Operational Satellite Research Articles

Performance Investigation of the Conjunction Filter Methods and Enhancement of Computation Speed on Conjunction Assessment Analysis with CUDA Techniques

The growing number of space objects leads to increases in the potential risks of damage to satellites and generates space debris after colliding. Conjunction assessment analysis is the one of keys to evaluating the collision risk of satellites and satellite operators require the analyzed results as fast as possible to decide and execute collision maneuver planning. However, the computation time to analyze the potential risk of all satellites is proportional to the number of space objects. The conjunction filters and parallel computing techniques can shorten the computation cost of conjunction analysis to provide the analyzed results. Therefore, this paper shows the investigation of the conjunction filter performances (accuracy and computation speed): Smart Sieve, CSieve and CAOS-D (combination of both Smart Sieve and CSieve) in both a single satellite (one vs. all) and all space objects (all vs. all) cases. Then, all the screening filters are developed to implement an algorithm that executes General-purpose computing on graphics processing units (GPGPU) by using NVIDIAs Compute Unified Device Architecture (CUDA). The analyzed results show the comparison results of the accuracy of conjunction screening analysis and computation times of each filter when implemented with the parallel computation techniques.

Multispectral Satellite Imagery Products for Fire Weather Applications

Abstract Two multispectral satellite imagery products are presented that were developed for use within the fire management community. These products, which take the form of false color red–green–blue composites, were designed to aid fire detection and characterization, and for assessment of the environment surrounding a fire. The first, named the Fire Temperature RGB, uses spectral channels near 1.6, 2.2, and 3.9 μm for fire detection and rapid assessment of the range of fire intensity through intuitive coloration. The second, named the Day Fire RGB, uses spectral channels near 0.64, 0.86, and 3.9 μm for rapid scene assessment. The 0.64 μm channel provides information on smoke, the 0.86 μm channel provides information on vegetation health and burn scars, and the 3.9 μm channel provides active fire detections. Examples of these red–green–blue composite images developed from observations collected by three operational satellite imagers (VIIRS on the polar-orbiting platform and the Advanced Baseline Imager and Advanced Himawari Imager on the geostationary platform) demonstrate that both red–green–blue composites are useful for fire detection and contain valuable information that is not present within operational fire detection algorithms. In particular, it is shown that Fire Temperature RGB and Day Fire RGB images from VIIRS have similar utility for fire detection as the operational VIIRS Active Fire products, with the added benefit that the imagery provides context for more than just the fires themselves. Significance Statement The current generation of operational polar-orbiting weather satellites that began with the launch of Suomi NPP offers new capabilities with regard to fire detection and monitoring. In particular, false color red–green–blue composite imagery is now being used by fire managers, incident meteorologists, and others in the fire management community to visualize a fire’s behavior and the context in which it occurs. This paper outlines two of these red–green–blue composites that have gained widespread use throughout the U.S. National Weather Service and the Alaska Fire Service. These red–green–blue composites have been applied to the current generation of geostationary and polar-orbiting satellites to great effect and have changed how incident management teams respond to wildland fires.

Robust estimation of distribution algorithms via fitness landscape analysis for optimal low-thrust orbital maneuvers

One particular kind of evolutionary algorithms known as Estimation of Distribution Algorithms (EDAs) has gained the attention of the aerospace industry for its ability to solve nonlinear and complicated problems, particularly in the optimization of space trajectories during on-orbit operations of satellites. This article describes an effective method for optimizing the trajectory of a spacecraft using an evolutionary approach based on EDAs, incorporated with fitness landscape analysis (FLA). The approach utilizes flexible operators that are paired with seeding and selection mechanisms of EDAs. Initially, the orbit transfer problem is mathematically modeled and the objectives and constraints are identified. The landscape feature of the search space is analyzed via the dispersion metric to measure the modality and ruggedness of the search domain. The obtained information are used as feedback in developing adaptive operators for truncation factor and constraints separation threshold of the employed EDA. A framework for spacecraft trajectory optimization has been presented where the dispersion value for a space mission is estimated using a k-nearest neighbors (k-NN) algorithm. The suggested method is used to solve several problems related to low-thrust orbit transfer of satellites in Earth’s orbit. Results demonstrate that the suggested framework for trajectory design and optimization of space transfers is effective enough to offer fuel-efficient and energy-efficient maneuvers for different thrust levels of the propulsion system. Moreover, the performance of the proposed approach is evaluated against non-adaptive EDA and other advanced evolutionary algorithms. The obtained results certify that the proposed adaptive evolutionary approach is superior in identifying feasible minimum-fuel and minimum-energy transfer trajectories.

