Space Environment Monitoring Research Articles

Efficient Fourth-Order PSTD Algorithm with Moving Window for Long-Distance EMP Propagation.

Satellite-borne electromagnetic pulse (EMP) detection technology plays an important role in military reconnaissance, space environment monitoring, and early warning of natural disasters. However, the complex ionosphere greatly distorts the waveform during propagation and poses a challenge to EMP detection. Therefore, it is necessary to conduct theoretical research on EMP propagation in the ionosphere. Conventional second-order pseudo-spectral time-domain (PSTD-2) algorithm has difficulties in keeping the stability and accuracy of waveforms in calculations over hundreds of kilometers of propagation. To overcome the difficulties, a fourth-order PSTD algorithm incorporating the moving window technique (MWPSTD-4) is proposed. In the numerical examples, the performance of MWPSTD-4 is compared with PSTD-4 and PSTD-2 in the long-distance propagation of EMP. The results show that the MWPSTD-4 improves efficiency while guaranteeing accuracy and is suitable for large-scale electromagnetic field simulation. The proposed method provides a basic algorithm to eliminate the numerical dispersion interference for calculating the long-distance propagation of EMP in complex spaces and is helpful for the design and calibration of satellite-borne EMP detectors.

Design and Application of an Onboard Particle Identification Platform Based on Convolutional Neural Networks

Space radiation particle detection plays a crucial role in scientific research and engineering practice, especially in particle species identification. Currently, commonly used in-orbit particle identification techniques include telescope methods, electrostatic analysis time of flight (ESA × TOF), time-of-flight energy (TOF × E), and pulse shape discrimination (PSD). However, these methods usually fail to utilize the full waveform information containing rich features, and their particle identification results may be affected by the random rise and fall of particle deposition and noise interference. In this study, a low-latency and lightweight onboard FPGA real-time particle identification platform based on full waveform information was developed utilizing the superior target classification, robustness, and generalization capabilities of convolutional neural networks (CNNs). The platform constructs diversified input datasets based on the physical features of waveforms and uses Optuna and Pytorch software architectures for model training. The hardware platform is responsible for the real-time inference of waveform data and the dynamic expansion of the dataset. The platform was utilized for deep learning training and the testing of the historical waveform data of neutron and gamma rays, and the inference time of a single waveform takes 4.9 microseconds, with an accuracy rate of over 97%. The classification expectation FOM (figure-of-merit) value of this CNN model is 133, which is better than the traditional pulse shape discrimination (PSD) algorithm’s FOM value of 0.8. The development of this platform not only improves the accuracy and efficiency of space particle discrimination but also provides an advanced tool for future space environment monitoring, which is of great value for engineering applications.

China's Ground‐Based Space Environment Monitoring Network—Chinese Meridian Project (CMP)

AbstractMonitoring and investigation of the solar‐terrestrial space environment is a huge challenge for humans in space age. To this end, China has established the Ground‐based Space Environment Monitoring Network, namely Chinese Meridian Project (CMP). The project comprises three major systems: the Space Environment Monitoring System, Data and Communication System, and Scientific Application System. The Space Environment Monitoring System adopts a well‐designed monitoring architecture, known as “One Chain, Three Networks, and Four Focuses,” to achieve stereoscopic and comprehensive monitoring of the entire solar‐terrestrial space. The “One‐Chain” component utilizes optical, radio, interplanetary scintillation, cosmic ray instruments to cover the causal chain of space weather disturbances from the solar surface to near‐Earth space. For the ionosphere, middle and upper atmosphere, and magnetic field, instruments are deployed along longitudes of 120° and 100°E, and latitudes of 30° and 40°N, forming the “Three Networks.” Furthermore, more powerful monitoring facilities or large‐scale instruments have been deployed in four key regions: the high‐latitude polar region, mid‐latitude region in northern China, low‐latitude region at Hainan Island, and the Tibet region. These four regions are crucial for disturbances propagation and evolution, or possess unique geographical and topographical characteristics. The Data and Communication System and Scientific Application System are designed for data collecting, processing, storage, mining, and providing user service based on data acquired by the Space Environment Monitoring System. The data obtained by CMP will be shared with the global scientific community, facilitating enhanced collaboration on space weather and space physics research.

Filter-Free UV Photodetectors Based on Unipolar Barrier Van der Waals α-In2Se3/h-BN Heterostructures.

