A method is presented for determining instant values of Earth’s polar motion(PM)using a set of lunar laser ranging(LLR)measurements acquired simultaneously by tri-static common view(TCV)at three LLR stations in Europ...A method is presented for determining instant values of Earth’s polar motion(PM)using a set of lunar laser ranging(LLR)measurements acquired simultaneously by tri-static common view(TCV)at three LLR stations in Europe.We developed a model of the LLR TCV measurements,then formulated the linear equation for solving PM.Although there was no actual TCV event in the data,we conducted a two-phase study to test our method using actual LLR normal points(NPs)acquired by the European stations during 2012-2022.In the first phase,we simulated TCV events and PM solutions.The robustness of our method was assessed by introducing Universal Time(UT1)errors and per-station range errors in this phase.In the second phase,we augmented the actual LLR NPs with simulated data to generate realistic TCV events and solutions,using the‘1+2’and‘2+1’strategies,which differed in terms of data composition.Results indicated that a UT1 error of 0.1 ms caused PM errors of<18 mas,while a uniform range error of 50 mm resulted in PM errors of<180 mas.In the augmentation phase,the maximum solution errors were 752 and 899 mas,and 88.5% and 91.2% of the solutions were better than the predictions for the‘1+2’and‘2+1’strategies,respectively.The presented approach relies on precise geodetic data,and therefore,it is not intended to replace the traditional method.However,this study demonstrated that instant determination of PM is feasible and robust,although the accuracy requires further enhancement.展开更多
To improve the performance of composite pseudo-noise （PN） code clock recovery in a regenerative PN ranging system at a low symbol signal-to-noise ratio （SNR）, a novel chip tracking loop （CTL） used for regenerati...To improve the performance of composite pseudo-noise （PN） code clock recovery in a regenerative PN ranging system at a low symbol signal-to-noise ratio （SNR）, a novel chip tracking loop （CTL） used for regenerative PN ranging clock recovery is adopted. The CTL is a modified data transition tracking loop （DTTL）. The difference between them is that the Q channel output of the CTL is directly multiplied by a clock component, while that of the DTTL is multiplied by the Ⅰ channel transition detector output. Under the condition of a quasi-squareware PN ranging code, the tracking （ mean square timing jitter） performance of the CTL is analyzed. The tracking performances of the CTL and the DTTL, are compared over a wide range of symbol SNRs. The result shows that the CTL and the DTTL have the same performance at a large symbol SNR, while at a low symbol SNR, the former offers a noticeable enhancement.展开更多
Sound multipath propagation is very important for target localization and identification in different acoustical zones of deep water. In order to distinguish the multipath characteristics in deep water, the Northwest ...Sound multipath propagation is very important for target localization and identification in different acoustical zones of deep water. In order to distinguish the multipath characteristics in deep water, the Northwest Pacific Acoustic Experiment was conducted in 2015. A low-frequency horizontal line array towed at the depth of around 150 m on a receiving ship was used to receive the noise radiated by the source ship. During this experiment, a beating-splitting phenomenon in the direct zone was observed through conventional beamforming of the horizontal line array within the frequency band 160 Hz- 360 Hz. In this paper, this phenomenon is explained based on ray theory. In principle, the received signal in the direct zone of deep water arrives from two general paths including a direct one and bottom bounced one, which vary considerably in arrival angles. The split bearings correspond to the contributions of these two paths. The beating-splitting phenomenon is demonstrated by numerical simulations of the bearing-time records and experimental results, and they are well consistent with each other. Then a near-surface source ranging approach based on the arrival angles of direct path and bottom bounced path in the direct zone is presented as an application of bearing splitting and is verified by experimental results. Finally, the applicability of the proposed ranging approach for an underwater source within several hundred meters in depth in the direct zone is also analyzed and demonstrated by simulations.展开更多
Absolute distance measurement is a fundamental technique in mobile and large-scale dimensional metrology.Dual-comb ranging is emerging as a powerful tool that exploits phase resolution and frequency accuracy for high-...Absolute distance measurement is a fundamental technique in mobile and large-scale dimensional metrology.Dual-comb ranging is emerging as a powerful tool that exploits phase resolution and frequency accuracy for high-precision and fast-rate distance measurement.Using two coherent frequency combs,dual-comb ranging allows time and phase response to be measured rapidly.It breaks through the limitations related to the responsive bandwidth,ambiguity range,and dynamic measurement characteristics of conventional ranging tools.This review introduces dual-comb ranging and summarizes the key techniques for realizing this ranging tool.As optical frequency comb technology progresses,dualcomb ranging shows promise for various professional applications.展开更多
