Subjects: Astronomy submitted time 2025-07-02 Cooperative journals: 《天文学进展》
Abstract： Over the past two years, China has achieved significant breakthroughs in the development of infrared detectors. Guided by the demands of astronomical observation, we have conducted comprehensive tests on all astronomical detection parameters of the infrared detector and obtained key indicators such as readout noise, dark current, full well capacity, dynamic range, nonlinearity, nonuniformity, and quantum efficiency. These tests have enabled us to assess the detector’s capabilities in infrared astronomy. Additionally, we utilized the 1.56 m Telescope at the Shanghai Astronomical Observatory’s Sheshan site for real-world observations. These observations confirmed that the detector’s ground-based application performance is comparable to that of foreign detectors, indicating that China’s infrared astronomy has advanced to a stage where it can employ domestically developed infrared detectors for astronomical observations in specific near-infrared bands.
Subjects: Astronomy submitted time 2025-07-02 Cooperative journals: 《天文学进展》
Abstract： As one of the important methods to detect the cosmic reionization epoch, the core goal of the low-frequency all-sky total power experiment is to detect the extremely weak neutral hydrogen 21 cm signal during the cosmic reionization period in the all-sky total power spectrum with a spectrum range of 50∼200 MHz. At present, the fast Fourier transform (FFT) is usually used to calculate the power spectrum, and the spectral leakage problem makes it impossible to completely deduct Radio Frequency Interference (RFI), which seriously interferes with the extraction of weak cosmic reionization signals. Polyphase filter banks (PFB) is a technique that evenly divides signals by frequency, which can replace FFT to calculate the power spectrum. In this paper, the basic principle of PFB and its implementation based on compute unified device architecture (CUDA) are introduced, and the performance of PFB and FFT is compared through simulation, and the performance differences of PFB of different orders are compared. Finally, the measured and experimental data are processed to verify the superiority of PFB technology, which provides an effective solution for the spectrum analysis of the all-sky total power experiment.
Subjects: Astronomy submitted time 2025-07-02 Cooperative journals: 《天文学进展》
Abstract： Mantle convection plays a key role in the evolution of terrestrial planets. The latest research progress on mantle convection in terrestrial planets and large satellites is reviewed in this paper with the method of comparative planetology, which concentrates on three main issues, which are (1) Does mantle convection exist within terrestrial planets? (2) If mantle convection exists, what are its convection regime and characteristics? (3) What conditions are required for mantle convection to occur in terrestrial planets? The principal factors that significantly influence mantle convection are also discussed, in#2;cluding the mantle geometry and scale, material property, driving mechanism, fluid viscosity, thermal and kinematic boundary conditions, differentiation and phase transformation. It further addresses mantle convection and convection in ice shell of some large satellites. Elu#2;cidating the causes, mechanisms, and effects of mantle convection across different celestial bodies holds significant implications for understanding the planetary internal dynamics and planetary evolutions.
Subjects: Astronomy submitted time 2025-04-02 Cooperative journals: 《天文学进展》
Abstract： The formation mechanisms of open cluster groups remain unclear due to limited samples and data precision. Therefore, there is a need to expand the sample size of primordial open cluster groups to provide reliable observational constraints for further studies on the formation and evolution mechanism of open clusters. Based on Gaia DR3 data, the parameters of previously reported open clusters have been redetermined. Four new open cluster groups, G1, G2, G3, and G4, were discovered in the Cygnus region based on the spatial distribution and kinematic properties. These four open cluster groups each occupy a distinct spatial region, with member clusters closely adjacent and exhibiting consistent velocities, indicating that they formed within the same giant molecular cloud. The star formation durations of the four open cluster groups are 13 Ma, 29 Ma, 10 Ma, and 12 Ma, respectively. These durations align with the timescales of continuous star formation events, suggesting that the members of the open cluster group may have formed sequentially. After distance correction using Bayesian methods, G1 and G2 exhibit filamentary distributions, while G3 and G4 are more concentrated. Additionally, some members in G1 and G2 show less apparent interactions, while those in G3 and G4 exhibit significant interactions. Finally, the analysis of the orbital motion of these four open cluster groups within the Milky Way indicates that their members will gradually disperse, eventually evolving into independent open clusters.