Visible-blind ultraviolet (UV) light detection has a wide application range in scenes like space environment monitoring and medical imaging. To realize miniaturized UV detectors with high performance and high integration ability, new device structures without bulky light filters need to be developed based on advanced mechanisms. Here the unipolar barrier van der Waals heterostructure (UB-vdWH) photodetector is reported that realizes filter-free visible-blind UV detection with good stability, robustness, selectivity, and high detection performance. The UB-vdWH shows a responsivity of 2452AW-1, a photo on-off ratio of 2.94×105 and a detectivity of 1.26×1015Jones as a UV detector, owing to the intentionally designed barrier height that suppresses dark current and photoresponse to visible light during the transport process. The good performance remains intact during 104 test cycles or even under high temperatures, which proves the stability, and robustness of the UB-vdWH, thus shows the huge potential for a wider application range.

Pathways to global coordination in space weather: International organizations, initiatives, and space agencies

This paper is the second part of two papers on global coordination in space weather. In this paper the activities of established and emerging international organizations and initiatives related to space weather research and operations are introduced. As shown in the accompanying paper “Global Landscape of Space Weather Observations, Research and Operations”, most of instrumentations for space environment monitoring are operated by each country. On the other hand, it is necessary to integrate the global observation to detect space weather phenomena, and it is essential to coordinate among nations for data sharing, set standard formats and protocols, fill observational gaps, etc. There are multiple international organizations and other actors in the field of space weather, and they have their own purposes and goals. In 2022, three international organizations, WMO, ISES and COSPAR reached an agreement to explore pathways to increased coordination of activities. There is also an emerging movement by various space agencies that fund space weather research missions to establish a forum to share plans and foster discussions leading to possible collaborations that advance understanding and enable progress of space weather operations and applications.

Unlocking Synergy: Solar Cell Integration with Radio Waves for AI, IT, and Business Advancements

Combining radio waves and solar cells is a ground-breaking technological convergence that has significant ramifications for wireless communication, energy production, and a wide range of other uses. This study investigates the underlying concepts, applications, prospects, and challenges of solar cell radio wave integration, covering a broad range of topics. We start with a summary of solar cells and their various uses before delving into the photovoltaic effect, solar cell varieties, and how they power buildings for homes and businesses, solar farms, off-grid systems, and even space exploration. Since their invention, solar cells have advanced significantly, and they are now essential to the world's transition to renewable energy sources. Modern technology relies heavily on radio waves, the unsung heroes of our globalized society. We reveal the role that radio waves play in wireless communication, covering everything from radar systems, satellite communication, and the Internet of Things (IoT) to broadcasting and wireless communication networks. Combining these two technologies results in better energy harvesting, sustainability, wireless device power, energy independence, cost savings, and dependability. Solar cells use radiation from the environment and sunshine. Nevertheless, there are drawbacks to this integration as well, including compatibility, efficiency, cost concerns, and regulatory compliance. The paper then looks at actual case studies that show how solar cell radio wave integration can be implemented successfully. These examples show the many and revolutionary uses of this technology, from off-grid communication and smart building energy efficiency to IoT environmental monitoring in remote locations and solar-powered wearables. We investigate future directions for solar cell radio wave integration advances. These include improved energy harvesting, incorporation into commonplace items, wearable medical and health technology, smart cities and infrastructure, satellite technology and space exploration, environmental monitoring and conservation, emergency response and disaster recovery, and microgrids for energy resilience. Finally, this research shows how solar cell radio wave integration can change the world by revealing its intricate workings. The convergence of these technologies is transforming wireless communication, artificial intelligence (AI), information technology (IT), and corporate operations in addition to altering how we produce and utilize energy. Sustainable, effective, and networked systems have the potential to build a more resilient and sustainable world in the future.

Plasma Analyzer for the Chinese FY-3E Satellite: In-Orbit Performance and Ground Calibration

The plasma analyzer (PMA) on the Fengyun-3E (FY-3E) meteorological satellite series is a critical sensor of the space environment monitoring package that is capable of the comprehensive in situ detection of the thermal plasma environment and surface discharge effects. In this paper, we conducted a thorough evaluation of the PMA’s performance and reliability through a combination of ground-based laboratory calibration and in-orbit testing. During the ground-based calibration, the PMA underwent assessments for the energy range, field of view (FOV), and measurement accuracy, and obtained the detection accuracy and the geometric factors. During the in-orbit testing, the PMA successfully obtained the typical distribution characteristics of low-energy ions and electrons in orbital space regions, as well as the precipitating particles in the middle and high latitudes of both hemispheres. Notably, the PMA observed an expansion of the particle distribution in the high-latitude regions during a moderate geomagnetic storm. The results from both the ground-based calibration and in-orbit testing demonstrated that the PMA met the requirements for thermal plasma detection, with reliable and scientifically valid in-orbit detection data. These results provide a crucial foundation for studying spatial weather variations, improving the accuracy of space environment forecasts and enhancing disaster detection and monitoring capabilities.

