Due to the impact of global climate change, extreme weather events have become more frequent in recent years, with a corresponding increase in both the frequency and intensity of typhoons. As typhoons have extremely strong destructive power, they can have a significant impact on economic and social development, human life and property, as well as maritime activities. Therefore, the real-time tracking and positioning of typhoons is critical for mitigating their adverse impacts. Based on the infrared cloud image data from the multi-channel scanning imaging radiometer aboard the Fengyun-4 geostationary satellite, combined with the tropical cyclone best track dataset, this study uses the YOLOv8 object detection algorithm to achieve automatic identification and rapid positioning of typhoons. The verification results show that the recognition accuracy for typhoons with strong tropical storm intensity and above exceeds 83%, with a precision rate of over 88%. This achievement provides robust data support for maritime activities, maritime transportation, and oceanographic research, effectively improving the accuracy and timeliness of typhoon monitoring and enhancing safety in related fields.

The adaptive monopulse technology is a common method for phased array radar to achieve target detection and angle estimation. In order to solve the problem that the performance of the traditional adaptive beamforming algorithm is reduced and the monopulse angle estimation results are greatly deviated in the complex environment where the mainlobe and sidelobe interference coexists, a two-stage mainlobe and sidelobe interference suppression method of adaptive monopulse is designed. The first stage of adaptive processing uses the improved GSC structure to complete the suppression of sidelobe interference, and at the same time, the blocking matrix is constructed to protect the target signal and mainlobe interference from being cancelled in the suppression process of sidelobe interference, so as to improve the mainlobe maintenance effect remarkably. The second stage of adaptive processing uses the sum-difference four-channel mainlobe interference suppression to complete the directional suppression of mainlobe interference,that is, while the mainlobe interference in the elevation or azimuth direction is adaptively suppressed, the non-adaptive array pattern of the azimuth or elevation direction is maintained, and then the monopulse ratio maintains undistorted relative to the quiescent monopulse ratio. The simulation results demonstrate that the proposed method can effectively suppress the mainlobe and sidelobe interferences without distortion of monopulse ratio at the same time.

To address the multiple requirements of low cost, low power consumption, and high accuracy (sub-nanosecond level)for time-frequency systems in large-scale low Earth orbit (LEO) navigation constellations, a precision frequency control method based on micro-step adjustment is proposed for oven-controlled crystal oscillators (OCXOs), targeting the mitigation of long-term frequency drift. A quantization noise model was established, and a 48-bit direct digital synthesizer (DDS) was employed to achieve high-resolution real-time frequency correction at 5×10^-13 resolution. A constraint framework and frequency adjustment procedure compatible with rapid precise position services were constructed. Experimental results demonstrate that during 24-hour continuous operation, a clock bias accuracy (RMS) of 0.24 ns was achieved. Compared to free-running state, a long-term frequency stability was significantly improved by three orders of magnitude, with a slight degradation of 25% in short-term stability (1 s-20 s). This approach provides a cost-effective, high-precision, and stable time-frequency reference solution for LEO constellation construction.

The sum and difference channels of S-band single-channel measurement and control equipment exhibit phase differences, which may vary with environmental changes, transmission media, and assembly processes. Phase difference correction must be completed before the signal enters the baseband terminal for demodulation, to ensure the correct angular error signal is demodulated and stable target tracking is ultimately achieved. In practical work, the phase difference correction is basically carried out by setting up beacon machines at high positions, which can effectively solve the problem of inconsistent phase difference. However, with the expansion of the distribution area of measurement and control equipment and the shortening of state preparation time, traditional phase correction methods are no longer applicable. This article focuses on the research of S-band single-channel measurement and control equipment within a certain frequency working range. By pre-testing its phase difference and adopting methods such as cable compensation or adding phase shifters, the impact of phase difference on angular error is reduced within a certain error range at the design stage. In the later stage, during the operation of the equipment, the complex workflow of phase correction is eliminated. This article presents the principle and method of phase free calibration for S-band single channel measurement and control equipment,and verifies the effectiveness of the proposed method through experiments.

This paper conducts an engineering feasibility study on the dielectric absorption coefficient test requirements stipulated by relevant fixed capacitor standards. The study includes equivalent circuit analysis and physical verification, achieving satisfactory results: confirming the reasonable feasibility of the single-branch model, which effectively simplifies circuit analysis. The residual voltage and current measured after capacitor charge/discharge cycles exhibit distinct peak characteristics, clearly reflecting the presence and variation pattern of the absorption effect. Analysis of the peak conditions readily reveals the necessity for test capacitors to have identical capacitance values, facilitating comparative grading. Expressions for the dielectric absorption coefficient include voltage-based and current-based types. High-input-impedance test instruments must be matched to the source impedance.

