This paper proposes a method to generate a low-noise 10.23 MHz time-frequency reference signal based on high-order harmonic locking of the repetition rate (fr) of an optical frequency comb (OFC). An all-polarization-maintaining (PM) Erbium-doped fiber laser with a 122.76 MHz fr is constructed using the nonlinear amplifying loop mirror (NALM) principle. By applying a feedback control to the intracavity piezoelectric actuator (PZT) and electro-optic modulator (EOM), the 10th harmonic of fr is phase-locked to a high-performance rubidium atomic clock (Rb clock), achieving low-noise conversion from the Rb clock to the target signal. Experimental results show that the generated 10.23 MHz signal exhibits residual phase noise of −123.4 dBc/Hz at 1 Hz offset and −158 dBc/Hz at 1 MHz offset, and achieves a residual frequency stability of 3.52 × 10−13 @ 1 s and 3.65 × 10−15 @ 10,000 s. This harmonic locking scheme validates the advantages of photonic microwave generation in achieving ultra-low phase noise while preserving the long-term stability of atomic clocks, providing a strategic solution for next-generation BeiDou Navigation Satellite System (BDS) time-frequency payloads.

The Fo content of olivine is a key parameter for understanding the processes of lunar magmatic evolution. However, limited by detection methods, obtaining the Fo content of olivine on the lunar surface has long been confronted with numerous challenges. Traditional methods such as Electron Probe Microanalysis (EPMA) require polishing and sample preparation, making them unsuitable for future in-situ exploration missions. This study employed microscopic infrared spectroscopy, microscopic Raman spectroscopy, and Energy Dispersive Spectroscopy (EDS) to conduct compositional analysis on olivine grains in Chang'e-5 (CE-5) lunar soil samples. We verified the reliability of the infrared spectroscopy Reststrahlen Band (RB) characteristic peak position method and the Raman spectroscopy main peak shift method for the quantitative inversion of olivine Fo content by comparative analysis. Furthermore, the Fo contents derived from the three analytical techniques exhibit systematic deviations, reflecting differences in their respective technical principles and information depths. The low Fo contents suggest that the basalts at the CE-5 landing site have undergone intense crystallization differentiation, while the coexistence of olivines with distinct compositions may stem from magma mixing events. Not only does this study deepen the understanding of the magmatic history of CE-5 samples, but the spectroscopic methods validated herein also enable the systematic acquisition of olivine Fo contents on the lunar surface during the future Chang'e-7 mission, through a combination of orbiter-based infrared surveys and lander-based high-precision Raman detection, thereby providing a novel approach for in-depth studies of lunar magmatic evolution.

Scanning LiDARs remain mature, mainstream, and essential sensors for pose estimation tasks, yet their performance in the terminal approach phase is dictated by the complex interplay between field-of-view (FoV) and angular resolution. This paper characterizes the pose-estimation performance envelope across the full approach trajectory through theoretical analysis, numerical simulations, and semi-physical experiments. We demonstrate that FoV and spatial resolution play distinct yet equally indispensable roles in system reliability. Specifically, FoV establishes the fundamental geometric boundary and proximity limit; as the Geometric Visibility Ratio ($R_{vis}$) drops below the "Geometric Wall'' of approximately 0.8, the truncation of peripheral structures triggers a rapid decay in geometric stiffness. Further FoV truncation that degenerates the observable target into a quasi-planar manifold induces a severe topological rank deficiency, resulting in a total loss of rotational observability. Conversely, angular resolution governs the precision level and numerical stability; within the geometry-preserving regime, sufficient point density is mandatory to suppress estimation jitter and bound rotational errors within safety limits. These findings emphasize the necessity of co-optimizing both parameters, providing quantitative guidance for geometry-aware FoV management and dynamic resolution scheduling to maximize the reliable operating window during terminal approach.

