrial network towards 6G from the perspective of systematic design. Firstly, with respect to the problem of how to integrate the satellite network with the terrestrial network, we discuss the potential integration architecture from three different levels. Then, we define a more fundamental performance indicator called effective network efficiency to characterize the actual network performance. By designing the communication system from service to network, we propose the integrated satellite-terrestrial network architecture, in which the MEO satellite network and the terrestrial network are integrated at the air interface level. The proposed architecture can achieve high effective network efficiency for global communication of everyone and everything, breaking through the bottleneck of the fixed development mode of existing networks. This article will provide valuable guideline on future research and development of integrated satellite-terrestrial networks.

Validation and evaluation on B1IB3I-based and B1CB2a-based BDS-3 precise orbits from iGMAS

The quality analysis of precise orbit products are important for the BeiDou global navigation satellite system (BDS-3) to provide precise positioning, navigation and timing (PNT) services to users. The International GNSS Monitoring and Assessment System (iGMAS) is simultaneously been provided with B1IB3I-based and B1CB2a-based BDS-3 precise orbits since September 29, 2019. However, a comprehensive comparison and analysis of these two types of orbit products is still missing. In this contribution, we study the performance of these precise orbits by analyzing the day boundary discontinuity and Satellite Laser Ranging (SLR). Moreover, we compare these precise orbits with the BDS-3 orbit products from the multi-GNSS Experiment (MGEX) analysis center. The test period is more than two years from September 29, 2019 to October 21, 2021. We found that: First, compare them with the MGEX BDS-3 precise orbits provided by GFZ and WHU, the average root mean square (RMS) value of the position deviation in the 3D directions orbit component is 0.081 ∼ 0.154 m for MEO satellites and 0.202 ∼ 0.255 m for IGSO satellites. The ranks of different BDS-3 orbit consistency are MEO SECM > MEO CAST > IGSO and we observe that the orbit consistency in eclipse period is better than the ones in non-eclipse period expect for rare cases; Secondly, the RMS of SLR residuals is 5.0 ∼ 6.0 cm, and compared to the orbit in non-eclipse period, the decrease of orbit in eclipse period in percentage is 1.72%∼8.00%. In addition, the radial performance of B1IB3I-based precise orbits for MEO CAST satellites is better than that of B1CB2a-based precise orbits, but it is opposite for MEO SECM satellites; Thirdly, combine with the CODE’s new solar radiation pressure model, namely ECOM2, by using the day boundary discontinuity, the preliminary results illustrate that the average RMS value of the day boundary discontinuity for BDS-3 MEO satellites in the 3D directions orbit component is 0.546 ∼ 0.639 m, and it is 0.881 ∼ 0.897 m for BDS-3 IGSO satellites. The performance ranking of day boundary discontinuity of BDS-3 precise orbits in the 3D directions orbit component is B1IB3I-based MEO CAST > B1IB3I-based MEO SECM > B1CB2a-based MEO CAST > B1CB2a-based MEO SECM > B1CB2a-based IGSO > B1IB3I-based IGSO satellites.

Modeling and predicting inter-frequency clock bias of BDS-2 GEO, IGSO and MEO satellites for triple-frequency precise point positioning

Modeling and predicting inter-frequency clock bias of BDS-2 GEO, IGSO and MEO satellites for triple-frequency precise point positioning

Inter-satellite time synchronization and ranging link assignment for autonomous navigation satellite constellations

The BeiDou Navigation Satellite System (BDS) has equipped its new-generation satellites with inter-satellite link (ISL) payloads for the autonomous operation. In the autonomous operation mode, the navigation constellation realizes the time unification and orbit determination through inter-satellite time synchronization and ranging, so as to self-maintain the time-space reference. For solving the problem of inter-satellite time synchronization and ranging link assignment for autonomous navigation constellations, assignment algorithms of time synchronization links based on satellite layers, as well as ranging links combining satellite selection and weighting, were proposed. The ISL assignment simulation of the BeiDou-3 global constellation was implemented using our algorithms, and the assignment was completed almost within 5 cycles. According to the statistical results, using 56.6% of ISL timeslots, the constellation had achieved the optimal mode of inter-satellite time synchronization with the least skips; the number of inter-satellite ranging links established per minute of each satellite was not less than 10, which met the constraint of the minimum links; the average PDOP of ranging links of the MEO, GEO and IGSO satellite was about 1, 1.6 and 1.5 respectively, close to the lower reference limit. It was demonstrated that the ISLs were reasonably assigned for the demand of inter-satellite time synchronization and ranging with constraints of the TDMA system, narrow beams, the quantity of payloads and inter-satellite visibility.

