We present the design and implementation of a fringe detection pipeline for the Lunar Orbit VLBI Experiment (LOVEX) on board China’s Queqiao-2 cislunar relay satellite. To address the challenge posed by limited space–ground time synchronization accuracy, we developed a dedicated initial clock offset search scheme based on a modified version of the Chinese VLBI Network software correlator. Key features of the pipeline include raw data validation, wide-range clock offset search, iterative fringe fitting, and GPU-accelerated processing. The pipeline was successfully applied to the initial clock offset determination in LOVEX observations. In particular, we report the detection of fringes for blazar AO0235+164 in the s5123m session, where a projected baseline length of 5.5 Earth diameters was achieved. We further discuss technical approaches for enhancing sensitivity to weak signals, with an emphasis on the need for advanced phase calibration techniques. The potential application of tensor core acceleration is also discussed.

China's Tianwen-2 probe, launched on 29 May 2025, will sample asteroid 2016 HO3 and exploring comet 311P. The precise positioning of the Tianwen-2 probe will benefit its mission goals. Phase-referencing VLBI imaging offers significant potential to improve the positional precision of deep space probes. However, traditional phase-referencing VLBI imaging assumes a nearly constant angular position, thereby limiting positioning precision for moving targets, particularly with sparse arrays or long-duration observations. To enhance the tracking precision of moving targets, an improved Kinematic Phase-Referencing (KPR) VLBI method is investigated. By directly integrating a kinematic orbital model-parameterized by polynomial coefficients-into the phase-referencing VLBI process, KPR-VLBI removes the need for the nearly constant-position assumption. Observations of the Tianwen-2 probe were carried out using the five stations of the Chinese VLBI Network to validate the KPR-VLBI method. Results indicate that the final angular position precision is at the sub-milliarcsecond level, which is primarily constrained by tropospheric and ionospheric errors as well as calibrator position errors, while the 1 sigma formal error of angular position is better than 10 micro-arcseconds. Furthermore, compared with conventional phase-referencing VLBI imaging, KPR-VLBI is able to effectively suppress sidelobes arising from the target motion in synthesized images, thereby leading to more reliable results.

In mobile wireless sensor networks, localization accuracy and cost are the key issues to be considered. This paper is committed to solving the localization problem of mobile sensor networks. We propose an improved Black Hole (BH) algorithm based on compact strategy and elitist learning strategy. An improved Monte Carlo localization (IMCL) algorithm based on multi-hop combines the novel algorithm to deal with the localization problem of mobile sensor networks. The performance of the novel algorithm is verified on 28 test functions of CEC 2013 and compared with other standard optimization algorithms. The results reveal that the novel algorithm has first-class performance. In the simulation experiment, the novel algorithm and several optimization algorithms are applied to IMCL. The comparison results show that the new heuristic algorithm combined with IMCL can provide more competitive results in mobile node localization.

This paper presents the new progress of the Chinese Very Long Baseline Interferometry Network (CVN). CVN currently consists of six ground based radio telescopes and a data processing center at the Shanghai Astronomical Observatory. Two newly commissioned 40-meter telescopes in Shigatse, Tibet and Changbai Mountain, Jilin, along with a 4.2-meter space VLBI telescope on the Queqiao-2 lunar relay satellite added in 2024, have expanded the network. These new telescopes, with S/X dual-frequency receiving systems and designed to operate from 700 MHz to 50 GHz (up to W-band), are equipped with thermal insulation and advanced technologies to ensure performance in extreme environments. The upgrade from a "4-station 1-center" to a "6-station 1-center" configuration extends the longest baseline from 3200 km to 3800 km, enhancing capabilities in various astronomy and deep space studies. The six-telescope setup enables the construction of two 3-station subnetworks for simultaneous observations, supporting space VLBI observation and deep-space probe orbit determination. CVN is evolving towards an integrated space-ground network, with Queqiao-2 becoming its first space VLBI unit. Currently, CVN has obtained VLBI fringes of radio source blazar AO0235+164 and the Chang’e-6 telemetry signal on the lunar - ground baseline. In the future, with the addition of more large-scale ground-based and space VLBI telescopes, CVN's sensitivity and resolution will be further improved, providing powerful tools for studying black holes, life origin, and transient source mechanisms. .

