The surface particle size and distribution characteristics of celestial bodies (e.g.,the Moon,asteroids,etc.) will affect the interpretation of hyperspectral remote sensing data and the implementation of sampling miss...The surface particle size and distribution characteristics of celestial bodies (e.g.,the Moon,asteroids,etc.) will affect the interpretation of hyperspectral remote sensing data and the implementation of sampling missions.Currently,the estimation of the surface particle sizes is mainly focusing on interpreting the thermal inertia with the infrared spectral data from ground-based or space telescopes,but this method show distinct errors compared with the imaging results of the orbiter.By analyzing some thermal infrared spectral data,a relationship between the particle sizes of the main rockforming minerals (e.g.pyroxene,feldspar,olivine) and the slopes of their thermal infrared spectrum was found.Based on this relationship,a preliminary model for estimating the grain sizes (~30–300μm) of lunar or S-type asteroids’surfaces which are silicate minerals dominated was established,and the correlation coefficients (R^(2)) for most of the rock-forming minerals were better than 90%.Six observational datasets of natural lunar and terrestrial samples are used to validate the model,and the results show a systematical overestimation of the ground-truth particle sizes,the potential causes are analyzed and an additional correction is used to eliminate the overestimation of the particle size prediction.These results are expected to provide guidance for interpretation of lunar and S-type asteroid surface sampling and spectral data.展开更多
Nowadays, astronomy has entered the era of Time-Domain Astronomy, and the study of the time-varying light curves of various types of objects is of great significance in revealing the physical properties and evolutiona...Nowadays, astronomy has entered the era of Time-Domain Astronomy, and the study of the time-varying light curves of various types of objects is of great significance in revealing the physical properties and evolutionary history of celestial bodies. The Ground-based Wide Angle Cameras telescope, on which this paper is based, has observed more than 10 million light curves, and the detection of anomalies in the light curves can be used to rapidly detect transient rare phenomena such as microgravity lensing events from the massive data. However, the traditional statistically based anomaly detection methods cannot realize the fast processing of massive data. In this paper, we propose a Discrete Wavelet(DW)-Gate Recurrent Unit-Attention(GRU-Attention) light curve warning model. Wavelet transform has good effect on data noise reduction processing and feature extraction, which can provide richer and more stable input features for a neural network, and the neural network can provide more flexible and powerful output model for wavelet transform. Comparison experiments show an average improvement of 61% compared to the previous pure long-short-term memory unit(LSTM) model, and an average improvement of 53.5% compared to the previous GRU model. The efficiency and accuracy of anomaly detection in previous paper work are not good enough, the method proposed in this paper possesses higher efficiency and accuracy,which incorporates the Attention mechanism to find out the key parts of the light curve that determine the anomalies. These parts are assigned higher weights, and in the actual anomaly detection, the star is detected with83.35% anomalies on average, and the DW-GRU-Attention model is compared with the DW-LSTM model, and the detection result f1 is improved by 5.75% on average, while having less training time, thus providing valuable information and guidance for astronomical observation and research.展开更多
Leighton Chajnantor Telescope(LCT)will be moved from the summit of Maunakea,Hawaii to Chajnantor Plateau,Chile and be refurbished there.Strong wind disturbance at the new site will bring great challenges to the servo ...Leighton Chajnantor Telescope(LCT)will be moved from the summit of Maunakea,Hawaii to Chajnantor Plateau,Chile and be refurbished there.Strong wind disturbance at the new site will bring great challenges to the servo control of LCT.It is necessary and important to develop a simulation platform that behaves as close as possible to the real telescope for testing the performance of the designed servo controller.In this paper,a collaborative simulation platform of LCT based on Adams and Matlab/Simulink is constructed.On this platform,the mechanical structure model of LCT can be integrated with its control system model such that a collaborative simulation of the mechanical structure and the control system of LCT can be conducted.The mechanical structure model of LCT,which contains both rigid body models(i.e.,the mount)and flexible body models(i.e.,the primary reflector),is developed by using Adams.The servo system model and the wind disturbance model are constructed by using Matlab/Simulink.By conducting collaborative simulation,the performances of the servo controller based on the rigid body model and the rigid-flexible coupling model of LCT are compared.The comparison shows that the controller designed based on the rigid body model does not perform well when it is employed to control the rigid-flexible coupling model of LCT.However,by readjusting parameters of the servo controller,its performance can be further improved when applied to the rigid-flexible coupling model.Therefore,an LCT model of integrated mechanical structure and control systems is very helpful for analyzing its performance more accurately and designing a better servo controller.展开更多