Resource- and Neighbor-Aware Observation Transmission Scheme in Satellite Networks.

The observation satellite can exploit its own storage and computational resources to reduce the transmission delay. However, too excessive usage of these resources can have negative effects on the queuing delay at the relay satellite and/or on conducting other tasks at each observation satellite. In this paper, we proposed a new resource- and neighbor-aware observation transmission scheme (RNA-OTS). In RNA-OTS, each observation satellite decides whether to use its resources and the resources of the relay satellite at each time epoch by considering its resource utilization and transmission policies of neighbor observation satellites. For the optimal decision of each observation satellite in a distributed manner, the operation of observation satellites is modeled by means of a constrained stochastic game, and a best-response-dynamics-based algorithm is devised to find the Nash equilibrium. The evaluation results demonstrate that RNA-OTS can decrease the delay to deliver the observation to the destination by up to 87% compared to a relay-satellite-based scheme while guaranteeing a sufficiently low average utilization of the resources of the observation satellite.

Potential improvement of XCO2 retrieval of the OCO-2 by having aerosol information from the A-train satellites

ABSTRACT Near-real time observations of aerosol properties could have a potential to improve the accuracy of XCO2 retrieval algorithm in operational satellite missions. In this study, we developed a retrieval algorithm of XCO2 (Yonsei Retrieval Algorithm; YCAR) based on the Optimal Estimation (OE) method that used aerosol information at the location of the Orbiting Carbon Observatory-2 (OCO-2) measurement from co-located measurement of the Afternoon constellation (A-train) such as the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Observation (CALIPSO) and the MODerate-resolution Imaging Spectrometer (MODIS) onboard the Aqua. Specifically, we used optical depth, vertical profile, and optical properties of aerosol from MODIS and CALIOP data. We validated retrieval results to the Total Carbon Column Observing Network (TCCON) ground-based measurements and found general consistency. The impact of observed aerosol information and its constraint was examined by retrieval tests using different settings. The effect of using additional aerosol information was analyzed in connection with the bias correction process of the operational retrieval algorithm. YCAR using a priori aerosol loading parameters from co-located satellite measurements and less constraint of aerosol optical properties made comparable results with operational data with the bias correction process in three of the four cases subject to this study. Our work provides evidence supporting the bias correction process of operational algorithms and quantitatively presents the effectiveness of synergic use of multiple satellites (e.g. A-train) and better treatment of aerosol information.

Simulating satellite urban land surface temperatures: sensitivity to sensor view angle and assumed landscape complexity

Urban land surface temperature (LST) from satellite earth observation (EO) varies with sensor view angle. Where these variations are not accounted for, urban LST products are inconsistent through time, limiting their use in urban weather and climate model evaluations and process studies (e.g. urban heat island, building energy balance, human thermal comfort). Obstacle-resolving numerical models (ORM) of urban form and radiation exchanges are being used to: (a) understand relations between EO view angle, the 3-dimensional urban surface, and the surface temperatures from urban land surface models, and (b) evaluate parameterisations (parametric models) that aim to account for LST angular effects for the next operational satellite products. Most ORM are limited to simplified buildings (e.g. cuboids) and surface temperatures by lack of datasets. Novelly, we use both a realistic urban form model and observed surface temperatures to assess the impact of simplifying the urban form and temperature on the modelled LST anisotropy. We test various sets of assumptions in central London by combining ground-based thermal camera observations and the state-of-the-art Discrete Anisotropic Radiative Transfer (DART) model. The high resolution realistic model (< 1 m) includes thermal (surface temperatures varying by sun-surface geometry, shadow history and materials every 30 min) and geometry (sloped roofs, chimneys and vegetation) data. These data are used to simulate brightness temperatures of EO pixels to quantify LST view angle variations.During daytime, a change of view angle of 47° off-nadir corresponds to a difference in LST of up to 5.1 K for the realistic building model. The intermediate-complexity landscape (easily obtainable building geometry/footprints and more idealised surface temperature distributions driven only by shadow patterns) gives the best agreement in simulated LST to the realistic landscape. The directional variations are still captured in total (daytime mean absolute error 0.44 K) when using an idealised ORM representation of the same landscape (cuboid buildings, simplified surface temperature) except for roofs which are near-isotropic. Results suggest that geometry assumptions used in current ORM are suited for evaluation of parametric models used to develop and verify operational LST sensor view angle corrections. Future work should consider more realistic materials and scattering processes including low emissivity glass and metals with challenging specular properties.

