Laser Range Research Articles

Analysis and comparison of the orbit determination accuracy of TianQin based on multiple ground-based measurements

TianQin project, a Chinese initiative in space gravitational wave detection, demands high precision in satellite orbit during both entry and scientific operations. As means of developmental maturation, ground-based measurements play a vital role in ensuring the smooth execution of TianQin satellite’s detection mission. This paper conducts a simulation analysis by utilizing various ground-based measurement data, including the China Deep Space Network (CDSN), S/Ka-band ranging system, and Satellite Laser Ranging (SLR). The main focus is to explore the distinctions in Precise Orbit Determination (POD) capabilities among different methods and to enhance POD accuracy through the integration of multiple techniques for TianQin satellites. The results indicate: (1) Leveraging a strategically positioned station distribution, CDSN stations offer extended observation time, averaging 17.3 h per satellite daily, compared to S/Ka’s 10.5 h. (2) In single-measurement POD scenarios, S/Ka proves superior, achieving accuracy better than 10 m and 0.4 mm s−1 for TianQin satellites with a 7-day orbit arc length. This superiority is attributed to its exceptional observational accuracy, outperforming CDSN’s 40 m and 2.2 mm s−1 for POD accuracy. (3) By integrating high-precision SLR data on the foundation of CDSN or S/Ka observations, the POD accuracy of TianQin satellites is further enhanced, despite the limited SLR data quantity.

2 W monolithic fiber laser at 3.8 µm

We report a dual-wavelength-pumped all-fiber continuous-wave laser operating at the extended wavelength of 3.79 µm that reaches a record output power of 2.0 W. This represents, to the best of our knowledge, the highest output power reported at the longest spectral range for a fiber laser. The laser cavity, made of a heavily erbium-doped fluoride fiber and bounded by two photo-inscribed fiber Bragg gratings, reaches a slope efficiency of 46.5% with respect to the absorbed 1976 nm pump power. The system exhibits an absorption dependency of the 1976 nm pump on the launched 976 nm pump and a quenching behavior dependency on the output coupler reflectivity. The all-fiber design of the cavity allows significant power scaling of the laser and ensures its long-term stability.

Precise Orbit Determination for Maneuvering HY2D Using Onboard GNSS Data

The Haiyang-2D (HY2D) satellite is the fourth ocean dynamics environment monitoring satellite launched by China. The satellite operates on a re-entry frozen orbit, which necessitates orbital maneuvers to maintain its designated path once the satellite’s sub-satellite point deviates beyond a certain threshold. However, the execution of orbit maneuvers presents a significant challenge to the field of Precise Orbit Determination (POD). The thesis selects the on-board GPS data of HY2D satellite in December 2023 and five maneuvering days of that year. Employing a multifaceted approach that includes the assessment of observational data quality, orbit overlap, external orbit validation, and SLR (Satellite Laser Ranging) verification, the research delves into precise orbit determination during both maneuver and non-maneuver periods. The results indicate that: (1) The average number of satellites tracked by the receiver is 6.4; (2) During the non-maneuver periods, the average RMS (Root Mean Square) value of the radial difference in the 6-h overlapping arc segment is 0.66 cm, and the three-dimensional position difference is about 1.16 cm; (3) When compared with the precision science orbits (PSO) provided by CNES (Centre National d’Études Spatiales), the average values of the RMS values of the differences in the radial (R), transverse (T), and normal (N) directions during the non-maneuver and maneuver periods are respectively 1.32 cm, 2.31 cm, 1.92 cm and 3.04 cm, 8.78 cm, 2.72 cm. (4) The SLR verification of the orbit revealed a residual RMS of 2.24 cm. This suggests that by incorporating the modeling of maneuver forces during the maneuver periods, the impact of orbital maneuvers on orbit determination can be mitigated.