To improve the link efficiency and decrease the payloads in space explorations, a novel simultaneous communication and ranging method based on x-ray communication（XCOM） is proposed in this paper. A delicate signal s...To improve the link efficiency and decrease the payloads in space explorations, a novel simultaneous communication and ranging method based on x-ray communication（XCOM） is proposed in this paper. A delicate signal symbol structure is utilized to achieve simultaneous data transmission and range measurement. With the designed symbol structure, the ranging information is imbedded into the communication signal and transmitted with it simultaneously. The range measurement is realized by the two-way transmission of the range information. To illustrate the proposed method, firstly, the principle of the method is introduced and the signal processing procedure is presented. Then, the performance of the proposed method is analyzed theoretically in various aspects, including the acquisition probability, the bit error rate, the ranging jitter,etc. Besides, numerical experiments are conducted to verify the proposed method and evaluate the system performance.The simulation results show that the proposed method is feasible and that the system performance is influenced by the parameters concerning the signal symbol structure. Compared with the previous methods, the proposed method improves the link efficiency and is beneficial for system miniaturization and integration, which could provide a potential option for future deep space explorations.展开更多
In a satellite laser ranging telescope system, well-aligned encoders of the elevation and azimuth axes are essential for tracking objects. However, it is very difficult and time-consuming to correct the bias between t...In a satellite laser ranging telescope system, well-aligned encoders of the elevation and azimuth axes are essential for tracking objects. However, it is very difficult and time-consuming to correct the bias between the absolute-position indices of the encoders and the astronomical coordinates, especially in the absence of a finder scope for our system. To solve this problem, a method is presented based on the phenomenon that all stars move anti-clockwise around Polaris in the northern hemisphere. Tests of the proposed adjustment procedure in a satellite laser ranging （SLR）system demonstrated the effectiveness and the time saved by using the approach, which greatly facilitates the optimization of a trackin~ svstem.展开更多
Space debris is a major problem for all the nations that are currently active in space. Adopting high-precision measuring techniques will help produce a reliable and accurate catalog for space debris and collision avo...Space debris is a major problem for all the nations that are currently active in space. Adopting high-precision measuring techniques will help produce a reliable and accurate catalog for space debris and collision avoidance. Laser ranging is a kind of real-time measuring technology with high precision for space debris observation. The first space-debris laser-ranging experiment in China was performed at the Shanghai Observatory in July 2008 with a ranging precision of about 60-80 cm. The experi- mental results showed that the return signals from the targets with a range of 900 km were quite strong, with a power of 40W （2J at 20 Hz） using a 10ns pulse width laser at 532 nm wavelength. The performance of the preliminary laser ranging system and the observed results in 2008 and 2010 are also introduced.展开更多
To evaluate the ranging performance of impulse radio ultra wideband （IR-UWB） signals, an experiment is performed in a typical indoor environment. In order to mitigate the ranging error caused by theoretical algorith...To evaluate the ranging performance of impulse radio ultra wideband （IR-UWB） signals, an experiment is performed in a typical indoor environment. In order to mitigate the ranging error caused by theoretical algorithm and practical circuits, one way-time difference of the arrival （OW-TDOA） ranging method and corresponding approaches are proposed and carried out according to the structure of UWB transceivers. Generalized maximum likelihood （GML） estimator based on energy detection is applied for the time of arrival estimation. The obtained results show that this UWB ranging system can achieve a relative high ranging accuracy in a multipath environment （e.g. about 5 cm at ranges up to 6 m）, which is practical and meaningful for many sensor applications.展开更多