Space Very Long Baseline Interferometry (SVLBI) can significantly improve angular resolution by extending interferometric baselines beyond Earth's diameter. China is actively promoting the development and scientific applications of SVLBI, including the proposal to deploy a radio telescope on the lunar surface through the International Lunar Research Station (ILRS), as well as the long-term goal of establishing a cislunar SVLBI array. In this research, the \enquote{lunar far side configuration} refers to placing a telescope directly at the lunar south pole, while the \enquote{multiple space configuration} broadly encompasses telescopes in lunar orbit, in Earth orbit, and at equilibrium points such as the Earth-Moon L2 or Sun-Earth L2. Based on detailed simulations with multiple configurations derived from the Event Horizon Telescope (EHT) ground network, we systematically evaluate the uv coverage and angular resolution of the proposed SVLBI array. The results show that: (1) in the lunar far side configuration, deploying a telescope extends the baseline and improves uv coverage, but only yields limited gains in angular resolution; (2) in the multiple space configuration, deploying telescopes achieves substantial improvements in both $uv$ coverage and angular resolution, owing to the significantly longer baselines. These findings provide important theoretical and technical support for the future development of SVLBI in China.

The Lunar Orbital VLBI Experiment (LOVEX) is a scientific component of the Chinese Lunar Exploration Project (CLEP) Chang’E-7. The spaceborne component of LOVEX is implemented onboard the relay satellite QueQiao-2, which was launched on 20 March 2024, and later placed into an elliptical selenocentric orbit. The LOVEX-specific payload consists of an X-band cryogenic receiver, a hydrogen maser frequency standard, and VLBI data formatting and acquisition electronics. Several components of the QueQiao-2 nominal onboard instrumentation, such as the 4.2-m antenna, the data storage device, and the downlink communication system, contribute to the overall spaceborne VLBI instrumentation. This allows us to form a space radio telescope capable of co-observing with Earth-based radio telescopes in VLBI mode. In this space VLBI system, the length of the baseline extends up to approximately 380000 km. This paper presents the LOVEX scientific objectives, architecture, instrumentation, prelaunch tests, in-flight verification and calibration, and the first in-flight detections of interferometric response (“fringes”) achieved through observations of the quasar AO 0235+164 and the Chang’E-6 orbital module, positioned at the Sun-Earth Lagrange point L2. These initial results demonstrate the successful performance of LOVEX, verifying its capability for both astronomical and spacecraft tracking observations at ultra-long VLBI baselines.

In Transmission Control Protocol/Internet Protocol (TCP/IP) networks, the sudden surge traffic has exacerbated the buffering burden on the intermediate routing nodes, leading to increasingly serious problems such as data packet loss, delay, and instability. Therefore, congestion control methods are crucial for improving network performance. To solve the problem of buffer overflow at routing nodes in the network, an Active Queue Management (AQM) method is introduced to improve congestion and enhance network performance. In this paper, Proportional-Integral-Derivative (PID) control is used to implement a simple and reliable AQM controller, and an improved Red-Tailed Hawk optimization algorithm is applied to optimize the parameters to achieve the optimal control effect. Comparisons with other types of controllers are made to reflect the effect and stability of the controller. Under the same simulation parameters in MATLAB, the good control effect is reflected in the simulation experiments, and the proposed controller will converge the TCP/AQM system to a stable operating point, with lower packet loss/marking probability and queue error.