Design of a Technology-Based Magic Show System with Virtual User Interfacing to Enhance the Entertainment Effects

The integration of interactive technology into magic performances was explored in this study, with a focus on leveraging virtual user interfacing and interactive video projection techniques to enhance the entertainment effects. A thorough literature review identified transformation techniques between virtual and real forms in the magic performance, along with various digital magic effects. Design principles derived from the review were applied in constructing a magic show system named “FUI Magic”, where FUI stands for fantasy user interface. The system is based on virtual user interfacing, implemented via laser range-finding and video projection techniques. The “FUI Magic” system facilitated the development and presentation of a digital-multimedia magic show titled “Fantasy Doves”, publicly showcased in an exhibition. Statistical evaluation of the feedback from expert interviews and a questionnaire survey revealed positive audience impressions and confirmed the effectiveness of incorporating virtual user-interfacing technology for captivating entertainment. This study affirms the significance of visual design through virtual user interfacing in enhancing technological ambiance and magic effects, suggesting its practicality for further exploration in diverse applications.

An analysis of laser distance measuring by different laser rangefinders

Laser rangefinders have emerged as indispensable tools in various fields, enabling accurate distance measurements through the utilization of laser technology. This paper provides a comprehensive overview of laser rangefinders, including the principle of laser rangefinders, classification, practical applications, and calibration methods. Different types of laser rangefinders are discussed based on their operating principles, while the various fields in which laser rangefinders are widely used are highlighted. The importance of accurate calibration is also discussed in depth, and the various techniques used to calibrate laser rangefinders are explored. In addition, accuracy and measuring range of each kind of laser rangefinder will also be discussed. This paper aims to provide a comprehensive understanding of laser rangefinders, including their classification, practical applications, and calibration methods. It also highlights the importance of accurate distance measurements in various industries and the role of laser rangefinders in meeting these requirements.

Accurate extrinsic calibration for the invisible-light 1D laser rangefinder and camera

Abstract A combined sensor, comprising a camera and a one-dimensional laser rangefinder (1D LRF), has wide application across engineering sectors, notably in aerospace. This combined sensor is pivotal for earth observation and deep space exploration. To achieve precise and stable external parameters for this combined sensor, an accurate external calibration method is proposed. Initially, a technique for localized registration of laser spots is introduced to ensure precise determination of their positions, addressing the challenge of laser invisibility in a 1D LRF. Subsequently, a data evaluation criterion known as the data synthesis criterion is presented, addressing the issue of limited constraints in traditional calibration methods. This criterion evaluates relative errors encompassing 1D LRF ranging values, camera external parameters, and laser spot positions. Finally, based on the proposed criteria, a robust extrinsic calibration method is introduced that automatically filters observation data with significant errors and utilizes the growth rate of camera spatial resolution as the termination condition. The efficacy of the proposed method is confirmed through simulation experiments and real-world data experiments.

Design of intelligent controller for obstacle avoidance and navigation of electric patrol mobile robot based on PLC

Currently, the obstacle avoidance control of patrol robots based on intelligent vision lacks professional controller module assistance. Therefore, this paper proposes a design method of intelligent controller for obstacle avoidance and navigation of electrical inspection mobile robot based on PLC control. The controller designs a laser range finder to determine the required position of electrical patrol inspection. Use PLC as the core controller, and combine sensors, actuators, communication module and PLC selection module in the process of hardware design to achieve autonomous navigation and obstacle avoidance functions of the robot. Then design the software including the PLC compiler system and the virtual machine module. Based on the above steps, design the control module of obstacle avoidance navigation, which realizes the key link of robot autonomous navigation. The test results show that the controller can successfully avoid obstacles, improve the efficiency and quality of inspection, and achieve accurate and fast obstacle avoidance navigation for the electrical inspection mobile robot.

Broadband tunable resonance modes from multi-composition monolayer MoS2(1−x)Se2x with SiO2 microsphere cavity

Two-dimensional (2D) monolayer transition metal dichalcogenides (TMDCs) that are compatible with Si-based substrates have already exhibited huge application potential in optoelectronics and photonics. The MoS2(1−x)Se2x ternary alloy consisting of two different chalcogens, as a class of lasing gain medium, enriches the family of 2D TMDC materials. Here, monolayer MoS2(1−x)Se2x ternary alloys with tunable composition have been synthesized via single-step chemical vapor deposition method. Raman and photoluminescence studies demonstrate that the bandgap of grown monolayer MoS2(1−x)Se2x alloys can be gradually tuned from 1.59 to 1.82 eV, indicating the continuous changes of the chemical composition x from 0.82 to 0. The oscillation characteristic is further investigated, where the MoS2(1−x)Se2x alloy provides optical gain for the SiO2 microsphere resonant cavity. The achieved resonance modes in a broadband range from 610 to 810 nm not only extend the range of potential TMDC-based lasers, but also drive the applications of alloy materials in various optoelectronics devices.