Subjects: Astronomy submitted time 2024-12-31 Cooperative journals: 《天文学进展》
Abstract： With the continuous deepening of astronomical research, the construction and operation of the International Astronomical Large Facility (IALF) has increasingly become an essential factor in promoting scientific progress. This study summarizes the current construction and operation mechanism of the International Astronomical Large Devices (IALDs) science regional centers and discusses their roles in data management, scientific cooperation, and user support. Firstly, it introduces the definition of science regional centers and their importance in astronomical research and then analyzes the successful cases of several typical regional centers, including the Low-Frequency Array (LOFAR) telescope and the Atacama Large Millimeter/submillimeter Array (ALMA), emphasizing the impact of infrastructure, technology investments, and management structures on their success. In addition, this study discusses the current challenges, such as resource allocation, data sharing, and cooperation mechanisms, and anticipates future directions and trends. By summarizing the practical experiences at home and abroad, this paper aims to provide references and lessons for the construction and operation of future scientific regional centers for astronomical mega facilities.
Subjects: Astronomy submitted time 2024-10-10 Cooperative journals: 《天文学进展》
Abstract： In this paper, we examine the influence of the surrounding mountains around the experimental antenna on the extraction of signals in the global 21 cm experiment. The change in antenna gains introduced by varying the height of the mountain, the angle of slope, the composition of the mountain, the consistency of the composition of the mountain, the distance from the mountain to the antenna, and other factors of the model is simulated using the moment hybrid numerical algorithm. We further analyze the impact of these factors on the antenna in obtaining neutral hydrogen signals. The results show that the characteristics of the mountain, including its height, distance from the observation point, inclination angle, composition material, and surface composition consistency, not only affect the antenna gain, but also further affect the polynomial fitting subtraction of the foreground in the experiment. Specifically, for antenna gain, when the mountain height remains unchanged, the farther the mountain is from the antenna, the smaller the effect on antenna gain.
Subjects: Astronomy submitted time 2024-10-10 Cooperative journals: 《天文学进展》
Abstract： The fourth phase of the Lunar Exploration Project will launch the Chang’e-7 relay satellite, carrying a 4.2-meter parabolic telescope. Together with ground-based radio telescope, it will form the first Lunar Orbit Space VLBI system. Space VLBI is influenced by the relay satellite’s orbit perturbations and onboard equipment delays, and the predicted time delay model for radio source may not effectively guide the normal operation of the correlator. It is necessary to employ a fringe search based on actual measurement signals to find a high-precision time delay model that meets the requirements. Currently, fringe searches are accelerated using CPU cluster, but the search time is prolonged, lasting up to 2700s, which fails to meet the practical engineering requirements. A space VLBI radio source fringe search algorithm based on GPU cluster is proposed. The research involves studying task distribution for load balancing on GPU cluster and parallel implementation of corre#2;lation modules and residual value search modules. Validated with RadioAstron observation data, the processing speed of GPU cluster has improved about 27.0 times compared to CPU cluster. The research outcomes can be applied to subsequent space VLBI projects.
Subjects: Astronomy submitted time 2024-07-03 Cooperative journals: 《天文学进展》
Abstract： In 2019, the Event Horizon Telescope (EHT) used very long baseline interfer#2;ometry to capture the first-ever image of a black hole. To meet the demand for dynamic imaging of black holes, the next generation of the EHT array will incorporate more stations located in the eastern hemisphere. The Tibet Plateau in China is the highest region on average elevation in the world, and its unique meteorological conditions make it a potential candidate for site selection. In this paper, we conducted a preliminary evaluation of the high-frequency radio observation conditions in the Tibet Plateau region using MERRA-2 data from the past three years (2019―2021), consisting of 759 data grid points. Based on the opacity performance of these grid points in different seasons, we selected the optimal grid points for each of the four seasons. In addition to the meteorological conditions of the already established sites, we evaluated these four grid points based on three meteorological factors: precipitable water vapor (PWV), liquid water path (LWP), and wind speed. Furthermore, using the meteorological conditions of the Atacama Large Millimeter/submillimeter Array (ALMA) as a standard, we defined the preliminary range for the site selection of the new station.