This paper provides an overview of the current status and future trends in remote sensing satellite data transmission technology. The article begins by introducing the developmental history of remote sensing satellite data transmission. It then further elaborates on the technologies involved in remote sensing satellite data transmission, detailing key aspects such as data compression,data encryption, data framing, data encoding, data modulation, and data transmission. Subsequently the paper analyzes the challenges faced by remote sensing satellite data transmission, such as bandwidth limitations, signal processing, real-time requirements, and data handling. It also summarizes strategies to address these challenges, such as adopting laser-based data transmission, more complex modulation schemes, and multi-source fusion with computational transmission. Looking ahead, the paper envisions future trends, including inter-satellite laser relay transmission, on-board computational transmission, and the application of computational constellations for intelligent in-orbit fusion in remote sensing satellites. Research indicates that remote sensing satellite data transmission technology will evolve towards higher transmission rates, higher reliability, more convenient data processing, and more intelligent mission workflows.

With the development of electronic technology and motor PWM control technology, the electric servo system has gradually changed from analog system to digital system. Closed-loop control cycle is a key parameter in digital servo system, which is restricted by system maneuverability, hardware resources, power supply capacity, function performance and so on. At present,there are few literatures on the closed-loop cycle of servo system at home and abroad. This paper takes servo system of electric actuator as the research object. Firstly, the composition, working principle and signal transmission link of electric actuator servo system are analyzed in detail. Then the mathematical modeling of the servo system of the electric actuator is carried out, and the P-D control law is designed. Then the servo system simulation model is established based on Simulink to analyze the influence of different closed-loop control cycles on the servo system performance. Finally, an experimental platform is built to verify the effects of different closed-loop cycles on servo system performance. The simulation results show that the step response speed decreases with the increase of the closed-loop period. Appropriately increasing the closed-loop period can reduce the transient current to a certain extent,and avoid the risk of computer reset caused by large transient current pulling down the system voltage. The research in this paper has certain guiding significance for servo system and the platform system interacting with them.

In the orbital environment, spacecraft face challenges such as scarce fault samples, varying operating conditions, and a strong reliance on accurate models and labeled data in traditional diagnostic methods. This paper systematically reviews transfer learning techniques for spacecraft fault diagnosis, highlights their recent advancements, and outlines future research trends. Transfer learning strategies are categorized into four types: instance-based, feature-based, model-based, and domain-adaptive. The principles,advantages, limitations, and representative applications of each strategy are analyzed, along with key enabling techniques such as importance weighting, adaptive batch normalization, parameter fine-tuning, and adversarial training. The review shows that transfer learning effectively mitigates issues of data insufficiency and distribution shift by enabling knowledge transfer from source to target domains. In particular, multi-source domain adaptation and adversarial domain adaptation significantly improve cross-condition diagnostic performance by enhancing model generalization and robustness. It is concluded that transfer learning provides a promising framework for intelligent spacecraft fault diagnosis. Future research should focus on source-free domain adaptation, multi-modal data fusion, semi-supervised transfer learning, and model interpretability, aiming to support practical deployment in real-world aerospace missions.

Nowadays, spacecraft software is becoming increasingly complex and its functions are gradually increasing. If it can be split reasonably in different software, the project can be managed better. However, considering factors such as cost, power consumption, and wiring, it is difficult to use different processors to run different software. Now, multi-core processor is developing rapidly. One processor contains more than one core, so that different software can be run on different cores. Therefore, this paper proposes a design of a boot and monitor software based on multi-core processor which can enable 2 cores to run 2 different software. The ground tests and on-orbit experiments indicated that this scheme can correctly perform boot for different cores and accomplish refactor software for updating. The boot and monitor software based on this design runs well on the orbiting satellites.

The Media Access Control (MAC) protocol is a critical component of wireless communication systems. The Statistical Priority-based Multiple Access (SPMA) protocol optimizes channel resource allocation through priority thresholds and a backoff mechanism. However, in specific scenarios, the traditional SPMA protocol exhibits shortcomings in threshold setting and backoff time calculation. This paper proposes an improved protocol that combines dynamic threshold adjustment and a multi-factor backoff mechanism. For dynamic threshold adjustment, the protocol adapts the thresholds in real-time based on the transmission success rate of data packets at each priority level, ensuring alignment with dynamic service demands. Under high-load conditions, a circuit-breaker mechanism is employed to suppress low-priority transmissions. In terms of backoff time calculation, a channel load differential factor is introduced, integrating priority level, traffic proportion, and load variation speed to construct a multi-factor fusion back-off algorithm. Simulation results demonstrate that the improved protocol significantly outperforms the traditional SPMA protocol in network throughput, transmission success rate, and latency performance. Under low-load scenarios, the transmission success rate of low-priority traffic improves by approximately 5%. In high-load scenarios, the circuit breaker mechanism suppresses low-priority transmissions, ensuring that the transmission success rate of high-priority traffic remains above 80%. At the same time, the improved protocol controls the average end-to-end delay of all priority levels within 10 ms, with the highest priority delay being less than 2 ms, effectively meeting the requirements for differentiated service quality.