Satellite laser ranging （SLR） is one of the major space geodetic instruments, which has various applications in earth science. In this paper, we introduce several issues regarding the key technology implementation o...Satellite laser ranging （SLR） is one of the major space geodetic instruments, which has various applications in earth science. In this paper, we introduce several issues regarding the key technology implementation of high-repetition-rate SLR system. Compared with traditional technology, using kHz and 8ps pulse width laser component, the data quantity and quality of high-repetition-rate satellite laser ranging （SLR） can be significantly improved. The characteristics of high-repetition-rate laser ranging and the key technologies are presented, including the event timer with the precision of picosecond, the generation of range gate signal, and so on. All of them are based on the Field Programmable Gate Arrays （FPGA） and tested on China mobile SLR system-TROS1000. Finally, the observations of satellite Beacon-C are given.展开更多
The mobile satellite laser ranging system TROS1000, successfully developed in 2010, achieves a high repetition rate and enables daytime laser ranging. Its measurement range has reached up to 36000 km with an accuracy ...The mobile satellite laser ranging system TROS1000, successfully developed in 2010, achieves a high repetition rate and enables daytime laser ranging. Its measurement range has reached up to 36000 km with an accuracy as precise as 1 cm. Using recent observations in Wuhan, Jiufeng, Xianning, and Rongcheng, Shandong, we introduce the progress made using this mobile observation system.展开更多
Marine resource exploitation and marine cargo transportation were increasingly frequent. Due to the impact of the marine environment, ships or platforms were affected. In this paper, a servo electric cylinder was used...Marine resource exploitation and marine cargo transportation were increasingly frequent. Due to the impact of the marine environment, ships or platforms were affected. In this paper, a servo electric cylinder was used as a wave compensation actuator to design a wave compensation system. The laser sensor was used to measure the displacement in the direction of the heave platform, and the obtained displacement was applied to the wave compensation in the heave direction to verify the feasibility of the compensation system.展开更多
A high-precision pseudo-noise ranging system is often required in satellite-formation missions. But in an actual PN ranging system, digital signal processing limits the ranging accuracy, only level up with meter-scale...A high-precision pseudo-noise ranging system is often required in satellite-formation missions. But in an actual PN ranging system, digital signal processing limits the ranging accuracy, only level up with meter-scale. Using non-integer chip to sample time ratio, noncommensurate sampling was seen as an effective solution to cope with the drawback of digital effects. However, researchers only paid attention to selecting specific ratios or giving a simulation model to verify the effectiveness of the noncommensurate ratios. A qualitative analysis model is proposed to characterize the relationship between the range accuracy and the noncommensurate sampling parameters. Moreover, a method is also presented which can be used to choose the noncommensurate ratio and the correlation length to get higher phase delay distinguishability and lower range jitter. The simulation results indicate the correctness of our analyses and the optimal ranging accuracy can be up to centimeter-level with the proposed approach.展开更多
Collimating lenses are an important component of laser ranging systems,and high overload environments severely affect the beam shaping effect of such lenses.This study proposes a buffer isolation method on the basis o...Collimating lenses are an important component of laser ranging systems,and high overload environments severely affect the beam shaping effect of such lenses.This study proposes a buffer isolation method on the basis of impact stress wave attenuation theory for collimating lens spacers,ANSYS finite element software was applied to simulate the high load dynamics of collimating lenses,and the buffer isolation performance of different materials and composite structures was compared and analysed.Optical simulation analysis of the collimating lenses under different buffer conditions was performed using ZEMAX software to study the mechanism by which a high overload affects the collimating lenses.High overload and optical shaping experiments based on theoretical analysis were further conducted.Results showed the superiority of butadiene rubber to polytetrafluoroethylene after application of 70000 g impact acceleration.The combination-gasket method was superior to the single-gasket method,and the sandwich combination-gasket method was superior to the double-layer combination-gasket method.展开更多