For some space radio telescopes,the orbit determination accuracy is not high enough,the time synchronization accuracy provided by the satellite platforms is low,and GNSS devices are not available.As a result,a traditional method that relies on GNSS devices to obtain an initial clock offset followed by performing correlation with the calibration source may fail to obtain fringes.Moreover,a brutal force search across the 2D clock offset and fringe rate search plane is computationally expensive.In light of these challenges,we propose a novel time synchronization method that utilizes the spacecraft's telemetry tone signal.This method employs frequency polynomials derived from Doppler tracking for fringe rotation during the correlation process.By aligning the frequency of the target station precisely with that of the reference station,it is only necessary to split the clock offset search range into multiple time windows,perform correlation for each window,and identify the window with the highest signal-to-noise ratio(SNR).The precise clock offset is determined by combining the residual delay with the initial offset.To validate the method,we observe the Tianwen-1 telemetry signal with the 4.5 m small telescope in the Tianma campus of Shanghai Astronomical Observatory and 40 m telescope in Kunming.The results demonstrate that our method can accurately determine clock offset for a time range as wide as±10 ms,with an SNR slightly higher than that achieved with the delay model.This method is suitable for wide-range time synchronization for space Very Long Baseline Interferometry observations,especially in scenarios involving small antennas with low sensitivity and poor orbit determination accuracy.

The Lunar Orbital VLBI Experiment (LOVEX) aims to utilize the 4.2-m diameter antenna on the Queqiao-2 relay satellite of the Chang’E-7 mission, which is equipped with an X-band cryogenic receiver, an H-maser, and a VLBI data acquisition backend, thereby forming a space radio telescope in lunar orbit. The lunar orbital telescope will collaborate with Earth-based telescopes to conduct VLBI observations, thus forming a lunar-Earth space VLBI network. The length of the baseline will extend up to approximately 380000 km, which will be the longest VLBI baseline to date. This paper introduces the LOVEX VLBI data correlation system. The system is capable of generating VLBI delay models for both the lunar orbital and Earth-based telescopes; it also performs the initial clock search within a large clock offset window ranging from −10 ms to +10 ms for the lunar-Earth baseline leveraging both wideband blazar signals and spacecraft (SC) differential one-way ranging (DOR) signals—a distinctive feature of the system. To fulfill the scientific objectives of astrophysics, astrometry, and orbit determination of SC, the data correlation system outputs visibilities in various formats. Additionally, the system can directly output the VLBI residual delay and delay rate of SC after bandwidth synthesis. Anticipating the inclusion of more Earth-based stations in the future, the system is designed with the capability to correlate digital signals observed by 10 stations, with a bandwidth of 512 MHz and dual-polarization, running on an off-the-shelf central processing unit (CPU) + graphics processing unit (GPU) cluster. This system was applied to both the ground verification system and the first LOVEX observation experiment, and successfully detected VLBI fringes for signals from blazars and SC after fringe fitting.

Very long baseline interferometry (VLBI) plays a crucial role in geodesy and astrometry, and it is also being successfully used in spacecraft tracking. Phase referencing VLBI is a technique that uses phase information rather than the traditional VLBI group time delay to achieve higher measurement accuracy. The newly developed source-frequency phase referencing (SFPR) VLBI has been proven to be a powerful method to eliminate errors, but for positioning purposes, only "core shifts" are left in SFPR. Therefore, in this paper, an in-beam SFPR (IB-SFPR) VLBI method based on SFPR is proposed to overcome the positioning deficiency in SFPR, and to achieve high positioning accuracy. The proposed IB-SFPR method is further researched in more detail and shown to have the ability to achieve high positioning accuracy. For the first Martian rover of China, the IB-SFPR is first applied in its positioning. The positioning results of the rover have shown that the 1 sigma formal position error is hundreds of meters, with a formal error of post-fitted phase time delay of about 1.3 ps. However, the position discrepancies among the results of IB-SFPR, the guidance, navigation and control system, and the visual localization are at kilometer level, which are mainly affected by the orbit error of the orbiter. Therefore, considering the external reference's (the obiter) orbit error, the final positioning accuracy of the Martian rover is at the kilometer level.