Automatic Identification of Auroral Substorms Based on Ultraviolet Spectrographic Imager Aboard Defense Meteorological Satellite Program (DMSP) Satellite

An auroral substorm is an important physical process of energy accumulation and explosive release in the Earth’s magnetosphere, and is an important research object of space environment monitoring and space weather warnings. A westward traveling surge (WTS) is a typical auroral physical process of an auroral substorm. Its static characteristic is auroral folding at the polar boundary of an auroral oval and its dynamic characteristic is the westward motion of auroral folding. According to the static characteristic of a WTS, we defined a set of feature parameters based on the morphology and designed a set of automatic detection and discrimination methods; that is, the WTS was identified by using the extracted features and pattern recognition approaches. This approach was tested by using the aurora data of the ultraviolet auroral spectral imager of the Defense Meteorological Satellite Program (DMSP) satellite. The results showed that the accuracy rate of automatic recognition was 61.39%~63.61% and the precision rate was 55.52%~57.92%. The experimental results showed that the approach was effective at detecting the typical characteristics of an auroral substorm (WTS).

UAV Implementations in Urban Planning and Related Sectors of Rapidly Developing Nations: A Review and Future Perspectives for Malaysia

The rapid growth of urban populations and the need for sustainable urban planning and development has made Unmanned Aerial Vehicles (UAVs) a valuable tool for data collection, mapping, and monitoring. This article reviews the applications of UAV technology in sustainable urban development, particularly in Malaysia. It explores the potential of UAVs to transform infrastructure projects and enhance urban systems, underscoring the importance of advanced applications in Southeast Asia and developing nations worldwide. Following the PRISMA 2020 statement, this article adopts a systematic review process and identifies 98 relevant studies out of 591 records, specifically examining the use of UAVs in urban planning. The emergence of the UAV-as-a-service sector has led to specialized companies offering UAV operations for site inspections, 3D modeling of structures and terrain, boundary assessment, area estimation, master plan formulation, green space analysis, environmental monitoring, and archaeological monument mapping. UAVs have proven to be versatile tools with applications across multiple fields, including precision agriculture, forestry, construction, surveying, disaster response, security, and education. They offer advantages such as high-resolution imagery, accessibility, and operational safety. Varying policies and regulations concerning UAV usage across countries present challenges for commercial and research UAVs. In Malaysia, UAVs have become essential in addressing challenges associated with urbanization, including traffic congestion, urban sprawl, pollution, and inadequate social facilities. However, several obstacles need to be overcome before UAVs can be effectively deployed, including regulatory barriers, limited flight time and range, restricted awareness, lack of skilled personnel, and concerns regarding security and privacy. Successful implementation requires coordination among public bodies, industry stakeholders, and the public. Future research in Malaysia should prioritize 3D modeling and building identification, using the results of this study to propel advancements in other ASEAN countries.

Radiation dosimeter and charge detector onboard BeiDou navigation satellites in MEO

Abstract The orbit of BeiDou satellite system is a very ideal space environment monitoring area. The radiation dosimeters are present on this series of navigation satellites, and they are respectively installed in the x, y and z positions. A charge detector installed in the satellite cabin is used for monitoring satellite deep charging potential. Radiation dosimeters select the 100 nm P-channel metal oxide semiconductor (PMOS) sensors, whose monitoring range can reach 2 × 106 rad (Si). In the circuit design part, the “zero temperature coefficient” current of the PMOS is used as the constant current source for measuring, which effectively reduces the influence of temperature effect. Three radiation dosimeters realize the daily dose change monitoring during the satellite’s operation, and the detection accuracy is high. The deep charging potential sensor adopts the equivalent capacitor design which is composed of the outer optical quartz glass and the inner circular gold-plate. The two kinds of detection instruments have the characteristics of small volume, low power consumption and high detection accuracy. The detection results show that they have important application value for space environment prediction and guarantee.

