查看更多>>摘要：This paper provides a comprehensive overview of the development of Lunar Laser Ranging(LLR),covering key components such as ground observatories,lunar retro-reflectors,and data formats.The paper details the evolution of LLR experiments conducted by some major world-class observatories,with a particular focus on addressing critical issues associated with LLR technology.Additionally,the article highlights the latest advancements in the field,elucidating scientific achievements derived from LLR data,including its contributions to gravitational theory,Earth Orientation Parameters,lunar physics exploration,and lunar librations.The review summarizes new challenges in LLR modeling and concludes with prospects for the future development of LLR.
查看更多>>摘要：An observation control system is the foundation to support automatic observations by any radio telescope.Traditional observation control systems are usually coded using a compiled language,which is of higher efficiency compared with interpreted languages.Indeed,observation control systems are usually programmed using the C or C++languages.However,the high execution efficiency of C/C++is at the cost of a long development cycle,which is not only time consuming but also requires considerable skills for the developers.The development of computer hardware performance,as well as the optimization of the just-in-time compiler for new interpreted languages such as Python,provides a good balance between execution and development efficiency.In this paper,we introduce the observation control system developed for the Kunming 40-meter radio telescope run by Yunnan Observatories,Chinese Academy of Sciences.The system is developed mainly with the Python language,and we have optimized computationally intensive components with C++.We demonstrate that it is possible to achieve the required functionality and control precision with such a Python-C++programming paradigm.The performance of the control system is also assessed in this paper,demonstrating that satisfactory pointing accuracy and user experience can be attained.
查看更多>>摘要：We explore an end-to-end wavefront sensing approach based on deep learning,which aims to deal with the high-order turbulence and the discontinuous aberration caused by optical system obstructions commonly encountered in real-world ground-based telescope observations.We have considered factors such as the entrance pupil wavefront containing high-order turbulence and discontinuous aberrations due to obstruction by the secondary mirror and spider,realistically simulating the observation conditions of ground-based telescopes.By comparing with the Marechal criterion(0.075λ),we validate the effectiveness of the proposed approach.Experimental results show that the deep learning wavefront sensing approach can correct the distorted wavefront affect by high-order turbulence to close to the diffraction limit.We also analyze the limitations of this approach,using the direct zonal phase output method,where the residual wavefront stems from the fitting error.Furthermore,we have explored the wavefront reconstruction accuracy of different noise intensities and the central obstruction ratios.Within a noise intensity range of 1%-1.9%,the root mean square error(RMSE)of the residual wavefront is less than Marechal criterion.In the range of central obstruction ratios from 0.0 to 0.3 commonly used in ground-based telescopes,the RMSE of the residual wavefront is greater than 0.039λ and less than 0.041λ.This research provides an efficient and valid wavefront sensing approach for high-resolution observation with ground-based telescopes.
查看更多>>摘要：Radio astronomy necessitates radio frequency bands that are both stable and free from interference at observatory locations.To comprehensively evaluate the radio environment at radio observatories,we employ Monte Carlo methods to assess the quality of observational data and predict potential interference.With an extensive dataset,we used an algorithm to find the interference threshold within the L-band,automatically identifying disruptive signals.Monte Carlo simulations were conducted to estimate whether these interference signals surpass a predetermined threshold of the total observation period,facilitating a detailed analysis of the interference profile.A Monte Carlo analysis was used on 83 hours of continuous monitoring data using a wireless environment testing system,to forecast the proportion of time during which interference signals would surpass established harmful thresholds.Our findings indicate that,within the L-band spectrum at Fenghuang Hill,Kunming City,Yunnan Province,the incidence of interference within the frequency ranges of 1330-1440 MHz,1610-1613 MHz,and 1660-1670 MHz is acceptably low,with respective confidence levels of 96.9%,97.4%,and 97.4%that the proportion of time these interference signals occupy does not exceed 5%of the total observational time,as stipulated by the International Telecommunication Union.Conversely,the confidence level for the 1718-1722 MHz band not exceeding 5%of the total observational time is significantly lower at 88.5%.This study offers a valuable tool for assessing the radio environment in radio astronomy research and provides a foundational basis for the scientific management and safeguarding of radio frequency bands.
查看更多>>摘要：We present preliminary investigations of a potential optics system for wideband X-ray telescopes.The optical design adopts the conical approximation of the Wolter-I configuration and a combination of multilayer coatings and silicon pore optics.The total number of mirror modules is 79,distributed in 8 rows with the radii at the intersection plane between 250 mm and 500 mm.The optimization of the total effective area using the figure of merits method suggests that the focal length is 30 m and the mirror coating is a combination of the W/Si and Pt/C multilayers.This fulfills the on-axis effective area requirements of 2000 cm2 at 10 keV and 300 cm2 at 60 keV and provides a broad energy response between 3 keV and 78.4 keV.With the current geometry and coating compositions,we implement a mass modeling of the telescope in Geant4 to predict mirror performances via the ray-tracing algorithm,including the angular resolution and effective area.With the presumed metrological data as input,this can provide precision and finishing requirements for the manufacture of optics.This work demonstrates the feasibility of combining multilayer coatings and silicon pore optics for potential use in wideband X-ray telescopes and advances the development and progress of such missions.
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