西安空间无线电技术研究所

Space gravitational wave detection is a groundbreaking effort to observe spacetime ripples caused by cosmic events. It requires deploying laser interferometry systems with inter-satellite baselines ranging from hundreds of thousands to millions of kilometers. These systems need detect picometer-scale displacements induced by gravitational waves. However, this task faces significant technical challenges. Key challenges include ultra-long interferometric baselines (similar to 1 million kilometers), small telescope apertures (similar to 100 mm), and beam degradation due to space environmental factors such as thermal fluctuations, radiation, and residual gas interactions. These effects lead to substantial laser power attenuation (down to similar to 100 picowatts at the receiver) and distortions in beam parameters, including wavefront, polarization, and pointing stability. Achieving sub-nanoradian precision in beam pointing control is critical to maintaining phase stability and ensuring a sufficient signal-to-noise ratio. To address these issues, this study introduces an innovative electro-optic beam-pointing control system using lithium niobate (LiNbO3) crystals. This system is designed for high precision, environmental robustness, and scalability. We analyzed various beam-steering technologies, including non-mechanical methods (e. g., electro-optic, acousto-optic, and liquid crystal) and mechanical methods (e.g., fast steering mirrors and rotating prisms). Our analysis highlighted the limitations of current technologies, particularly in terms of precision, adaptability to space environments, and wavefront preservation. The proposed system leverages the superior electro-optic properties of LiNbO3 crystals. These crystals have a high electro-optic coefficient (r(33)=30.9 pm/V at 632.8 nm, r(33)=29.49 pm/V at 1 064 nm) and excellent optical transparency in the near-infrared range, making them ideal for high-precision beam steering. The core innovation is in the system's symmetric optical design. It actively compensates for effective thermo-optic effects, a critical bottleneck in conventional devices. By placing paired LiNbO3 crystal prisms in an antiparallel alignment of the optical axes, the design cancels out thermally induced refractive index gradients. The effective thermooptic induced refractive index is about 9.3x10(-9), smaller than the refractive index gradient of LiNbO3, ensuring stability in the harsh temperature conditions of space. We rigorously evaluated the system's performance through simulations and experiments. Voltage-deflection modeling showed a linear response, with 720 nrad of beam steering at 5 V and a resolution of <1 nrad/mV. These results demonstrate the feasibility of real-time adjustments in dynamic space conditions. Prototype devices were fabricated using ultra-precision diamond turning and optical bonding techniques. They achieved a central clear aperture of 2 mm with minimal wavefront distortion. Zygo interferometric measurements (lambda =632.8 nm) showed a transmitted wavefront error of 0.2 lambda RMS, mainly due to limitations in the optical bonding process and surface roughness. However, the error meets the minimal optical requirements for high-voltage deflection testing. Beam deflection tests using a high-resolution infrared CCD camera measured a maximum angular displacement of 1.88 milliradians (mrad) under a 15 kV driving voltage. This result closely matched theoretical predictions. Other metrics include a deflection sensitivity of 125 mu rad/kV, allowing precise control with moderate voltage inputs. The beam profile distribution was nearly Gaussian across the temperature range, ensuring minimal sensitivity degradation. These advancements demonstrate the feasibility of LiNbO3-based electro-optic systems for next-generation gravitational wave observatories like LISA (Laser Interferometer Space Antenna), TianQin, and Taiji. Our work contributes to ground verification platforms for testing million-kilometer-scale laser links, filling critical gaps in system-level testing. Moreover, the design is adaptable to other high-precision applications, including quantum communication terminals requiring sub-mu rad beam alignment and deep-space laser ranging systems that need robust performance in varying thermal environments. By solving thermo-optic stability and precision issues, this research accelerates the development of reliable large-scale space interferometry and opens new possibilities for advanced photonic technologies in astrophysics and beyond.

In response to the demand for relative/absolute navigation positioning in combat formation cooperative operations under GNSS-denied environment, a dual grid collaborative navigation method based on data link is proposed. Firstly, by adopting geographic navigation filtering algorithms and relative navigation filtering algorithms that closely combine ranging information with inertial navigation, precise relative positioning of mobile formations can be achieved without fixed ground station and GNSS. At the same time, accurate geographic location information existing within the formation can be adaptively accessed, achieving absolute positioning of formation members. In addition, to ensure the availability of collaborative navigation under conditions such as insufficient positioning benchmarks and poor geometric distribution, adopting a navigation source selection strategy based on quality grade, which enables the target node to efficiently utilize the positioning information of other user nodes, thereby improving positioning performance. Finally, a distributed computer simulation system is constructed by closely integrating the technical characteristics and error characteristics of the data link collaborative navigation system. The navigation capability based on the data link is verified in typical scenarios, and the simulation results fully demonstrate the effectiveness of the designed collaborative navigation method.

With the development of the information battlefield,the application of Link 16 data link in satellites is becoming an ir-reversible trend.Space-ground fusion is an important direction to achieve more efficient and real-time information exchange,but in practical applications,the challenges brought by Doppler effect and signal delay cannot be ignored.This paper proposes a location-equivalent Link16 data link terminal low-orbit satellite access design scheme.By calculating the delay value and Doppler value at the delay center and carrying out signal pre-compensation,the Doppler caused by signal transmission between the satel-lite and the earth is eliminated and the time reference of satellite-borne Link 16 is aligned.The Link 16 data link terminal low-orbit satellite access design is realized,and the simulation shows that the scheme is feasible and can support the application of data link earth and earth integration.

Satellite communication is moving toward multi-band, large bandwidth communication and high data rate space networking, which requires more processing, switching, and high-speed transmission capability of satellite communication payload. The electronic bottleneck of traditional microwave systems in processing speed and transmission bandwidth makes it difficult to adapt to the future demands of satellite communications. Aiming at the limitations of satellite communication based on traditional microwave technology, this article discusses the potential benefits of satellite communication payload based on microwave photonic (SCP-MP) to space information communication networks (SICN). Then it proposes the architecture of SCP-MP, along with its main components and functional structure. We also review the key technologies, such as low spurious frequency conversion, channelization, optical switching, chip, and integration, and discuss challenges. An outlook on the prospects of SCP-MP is also included.

As a laser passes through a scattering medium,the light interacts with the irregular reflections within the medium,re-sulting in light scattering and the formation of speckles.In this paper,an image sensor based on the combination of a coreless optical fiber and a digital camera is proposed for liquid refractive index sensing applications.The coreless fi-ber is used as a sensing unit,and the change in the speckle pattern is measured using the digital correlation method to detect the magnitude of the liquid's refractive index.The experimental results indicate that the laser image sensing technique is capable of effectively distinguishing liquid samples with refractive indices ranging from 1.332 8 to 1.390 8,with a sensing sensitivity of-1.306 RIU-1.Moreover,the laser image sensing technique,with its advantages of high experimental reproducibility,simple system design,remote over-control,holds great research significance and potential application in laser communication and sensor integration.