The phase of cross-correlation function of two different normal modes contains source range information, which can be extracted by warping transform due to the dispersive characteristics of the shallow water waveguide...The phase of cross-correlation function of two different normal modes contains source range information, which can be extracted by warping transform due to the dispersive characteristics of the shallow water waveguide. The autocorrelation function of the received pressure or particle velocity contains both modal autocorrelation component(MAC) and modal cross-correlation component(MCC), with the former part usually treated as interference for source ranging. Because the real part of the vertical intensity flux(RPVIF) only contains MCC, a passive impulsive source ranging method based on the frequency warping transform of RPVIF with a single vector receiver in shallow water is presented. Using a waveguide-invariant-based frequency warping operator, the cross-correlation components of two different modes in the vertical intensity flux are warped into separable impulsive sequences, the time delays of which are subsequently used for source ranging. The advantages of source ranging based on warping the vertical intensity flux compared with warping the pressure autocorrelation function are pointed out, and the experiment results are also presented.展开更多
As an important station of International Laser Ranging Service(ILRS),Shanghai Astronomical Observatory(SHAO)has upgraded Satellite Laser Ranging(SLR)system with high repetition rate and achieved some technological pro...As an important station of International Laser Ranging Service(ILRS),Shanghai Astronomical Observatory(SHAO)has upgraded Satellite Laser Ranging(SLR)system with high repetition rate and achieved some technological progress,There are a lot of improvements for overall system performance,such as annual observation passes,measurement precision and quality of observation data.SLR technology with repetition rate of 10 kHz is accomplished firstly in China,and space debris laser ranging technology with200 Hz laser is promoted and proved to be more detective for weak echo,which lead to successful measurement for 40,000 km satellites and space debris within 3000 km.At the same time,SLR based on multi-telescopes and 1064 nm wavelength are planned to make a breakthrough of detection capabilities,and also to expand its application fields.These progresses will be introduced in this paper in detail.展开更多
Over the past 50 years,lunar laser ranging has made great contributions to the understanding of the Earth–Moon system and the tests of general relativity.However,because of the lunar libration,the Apollo and Lunokhod...Over the past 50 years,lunar laser ranging has made great contributions to the understanding of the Earth–Moon system and the tests of general relativity.However,because of the lunar libration,the Apollo and Lunokhod corner-cube retroreflector(CCR)arrays placed on the Moon currently limit the ranging precision to a few centimeters for a single photon received.Therefore,it is necessary to deploy a new retroreflector with a single and large aperture to improve the ranging precision by at least one order of magnitude.Here we present a hollow retroreflector with a 170-mm aperture fabricated using hydroxide-catalysis bonding technology.The precisions of the two dihedral angles are achieved by the mirror processing with a sub-arc-second precision perpendicularity,and the remaining one is adjusted utilizing an auxiliary optical configuration including two autocollimators.The achieved precisions of the three dihedral angles are 0.10 arcsecond,0.30 arc-second,and 0.24 arc-second,indicating the 68.5%return signal intensity of ideal Apollo 11/14 based on the far field diffraction pattern simulation.We anticipate that this hollow CCR can be applied in the new generation of lunar laser ranging.展开更多
Aiming at the problems in a linear frequency modulation continuous wave(LFMCW)ranging lidar system,such as low signal-to-noise in echo beat frequency and difficult extraction of the signal frequency,a method with high...Aiming at the problems in a linear frequency modulation continuous wave(LFMCW)ranging lidar system,such as low signal-to-noise in echo beat frequency and difficult extraction of the signal frequency,a method with high-speed and high accuracy based on field programmable gate array(FPGA)is proposed.Firstly,the laser echo beat signal is sampled by high-speed analog to digital converter(ADC)and then processed in FPGA for data preprocessing.After the signal is processed by the 8192-point FPGA will obtain the frequency spectrum and then apply the frequency spectrum to data processing and adaptive noise signal peak detection.These two steps realize the real-time and accurate extraction process of the target echo beat signal frequency.Finally,the spectrum data is transmitted to the host computer and processed through the external data acquisition board for real-time spectrum display.Experimental results show that data preprocessing and spectrum data processing can effectively suppress DC bias and system modulation noise.Adaptive noise peak detection can accurately divide the threshold contour according to the dynamic noise of the system and realize the detection of target signal peak.When the sampling clock of the system is 100 MHz,the time needed for each calculation of the spectrum is 81.92μs,and the refresh rate of the spectrum reaches 12.2 kHz,which meets the real-time requirements of the system.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)(11673082 and 11903059).