Low-noise and high-stability constant-current drivers are critical components in precision electronic and optoelectronic systems, as current fluctuations directly limit the achievable system performance. This work presents a low-noise constant-current driver based on a current-sensing architecture combined with a parameters adjustable closed-loop control scheme, enabling effective suppression of current noise over a wide frequency range. The electrical performance of the proposed driver is first characterized at the circuit level. At an output current of 300 mA, a current noise spectral density of 15.22 nA root Hz @ 1 kHz is achieved, corresponding to an integrated RMS current noise of 942.88 nA over the 1 Hz-1 MHz bandwidth and a relative current fluctuation of 4.6 ppm. To further evaluate system-level performance, the driver is tested using a laser-based load, where current-induced noise is converted into measurable phase and frequency fluctuations through optical beat-note operation.The experimental results demonstrate that this design effectively suppresses current-induced noise and improves system stability. Owing to its low noise performance, this design provides a practical solution for precision electronic and optoelectronic applications requiring low-noise current power supply

We report an integrated gain polarizer through femtosecond-laser direct inscribed 45°-tilted fiber grating (45°-TFG) in erbium-doped fiber (EDF), serving as a unique mode-locking element to generate stable ultrafast pulses. Our monolithic device exhibits a polarization-dependent loss (PDL) exceeding 6dB within a range of 80nm while simultaneously serving as a gain medium. Subsequently, it was incorporated into a fiber laser and effectively initiated mode locking via the nonlinear polarization rotation mechanism. The laser produced a stable dispersion-managed soliton centered at 1563.5nm with a pulse duration of 127fs at a fundamental repetition rate of 80.8MHz. Numerical simulations corroborate the experimental results and further unveil the intracavity pulse evolution dynamics. These results contribute to the design of advanced ultrafast fiber lasers with a highly compact and robust configuration.

The Mars Surface Composition Detector (MarSCoDe) onboard the Zhurong rover, China's first Mars rover, includes a laser-induced breakdown spectroscopy (LIBS) instrument that enables quantitative analysis of Martian surface elemental composition. We developed quantitative models for manganese (Mn), barium (Ba), and copper (Cu) using respective lab datasets. The optimal model for each element is selected from combinations of various multivariate regression algorithms and feature extractions. Additionally, the model's accuracy and behaviors on the onboard MarSCoDe Calibration Targets (MCCTs) were evaluated. We obtained Mn, Ba, and Cu concentrations for 36 Martian targets detected by MarSCoDe LIBS during the first 300 sols (Martian days). For MarSCoDe rock targets, Mn is primarily associated with Fe, with olivines and pyroxenes being the main source of Mn; however, the overall contents of Ba and Cu are low in MarSCoDe rock targets, and their host minerals remain unclear. Based on the current results, MarSCoDe rocks should be primarily composed of igneous minerals, with minimal alteration preserving their original composition. Additionally, an Fe-Al-Mn-bearing phase was observed in a dune target, potentially clay minerals, suggesting that external inputs may have influenced the dune's composition. This work provides new evidence for the elemental and mineral composition as well as the potential geological processes of the Zhurong landing site.

Conventional single-channel photon-counting LiDAR systems suffer from saturation and limited dynamic range, constraining their performance across land–water transitions. We present an airborne LiDAR system equipped with dual 32-channel photon-number-resolving (PNR) detectors that independently record parallel and perpendicular polarization components. An adaptive processing framework exploits the depolarization ratio for environmental classification and integrates histogram analysis, continuous wavelet transform, and customized clustering to retrieve seamless bathymetry from the shoreline (∼0 m) to depths exceeding 30 m. Field experiments demonstrate penetration beyond five times the Secchi disk depth, with signal photon counts spanning over three orders of magnitude (>20 on land to <0.01 in deep water). The system achieves a dimensionless performance coefficient of Kd · Dmax ≈ 4.2—derived from LiDAR data and comparable to high-power linear-mode systems—while operating with a moderate pulse energy of 80 μJ at a 30 kHz repetition rate. This design paradigm yields exceptional Size, Weight, and Power (SWaP) efficiency: the complete payload weighs only 50 kg and consumes 350 W, approximately one-fifth and one-seventh of conventional high-performance bathymetric LiDARs, respectively. Validation against shipborne sonar confirms high accuracy (R2 =0.9835, mean relative error = 0.49%), even under extremely low-photon conditions. This work establishes a new paradigm for high-dynamic-range aquatic remote sensing, enabling deep-penetration coastal surveys from compact airborne platforms.