Initial Results of Modeling and Improvement of BDS-2/GPS Broadcast Ephemeris Satellite Orbit Based on BP and PSO-BP Neural Networks

With the rapid development and gradual perfection of GNSS in recent years, improving the real-time service performance of GNSS has become a research hotspot. In GNSS single-point positioning, broadcast ephemeris is used to provide a space–time reference. However, the orbit parameters of broadcast ephemeris have meter-level errors, and no mathematical model can simulate the variation of this, which restricts the real-time positioning accuracy of GNSS. Based on this research background, this paper uses a BP (Back Propagation) neural network and a PSO (Particle Swarm Optimization)–BP neural network to model the variation in the orbit error of GPS and BDS broadcast ephemeris to improve the accuracy of broadcast ephemeris. The experimental results showed that the two neural network models in GPS can model the broadcast ephemeris orbit errors, and the results of the two models were roughly the same. The one-day and three-day improvement rates of RMS(3D) were 30–50%, but the PSO–BP neural network model was better able to model the trend of errors and effectively improve the broadcast ephemeris orbit accuracy. In BDS, both of the neural network models were able to model the broadcast ephemeris orbit errors; however, the PSO–BP neural network model results were better than those of the BP neural network. In the GEO satellite outcome of the PSO–BP neural network, the STD and RMS of the orbit error in three directions were reduced by 20–70%, with a 20–30% improvement over the BP neural network results. The IGSO satellite results showed that the PSO–BP neural network model output accuracy of the along- and radial-track directions experienced a 70–80% improvement in one and three days. The one- and three-day RMS(3D) of the MEO satellites showed that the PSO–BP neural network has a greater ability to resist gross errors than that of the BP neural network for modeling the changing trend of the broadcast ephemeris orbit errors. These results demonstrate that using neural networks to model the orbit error of broadcast ephemeris is of great significance to improving the orbit accuracy of broadcast ephemeris.

LEO-Constellation-Augmented BDS Precise Orbit Determination Considering Spaceborne Observational Errors

The precise orbit determination (POD) accuracy of the Chinese BeiDou Navigation Satellite System (BDS) is still not comparable to that of the Global Positioning System because of the unfavorable geometry of the BDS and the uneven distribution of BDS ground monitoring stations. Fortunately, low Earth orbit (LEO) satellites, serving as fast moving stations, can efficiently improve BDS geometry. Nearly all studies on Global Navigation Satellite System POD enhancement using large LEO constellations are based on simulations and their results are usually overly optimistic. The receivers mounted on a spacecraft or an LEO satellite are usually different from geodetic receivers and the observation conditions in space are more challenging than those on the ground. The noise level of spaceborne observations needs to be carefully calibrated. Moreover, spaceborne observational errors caused by space weather events, i.e., solar geomagnetic storms, are usually ignored. Accordingly, in this study, the actual spaceborne observation noises are first analyzed and then used in subsequent observation simulations. Then, the observation residuals from the actual-processed LEO POD during a solar storm on 8 September 2017 are extracted and added to the simulated spaceborne observations. The effect of the observational errors on the BDS POD augmented with different LEO constellation configurations is analyzed. The results indicate that the noise levels from the Swarm-A, GRACE-A, and Sentinel-3A satellites are different and that the carrier-phase measurement noise ranges from 2 mm to 6 mm. Such different noise levels for LEO spaceborne observations cause considerable differences in the BDS POD solutions. Experiments calculating the augmented BDS POD for different LEO constellations considering spaceborne observational errors extracted from the solar storm indicate that these errors have a significant influence on the accuracy of the BDS POD. The 3D root mean squares of the BDS GEO, IGSO, and MEO satellite orbits are 1.30 m, 1.16 m, and 1.02 m, respectively, with a Walker 2/1/0 LEO constellation, and increase to 1.57 m, 1.72 m, and 1.32 m, respectively, with a Walker 12/3/1 constellation. When the number of LEO satellites increases to 60, the precision of the BDS POD improves significantly to 0.89 m, 0.77 m, and 0.69 m for the GEO, IGSO, and MEO satellites, respectively. While 12 satellites are sufficient to enhance the BDS POD to the sub-decimeter level, up to 60 satellites can effectively reduce the influence of large spaceborne observational errors, i.e., from solar storms.