文摘A method is presented for determining instant values of Earth’s polar motion(PM)using a set of lunar laser ranging(LLR)measurements acquired simultaneously by tri-static common view(TCV)at three LLR stations in Europe.We developed a model of the LLR TCV measurements,then formulated the linear equation for solving PM.Although there was no actual TCV event in the data,we conducted a two-phase study to test our method using actual LLR normal points(NPs)acquired by the European stations during 2012-2022.In the first phase,we simulated TCV events and PM solutions.The robustness of our method was assessed by introducing Universal Time(UT1)errors and per-station range errors in this phase.In the second phase,we augmented the actual LLR NPs with simulated data to generate realistic TCV events and solutions,using the‘1+2’and‘2+1’strategies,which differed in terms of data composition.Results indicated that a UT1 error of 0.1 ms caused PM errors of<18 mas,while a uniform range error of 50 mm resulted in PM errors of<180 mas.In the augmentation phase,the maximum solution errors were 752 and 899 mas,and 88.5% and 91.2% of the solutions were better than the predictions for the‘1+2’and‘2+1’strategies,respectively.The presented approach relies on precise geodetic data,and therefore,it is not intended to replace the traditional method.However,this study demonstrated that instant determination of PM is feasible and robust,although the accuracy requires further enhancement.
文摘To improve the performance of composite pseudo-noise （PN） code clock recovery in a regenerative PN ranging system at a low symbol signal-to-noise ratio （SNR）, a novel chip tracking loop （CTL） used for regenerative PN ranging clock recovery is adopted. The CTL is a modified data transition tracking loop （DTTL）. The difference between them is that the Q channel output of the CTL is directly multiplied by a clock component, while that of the DTTL is multiplied by the Ⅰ channel transition detector output. Under the condition of a quasi-squareware PN ranging code, the tracking （ mean square timing jitter） performance of the CTL is analyzed. The tracking performances of the CTL and the DTTL, are compared over a wide range of symbol SNRs. The result shows that the CTL and the DTTL have the same performance at a large symbol SNR, while at a low symbol SNR, the former offers a noticeable enhancement.
基金Project supported by the Program of One Hundred Talented People of the Chinese Academy of SciencesNational Natural Science Foundation of China(Grant Nos.11434012 and 41561144006)
文摘Sound multipath propagation is very important for target localization and identification in different acoustical zones of deep water. In order to distinguish the multipath characteristics in deep water, the Northwest Pacific Acoustic Experiment was conducted in 2015. A low-frequency horizontal line array towed at the depth of around 150 m on a receiving ship was used to receive the noise radiated by the source ship. During this experiment, a beating-splitting phenomenon in the direct zone was observed through conventional beamforming of the horizontal line array within the frequency band 160 Hz- 360 Hz. In this paper, this phenomenon is explained based on ray theory. In principle, the received signal in the direct zone of deep water arrives from two general paths including a direct one and bottom bounced one, which vary considerably in arrival angles. The split bearings correspond to the contributions of these two paths. The beating-splitting phenomenon is demonstrated by numerical simulations of the bearing-time records and experimental results, and they are well consistent with each other. Then a near-surface source ranging approach based on the arrival angles of direct path and bottom bounced path in the direct zone is presented as an application of bearing splitting and is verified by experimental results. Finally, the applicability of the proposed ranging approach for an underwater source within several hundred meters in depth in the direct zone is also analyzed and demonstrated by simulations.