Subjects: Astronomy submitted time 2024-07-03 Cooperative journals: 《天文学进展》
FANG Wen-feng
YAO Song
YU Yong
WANG Lei
SHAN Xing-mei
SHEN Lu-run
WANG Qi
CHEN Zhen-dong
LIN Qing
DU Zhi-mao
YAO Jia-wen
Abstract： The Double-focus One-meter Telescope, located at the Wangshu Observatory of the Shanghai Astronomy Museum, is currently the largest aperture telescope dedicated to popular science in China. The telescope adopts a dual-focus design scheme that allows manual switching between the prime and Nasmyth focus. The Nasmyth focus primarily serves visual observations for popular science, while the prime focus is equipped with a scientific-grade CMOS sensor, offering a field of view of 1.5 ◦ × 1.1 ◦ . The larger field of view is suitable not only for live broadcast events but also for extensive research on various topics such as surveys of novae and supernovae, investigations of small celestial bodies in the solar system, and monitoring of artificial satellites. The astrometric precison at the prime focus of the telescope was analyzed and evaluated based on actual observation data. The results indicate that for star images with a signal-to-noise ratio greater than 5, the repeatability of measured coordinates is better than 0.1 pixel. When the signal-to-noise ratio is 30, the repeatability improves to better than 0.05 pixel. Using the high-precision Gaia DR3 catalog as the reference, the analysis reveals the presence of significant non-linear characteristics in the observation images obtained at the prime focus of the telescope. Consequently, a 3-order model (20-parameter) is necessary for data reduction. For the test observation data, the observational precision for stars brighter than 15th magnitude is approximately 0.05′′ , with the precision decreasing gradually as the magnitude becomes fainter. The observational precision for 17.5th magnitude is around 0.1′′ .
Subjects: Astronomy submitted time 2024-07-03 Cooperative journals: 《天文学进展》
Abstract： The annual signals in the Global Navigation Satellite System (GNSS) surface deformation time series include not only load deformation but also thermal expansion caused by the change of Earth’s surficial temperature. Using a global three-dimensional thermoe#2;lastic deformation model, the thermal expansion effects of 39 crustal movement observation network of China (CMONOC) stations in the U, E, and N directions in southwestern China are estimated. Then the consistency between GNSS time series (before and after correcting thermal expansion effects) and load deformation derived from satellite gravity observations is analyzed, by comparing GNSS results with the calculations from Gravity Recovery and Climate Experience (GRACE) and GRACE Follow-On (GRACE-FO). After correcting for thermal expansion effects, the results indicate that the correspondence between the vertical component (U direction) of GNSS and the GRACE/GRACE-FO results is slightly weakened. On the horizontal component, the consistence in the E direction improves to some extent, but there exists a significant decrease in the N direction. The results presented in this paper in the southwest region are inconsistent with existing global or large-scale regional studies, indicating that the accuracy of estimating thermal expansion effects in different regions by using global thermoelastic deformation models needs to be further evaluated, and its impact on three-dimensional surface deformation is also worth further in-depth research.
Subjects: Astronomy submitted time 2024-07-03 Cooperative journals: 《天文学进展》
Abstract： We have collected and analyzed the limited the Very Large Array (VLA) archival data of J1458+4121, which is a possible candidate of neutrino event IC-220624A, based on which we observed the source first time with the Very Long Baseline Array (VLBA) at L and C bands. Through data processing and analysis, we obtained the VLBA images of J1458+4121. In addition, its more precise coordinate (α=14:58:20.772, δ=41:21:01.911) was obtained by phase reference technique. The total flux density observed by VLA decreases from 1.4 to 8.4 GHz, so its radio spectrum may be power-law. However, the total flux density observed by VLBA shows an increasing trend from 1.5 to 5 GHz, which means an inversted spectrum in the GHz band. Therefore, it is highly likely that J1458+4121 is a young radio source, and its neutrino production may be caused by the emergence of a new jet component. The results of this paper are beneficial to the follow-up study of J1458+4121, and extend the focus on neutrino origin from bright blazars to other types of active galactic nuclei.
Subjects: Astronomy submitted time 2024-07-03 Cooperative journals: 《天文学进展》
Abstract： Open clusters are ideal laboratories for studying star formation and evolution. However the pattern of the formation of star clusters remains a fundamental and unresolved question. To explore the formation of star clusters, it is essential to search physically con#2;nected pairs or multiple systems of open clusters that could constrain the theories of star cluster formation. Revealing the properties of binary clusters and cluster groups can also yield important insights into the hierarchical formation of stars. Additionally, binary star clusters and cluster groups provide exceptional opportunities to investigate the formation and evolution patterns of star clusters, which are born in the same molecular cloud and to reveal the connection between the cloud and star clusters in morphological and kinematic properties. This article begins by discussing the selection of samples and the patterns of formation for binary star clusters and cluster groups, providing a concise review of research conducted within the Milky Way, and focusing on recent advancements in this field during the Gaia era.