3D Camera and Single-Point Laser Sensor Integration for Apple Localization in Spindle-Type Orchard Systems.

Accurate localization of apples is the key factor that determines a successful harvesting cycle in the automation of apple harvesting for unmanned operations. In this regard, accurate depth sensing or positional information of apples is required for harvesting apples based on robotic systems, which is challenging in outdoor environments because of uneven light variations when using 3D cameras for the localization of apples. Therefore, this research attempted to overcome the effect of light variations for the 3D cameras during outdoor apple harvesting operations. Thus, integrated single-point laser sensors for the localization of apples using a state-of-the-art model, the EfficientDet object detection algorithm with an mAP@0.5 of 0.775 were used in this study. In the experiments, a RealSense D455f RGB-D camera was integrated with a single-point laser ranging sensor utilized to obtain precise apple localization coordinates for implementation in a harvesting robot. The single-point laser range sensor was attached to two servo motors capable of moving the center position of the detected apples based on the detection ID generated by the DeepSORT (online real-time tracking) algorithm. The experiments were conducted under indoor and outdoor conditions in a spindle-type apple orchard artificial architecture by mounting the combined sensor system behind a four-wheel tractor. The localization coordinates were compared between the RGB-D camera depth values and the combined sensor system under different light conditions. The results show that the root-mean-square error (RMSE) values of the RGB-D camera depth and integrated sensor mechanism varied from 3.91 to 8.36 cm and from 1.62 to 2.13 cm under 476~600 lx to 1023~1100 × 100 lx light conditions, respectively. The integrated sensor system can be used for an apple harvesting robotic manipulator with a positional accuracy of ±2 cm, except for some apples that were occluded due to leaves and branches. Further research will be carried out using changes in the position of the integrated system for recognition of the affected apples for harvesting operations.

SLR Validation and Evaluation of BDS-3 MEO Satellite Precise Orbits

Starting from February 2023, the International Laser Ranging Service (ILRS) began releasing satellite laser ranging (SLR) data for all BeiDou global navigation satellite system (BDS-3) medium earth orbit (MEO) satellites. SLR data serve as the best external reference for validating satellite orbits, providing a basis for comprehensive evaluation of the BDS-3 satellite orbit. We utilized the SLR data from February to May 2023 to comprehensively evaluate the orbits of BDS-3 MEO satellites from different analysis centers (ACs). The results show that, whether during the eclipse season or the yaw maneuver season, the accuracy was not significantly decreased in the BDS-3 MEO orbit products released from the Center for Orbit Determination in Europe (CODE), Wuhan University (WHU), and the Deutsches GeoForschungsZentrum (GFZ) ACs, and the STD (Standard Deviation) of SLR residuals of those three ACs are all less than 5 cm. Among these, CODE had the smallest SLR residuals, with 9% and 12% improvement over WHU and GFZ, respectively. Moreover, the WHU precise orbits exhibit the smallest systematic biases, whether during non-eclipse seasons, eclipse seasons, or satellite yaw maneuver seasons. Additionally, we found some BDS-3 satellites (C32, C33, C34, C35, C45, and C46) exhibit orbit errors related to the Sun elongation angle, which indicates that continued effort for the refinement of the non-conservative force model further to improve the orbit accuracy of BDS-3 MEO satellites are in need.

Research on a visual positioning method of paddy field weeding wheels based on laser rangefinder-camera calibration

The positioning of paddy field weeding wheels is of great significance for compensating the operation deviation between the weeding wheel and the seedling row in paddy field mechanical weeding. In this paper, a visual positioning method for determining the three-dimensional coordinates of weeding wheels in the camera coordinate system is proposed. By fixing the laser rangefinder with the weeding wheel, the proposed method converts the positioning of weeding wheels into solving the relative pose relationship between the laser rangefinder and the camera. Then, based on the constraints of the laser spots on the AprilTag calibration plane, a nonlinear optimization model is established to obtain the relative pose parameters. In the experiment, two evaluation indicators were proposed to evaluate the calibration accuracy. The experimental results showed that the proposed visual positioning method of the weeding wheel can reach a mean positioning error of 2.766 mm and a mean pixel error of 7.161 pixels.

