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In space gravitational wave detection (SGWD), the cascaded integrator–comb (CIC) antialiasing filter is always utilized for the down-sampling of the phasemeter. However, the passband of the CIC filter is not flat, which means that the attenuation is not the same at different frequencies. Therefore, in fields that require high accuracy of phase true value, such as differential wavefront sensing (DWS), the traditional down-sampling method is not applicable. In this article, the filter of CIC-interpolated second-order polynomials (ISOP) architecture is developed for the compensation of the attenuation effect. A phasemeter is also developed for the experimental demonstration. The results show that the passband attenuation at 1 Hz reduces from 0.1076 to $3.86 \times 10^{-4} \; \text {dB}$ , significantly reducing the droop in the passband. The noise performance of the phasemeter is also tested, which can reach the level of $2\pi \; \mu \text {rad/Hz}^{1/2}$ .

The detection mission of gravitational waves in space is that the accuracy of the long-baseline intersatellite laser interferometry on the million-kilometer order needs to reach the order of 8pm/Hz. Among all noise sources that affect the interferometry accuracy, tilt-to-length (TTL) coupling noise is the second largest source of noise after shot noise. This paper focuses on studying the contribution of TTL coupling noise of the telescope system in the intersatellite scientific interferometer. By referring to the laser interferometer space antenna (LISA)’s noise budget, TTL coupling noise is required to be within ±25μm/rad (±300μrad). Therefore, this paper focuses on studying both the mechanism of TTL coupling noise due to the noise sources of the telescope and the method of suppressing the TTL noise, which can lay a foundation for noise distribution and the development of engineering prototypes in subsequent tasks.

With the rapid advancements in surface mount technology (SMT), microelectronic packaging products are becoming smaller, denser, and defect-free. This has led to stricter requirements for surface quality inspection. In the realm of industrial visual inspection, there is a growing demand for three-dimensional imaging technology to achieve high-precision and fast image acquisition, as well as for AI-based online inspection models to enhance real-time defect detection. This article primarily focuses on first- and second-level package products for SMT microelectronics and discusses the main optical imaging technologies, analyzing the principles and limitations. Next, this article analyzes the current research status of intelligent detection models based on deep learning in industrial environments and discusses current technical issues in data augmentation, small object learning, and model lightweight. The article also summarizes the characteristics and applications of the latest representative products, comparatively analyzes the gap between developed and developing countries. Finally, this article outlines four major challenges and future research trends in this field, aiming to promote the intelligent evolution of related visual inspection equipment.

Gravitational wave (GW) astronomy is witnessing a transformative shift from terrestrial to space-based detection, with missions like Taiji at the forefront. While the transition brings unprecedented opportunities for exploring massive black hole binaries (MBHBs), it also imposes complex challenges in data analysis, particularly in parameter estimation amidst confusion noise. Addressing this gap, we utilize scalable normalizing flow models to achieve rapid and accurate inference within the Taiji environment. Innovatively, our approach simplifies the data’s complexity, employs a transformation mapping to overcome the year-period time-dependent response function, and unveils additional multimodality in the arrival time parameter. Our method estimates MBHBs several orders of magnitude faster than conventional techniques, maintaining high accuracy even in complex backgrounds. These findings significantly enhance the efficiency of GW data analysis, paving the way for rapid detection and alerting systems and enriching our ability to explore the universe through space-based GW observation.

In the acquisition stage of many space applications, such as the Taiji program, the spot center of weak laser light must be accurately determined. Under weak light conditions, the precision of most traditional positioning methods is greatly affected. In this paper, we present a high-precision laser spot center positioning method based on the theoretical analysis of influence factors of precision. It is shown through experimental study that the method’s precision can fulfill the requirement of the Taiji program.

An alternative acquisition scheme is introduced. The principle is to modulate power of the laser at a frequency within the photodiode’s bandwidth so that the photodiode in each satellite can detect the laser signal from the other satellite incoherently. Therefore, we can disentangle the degrees of freedom, two laser pointing directions per space craft and one frequency offset. Despite the employment of downlink and uplink data transferring, the total scanning time could be reduced from several hours to 160 s.