Mission-level performance assessment of scanning LiDAR systems is essential for non-cooperative proximity operations, where sensing configuration directly affects point-cloud geometry, pose-tracking observability, and reliable operating range. Existing studies on model-based pose estimation have mainly focused on acquisition and tracking algorithms under given sensing conditions, while the quantitative influence of configurable LiDAR parameters on terminal approach tracking capability remains insufficiently characterized. This paper presents a mission-oriented evaluation framework that links scanning LiDAR sensing parameters to ICP-based relative pose tracking performance. The framework derives an observability–uncertainty indicator from the linearized point-to-plane ICP objective. Defined as the trace of the inverse normal matrix, this indicator captures both the local geometric constraint strength of the visible point-to-plane correspondences and the uncertainty amplification of the pose estimate. Based on this formulation, Field of View (FoV) and angular resolution are interpreted through complementary mechanisms: FoV determines the visible target envelope and the onset of geometric observability degradation, while angular resolution controls the sampling density of the visible geometry and the resulting uncertainty amplification. A dynamic terminal approach simulation framework and a 64-line scanning LiDAR hardware-in-the-loop semi-physical testbed are established to evaluate these effects along representative approach trajectories. Multiple FoV and angular-resolution configurations are tested to map the trajectory-wide variation of ICP observability, uncertainty amplification, and tracking accuracy. The results provide quantitative performance boundaries for scanning LiDAR configuration design, sensing-parameter selection, and terminal approach GNC requirement co-design.

A quantum network provides an infrastructure connecting quantum devices with revolutionary computing, sensing, and communication capabilities. As the best-known application of a quantum network, quantum key distribution (QKD) shares secure keys guaranteed by the laws of quantum mechanics. A quantum satellite constellation offers a solution to facilitate the quantum network on a global scale. The Micius satellite has verified the feasibility of satellite quantum communications, however, scaling up quantum satellite constellations is challenging, requiring small lightweight satellites, portable ground stations and real-time secure key exchange. Here we tackle these challenges and report the development of a quantum microsatellite capable of performing space-to-ground QKD using portable ground stations. The quantum microsatellite features a payload weighing approximately 23 kg, while the portable ground station weighs about 100 kg. These weights represent reductions by more than an order and two orders of magnitude, respectively, compared to the Micius satellite. Additionally, we multiplex bidirectional satellite-ground optical communication with quantum communication, enabling key distillation and secure communication in real-time. Using the microsatellite and the portable ground stations, we demonstrate satellite-based QKD with multiple ground stations and achieve the sharing of up to 0.59 million bits of secure keys during a single satellite pass. The compact quantum payload can be readily assembled on existing space stations or small satellites, paving the way for a satellite-constellation-based quantum and classical network for widespread real-life applications.

For automatic exploration of specific areas with high scientific value on the moon and other planets, highprecision obstacle detection and hazard avoidance capabilities are required. Three-dimensional (3D) LiDAR can obtain a high-resolution 3D point cloud, offering significant advantages in landing obstacle avoidance. During the landing of the Chang'e lander, a laser 3D imaging sensor (L3DIS) is used to measure and generate accurate topographic maps of the candidate landing area in real-time to help find a safe landing zone. The L3DIS employs 16 beamlets split from a Gaussian laser beam and 16 channels of linear-array avalanche photodiodes within the same optical path and scans the object with a two-axis galvanometer in a field of view of 29 degrees x33 degrees. The calibration of the systematic errors and the performance of obstacle detection on this sensor are conducted in this paper. First, the instrument components and main error sources of the sensor are introduced, and the systematic errors are calibrated based on planar targets, indicating that the sensor's accuracy is greater than 4 cm, and the corresponding obstacle detection accuracy is better than 12 cm. Second, the ground validation of obstacle detection is demonstrated, and the obtained point cloud is compared with that obtained by a terrestrial laser scanner, indicating that the sensor has good performance. Finally, the performance of onboard measurement and obstacle detection is analyzed, showing that the sensor can identify obvious craters and rocks, i.e., nine major craters with a maximum and minimum depth of 1.36 m and 0.16 m, respectively, and major rocks with a maximum and minimum height of 0.1 m and 0.05 m, respectively, and main landing area with slop less than 10 degrees except for the edges of craters and rocks.