基金supported by China’s first Asteroid exploration program and China National Space Administration(CNSA)was also funded by the National Natural Science Foundation of China (NSFC,Grant No.12373068)。
文摘The surface particle size and distribution characteristics of celestial bodies (e.g.,the Moon,asteroids,etc.) will affect the interpretation of hyperspectral remote sensing data and the implementation of sampling missions.Currently,the estimation of the surface particle sizes is mainly focusing on interpreting the thermal inertia with the infrared spectral data from ground-based or space telescopes,but this method show distinct errors compared with the imaging results of the orbiter.By analyzing some thermal infrared spectral data,a relationship between the particle sizes of the main rockforming minerals (e.g.pyroxene,feldspar,olivine) and the slopes of their thermal infrared spectrum was found.Based on this relationship,a preliminary model for estimating the grain sizes (~30–300μm) of lunar or S-type asteroids’surfaces which are silicate minerals dominated was established,and the correlation coefficients (R^(2)) for most of the rock-forming minerals were better than 90%.Six observational datasets of natural lunar and terrestrial samples are used to validate the model,and the results show a systematical overestimation of the ground-truth particle sizes,the potential causes are analyzed and an additional correction is used to eliminate the overestimation of the particle size prediction.These results are expected to provide guidance for interpretation of lunar and S-type asteroid surface sampling and spectral data.
基金supported by the National Key Research and Development Program of China(grant id:2022YFF0711500)the National Natural Science Foundation of China(grant id:11803022 and grant id:1227307712273077)。
文摘Nowadays, astronomy has entered the era of Time-Domain Astronomy, and the study of the time-varying light curves of various types of objects is of great significance in revealing the physical properties and evolutionary history of celestial bodies. The Ground-based Wide Angle Cameras telescope, on which this paper is based, has observed more than 10 million light curves, and the detection of anomalies in the light curves can be used to rapidly detect transient rare phenomena such as microgravity lensing events from the massive data. However, the traditional statistically based anomaly detection methods cannot realize the fast processing of massive data. In this paper, we propose a Discrete Wavelet(DW)-Gate Recurrent Unit-Attention(GRU-Attention) light curve warning model. Wavelet transform has good effect on data noise reduction processing and feature extraction, which can provide richer and more stable input features for a neural network, and the neural network can provide more flexible and powerful output model for wavelet transform. Comparison experiments show an average improvement of 61% compared to the previous pure long-short-term memory unit(LSTM) model, and an average improvement of 53.5% compared to the previous GRU model. The efficiency and accuracy of anomaly detection in previous paper work are not good enough, the method proposed in this paper possesses higher efficiency and accuracy,which incorporates the Attention mechanism to find out the key parts of the light curve that determine the anomalies. These parts are assigned higher weights, and in the actual anomaly detection, the star is detected with83.35% anomalies on average, and the DW-GRU-Attention model is compared with the DW-LSTM model, and the detection result f1 is improved by 5.75% on average, while having less training time, thus providing valuable information and guidance for astronomical observation and research.
文摘Leighton Chajnantor Telescope(LCT)will be moved from the summit of Maunakea,Hawaii to Chajnantor Plateau,Chile and be refurbished there.Strong wind disturbance at the new site will bring great challenges to the servo control of LCT.It is necessary and important to develop a simulation platform that behaves as close as possible to the real telescope for testing the performance of the designed servo controller.In this paper,a collaborative simulation platform of LCT based on Adams and Matlab/Simulink is constructed.On this platform,the mechanical structure model of LCT can be integrated with its control system model such that a collaborative simulation of the mechanical structure and the control system of LCT can be conducted.The mechanical structure model of LCT,which contains both rigid body models(i.e.,the mount)and flexible body models(i.e.,the primary reflector),is developed by using Adams.The servo system model and the wind disturbance model are constructed by using Matlab/Simulink.By conducting collaborative simulation,the performances of the servo controller based on the rigid body model and the rigid-flexible coupling model of LCT are compared.The comparison shows that the controller designed based on the rigid body model does not perform well when it is employed to control the rigid-flexible coupling model of LCT.However,by readjusting parameters of the servo controller,its performance can be further improved when applied to the rigid-flexible coupling model.Therefore,an LCT model of integrated mechanical structure and control systems is very helpful for analyzing its performance more accurately and designing a better servo controller.