A supermassive binary black-hole candidate SDSS J1430+2303 reported recently motivates us to investigate an imminent binary of supermassive black holes as potential gravitational wave source, and the radiated gravitational waves at the end of the merger are shown to be in the band of space-borne detectors. We provide a general analysis on the required detecting sensitivity needed for probing such type gravitational wave sources and make a full discussion by considering two typically designed configurations of space-borne antennas. If a source is so close, it is possible to be detected with Taiji pathfinder-plus which is proposed to be an extension for the planned Taiji pathfinder by just adding an additional satellite to the initial two satellites. The gravitational wave detection on such kind of source enables us to explore the properties of supermassive black holes and the nature of gravity.

A comprehensive simulation was performed to better understand the impacts and effects of the additional technical noises on weak-light phase-locking for LISA. The result showed that the phase of the slave laser tracked well with the received transmitting light under different noise level, and the locking precision was limited by the phase readout noise when the laser frequency noise and clock jitter noise were removed. This result was then confirmed by a benchtop experimental test. The required LISA noise floor was recovered from the simulation which proved the validity of the simulation program. In order to convert the noise function into real time data with random characteristics, an algorism based on Fourier transform was also invented.

In the centenary year of Einstein’s General Theory of Relativity, this paper reviews the current status of gravitational wave astronomy across a spectrum which stretches from attohertz to kilohertz frequencies. Sect. 1 of this paper reviews the historical development of gravitational wave astronomy from Einstein’s first prediction to our current understanding the spectrum. It is shown that detection of signals in the audio frequency spectrum can be expected very soon, and that a north-south pair of next generation detectors would provide large scientific benefits. Sect. 2 reviews the theory of gravitational waves and the principles of detection using laser interferometry. The state of the art Advanced LIGO detectors are then described. These detectors have a high chance of detecting the first events in the near future. Sect. 3 reviews the KAGRA detector currently under development in Japan, which will be the first laser interferometer detector to use cryogenic test masses. Sect. 4 of this paper reviews gravitational wave detection in the nanohertz frequency band using the technique of pulsar timing. Sect. 5 reviews the status of gravitational wave detection in the attohertz frequency band, detectable in the polarisation of the cosmic microwave background, and discusses the prospects for detection of primordial waves from the big bang. The techniques described in sects. 1–5 have already placed significant limits on the strength of gravitational wave sources. Sects. 6 and 7 review ambitious plans for future space based gravitational wave detectors in the millihertz frequency band. Sect. 6 presents a roadmap for development of space based gravitational wave detectors by China while sect. 7 discusses a key enabling technology for space interferometry known as time delay interferometry.

With the Gravity Recovery and Climate Experiment (GRACE) mission as the prime example, an overview is given on the management and processing of Level 1A data of a low–low satellite to satellite tracking mission. To illustrate the underlying principle and algorithm, a detailed study is made on the K-band ranging (KBR) assembly, which includes the measurement principles, modeling of noises, the generation of Level 1A data from that of Level 0 as well as Level 1A to Level 1B data processing.

The mission to detect gravitational wave in space requires a not only sophisticated but also ultra-precise laser interferometric measurement system. Within a single spacecraft, tens of interferometric beat signals are generated at the same time and they also need to be processed simultaneously. In this paper, a multi-channel phasemeter which can parallelly process the signals is constructed. The test shows that a sensitivity of 2π μrad/√Hz could be achieved in the frequency range of 0.1 to 10 Hz. We also utilize the phasemeter to evaluate the performance of a heterodyne laser interferometer.

Due to high data rates and reliability, inter-satellite laser communication has developed rapidly in these days. However, the stability of the laser beam pointing is still a key technique which needs to be solved; otherwise, the beam pointing jitter noise would reduce the communication quality or, even worse, would make the inter-satellite laser communication impossible. For this purpose, a bench-top of the fine beam pointing control system has been built and tested for inter-satellite laser communication. The pointing offset of more than 100 μrad is produced by the steering mirror. With beam pointing control system turned on, the offset could be rapidly suppressed to lower than 100 nrad in less than 0.5 s. Moreover, the pointing stability can be kept at 40 nrad for yaw motion and 62 nrad for pitch motion, when the received beam jitter is set at 20 μrad.