Flexible automated system for laser modified layer by layer assembly.

An open-source automated system for laser modified layer by layer assembly is described. This flexible system, the first designed to be used with this process, can be used to fabricate a range of laser patterned, layer by layer thin films. The Arduino microcontroller-based system features a stepper motor-controlled turntable that holds solutions and water rinses for dipping. The substrate can be moved vertically to be dipped into each of the solutions throughout the process. A semiconductor laser is used to modify the thickness of the thin film during the chosen dipping cycles. Several aspects of the robotic system are easily controlled via software, including the average laser power, irradiation time, horizontal laser position, and vertical substrate position. The system is fully automated and, once started, does not require any user interaction. To demonstrate the capability of the automated system for patterning, electrochromic thin film devices using 50-bilayer laser patterned films using the polymers poly(allylamine hydrochloride) and sodium poly[2-(3-thienyl)-ethoxy-4-butylsulfonate] are presented. One device is patterned with the shape of a large "C," created by irradiating the sample (55 mW average power, 405nm) while the substrate was moved vertically up and down or the laser was moved horizontally. The laser irradiates the sample during only the dipping in the polycation polymer solution. A second electrochromic thin film device is based on a sample with five parallel laser patterned lines, where each line is fabricated with different average laser powers and, hence, different thicknesses. The thicknesses of the lines vary by about 30nm.

A FeCrAl-Al2O3 Composite Produced Via Laser Powder Bed Fusion of a Mixed Powder for Porous Catalyst Scaffolds

Abstract This study proposes a novel approach for synthesizing and etching bicontinuous FeCrAl-Al2O3 composites as a means for replacing FeCrAl foams as catalyst scaffolds in biodriven alcohol reactors for jet-fuel production. Conventional FeCrAl foams suffer from poor availability and consequent high costs. New additive manufacturing techniques provide an opportunity to produce tailored foams at reasonable times and at acceptable costs. This research aimed to generate a porous FeCrAl structure by etching a bicontinuous FeCrAl-Al2O3 composite produced by laser powder bed fusion of amalgamated FeCrAl and Al2O3 powders. The composite powder for laser powder bed fusion is created by ball-milling FeCrAl and Al2O3 powders. This research focuses on achieving a bi-continuous FeCrAl-Al2O3 structure, essential for the selective removal of the ceramic phase. The influence of laser processing parameters on the microstructure was examined across a range of laser powers (60–120 W) and scan speeds (100–400 mm/s), showing that higher powers and speeds produce finer metal struts. A bi-continuous microstructure was consistently obtained, marking a key achievement. The Al2O3 removal process involved a two-step etching method using hydrochloric and phosphoric acids, tested across various etching times. The alumina phase was reduced from 36 vol% to 17 vol% (corresponding to an increase in porosity from 24 vol% to 43 vol%), showing the potential for use as a porous catalyst scaffold. This research demonstrates the potential for using additive manufacturing to produce porous FeCrAl structures capable of replacing hard-to-source FeCrAl foams.

Non-uniform line-of-sight measurements of nitric oxide using mid-infrared Faraday rotation spectroscopy

Traditional absorption spectroscopy relies on detecting intensity variations along the line-of-sight to gauge average concentration and temperature. While methods like profile fitting and temperature binning offer insights into the non-uniformity of the path, they fall short of accurately capturing the precise spatial distribution with a single line-of-sight measurement. We propose a novel measurement scheme for non-uniformly distributed concentration of nitric oxide (NO) along the line-of-sight utilizing a single laser and path, by incorporating Faraday rotation spectroscopy with magnetic fields changing over time and space. We validate the proposed scheme by measuring a path of two regions in series with different NO concentrations, and comparing the measurement results with direct absorption spectroscopy of each respective region. In this work, the tuning range of the interband cascade laser used is from 1899.42 to 1900.97 cm−1, encompassing two sets of spectral lines corresponding to the 2Π1/2 and 2Π3/2 transitions of NO’s R(6.5). The average relative uncertainty in the concentration measurement for each region is estimated to be within 1.5%, with the concentration for individual absorption cells ranging from 0.2% to 0.8%.