Broad Spectrum Detector Based on AlN Crystal

Aluminum nitride(AlN) has an ultra-wide bandgap, which is one of the ideal materials for developing ultraviolet optoelectronic devices and has promising applications in the fields of space environment monitoring and materials science. Due to the existence of defects in the crystal growth process, broad-spectrum detectors were fabricated based on defective state AlN crystals. In this paper, AlN crystal detectors were fabricated and investigated the effect of different electrode work functions on the turn-on voltage. The vertical structure W-AlN-W device achieved broad spectral detection from ultraviolet(UV) to near-infrared(NIR) due to the presence of defects in the crystal, and persistent photoconductivity effect was observed for band-edge excitation. The present work provides implications for the development of AlN crystal-based detectors.

An Ionospheric TEC Forecasting Model Based on a CNN-LSTM-Attention Mechanism Neural Network

Ionospheric forecasts are critical for space-weather anomaly detection. Forecasting ionospheric total electron content (TEC) from the global navigation satellite system (GNSS) is of great significance to near-earth space environment monitoring. In this study, we propose a novel ionospheric TEC forecasting model based on deep learning, which consists of a convolutional neural network (CNN), long-short term memory (LSTM) neural network, and attention mechanism. The attention mechanism is added to the pooling layer and the fully connected layer to assign weights to improve the model. We use observation data from 24 GNSS stations from the Crustal Movement Observation Network of China (CMONOC) to model and forecast ionospheric TEC. We drive the model with six parameters of the TEC time series, Bz, Kp, Dst, and F10.7 indices and hour of day (HD). The new model is compared with the empirical model and the traditional neural network model. Experimental results show the CNN-LSTM-Attention neural network model performs well when compared to NeQuick, LSTM, and CNN-LSTM forecast models with a root mean square error (RMSE) and R2 of 1.87 TECU and 0.90, respectively. The accuracy and correlation of the prediction results remained stable in different months and under different geomagnetic conditions.

Vertical 1D/2D Heterojunction Architectures for Self-Powered Photodetection Application: GaN Nanorods Grown on Transition Metal Dichalcogenides.

Van der Waals (vdW) heterojunctions based on two-dimensional (2D) transition metal dichalcogenide (TMD) materials have attracted the attention of researchers to conduct fundamental investigations on emerging physical phenomena and expanding diverse nano-optoelectronic devices. Herein, the quasi-van der Waals epitaxial (QvdWE) growth of vertically aligned one-dimensional (1D) GaN nanorod arrays (NRAs) on TMDs/Si substrates is reported, and their vdW heterojunctions in the applications of high-performance self-powered photodetection are demonstrated accordingly. Such 1D/2D hybrid systems fully combine the advantages of the strong light absorption of 1D GaN nanoarrays and the excellent electrical properties of 2D TMD materials, boosting the photogenerated current density, which demonstrates a light on/off ratio above 105. The device exhibits a competitive photovoltaic photoresponsivity over 10 A W-1 under a weak detectable light signal without any external bias, which is attributed to the efficient photogenerated charge separation under the strong built-in potential from the type-II band alignment of GaN NRAs/TMDs. This work presents a QvdWE route to prepare 1D/2D heterostructures for the fabrication of self-powered photodetectors, which shows promising potentials for practical applications of space communications, sensing networks, and environmental monitoring.

Deep Learning Based Identification Method for Signal-Level Wireless Protocol

Electromagnetic spectrum surveillance is the basis of space environment monitoring and management, while protocol identification is one of the most important methods. Protocol identification has been applied in many fields, such as target recognition, anomaly detection, security management and information countermeasure. In the past decade, a lot of deep learning based protocol identification methods have been proposed, based on the bit-level protocol. However, the data needs to be demodulated and decoded, depending on the prior information of the target system. In this paper, we focus on signal-level protocol, and introduce the deep learning based identification method. We first develop a multi-dimensional convolutional neural network based method for feature extraction of signal-level protocol. Then, a spatial pooling convolutional neural network is introduced for variable length protocol identification. At last, an unsupervised training network is proposed for feature extraction of unlabelled signal-level protocol. The proposed methods are evaluated by using the practical wireless protocols, and the effectiveness is verified by simulation results.