This paper proposes an improved blind watermarking approach combined with a meta-heuristic algorithm. For the purpose of enhancing convergence accuracy in the original artificial rabbit optimization algorithm, a parallel artificial rabbit optimization algorithm is proposed. It prevents the algorithm from getting trapped in local optima by employing inter-group communication strategies. And a mixed-domain watermarking algorithm is proposed. In order to balance the invisibility and robustness of the watermarking, the improved artificial rabbit optimization algorithm is applied to the watermarking algorithm. The experiment proves that the improved algorithm has better convergence. accuracy, and can balance the performance of the blind watermarking algorithm.

The Fetal Electrocardiogram (FECG) signal plays a crucial role in monitoring the health of the fetus, but there are numerous challenges in eliminating the maternal thorax signal and reducing noise interference. This paper proposes a novel objective function that combines a Least Mean Squares (LMS) adaptive filter with a heuristic algorithms to enhance the quality of the extracted FECG signal. To achieve better results, we introduce the Discrete Artificial Bee Colony (DABC) algorithm with a new initialization strategy, a random wavelet basic function strategy, and Gaussian distribution. These improvements enhance global search capabilities and ensure a faster convergence rate. The application of heuristic algorithms can reduce noise signals and provides clearer and more accurate results compared to the traditional LMS filter. Furthermore, the effectiveness of this innovative algorithm is compared with other widely used heuristic algorithms. The experiment results demonstrate that the novel algorithm significantly enhances performance by up to 8% compared to other conventional extraction methods in some indicators.

The rapid development of metaheuristic algorithms proves their advantages in optimization. Data clustering, as an optimization problem, faces challenges for high accuracy. The K-means algorithm is traditaaional but has low clustering accuracy. In this paper, the phase-angle-encoded snake optimization algorithm (θ-SO), based on mapping strategy, is proposed for data clustering. The disadvantages of traditional snake optimization include slow convergence speed and poor optimization accuracy. The improved θ-SO uses phase angles for boundary setting and enables efficient adjustments in the phase angle vector to accelerate convergence, while employing a Gaussian distribution strategy to enhance optimization accuracy. The optimization performance of θ-SO is evaluated by CEC2013 datasets and compared with other metaheuristic algorithms. Additionally, its clustering optimization capabilities are tested on Iris, Wine, Seeds, and CMC datasets, using the classification error rate and sum of intra-cluster distances. Experimental results show θ-SO surpasses other algorithms on over 2/3 of CEC2013 test functions, hitting a 90% high-performance mark across all clustering optimization tasks. The method proposed in this paper effectively addresses the issues of data clustering difficulty and low clustering accuracy.

Chang'e-5 is the most complicated mission of Chinese lunar project. Many separations of several detectors and unmanned rendezvous and docking in lunar orbit are accomplished. During the course of separating and approaching of two detectors, the same-beam very long baseline interferometry (VLBI) observations are carried on. We firstly present the real-time positioning for multi-detectors and differential positioning of CE-5 ascender and combination of orbiter-returner, which is the more direct and quick method to charge the orbit status. The CE-5 mission first achieved the orbital maneuver of CE-5 orbiter-returner combination from the lunar gravity back to the Earth at the distance of lunar orbit. We use the method of instantaneous states reduction to monitor the twice orbital transfer from the lunar to the Earth in real time, and precisely present the status of orbital maneuver, which provides the important reference for the positioning and orbit determination in the future deep-space exploration.