Global tropopause height determination using GNSS radio occultation

The tropopause layer is a crucial stratum of the earth's atmosphere that attracts more interest from climate and atmospheric researchers. The observables of the global navigation satellite system (GNSS) allow for continuous and long-term research of the atmosphere. The Meteorological Operational Satellite Program (MetOp) mission has a large number of radio occultation (RO) events globally with a high vertical resolution. For investigating the atmosphere, GNSS RO is regarded as a great active remote sensing approach. The present paper investigates the tropopause height (TPH) globally using 5,738,483 GNSS RO measurements of MetOp from 2007 to 2021 to analyze the monthly and yearly variability patterns of TPHs. The spatiotemporal variation of TPH confirms a bell shape. According to the analysis, the TPH varies with latitude, with the highest level reaching up to 17 km in the equatorial region and decreasing gradually to get its lowest value of 8 km at the poles. The global TPH estimated from GNSS RO is very well matched with the TPH estimated from the ECMWF Reanalysis v5 (ERA5) model with a correlation of 0.9997 in 2021. The findings of this study will contribute to a better understanding of TPH variations. As a result, our findings may be helpful in advancing atmospheric modeling and estimating wet delay for GNSS observations.

Enhancing the radar system simulator tool suite to allow the simulation of sensor networks

The number of human-made objects orbiting the Earth is growing steadily. This trend is further accelerating during recent years due to increasing commercialization in the field of satellite operations and an increasing launch rate. Concerning the area of space surveillance and tracking (SST), this leads to higher demands with respect to object observation capabilities. In order to ensure the safe usability of the different Earth orbits for all spacecraft operators, it is of great importance to continuously observe and catalog as many of the human-made objects as possible. This is especially true for inactive and uncontrollable objects, i.e. space debris. Only by maintaining accurate catalogs of the space debris environment, involuntary collisions can be avoided and risks of losing a spacecraft kept low. While the number of space debris objects can only be expected to further increase, it is not trivial to increase the number of observation sites, such as telescopes and radars, or their capabilities to counter this. One way to increase the observation capabilities without constructing new observation sites is to search for possibilities to improve the efficiency with which the existing sensors observe objects.With the goal to study and analyze single sensors, sensor networks, and how they can be used in the most efficient way, a sensor network simulator tool suite has been developed at the Institute of Space Systems of the Technical University of Braunschweig. Originally, the tool suite was developed as a radar system simulator concentrating on the different radar system configurations, such as reflector antennas or phased arrays that are used in a mono- or bistatic mode. Additionally, the corresponding radar performance model is able to simulate a tracking as well as a scanning mode. Building upon this tool suite, it is now extended to include an optical performance model and the possibility to simulate not only ground-based but also space-based sensors. Within this work, the preliminary results obtained with the newly implemented optical performance model are shown.Using the enhanced version of this sensor network simulator tool suite, thorough analyses can now be made using the radar and optical performance models. Sensor networks consisting of radars and telescopes being both ground- or space-based can be studied in different configurations. Thereby, different aspects, such as observation strategies, sensor tasking, or choosing the right location and sensor to reach a certain goal can be investigated.

Can Regulating Large Satellite Constellations as Monopolies Improve Sustainability Standards While Providing Effective and Equitable Internet Access?