基金the National Natural Science Foundation of China(61575105,61611140125)Beijing Natural Science Foundation(3182011)Shenzhen Fundamental Research Funding(JCYJ20170412171535171).
文摘Absolute distance measurement is a fundamental technique in mobile and large-scale dimensional metrology.Dual-comb ranging is emerging as a powerful tool that exploits phase resolution and frequency accuracy for high-precision and fast-rate distance measurement.Using two coherent frequency combs,dual-comb ranging allows time and phase response to be measured rapidly.It breaks through the limitations related to the responsive bandwidth,ambiguity range,and dynamic measurement characteristics of conventional ranging tools.This review introduces dual-comb ranging and summarizes the key techniques for realizing this ranging tool.As optical frequency comb technology progresses,dualcomb ranging shows promise for various professional applications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61172138 and 61401340)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20130203120004)the Fundamental Research Funds for the Central Universities,China(Grant Nos.201413B,201412B,and JB141303)
文摘To improve the link efficiency and decrease the payloads in space explorations, a novel simultaneous communication and ranging method based on x-ray communication（XCOM） is proposed in this paper. A delicate signal symbol structure is utilized to achieve simultaneous data transmission and range measurement. With the designed symbol structure, the ranging information is imbedded into the communication signal and transmitted with it simultaneously. The range measurement is realized by the two-way transmission of the range information. To illustrate the proposed method, firstly, the principle of the method is introduced and the signal processing procedure is presented. Then, the performance of the proposed method is analyzed theoretically in various aspects, including the acquisition probability, the bit error rate, the ranging jitter,etc. Besides, numerical experiments are conducted to verify the proposed method and evaluate the system performance.The simulation results show that the proposed method is feasible and that the system performance is influenced by the parameters concerning the signal symbol structure. Compared with the previous methods, the proposed method improves the link efficiency and is beneficial for system miniaturization and integration, which could provide a potential option for future deep space explorations.
基金supported by the National Natural Science Foundation of China(41274189)
文摘In a satellite laser ranging telescope system, well-aligned encoders of the elevation and azimuth axes are essential for tracking objects. However, it is very difficult and time-consuming to correct the bias between the absolute-position indices of the encoders and the astronomical coordinates, especially in the absence of a finder scope for our system. To solve this problem, a method is presented based on the phenomenon that all stars move anti-clockwise around Polaris in the northern hemisphere. Tests of the proposed adjustment procedure in a satellite laser ranging （SLR）system demonstrated the effectiveness and the time saved by using the approach, which greatly facilitates the optimization of a trackin~ svstem.
基金supported by the Chinese Space Agency and the Instrument Developing Project of the Chinese Academy of Sciences (Grant No. 2920100701)
文摘Space debris is a major problem for all the nations that are currently active in space. Adopting high-precision measuring techniques will help produce a reliable and accurate catalog for space debris and collision avoidance. Laser ranging is a kind of real-time measuring technology with high precision for space debris observation. The first space-debris laser-ranging experiment in China was performed at the Shanghai Observatory in July 2008 with a ranging precision of about 60-80 cm. The experi- mental results showed that the return signals from the targets with a range of 900 km were quite strong, with a power of 40W （2J at 20 Hz） using a 10ns pulse width laser at 532 nm wavelength. The performance of the preliminary laser ranging system and the observed results in 2008 and 2010 are also introduced.
基金supported by the Key Program of the National Natural Science Foundation of China(60432040)the Program of National Natural Science Foundation of China(60702034).
文摘To evaluate the ranging performance of impulse radio ultra wideband （IR-UWB） signals, an experiment is performed in a typical indoor environment. In order to mitigate the ranging error caused by theoretical algorithm and practical circuits, one way-time difference of the arrival （OW-TDOA） ranging method and corresponding approaches are proposed and carried out according to the structure of UWB transceivers. Generalized maximum likelihood （GML） estimator based on energy detection is applied for the time of arrival estimation. The obtained results show that this UWB ranging system can achieve a relative high ranging accuracy in a multipath environment （e.g. about 5 cm at ranges up to 6 m）, which is practical and meaningful for many sensor applications.