In the Chang'E-7 mission of the fourth stage of China's Lunar Exploration Project, the relay satellite will carry a 4.1-m aperture X-band parabolic telescope. This and the ground-based telescopes will form a lunar orbit very long baseline interferometry (VLBI) experimental system with the space-ground baseline up to 400000 km. To improve the sensitivity of this baseline, we propose a weighted full-spectrum signal combining method. First, we derive the optimal weighting coefficient ratio for combining the signals of the two telescopes. Then, we propose the VLBI weighted full-spectrum combining method whose optimal weight coefficient is determined by investigating the data, and the obtained result is consistent with the theoretical derivation. Finally, we use Chang'E-4 original VLBI observation data for method testing. The results show that the signal combining method proposed in this work can greatly improve the signal-to-noise ratio for VLBI observations.

In the Chang’E-7 mission of the fourth stage of China’s Lunar Exploration Project, the relay satellite will carry a 4.1-m-aperture X-band parabolic telescope. This and the ground-based telescopes will form a lunar orbit very long baseline interferometry (VLBI) experimental system with the space-ground baseline up to 400000 km. To improve the sensitivity of this baseline, we propose a weighted full-spectrum signal combining method. First, we derive the optimal weighting coefficient ratio for combining the signals of the two telescopes. Then, we propose the VLBI weighted full-spectrum combining method whose optimal weight coefficient is determined by investigating the data, and the obtained result is consistent with the theoretical derivation. Finally, we use Chang’E-4 original VLBI observation data for method testing. The results show that the signal combining method proposed in this work can greatly improve the signal-to-noise ratio for VLBI observations.

Optimization problems are ubiquitous, and obtaining ideal solutions to optimization problems is a challenging task. In terms of denoising the electrocardiogram (ECG) signal, the weight parameters of the adaptive filtering algorithm determine the quality of the output ECG signal to a large extent. However, adaptive filters need to adjust too many parameters, which is a challenging problem. Heuristic algorithm is a powerful tool for solving various optimization problems, and it is very suitable for solving such complex problems. In this paper, a novel ECG denoising method is proposed, which combines a heuristic algorithm with an adaptive filtering algorithm to adjust the weight parameters of the filter. In addition, a new heuristic algorithm, Chaotic Adaptive Fish Migration Optimization (CAFMO), is proposed to introduce the chaotic strategy into the Adaptive Fish Migration Optimization (AFMO) algorithm. The efficiency of a novel denoising method is validated through the use of synthetic data generated by the FECGSYN toolbox. The CAFMO algorithm exhibits superior performance in noise mitigation in ECG data, outperforming other algorithms such as PSO, ABC, BH, GWO, SO and AFMO. The combination of CAFMO algorithm and adaptive filter produces a significant 28% improvement over traditional LMS adaptive filter, with another 20% improvement over other heuristic algorithms combined with adaptive filter.

The population-based evolutionary algorithm simulates the behavior of different organisms. Randomness, diversity, exploration, and exploitation make the population quickly converge to the optimal solution in the evolution process. For the swarm intelligence algorithm, it is essential to balance the exploration and exploitation ability of the algorithm. This paper proposes an opposition-based beluga whale optimization (OBWO) and uses an adaptive strategy to improve the algorithm’s performance. To prove the capability of the OBWO, we verified the new algorithm on CEC_2013 and compared it with other excellent algorithms. The results show that the performance of the OBWO is first-rate and far exceeds that of the original algorithm.

<p indent="0mm">In the Chang’E-7 mission of the fourth stage of China’s Lunar Exploration Project, the relay satellite will carry a 4.1-m-aperture X-band parabolic telescope. This and the ground-based telescopes will form a lunar orbit very long baseline interferometry (VLBI) experimental system with the space-ground baseline up to 400000 km. To improve the sensitivity of this baseline, we propose a weighted full-spectrum signal combining method. First, we derive the optimal weighting coefficient ratio for combining the signals of the two telescopes. Then, we propose the VLBI weighted full-spectrum combining method whose optimal weight coefficient is determined by investigating the data, and the obtained result is consistent with the theoretical derivation. Finally, we use Chang’E-4 original VLBI observation data for method testing. The results show that the signal combining method proposed in this work can greatly improve the signal-to-noise ratio for VLBI observations.