Visibility analysis of Phobos to support a science and exploration platform

The surfaces of the Martian moons, Phobos and Deimos may offer a stable environment for long-term operation of platforms. We present a broad assessment of potential scientific investigations, as well as strategic and operational opportunities offered by long-term operation of an instrumented lander. Studies using observations of Mars’ moons, and the detailed new findings expected from the JAXA Martian Moons eXploration (MMX) mission, International Mars Sample Return (MSR) Campaign and other upcoming Mars missions, provide a driver for feasibility and trade studies for follow-on missions that would build on the knowledge gain from those missions. We discuss the scientific questions and operational objectives that may be pertinent for landed platforms on the martian moons, including (1) monitoring and scientific investigations of Mars’ surface and atmosphere, (2) scientific investigations of the martian moons, (3) monitoring and scientific investigations of the space environment, (4) data relay for Mars surface assets or interplanetary missions and 5) use in a Mars navigation/positioning system. We present results from visibility calculations performed using the SPICE observation geometry system for space science missions, and a Phobos shape model. We compute as a function of location on Phobos, visibility quantities that are most relevant to science and operational objectives. These include visibility from Phobos of the Sun, Earth, Mars surface and atmosphere, Deimos, and Jupiter. We also consider occultation events by the Mars atmosphere of Earth and Deimos that may provide opportunities for radio science. Calculations are performed for a study period spanning one Mars year in a hypothetical future operational scenario (1 Jan 2030–18 Nov 2031). We combine visibility metrics to identify locations on Phobos most suitable for long-term operation of a platform. We find the Mars-facing side of Phobos, and limited areas on the leading and trailing sides, satisfy the most requirements defined for Mars and Phobos science, space environment monitoring, and data relay/navigation. We demonstrate that compliance with requirements related to visibility of Mars and its atmosphere are not mutually exclusive with those that are better satisfied on Phobos’ anti-Mars side, such as those aided by maximizing their cumulative view factor to the ecliptic plane (i.e. visibility to the Sun, Earth or outer solar system). Finally, our methodology allows to assess the extent to which combined visibility metrics can meet mission requirements. The process we describe can be used to support landing site identification and selection on planets, moons and small bodies.Graphical

Investigation of Mid-Infrared Broadband Second-Harmonic Generation in Non-Oxide Nonlinear Optic Crystals

The mid-infrared (mid-IR) continuum generation based on broadband second harmonic generation (SHG) (or difference frequency generation) is of great interest in a wide range of applications such as free space communications, environmental monitoring, thermal imaging, high-sensitivity metrology, gas sensing, and molecular fingerprint spectroscopy. The second-order nonlinear optic (NLO) crystals have been spotlighted as a material platform for converting the wavelengths of existing lasers into the mid-IR spectral region or for realizing tunable lasers. In particular, the spectral coverage could be extended to ~19 µm with non-oxide NLO crystals. In this paper, we theoretically and numerically investigated the broadband SHG properties of non-oxide mid-IR crystals in three categories: chalcopyrite semiconductors, defect chalcopyrite, and orthorhombic ternary chalcogenides. The technique is based on group velocity matching between interacting waves in addition to birefringent phase matching. We will describe broadband SHG characteristics in terms of beam propagation directions, spectral positions of resonance, effective nonlinearities, spatial walk-offs between interacting beams, and spectral bandwidths. The results will show that the spectral bandwidths of the fundamental wave allowed for broadband SHG to reach several hundreds of nm. The corresponding SH spectral range spans from 1758.58 to 4737.18 nm in the non-oxide crystals considered in this study. Such broadband SHG using short pulse trains can potentially be applied to frequency up-conversion imaging in the mid-IR region, in information transmission, and in nonlinear optical signal processing.