基金supported by the National Natural Science Foundation of China(40774013)
文摘Satellite laser ranging （SLR） is one of the major space geodetic instruments, which has various applications in earth science. In this paper, we introduce several issues regarding the key technology implementation of high-repetition-rate SLR system. Compared with traditional technology, using kHz and 8ps pulse width laser component, the data quantity and quality of high-repetition-rate satellite laser ranging （SLR） can be significantly improved. The characteristics of high-repetition-rate laser ranging and the key technologies are presented, including the event timer with the precision of picosecond, the generation of range gate signal, and so on. All of them are based on the Field Programmable Gate Arrays （FPGA） and tested on China mobile SLR system-TROS1000. Finally, the observations of satellite Beacon-C are given.
基金supported by the National Natural Science Foundation of China (40774013, 41274189)
文摘The mobile satellite laser ranging system TROS1000, successfully developed in 2010, achieves a high repetition rate and enables daytime laser ranging. Its measurement range has reached up to 36000 km with an accuracy as precise as 1 cm. Using recent observations in Wuhan, Jiufeng, Xianning, and Rongcheng, Shandong, we introduce the progress made using this mobile observation system.
文摘Marine resource exploitation and marine cargo transportation were increasingly frequent. Due to the impact of the marine environment, ships or platforms were affected. In this paper, a servo electric cylinder was used as a wave compensation actuator to design a wave compensation system. The laser sensor was used to measure the displacement in the direction of the heave platform, and the obtained displacement was applied to the wave compensation in the heave direction to verify the feasibility of the compensation system.
基金Project(60904090) supported by the National Natural Science Foundation of China
文摘A high-precision pseudo-noise ranging system is often required in satellite-formation missions. But in an actual PN ranging system, digital signal processing limits the ranging accuracy, only level up with meter-scale. Using non-integer chip to sample time ratio, noncommensurate sampling was seen as an effective solution to cope with the drawback of digital effects. However, researchers only paid attention to selecting specific ratios or giving a simulation model to verify the effectiveness of the noncommensurate ratios. A qualitative analysis model is proposed to characterize the relationship between the range accuracy and the noncommensurate sampling parameters. Moreover, a method is also presented which can be used to choose the noncommensurate ratio and the correlation length to get higher phase delay distinguishability and lower range jitter. The simulation results indicate the correctness of our analyses and the optimal ranging accuracy can be up to centimeter-level with the proposed approach.
基金National Natural Science Foundation of China(51605227)the Fundamental Research Funds for the Central Universities(NUST30915011303)。
文摘Collimating lenses are an important component of laser ranging systems,and high overload environments severely affect the beam shaping effect of such lenses.This study proposes a buffer isolation method on the basis of impact stress wave attenuation theory for collimating lens spacers,ANSYS finite element software was applied to simulate the high load dynamics of collimating lenses,and the buffer isolation performance of different materials and composite structures was compared and analysed.Optical simulation analysis of the collimating lenses under different buffer conditions was performed using ZEMAX software to study the mechanism by which a high overload affects the collimating lenses.High overload and optical shaping experiments based on theoretical analysis were further conducted.Results showed the superiority of butadiene rubber to polytetrafluoroethylene after application of 70000 g impact acceleration.The combination-gasket method was superior to the single-gasket method,and the sandwich combination-gasket method was superior to the double-layer combination-gasket method.