Laser-induced breakdown spectroscopy (LIBS) has been used to explore the chemistry of three regions of Mars on respective missions by NASA and CNSA, with CNES contributions. All three LIBS instruments use ~100 mm diameter telescopes projecting pulsed infrared laser beams of 10–14 mJ to enable LIBS at 2–10 m distances, eliminating the need to position the rover and instrument directly onto targets. Over 1.3 million LIBS spectra have been used to provide routine compositions for eight major elements and several minor and trace elements on >3000 targets on Mars. Onboard calibration targets common to all three instruments allow careful intercomparison of results. Operating over thirteen years, ChemCam on Curiosity has explored lacustrine sediments and diagenetic features in Gale crater, which was a long-lasting (>1 My) lake during Mars’ Hesperian period. SuperCam on Perseverance is exploring the ultramafic igneous floor, fluvial–deltaic features, and the rim of Jezero crater. MarSCoDe on the Zhurong rover investigated for one year the local blocks, soils, and transverse aeolian ridges of Utopia Planitia. The pioneering work of these three stand-off LIBS instruments paves the way for future space exploration with LIBS, where advantages of light-element (H, C, N, O) quantification can be used on icy regions.

We report a frequency stepwise pulse train (FSPT) generation system based on an amplified frequency shifting loop (AFSL) with switchable frequency spacing. The frequency spacing switching was achieved with a composite module with two acousto-optic modulators, providing different frequency shifts per round trip. In this way, one single frequency laser pulse can be extended to an equidistant pulse train in the time domain and the generated pulses possess frequency stepwise behavior with nonuniform spacing in the optical frequency domain. In a FSPT generation prototype, 52 pulses with different frequency spacing of 800 MHz and 200 MHz, covering the two absorption wings and the peak of the R16 line for CO2, respectively, were obtained with the specially designed AFSL. Both static and dynamic CO2 spectroscopy were carried out to verify the performance of the FSPT with switchable frequency spacing. Good agreement was obtained between the retrieved spectral transmittance and theoretical curves calculated from the HITRAN database. It is believed that such a FSPT generation method with switchable frequency spacing has paved a promising path towards practical spectroscopy, especially for varying atmosphere such as laser occultation.

Raman spectroscopy has emerged as a crucial mineral analysis technique in planetary surface exploration missions. Nonetheless, the inherently low Raman scattering efficiency of planetary silicate materials makes it challenging to extract enough Raman information. Theoretical and experimental studies of the remote Raman scattering properties of planetary materials are also urgent requirements for future lunar and planetary explorations. Here, Shandong University Remote Raman Spectrometer (SDU-RRS) was developed to demonstrate the feasibility of lunar remote Raman technology and conduct preliminary research on remote Raman scattering properties. SDU-RRS utilizes a pulsed 532 nm laser, a non-focal Cassegrain telescope, a volume phase holographic grating, an intensified charge-coupled device, and the time-gating technique to detect weak-signal silicate minerals. The spectral resolution obtained with atomic emission lamps was <4.91 cm(-1), and the wavelength accuracy was <1 cm(-1), across the spectral range of 241-2430 cm(-1). SDU-RRS can detect natural augite within a feldspar-olivine-augite matrix at a concentration of 20 % at similar to 1 m under ambient lighting conditions. A series of experiments were conducted to evaluate the influence of measurement conditions and physical matrix effects on acquired Raman signals, either qualitatively or quantitatively, on geological materials. The study indicates that the transmission of Raman-scattered light conforms to Lambert's cosine law, and a linear correlation exists between Raman intensity and laser power. The study also evaluated the impact of grain size, surface roughness, porosity, and shadow-hiding effects. Reducing grain size decreases Raman intensity and broadens Raman spectra. These characteristics are essential for achieving definitive mineralogical information from granular materials by remote Raman spectroscopy in lunar and planetary explorations.