Subjects: Astronomy submitted time 2024-03-22 Cooperative journals: 《天文学进展》
Abstract： Temperature is one of the key factors influencing the performance of large-scale radio telescopes. Taking the Tianma Radio Telescope (TMRT) as an example, this study investigates the relationship between the temperature of the alidade’s nodes and antenna pointing accuracy. A method is proposed for constructing a correction model for pointing errors based on node temperatures. The pointing error is treated as a linear combination of the alidade’s node temperatures. The number of independent variables is optimized using the temperature sensitivity of the nodes as feature conditions. The pointing test results of the source 2344+8226 near the North Pole are used as the sample set to compare the effec#2;tiveness of the temperature model before and after variable simplification. Both the model calculations and finite element analysis validate the two temperature models, which align with the sample set. Furthermore, to assess model generalization, the performance of the models is compared across four seasons before and after simplification. The results indicate that the simplified temperature model offers improved predictive accuracy. The established node temperature-based pointing error correction model’s rapid calculation outcomes pro#2;vide data for real-time mitigation of thermally induced pointing errors in the moun
Subjects: Astronomy submitted time 2024-03-22 Cooperative journals: 《天文学进展》
Abstract： In this paper, a single panel deformation of the main reflector of a large radio telescope is studied and the six degrees of freedom attitude change of robotics is applied to the deformation of the reflector panel of a large radio telescope. A characterization method of panel deformation based on six degrees of freedom deformation of rigid body is proposed. Based on the six-DOF attitude deformation theory of rigid body, an optical reconstruction technique of antenna panel deformation is proposed in this paper. This technology can reconstruct the deformation of the panel quickly and accurately by the spot image presented by the laser unit consolidated on the panel. In this paper, the mapping relationship between laser spot and antenna panel deformation is deeply explored, and the spatial deformation problem of antenna panel is transformed into the laser spot displacement problem in a finite region. And the light spot image of this scheme is studied, and an effective light spot image processing algorithm is provided. It integrates the image difference method and Canny edge detection algorithm, which can effectively solve the problem of traditional Canny algorithm in dealing with small targets. It also uses the high-precision sub-pixel centroid localization algorithm, which can locate light spots at sub-pixel level. It provides a new and reliable image processing method for antenna panel measurement. This study also provides a new idea and method for improving the accuracy and efficiency of antenna panel measurement.
Subjects: Astronomy submitted time 2024-03-22 Cooperative journals: 《天文学进展》
Abstract： Electromagnetic waves will be absorbed when they pass through the atmo#2;sphere. Electromagnetic waves with some frequencies are absorbed more, while electromag#2;netic waves with other frequencies are absorbed less. The frequency range within which the electromagnetic waves are less absorbed is called the atmospheric window of electro#2;magnetic waves. Similarly, the propagation of electromagnetic waves in the universe will be absorbed by the galactic medium. This paper investigates the problem of the absorption of electromagnetic wave when it propagates in the Milky Way. Our analysis shows that there is a lower cut-off frequency for the electromagnetic waves which can reach the earth passing through the Milky Way. Interestingly, the lower cut-off frequency is different respect to different direction on the celestial sphere, which gives a distribution. This distribution is closely related to the distribution of free electron gas in the Milky Way. We propose to determine the distribution of free electron gas in the Milky Way by measuring the cut-off frequency distribution.
Subjects: Astronomy submitted time 2024-01-05 Cooperative journals: 《天文学进展》
Abstract： Phase fluctuation error is one of the important errors of VLBI orbit system in the lunar exploration and deep space exploration. It is caused by the different spectrum structure of DOR and radio source signal, which leads to the inconsistency of phase fluctuation of receiving equipment. The novel PN-DOR beacon realizes the spectrum structure similar to the radio signal through the spread spectrum modulation of the existing DOR beacon by the pseudo random sequence, which can effectively reduce the phase fluctuation error. This paper studies the calculation methods of phase error and bandwidth synthesis group delay error of PN-DOR beacon in VLBI orbit measurement. On this basis, by comparing the total delay error of PN-DOR and DOR beacon under the same transmission power, the applicable condition of PN-DOR is analyzed.