거리측정용 레이저가 야간투시경의 흑점 발생에 미치는 영향 연구

거리측정용 레이저가 야간투시경의 흑점 발생에 미치는 영향 연구

Study of Earth’s Obliquity Evolutionary History by Advanced Kinematic Model

NASA’s press release of ‘Moon having receded by 1 m from Earth in a quarter of century’ on the Silver Jubilee Anniversary (20 July 1994) of Man’s landing on Moon led to the development of the Kinematic Model (KM) of evolving Earth-Moon System (E-M system). Best fit KM parameters is adopted for the analysis of evolving E-M system assuming the present length of day of Earth to be 24 hours, sidereal orbital period of Moon divided by spin period of Earth = LOM(length of month)/LOD(length of day) = 27.322 and the age of Moon=4.467Gy. Using the best fit model parameters the velocity of recession of Moon is derived as 2.3cm/y as compared to 3.7cm/y by Lunar Laser Ranging experiment (Dickey et.al. 1994) [1]. Matija Cuk et.al (2016) have proposed a new model for the birth and tidal evolution of our natural satellite Moon born from impact generated terrestrial debris in the equatorial plane of high obliquity, high angular momentum Earth [2]. Using Moon’s orbital plane inclination angle (α), Moon’s obliquity (β) and eccentricity(e) of Moon’s orbit around Earth the advanced KM was developed and used for predicting the evolutionary history of Earth’s obliquity from a (semimajor axis of Moon) = 45RE = 2.96695×108 m (Cassini State Transition orbit) to the present a = 60.336RE = 3.844×108 m [3]. The present paper is sequel to the paper Sharma (2024) [5]. In the Advanced KM. (Φ)-Earth’s obliquity, (α)-Lunar orbital plane inclination, (β)-Lunar Obliquity and (e)-eccentricity of Moon’s orbit around Earth have been included. It has been shown that with the present epoch value of Φ = 23.4°, α = 5.14° , β = 1.54° and e = 0.0549, the general equation describing the evolution of E-M system from 45RE=2.96695×108 m to the present a = 60.336RE = 3.844×108 m yields (Length of Month/Length of Day) = 27.32 with fine tuning of globe-orbit parameters within its measurement error margin. But the tension between the predicted and the observed velocity of recession could not be removed even in the Advanced KM. This tension constrains Moon to be in an accelerated expanding spiral orbit where it recedes from 3.274×108 m to the present orbit 3.844×108 m in 1.2Gy time span. In the classical model this spiral expansion took 1.9Gy where it monotonically expanded spirally from 18,000Km to 384,440Km.. In the new hypothesis according to Cuk et.al. of Moon’s origin from high obliquity, high angular momentum Earth, Moon initially spirals out in chaotic manner with the lunar expansion getting stalled at Laplace Plane Transition as well as in Cassini State transition [2]. Plus in multiple-impact scenario of Moon formation according to Rufu et.al. also results in a delayed formation of full size Moon [4]. Both these factors result in a longer transit time from 18,000Km to 3.012×108 m of 3.267Gy. This results in an accelerated phase from 3.012×108 m to 3.844×108 m in 1.2Gy subsequently resulting into radial recession rate of 3.7cm/y. In the Advanced KM, 3.267Gy is spent in spiral orbital expansion from 3RE to 45RE but in fits and 1.2Gy is spent in accelerated monotonic spiral expansion from 45RE to 60.336RE. Hence this model is called fits and bound model. This also results in a much better match between observed LOD curve and theoretical LOD curve as is shown in a sequel paper [5]. In the present paper Advanced Kinematic Model analyzes the history of the evolution of Earth’s Obliqquity from the birth of Moon 4.467Gy ago to the present modern times.

Dynamiczny pomiar prędkości pojazdu oparty na laserowej kontroli odległości

The article presents the issue of using a popular driving video recorder Videorapid 2a and proposes an original solution which eliminates the need for keeping the same distance between both vehicles the speed of a vehicle is being measured. The use of such solution by police vehicles would eliminate the need for keeping a constant distance between vehicles, because the speed of the controlled vehicle can still be calculated even when the distance between vehicles is changed. The electronic and IT solution, which is a modern driving video recorder that uses a laser distance sensor, additionally recognizes the vehicle's registration number, which allows its automatic check in, for instance, Central Register of Vehicles and Drivers.