Large satellite constellations (LSC) in Low Earth Orbit (LEO) provide the means to deliver internet to previously underserved populations. The LSC’s economic potential combined with a growing demand for internet access has led to multiple companies pledging their own internet LSCs in hopes of capitalizing on this need. This, in addition to growing interest in LEO, risks destabilizing the LEO environment if not regulated properly. The current U.S. Orbital Debris Standard Mitigation Practices (USODSMP) are woefully outdated and only sporadically followed by operators. Furthermore, there are no licensing regulations for other key sustainability requirements, such as propulsion and tracking. Accelerated growth of internet LSCs without proper regulation will lead to an unsafe and unsustainable LEO environment. There needs to be a change in how governments regulate private and public LSCs, in particular those providing internet telecommunications. Internet LSCs are the fastest growing population in LEO, often directly competing for orbits and broadband frequencies. In this thesis I investigate whether the U.S. could apply aspects of terrestrial utility infrastructure to better regulate satellite internet. In particular, I question whether the U.S. government could regulate internet LSCs as monopolies. Such regulatory control would allow the U.S. to better enforce and revise sustainability regulations and ensure fair access to internet services. Viewing internet as a utility, as a necessity of modern life to which all citizens deserve access, this thesis proposes the U.S. license a single internet LSC from within its borders. I explored two potential regulatory approaches: one based on the U.S.’s public utility system and one based on European internet infrastructure. I then presented these approaches to five experts in the field of space sustainability and solicited their feedback. From these results, I determined that both of my regulatory approaches are not feasible in their current forms within the U.S.; however, both approaches produce potential partial applications and variations of their initial design that may find traction. This thesis concludes that adopting an interoperability framework in LEO would allow for precise and targeted sustainability, technology, and capacity standards for each orbital corridor, empower regulatory bodies to enforce these standards, and preserve competition among Commerical Satellite Operators (CSOs). Finally, a government internet LSC competing against commercial internet LSCs, akin to terrestrial municipal internet, would demonstrate technological feasibility, satisfy equity requirements, and provide a baseline LSC for CSOs to compete against. To see the complete thesis, please visit https://scholar.colorado.edu/concern/undergraduate_honors_theses/5138jg42t.

Integrated Design and Power Loss Minimization of Reaction Wheel Motor for Satellite Attitude Control

This paper develops a coreless-stator permanent magnet synchronous motor (PMSM) for reaction wheels applied to attitude control of satellites. The reaction wheel motor requires a design of lightweight, low operation loss, high efficiency and high inertia to keep the satellite operation stable with minimized power consumption. A coreless-stator design possesses the advantages of low core loss and lightweight and is considered suitable. However, this design may suffer significant eddy current loss induced in the conductors by the rotor alternating magnetic field, and this is unbeneficial to loss reduction. Moreover, due to the high inertia of the reaction wheel, torque and current would persist for a long duration, leading to copper losses that should not be disregarded. Therefore, the operation scenarios of the satellites should be considered in the reaction wheel design. In this paper, a comprehensive analysis for various design factors is conducted to minimize the power loss of the reaction wheel, taking the satellite operation scenarios into account. Finally, a lightweight and low-loss reaction wheel motor is designed and simulated. Experiments are conducted to validate the design and analysis.

Study on the effect of cartoon video education before orbital operation.

Study on the effect of cartoon video education before orbital operation.

Analysis and application of deep space exploration satellite telemetry data combined with empirical mode decomposition and ARIMA model

With China’s deep space exploration program constantly expanding, the number of satellites on-orbit is increasing year by year. The stable operation of satellites in orbit hinges on long-term monitoring and analysis of the telemetry data downloaded from the satellite on the ground, which enables quick detection of any irregularities. If we can grasp the changing trend and operation law of satellite telemetry data, we can monitor and control satellites and reduce losses better. Aiming at a large amount of telemetry data of deep space exploration satellites, the data presents non-stationary and nonlinear characteristics, The time series to be processed is constructed sequentially using the acquired telemetry data, and it is decomposed using the empirical mode decomposition approach. The non-stationary signal is divided into a stationary sequence and the sum of a series of stationary intrinsic mode functions. Then the decomposed sets of results are used as the input of the ARIMA model, and the ARIMA model is constructed to predict the predicted value of each decomposed sequence, and the weighted summation of the predicted values is performed to reconstruct the predicted results. Lastly, actual satellite telemetry data is used to confirm the method’s viability. The experimental findings demonstrate that the model can more successfully anticipate the short-term trend of satellite telemetry data.

An integrated image task planning in satellite networks: From instruction release and observation perspective

The unreasonable observation arrangements in the satellite operation control center (SOCC) may result in the observation data cannot be downloaded as scheduled. Meanwhile, if the operation instructions released by the satellite telemetry tracking center (STTC) for the on-board payloads are not injected on the specific satellites in time, the corresponding satellites cannot perform the observation operations as planned. Therefore, there is an urgent need to design an integrated instruction release, and observation task planning (I-IRO-TP) scheme by efficiently collaborating the SOCC and STTC. Motivated by this fact, we design an interaction mechanism between the SOCC and the STTC, where we first formulate the I-IRO-TP problem as a constraint satisfaction problem aiming at maximizing the number of completed tasks. Furthermore, we propose an interactive imaging task planning algorithm based on the analysis of resource distribution in the STTC during the previous planning periods to preferentially select the observation arcs that not only satisfy the requirements in the observation resource allocation phase but also facilitate the arrangement of measurement and control instruction release. We conduct extensive simulations to demonstrate the effectiveness of the proposed algorithm in terms of the number of completed tasks.