The intensified charge-coupled device (ICCD), known for its exceptional low-light detection performance and time-gating capability, has been widely applied in remote Raman spectroscopy systems. However, existing ICCDs face significant challenges in meeting the comprehensive requirements of high gating speed, high sensitivity, high resolution, miniaturization, and adaptability to extreme environments for the upcoming lunar remote Raman spectroscopy missions. To address these challenges, this study developed a microstrip photocathode (MP-ICCD) specifically designed for lunar remote Raman spectroscopy. A comprehensive testing method was also proposed to evaluate critical performance parameters, including optical gating width, optimal gain voltage, and relative resolution. The MP-ICCD was integrated into a prototype remote Raman spectrometer equipped with a 40 mm aperture telescope and tested under outdoor sunlight conditions. The experimental results demonstrated that the developed MP-ICCD successfully achieved a minimum optical gating width of 6.0 ns and an optimal gain voltage of 870 V, with resolution meeting the requirements for Raman spectroscopy detection. Under outdoor solar illumination, the prototype remote Raman spectrometer utilizing the MP-ICCD accurately detected the Raman spectra of typical lunar minerals, including quartz, olivine, pyroxene, and plagioclase, at a distance of 1.5 m. This study provides essential technical support and experimental validation for the application of MP-ICCD in lunar Raman spectroscopy missions.

Laser-induced breakdown spectroscopy (LIBS) is a stand-off chemical analysis technique. In scenarios where the LIBS detection distance varies (e.g. Mars exploration), the distance effect poses a significant challenge to data analysis. In our prior work, a deep convolutional neural network (CNN) model was developed to directly process LIBS multi-distance spectra, achieving high classification accuracy even without performing conventional “distance correction”. The present study proposes a spectral sample weight optimization strategy to further improve the CNN model training process. Unlike the default equal-weight scheme, the new strategy tailors a specific weight value for every training spectral sample. On an eight-distance LIBS dataset acquired by the MarSCoDe duplicate instrument, the CNN model with the new weighting strategy can achieve a maximum testing accuracy of 92.06%, representing an improvement of 8.45 percentage points over our original CNN model. Besides accuracy, three other supplementary metrics also demonstrate the superiority of the new strategy: the precision, recall and F1-score can be averagely increased by 6.4, 7.0 and 8.2 percentage points, respectively. Moreover, the training time per epoch of the weight optimization strategy is almost identical to that of the original equal-weight scheme. These results indicate that the proposed methodology has great application potential in planetary exploration, and other LIBS-adopted scenarios involving varying detection distances.

The photon-counting camera has single-photon sensitivity and picosecond time resolution, enabling the acquisition of beacons from thousands of kilometers away for deep-space optical sensing and communication. However, the accurate estimation of the beacon beam center is challenged by the random fluctuations of signal photons and the presence of randomly and widely distributed noise photons. In this paper, we propose a deep-learning-based super-resolution beam position estimator (DSRBPE), which improves the accuracy of beam position estimation through reasonable photon data modeling, as well as optimizing the design of the super-resolution convolutional neural network framework and loss function. Simulation and experimental results show that DSRBPE can achieve sub-pixel precision of 0.2 pixels for super-resolution centroid extraction of an extremely weak 4×4 pixel size Gaussian spot on a 32×32 single-photon array detector, and exhibits superior robustness under low signal-to-noise ratio conditions compared with conventional algorithms.