A Novel Method to Mitigate the Multipath Error for BDS-2 Dam Deformation Monitoring

The multipath effect on carrier-phase observations is related to the observational environment of the station, and cannot be eliminated or attenuated by the differential method. In the actual dam environment of deformation monitoring, multipath is very complicated. It is the main error source of BDS-2 for high precision data processing. In this paper, a new method called the multi-point hemispherical grid model (MHGM) is studied and evaluated. This method uses the hemispheric grid model to attenuate the influence of multipath errors. The effectiveness and improvement of the new method with respect to the popular sidereal filter (SF) method were assessed and verified by the actual dam monitoring data with only the BDS-2. The MHGM and SF approach calculates the multipath corrections from multi-days historical data, and then corrects the multipath error from the observations on the day of interest. Compared with the SF method, the MHGM can also effectively provide a graphical display of multipath error interference around the stations, which matches the surrounding observation environment. The results show that the double-differenced (DD) residuals of the MHGM for GEO/IGSO and MEO satellites are slightly better than those of SF, but the RMS of MHGM for GEO/IGSO+MEO DD residuals is improved by about 17.0%. The performance of the MHGM method for different satellite constellations is consistent and not affected by the different orbital repeat times, which could solve the “zero mean” assumption problem of the SF method. Meanwhile, the RMS of static with a 2 h interval and kinematic positioning errors of the MHGM method in the horizontal and vertical direction can be up to 1.7, 3.6 and 2.4, 8.1 mm, respectively. The MHGM model could avoid the multipath reference problem caused by different orbital repetition periods, making it more suitable for the combined multipath modeling of BDS-2 and BDS-3.

Non-Radiation Degradation of Solar Array Energy Performances for MEO Satellites

Non-Radiation Degradation of Solar Array Energy Performances for MEO Satellites

Performaces and telemetres analysis of BD satellite passive hydrogen maser

An atomic clock is one of the most important payloads in navigation satellites. It is in charge of generating and maintaining the satellite time. The performance and on-orbit adaptability of a 23-kg passive hydrogen maser (PHM) have been verified using the experimental satellite of the third-generation Beidou satellite navigation system (BDS-3). The clock offset of the PHM is less than 1 ns per day. In BDS-3, PHMs operate as the master clocks in the GEO, IGSO, and MEO satellites; therefore, they are important in the system operation. Herein, we present the design and performance evaluation of the PHM and compare the hydrogen maser, rubidium atomic clock, and cesium atomic clock. Using the satellite-ground time-difference data, we analyze the frequency stability and time prediction accuracy. Furthermore, we perform a preliminary analysis of the operating status and aging trend based on the satellite telemetry data.

Scintillation due to atmospheric turbulence on optical GEO and MEO satellite links: Time series synthesizer for system level simulations

SummaryOptical satellite links have been proposed in order to cover the increasing capacity demand for satellite networks. The reliable design of the performance of optical satellite links is of utmost importance. In the present paper, an analytical methodology for the generation of time series of scintillation due to atmospheric turbulence of optical satellite links is proposed. Under cloud‐free line of sight, scintillation causes the degradation of link's quality. In order to design adaptive transmission techniques for scintillation compensation, an accurate channel model for time series synthesis is required. The proposed synthesizer is based on stochastic differential equations (SDEs) driven by fractional Brownian motion and generates log‐amplitude time series for plane and spherical waves affected by turbulence. The links are considered between Ground and Geostationary or Medium Earth Orbit satellites. The synthesizer is validated using the theoretical aspects of scintillation considering the first‐ and second‐order statistics. Additionally, the performance of the synthesizer for the case of Geostationary is validated with data from ARTEMIS optical satellite link experiment carried out by European Space Agency. The proposed synthesizer can be directly employed for the system performance of transmission techniques for optical satellite forward and reverse links taking into account the scintillation effects.