Shape Adjustment and Experimental Study of a Shape Memory Cable (SMC) Structure.

Large deployable cable net antennas have attracted extensive attention worldwide because of their simple structure and high storage ratio. The cable net structure is affected by long exposure in a harsh space environment during satellite operation, resulting in large thermal deformation and stress relaxation, which leads to a degradation of antenna performance. To address the thermal deformation of the cable net structure, a shape memory cable (SMC) net structure model was proposed with surface accuracy as the research objective. Specifically, we aimed to utilize its phase transition characteristics to adjust the thermal deformation of cable net structure and improve its surface accuracy. A shape memory cable net structure model with a diameter of 2.2 m was built, and a normal temperature experiment and high- and low-temperature experiments were carried out. High- and low-temperature test refers to environmental simulation testing of shape memory cable net structures under high- and low-temperature conditions. This was done to determine whether the adjustment method for surface accuracy meets the requirements. The results showed that the shape memory alloy wire has a relatively stable ability to adjust the surface accuracy of the cable net structure at room temperature. During temperature cycling, the thermal deformation of the shape memory cable net structure is slight, and the surface accuracy is good. Compared with ordinary cable net structures, the shape memory cable net structure has improved surface accuracy by 44.4% and 45.2% at high and low temperatures, respectively. This proved the effectiveness of the method for adjusting surface accuracy. These experimental results offer guiding significance for engineering applications.

Observing the Near‐Surface Properties of the Greenland Ice Sheet

AbstractSpaceborne radar altimetry over ice sheets has exclusively focused on assessing volume changes through changes in surface elevation. For use in mass balance calculations, these measurements are supplemented with surface property information derived from regional climate models with limited large‐scale observational validation. Simultaneously, the strength at which a radar signal is reflected from the surface contains information on these same near‐surface properties. Here we show that a quantitative interpretation of European (ESA) CryoSat‐2 and French/Indian (CNES/ISRO) SARAL surface echo powers yields timeseries of pan‐Greenland wavelength‐scale roughness and surface density. Individually, the CryoSat‐2 and SARAL results strive toward providing an observational lens to enhance our current understanding of the surface processes affecting ice sheet mass balance and validate their representation by computational models. Taken together, they highlight how diversity in currently operational and future radar satellite altimetry missions can shed light on near‐surface vertical heterogeneity.

DESIGN OF A SPACE-BORNE HYPERSPECTRAL IMAGER FOR MICRO-SATELLITES

Abstract. We present an optical design of a space-borne hyperspectral imager (HSI) for Earth observation micro-satellite platforms. Space-borne hyperspectral imaging has many crucial applications in fields such as agriculture, water management, environmental monitoring, mineralogy, and remote sensing. An HSI system capable of ground sampling distance (GSD) less than 15 m with a swath width greater than 15 km, spectral resolution less than 10 nm and operating in Low Earth Orbit (LEO) is designed. The system dimensions are restricted to fit in a volume of less than 0.125 m3. A commercial, cooled HgCdTe type imaging sensor is selected to operate 400–2500 nm of the spectrum for the designed imager. The HSI optical design comprises of an off-axis three mirror anastigmat (TMA) type telescope and a modified-Offner type spectrometer. Modified-Offner type spectrometer design with two Féry prisms as a diffractive element is used. The overall HSI system design meets the performance goals described in this paper work.

FSTSMC Compliance Control for Dual-Arm Space Robot With SDBD Capture Satellite Operation

Abstract A space robot inevitably impacts a satellite in a capture operation. If its fragile joints are not protected, they may be damaged, resulting in failure of the capture operation. Thus, a spring damper buffer device (SDBD) is added between the joint motors and manipulators to absorb the impact energy, and provide a compliance strategy matched with the SDBD for stable control of the hybrid system. The dynamic modes of the dual-arm space robot open-loop system and target satellite system are established by the Lagrange function before capture. From the momentum theorem, velocity constraints, closed-chain geometric constraints, and Newton's third law, the closed-chain dynamic model of the hybrid system after capture is obtained, and the impact effect and impact force are calculated. For stable control of the hybrid system while limiting joint? impact torque within the safe range, an adaptive fractional-order super-twisting sliding mode compliance control strategy matching the SDBD is proposed. It can effectively improve the fast convergence and trajectory tracking performance of the system whose velocity and acceleration cannot be measured. The stability of the hybrid system is demonstrated by the Lyapunov theorem, and the anti-impact performance of the SDBD and the effectiveness of the compliance strategy are demonstrated through numerical simulation.

