The spaceborne gravitational wave (GW) detectors LISA and TAIJI are planned to be launched in the 2030s. The dual detectors with comparable sensitivities will form a network observing GWs with significant advantages. In this work, we investigate the three possible LISA-TAIJI networks for the different location and orientation compositions of the LISA orbit ($+60°$ inclination and trailing the Earth by 20°) and alternative TAIJI orbit configurations, including TAIJIp ($+60°$ inclination and leading the Earth by 20°), TAIJIc ($+60°$ inclination and colocated with LISA), and TAIJIm ($-60°$ inclination and leading the Earth by 20°). Of the three LISA-TAIJI configurations, the LISA-TAIJIm network shows the best performance in the sky localization and polarization determination for massive binary systems due to its better complementary antenna pattern, and LISA-TAIJIc could achieve the best cross-correlation and observe the stochastic GW background with optimal sensitivity.

For the Taiji space gravitational wave detection and its pathfinder mission, ultraprecise technology for optical assembly must be adopted to satisfy the high measurement sensitivities required. In this paper, we construct and evaluate an optical bench to assess its precision in optical assembly and bonding. We opted for hydroxide-catalysis bonding technology and designed a corresponding adjustment scheme to achieve an ultraprecise assembly for the optical bench. After alignment, the angular deviation between the interference beam and its ideal position in the global coordinate system is no more than 45 μrad, and positional deviation is less than 10 μm. The final experimental results indicate that the measurement precision of the evaluated board is 6 pm/√Hz, which meets the specifications required for the Taiji pathfinder.

The Taiji program plans to utilize the laser interferometer to measure the movement at the picometer level between free-floating test masses. As the phase readout equipment, the phasemeter needs to obtain the beat note with an accuracy of μrad/$\sqrt{\text{Hz}}$ . The main source of noise in the phasemeter is the analog frontend of the analog to digital converter. A self-designed phasemeter prototype with a low-noise analog frontend, which includes the theme of the pilot tone correction, has been developed and tested for the Taiji program in this Note. The experimental results show that the performance of the developed phasemeter can satisfy the Taiji sensitivity requirement in the whole frequency range. The sensitivity of the board can reach 0.5 μrad/$\sqrt{\text{Hz}}$ in the frequency range of 0.1–1 Hz. Therefore, the prototype gives us a good model for the fully functional Taiji phasemeter.

The predecessor of China Optics was China Optics and Applied Optics Digest, which was founded in 1985. At that time, it was the only retrieval journal in the field of optics in China. At the end of 2008, China Optics and Applied Optics Digest was renamed 《中国光学》的前身是1985年创办的《中国光学与应用光学文摘》，当时是国内光学领域唯一的检索刊物。2008年底《中国光学与应用光学文摘》转型更名为《中国光学与应用光学》期刊，刊载内容突破了文摘的限制，正式成为学术刊物。

Taiji-1 is the first technology demonstration satellite of the Taiji program of China’s space-borne gravitational wave antenna. After the demonstration of the key individual technologies, Taiji-1 continues collecting the data of the precision orbit determinations, satellite attitudes, and non-conservative forces exerted on the S/C. Therefore, during its free-fall, Taiji-1 can be viewed as operating in the high-low satellite-to-satellite tracking mode of a gravity recovery mission. In this work, we have selected and analyzed the one month data from Taiji-1’s observations, and developed the techniques to resolve the long term interruptions and disturbances in the data due to the scheduled technology demonstration experiments. The first global gravity model TJGM-r1911, that independently derived from China’s own satellite mission, is successfully built from Taiji-1’s observations. Compared with gravity models from CHAMP and other satellite gravity missions, the accuracy discrepancies exist, which is mainly caused by the data discontinuity problem. As the extended free-falling phase been approved, Taiji-1 could serve as a gravity recovery mission for China since 2022 and it will provide us the independent measurement of both the static and the monthly time-variable global gravity field.