Operating point control method for the Mach-Zehnder modulator in a phase-shift laser range finder

An operating point control method is proposed for the Mach-Zehnder modulator (MZM) based on a dual-cascaded MZM structure. Unlike traditional methods with dither signals, the proposed method is advantageous because the components monitored in the control process are not masked by the spectrum noise floor and the drift direction is clearly determined at the quadrature point, thus imparting greater control stability. Additionally, the proposed control method is suitable for phase-shift laser range finders (PSLRFs). Compared with traditional methods, experimental results reveal that the proposed method increases the operating point stability of MZM from ±0.59° to ±0.36° within 2 h, resulting in better ranging stability than 17 μm in 1 min and 39 μm in 1 h in a PSLRF with a 200 MHz modulation frequency.

Analysis and diagnosis of abnormal SLR validation results for BeiDou-3 SECM-B MEO C225 and C226 satellite orbits

Satellite laser ranging (SLR) is the only stand-alone and external tool for verifying the accuracy of microwave-based GNSS orbits. On February 2, 2023, the International Laser Ranging Service initiated the SLR global tracking campaign for the complete BeiDou-3 medium Earth orbit (MEO) constellation. This initiative provides an opportunity to unveil the potential issue for BeiDou-3 MEO orbit modeling. An examination of the SLR validation results of precise BeiDou-3 MEO orbits across different IGS/Multi-GNSS Experiment (MGEX) analysis centres (ACs) reveals that the SLR residual standard deviation for BeiDou-3 SECM-B MEOs C225 and C226 orbits reaches 18 cm. This figure is approximately four to nine times those for other BeiDou-3 MEOs. This contradicts the fact that the orbit quality of C225 and C226 is comparable to other satellites. By analyzing the correlation between SLR residuals and de-trend clock residuals, detector-specific bias performance, and the distribution characteristics of SLR residuals relative to satellite azimuth and nadir angles, we diagnose that abnormal SLR validation results for C225 and C226 originate from a large deviation in the official horizontal offsets for the laser retroreflector arrays (LRAs) in the satellite reference frame. LRA horizontal offsets for C225 and C226 are estimated based on SLR residuals. With our adjusted LRA offset estimates, the SLR residual metrics for C225 and C226 orbits (across various IGS/MGEX ACs) are comparable to the results obtained for other BeiDou-3 MEOs. Additionally, our adjustments enable the identification of their orbit modeling errors across different IGS/MGEX ACs according to the pattern of SLR residual variation. From the study, spacecraft manufacturers should be encouraged to conduct a comprehensive review of ground calibrations for BeiDou LRA offsets. This is crucial for optimizing BeiDou orbit model and enhancing its applications in high-precision geosciences.

Determination of global geodetic parameters using satellite laser ranging to Galileo, GLONASS, and BeiDou satellites

The new Global Navigation Satellite System (GNSS) satellites, including GLONASS, Galileo, and BeiDou system, are equipped with Laser Retroreflector Arrays (LRA) to support Satellite Laser Ranging (SLR) tracking, which contributes to the estimation of global geodetic parameters. In this study, we estimate the global geodetic parameters using the SLR observations to GNSS satellites and also investigate the effects of different data processing strategies on the estimated Earth Rotation Parameters (ERP), geocenter motion, and terrestrial scale. The results indicate that setting range bias parameters for each satellite-station pair can effectively account for the satellite-specific biases induced by LRAs, leading to smaller Root Mean Square Errors (RMSE) of the post-fit SLR residuals. Furthermore, estimating the range biases for each satellite-station pair improves the accuracy of the estimated station coordinates and ERP. We also examine the impact of different arc lengths on the estimates of ERP, geocenter motion, and terrestrial scale. The results show that extending arc length can significantly reduce the formal error of ERP. The 7-day strategy produces the smallest RMSEs of 473 microarcseconds and 495 microarcseconds for the estimated X- and Y-component of pole coordinates, and 52 microseconds for length-of-day, respectively. However, the estimated geocenter motion is less affected by the arc length, even the shortest 1-day arc strategy can capture the seasonal variations of geocenter motion in Z component. For scale estimation, extending the arc length notably improves the accuracy of the estimated station coordinates and scale, but this advantage becomes less noticeable in longer arcs. The 7-day solution also obtains the closet scale results compared to ITRF2014, with the RMSE of 2.10 × 10–9.