Preselection of the reference orbit for an Earth remote sensing satellite

Low near-circular orbits of Earth remote sensing (ERS) satellites are considered. The objective is to select the orbits most suitable for a particular satellite mission. In particular, the problem of an approximate determination of the orbit parameters that allow a satisfactory satellite survey of the target surface of the Earth is considered. The main desires of observation system developers regarding the conditions of the Earth's surface survey are considered. To reconcile these desires with the regularities of satellite motion in low Earth orbits, use may be made of simple models that describe these regularities. In doing so, it is desirable to visualize viewing swaths on the Earth's surface. A compromise between the desires of observation system developers and the satellite motion regularities is the selection of orbits that best meet the characteristics of a particular satellite and its observation system. This article presents a simple model and algorithm that make it possible to preselect ERS satellite orbits. The proposed model is based on familiar relationships, and the novelty of the article lies in a compact and generalized presentation of the model for ERS satellite orbit preselection. The article presents models that make it possible to estimate the satellite swath width and choose the orbit inclination angle, a stable orbit shape, the orbit altitude, and the orbital period. The advantages and disadvantages of solar synchronous orbits are considered. Analytical expressions are constructed to fairly simply estimate the excursion of a satellite from its operational orbit under the action of the aerodynamic drag, estimate the rate of recovery of the orbit parameters under the action of a constant transversal control acceleration, and determine allowable time intervals between engine starts and engine operation intervals. The advantages of repeat ground track orbits are shown. The simplest model for calculating and visualizing satellite viewing swathes of the Earth's surface is constructed. Thus, the article proposes a simple algorithm for the preselection of low Earth orbits for ERS satellites with a satisfactory observation of the target surface of the Earth.

Method of solving single-event upset for heterogeneous dual field programmable logic gate array for infrared remote sensing camera in orbit

On-orbit reconstruction is a hotspot technology in the field of space infrared remote sensing cameras technology. Since the space infrared remote sensing cameras perform detection work under the space radiation environment, the core part of its image processing unit, which is a static random-access memory type field programmable logic gate array (FPGA), is susceptible to the impact of high-energy particles, especially during single-event upset events. The occurrence of point-like granular noise in remote sensing images will affect the normal imaging detection performance of the system, and even lead to abnormal timing of infrared detectors in severe cases, thereby affecting the normal operation of infrared remote sensing cameras. Aiming at the reliability requirements of the normal operation of space infrared remote sensing cameras in the space radiation environment, we propose a modular architecture of heterogeneous dual FPGA for XilinxVirtex-5 series FPGA, which carries out periodic refresh, reconstruction, and uploading of Virtex-5 series FPGA through antifuse FPGA. The antifuse FPGA periodically refreshes and reconstructs the Virtex-5 series FPGA from a one-time programmable read-only memory and injects the program into the program storage NOR flash device, and periodically refreshes and reconstructs the Virtex-5 series FPGA from NOR flash. This method can refresh and reconstruct the space infrared remote sensing camera in orbit. The in-orbit flight data verification shows that this method can effectively solve the impact of single-particle turnover event and improve the reliability of the infrared remote sensing camera in orbit operation.

A study of internal solitary waves in the Northern South China Sea using the Geo High-Speed Imager of the FY-4B satellite

ABSTRACT The FY-4B satellite is the first operational satellite of China’s new generation of geostationary-orbit meteorological satellites in the Fengyun-4 series. This study is the first to analyse the changes in the dynamic processes of internal solitary waves (ISWs) in the northern South China Sea using FY-4B Geo High-Speed Imager (GHI) data with a 250 m spatial resolution. By calculating the propagation direction, wave crest line length, distance between ISW packets and other characteristics of ISWs and comparing them with FY-3D and MODIS optical images, the feasibility and reliability of using the FY-4B GHI to observe ISWs are verified. This study analyses the dynamic processes of ISW propagation at a high temporal resolution of up to 1 minute and observes ISW propagation processes at different sea depths, ISW evolution dynamics, ISW interaction processes, and the change processes of ISWs as they pass islands and reefs. A comparison between these results and in situ measurements obtained in the northern South China Sea demonstrates that the FY-4B GHI has the unique advantage of continuously tracking and observing ISWs in the northern South China Sea and can provide new tracking observations for the study of ISWs in the South China Sea.