基金Project supported by the Frontier Science Research of Chinese Academy of Sciences(Grant No.QYZDY-SSW-SLH005)
文摘The phase of cross-correlation function of two different normal modes contains source range information, which can be extracted by warping transform due to the dispersive characteristics of the shallow water waveguide. The autocorrelation function of the received pressure or particle velocity contains both modal autocorrelation component(MAC) and modal cross-correlation component(MCC), with the former part usually treated as interference for source ranging. Because the real part of the vertical intensity flux(RPVIF) only contains MCC, a passive impulsive source ranging method based on the frequency warping transform of RPVIF with a single vector receiver in shallow water is presented. Using a waveguide-invariant-based frequency warping operator, the cross-correlation components of two different modes in the vertical intensity flux are warped into separable impulsive sequences, the time delays of which are subsequently used for source ranging. The advantages of source ranging based on warping the vertical intensity flux compared with warping the pressure autocorrelation function are pointed out, and the experiment results are also presented.
基金The National Natural Science Foundation (NSF) of China (U1631240 and 11503068)CAS Key Technology Talent Program
文摘As an important station of International Laser Ranging Service(ILRS),Shanghai Astronomical Observatory(SHAO)has upgraded Satellite Laser Ranging(SLR)system with high repetition rate and achieved some technological progress,There are a lot of improvements for overall system performance,such as annual observation passes,measurement precision and quality of observation data.SLR technology with repetition rate of 10 kHz is accomplished firstly in China,and space debris laser ranging technology with200 Hz laser is promoted and proved to be more detective for weak echo,which lead to successful measurement for 40,000 km satellites and space debris within 3000 km.At the same time,SLR based on multi-telescopes and 1064 nm wavelength are planned to make a breakthrough of detection capabilities,and also to expand its application fields.These progresses will be introduced in this paper in detail.
基金supported by the National Natural Science Foundation of China(Grant Nos.11655001 and 11605065)
文摘Over the past 50 years,lunar laser ranging has made great contributions to the understanding of the Earth–Moon system and the tests of general relativity.However,because of the lunar libration,the Apollo and Lunokhod corner-cube retroreflector(CCR)arrays placed on the Moon currently limit the ranging precision to a few centimeters for a single photon received.Therefore,it is necessary to deploy a new retroreflector with a single and large aperture to improve the ranging precision by at least one order of magnitude.Here we present a hollow retroreflector with a 170-mm aperture fabricated using hydroxide-catalysis bonding technology.The precisions of the two dihedral angles are achieved by the mirror processing with a sub-arc-second precision perpendicularity,and the remaining one is adjusted utilizing an auxiliary optical configuration including two autocollimators.The achieved precisions of the three dihedral angles are 0.10 arcsecond,0.30 arc-second,and 0.24 arc-second,indicating the 68.5%return signal intensity of ideal Apollo 11/14 based on the far field diffraction pattern simulation.We anticipate that this hollow CCR can be applied in the new generation of lunar laser ranging.
基金Supported by Joint Astronomical Fund of National Natural Science Foundation of China(U1831133)Key Laboratory of Space Active Opto-electronics Technology of Chinese Academy of Sciences(20212DKF4)Shanghai Natural Science Foundation(17ZR1443500)
文摘Aiming at the problems in a linear frequency modulation continuous wave(LFMCW)ranging lidar system,such as low signal-to-noise in echo beat frequency and difficult extraction of the signal frequency,a method with high-speed and high accuracy based on field programmable gate array(FPGA)is proposed.Firstly,the laser echo beat signal is sampled by high-speed analog to digital converter(ADC)and then processed in FPGA for data preprocessing.After the signal is processed by the 8192-point FPGA will obtain the frequency spectrum and then apply the frequency spectrum to data processing and adaptive noise signal peak detection.These two steps realize the real-time and accurate extraction process of the target echo beat signal frequency.Finally,the spectrum data is transmitted to the host computer and processed through the external data acquisition board for real-time spectrum display.Experimental results show that data preprocessing and spectrum data processing can effectively suppress DC bias and system modulation noise.Adaptive noise peak detection can accurately divide the threshold contour according to the dynamic noise of the system and realize the detection of target signal peak.When the sampling clock of the system is 100 MHz,the time needed for each calculation of the spectrum is 81.92μs,and the refresh rate of the spectrum reaches 12.2 kHz,which meets the real-time requirements of the system.