Subjects: Astronomy submitted time 2024-01-05 Cooperative journals: 《天文学进展》
Abstract： BeiDou navigation satellite system (BDS) is an independent global navigation satellite system (GNSS) developed by China. The three-step strategy was adopted from the very beginning and the third and final step, BDS-3, had been officially announced opera#2;tional on July 31, 2020. An essential and necessary task is to generate precise orbit and clock products in real time, only in this way can BDS-3 constellation be ready for widespread use from ordinary to high-precision real-time applications. In this work, keeping accuracy and efficiency in mind, several experiments are conducted to find an adequate size of tracking networks. It is shown that, up to 60 stations, the accuracy of BDS-3 orbit and clock products can not be improved by increasing the number of tracking stations. Further accuracy im#2;provements should depend on solving some modelling defects such as lack of antenna phase center corrections and imperfection of solar radiation pressure models.
Subjects: Astronomy submitted time 2024-01-05 Cooperative journals: 《天文学进展》
Abstract： The quality and orbit determination accuracy of the primary and backup on#2;board GNSS receivers were studied by using the HY2D satellite’s primary and backup GNSS receiver data from June 1 to 14 and June 19 to 27, 2021 based on reduced-dynamic method. The results showed that: (1) The RMS average values of the phase fitting residuals of the main and backup onboard GPS data were 6.9 mm and 8.2 mm, respectively. (2) The radial difference of the main receiver for a 4-hour arc overlap orbit was 0.2 cm, while the three#2;dimensional position differences was 0.6 cm. The radial difference of the backup receiver was 0.3 cm, while the three-dimensional position difference was 1.7 cm, indicating slightly larger differences from the backup receiver results. (3) The orbit determination accuracies of the primary and backup receivers were verified using precise orbit products provided by CNES, with average radial differences of 0.8 cm and 1.2 cm respectively. (4) The orbit determina#2;tion accuracies of the primary and backup receivers were also verified using observation data from global SLR core stations with elevation angles greater than 20◦ , with the RMS range residuals of 1.51 cm and 2.44 cm. It can be seen that the main and backup dual-frequency GNSS receivers carried by the HY2D satellite can meet the satellite’s centimeter-level radial orbit determination requirements.
Subjects: Astronomy submitted time 2023-12-15 Cooperative journals: 《天文学报》
Abstract： The Square Kilometre Array (SKA) project is an international collaboration to build the world's largest radio telescope, whose sensitivity and measurement speed will be an order of magnitude higher than those of all current radio telescopes. Radio continuum survey is one of the main observation mode of the SKA, and the establishment of a standard map of the survey area based on continuum imaging will provide an important foundation for subsequent astronomical science. The GaLactic and Extragalactic All-sky Murchison Widefield Array survey eXtended (GLEAM-X) is a project of the SKA pilot telescope Murchison Widefield Array (MWA) in 2018---2020. GLEAM-X is a new radio continuum survey project to be carried out with the MWA Phase II expansion array in 2018---2020. The experience of optimizing the imaging pipeline based on the distributed execution framework will help to solve the problem of massive data processing. In this paper, we describe the process steps of GLEAM-X imaging pipeline, integrate and improve it, and realize parallel processing of multiple pipelines on the China SKA Regional Centre Prototype (CSRC-P), and verify the deployment and test the correctness of the imaging pipeline system using GLEAM-X observation data. The GLEAM-X observations were used to validate the deployment of the imaging pipeline system and test its correctness. Then, to optimize the pipelines and improve the processing efficiency, the Data Activated Liu Graph Engine (DALiuGE) was used to integrate the imaging pipelines into the DALiuGE execution framework to automate the distributed parallel processing of the pipelines. Performance tests and results analysis show that the optimized imaging pipeline based on the DALiuGE execution framework has better performance, more flexible adaptability and scalability than the traditional parallel approach, and can support future large-scale continuum imaging experiments during the first phase of SKA commissioning.
Subjects: Astronomy submitted time 2023-12-13 Cooperative journals: 《天文学进展》
Abstract： This paper discusses the mass-energy relationship proposed by Einstein. That equations suggests the possibility that energy and matter may be converted into each other. It is well known that matter can be converted into energy via nuclear reaction. But whether energy can be converted into matter in some conditions? This paper discusses this issue.The relevant experiments in particle physics are reviewed. Especially, there is one type of model about mass loading in black hole jets. We suggest that this model likely serves as an example of energy-to-matter conversion.
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