Advances in Chinese polar scientific exploration using high-altitude balloons

Polar Regions, which generally refer to Antarctica and the Arctic, play a key role in global change and are optimal locations for space observation. The expansion of polar exploration and research regarding global climate issues and development of future environmental policies has become important and debated worldwide. China has been conducting research in Polar Regions since 1980 and has accomplished a series of scientific achievements. However, China’s polar investigations began somewhat later that those of Europe and the United States, with insufficient observational data and limited diversity of detection platforms. To solve the problem, high-altitude scientific balloons have been used as an important means to help China rapidly to advance exploration in Polar Regions. High-altitude balloons offer many advantages, such as stable flight for several months, strong carrying capacity, flexibility with experiments, low cost, and fast recovery. For many years, the United States, Japan, Europe, and other developed countries have used high-altitude scientific balloons to conduct polar scientific experiments. Polar Regions are ideal for long-term scientific exploration using high-altitude balloons due to polar vortices (atmospheric circulation), continuous solar radiation (summer polar days), and especially because there are no airspace restrictions in Antarctica. The Chinese Academy of Sciences has carried out multiple space exploration projects using high-altitude balloons at Xianghe Station since 1978 and has conducted a series of experiments using high-altitude balloons at the ice-laden “Third Pole” in the Qinghai-Tibet Plateau in collaboration with the Aerospace Information Research Institute. Sixteen high-altitude balloon flight tests were successfully deployed in 2019. Within the field of high-altitude balloons for near-space exploration, China has an excellent scientific research team and technical foundation that is at par with those of other countries. However, scientific exploration based on high-altitude balloon platforms in Polar Regions remains challenging. To serve the relevant national strategies, it is needed to define major scientific questions in polar exploration and conduct research in a timely manner. Owing to the unique advantages of polar regions, China can carry out polar exploration using high-altitude balloon platforms for a variety of tasks (e.g., in-situ measurement, dropsonde sounding, astronomical observation, and remote sensing) from different scientific disciplines, such as environmental science, atmospheric science, space weather, planetary observation, solar physics, and biological research). Based on China’s current balloon exploration capabilities, relevant work will be carried out step by step from earth observation, sky monitoring to near-space detection, aiming at an integrated capability. The specific research subjects include: (1) Polar ice sheet change; (2) polar geological environment studies; (3) polar habitat monitoring; (4) polar space environment monitoring; (5) polar atmosphere detection; (6) polar near-space biological research; (7) planetary science; and (8) astronomical observation. High-altitude balloons will also play an important role in future studies involving in-situ measurement and dropsonde sounding, astronomical observation, and remote sensing, which will further enhance China’s scientific research in the Polar Regions. This will enhance China’s status and legitimacy in the peaceful use and development of Polar Regions and would give China more clout internationally in polar affairs.

Space Phased Array Antenna Developments: A Perspective on Structural Design

As the “right-hand man” to space communications, navigation, environmental monitoring, and other satellite systems, the space active phased array antenna is capable of scanning and covering long distances and large scale ranges through its complex deployment mechanism, large physical aperture, and lightweight structural design. In comparison with mechanical scanning antennas, the space active phased array antennas can realize flexible beam scanning through the active phased array principle, while simultaneously achieving a high gain, low sidelobe, high resolution, and high reliability. Improving the comprehensive performance of the satellite is crucial with the rapid development requirement and large application field. In this article, the development history of the space active phased array antennas is summarized, and these antennas are characterized by the following structural features: large aperture, deployment mechanism, and lightweight configuration. The state of the art of space deployable active phased array antennas is also presented. Furthermore, seven crucial design technologies of antenna essential components are discussed, and the development trends of structural technologies of the space deployable active phased array antenna are demonstrated.

A Self‐Powered High‐Performance UV Photodetector Based on Core–Shell GaN/MoO3–x Nanorod Array Heterojunction

AbstractSelf‐powered UV photodetectors are highly desirable for applications in space communications and environmental monitoring. However, most self‐powered UV photodetectors exhibit unimpressive performance in weak signal detection. Herein, a self‐powered UV photodetector based on the core–shell GaN/MoO3–x nanorod array (NRA) heterojunction system is demonstrated. Homogeneous MoO3–x layers are deposited on GaN NRAs by a simple one‐step physical vapor deposition method. The photodetector device shows an ultrahigh specific detectivity of 2.7 × 1015 Jones at 355 nm without any power supply. Further analyses reveal a responsivity of 160 A W−1 and a high UV–vis rejection ratio (R355 nm/R400 nm) of 2.0 × 104 under zero bias. The self‐powered device also has a fast response speed with a rise/fall time of 73/90 µs. As a result, the self‐powered photodetector, featuring ultrahigh detectivity and responsivity along with fast response, exhibits great potential for applications in next‐generation UV detection. The core–shell NRA structure heterojunction design provides a valuable direction for realizing nanoscale self‐powered UV photodetectors.

Recent Advances in Research of the Chinese Meridian Project

The Chinese Meridian Project is a ground-based space environment monitoring facility in China. The first phase of the project has been put into formal operation since 2012 after 4-year's construction. It consists of 15 observatories located roughly along 120°E longitude and 30°N latitude, with each observatory equipped with multiple instruments to monitor space environment. Based on the huge observational data accumulated, significant scientific achievements have been made with more than 300 peer-reviewed journal papers published. In this report, scientific results from the past two years have been reviewed with topics covering fields of geomagnetic, atmosphere, ionosphere, and their responses to solar activities. The excellent achievements from the Phase I of Chinese Meridian Project lay a good foundation for Phase II, which has already been approved with the official kick-off of construction in November 2019. It will conceive an unprecedented contribution to global space weather community from China.