Subjects: Astronomy >> Astrophysics submitted time 2024-01-22
Abstract： Deconvolution of radio astronomy images is a key data processing technique. Its main goal is to remove the effects introduced by the instrument from the observed sky images to recover the original sky images.However, radio interferometer arrays employ sparse interferometric arrays, whose imaging principles differfrom those of optical telescopes. If the sampling points in the UV space are not sufficiently dense, this will lead to insufficient high-resolution information during image reconstruction. Traditional radio astronomy image reconstruction algorithms fail to fundamentally solve the problem of UV space undersampling. This paper adopts the compressed sensing theoretical framework, combines prior knowledge of the sparsity of radio astronomy images, and studies a new radio astronomy image deconvolution algorithm, namely the IUWT-CS-based radio interferometric image reconstruction algorithm. This algorithm transforms the dirty image deconvolution process into a convex optimization problem to find the global minimum. To evaluate the reconstruction performance of this algorithm, we used the OSKAR radio astronomy simulation software package to simulate low SKA1 observations and performed deconvolution processing on the extended radio sources obtained. Experimental results show that, compared with the HOGBOM-CLEAN, MS-CLEAN,and IUWT-FISTA methods, the IUWT-CS method significantly improves the reconstruction quality of radio images and achieves finer denoising and restoration effects.
Peer Review Status:
Awaiting Review
Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-03-28 Cooperative journals: 《中国科学院院刊》
Abstract： In this paper, the connotation of space-time reference and its relationship with space activities are described comprehensively. Time system, celestial reference frame, planetary ephemeris and pulsar timing are outlined. The gap between China and abroad development on space-time reference and its causes are analyzed. At the end, some suggestions for future development in China are proposed.
Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-03-28 Cooperative journals: 《中国科学院院刊》
Abstract： Numerous great discoveries have been made in the field of deep space exploration over the past 50 years, and they deepen our knowledge and synergetic comprehension greatly about the Earth, Planets, and the Solar system. The deep space exploration not only acts as impetus to drive the development of modern science and technology, but also fosters the planetary physics as a new interdiscipline. This study analyzes the background and current status for the discipline of planetary physics, and compares the progress made on the planetary physics of China with that of the other well-developed countries. The relationship of the Chinese planetary physics with the other traditional disciplines, like geophysics, space physics etc., as well as with the projects of deep space missions is elaborated. Based on the current status and developing trend of planetary study, this paper presents possible directions as well as instructive suggestions for the development of Chinese planetary physics in the near future.
Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-03-19 Cooperative journals: 《中国科学院院刊》
Abstract： The Square Kilometre Array (SKA) radio telescope to be built soon is the largest astronomical observing facility, and it is expected to make revolutionary breakthroughs in the major frontiers of natural sciences to answer fundamental questions of origins, such as the origin of the Universe, the origin of life, the origin of the cosmic magnetic field, the nature of gravity, and search for extraterrestrial civilization. The unprecedented power of the SKA, characterized by the extremely high sensitivity, wide field of view, ultra-fast survey speed, super high time, space, and frequency resolutions ensures the leading position of the SKA in radio astronomy in next decades, which also produces a vast amount of observational data at ExaByte (EB) level. The transportation, storage, reading, writing, computing, management, archiving of the SKA-level data and the release of SKA science products have posed serious challenges on the technologies in the field of information and computers. China SKA science team will work together with the information, communication, and computer industry to tackle the challenges of the SKA big data, as not only promotes major original scientific discoveries, but also applies the derived technological achievements to stimulate the national economy.
Subjects: Astronomy >> Astrophysics submitted time 2023-01-06
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Peer Review Status:Awaiting Review
Subjects: Computer Science >> Other Disciplines of Computer Science submitted time 2022-06-28
Abstract：
Data processing of the Square Kilometre Array (SKA) is carried out in pipeline mode, and the execution efficiency of pipeline is an important factor to be considered in SKA data processing. Continuum imaging is one of the main observation modes of SKA and is a prerequisite for many other scientific works. In this paper, we take the imaging pipeline of SKA low-frequency precursor Murchison Widefield Array (MWA), as an example and optimize the parallel processing pipeline on the China SKA Regional Centre prototype (CSRC-P). Previous optimization schemes have focused on a few performance hotspots and lacked systematic optimization of the overall pipeline, resulting in a relatively poor overall speedup ratio. In this paper, we propose a global optimization scheme that combines C++ multi-threading, Python multi-processing, and Shell multi-tasking parallelism for pipelines using multiple programming languages and image datasets that can be processed independently, and verify the accuracy of the optimization results. Experiments show taht the optimized pipeline achieves an overall speedup of 2.7 and 2.4 times on the x86 and ARM nodes of CSRC-P, respectively, and the ARM compute nodes shows good adaptability to SKA applications. The optimization strategies and methods in this paper are also applicable to other SKA applications and will be useful for the scientific operation and future operation of the SKA precursor telescope.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2022-06-28
Abstract：
After years of planning for the next generation of radio telescopes, the Square Kilometer Array (SKA), the construction of the SKA phase one (SKA1) had started in July 2021.After the formal operation of SKA1, it is expected that 750 petabytes of scientifically processed data will be generated every year. The data will be stored at SKA regional centers around the world for further analysis by researchers.In this paper, the models of SKA observation station, central signal processor, scientific data processing and regional center are quantitatively analyzed. Based on the high-priority scientific observation of SKA1, the data flow evaluation at each stage and the demand for computing power of scientific data processing are obtained. Taking the current SKA1-Low and SKA1-Mid arrays as examples, the key factors affecting the layout of interference arrays including resolution, sensitivity and UV coverage are summarized. Finally, OSKAR is used for data simulation of interference array. Through the simulation of SKA1-Mid, the scalability and stability of the system are obtained. Through the simulation of SKA1-Low on CSRC-P, it can be seen that the design of prototype SKA regional center in China has been fully optimized. And the detailed requirements of computing power and the detailed information of data volume are obtained. The SKA's demand for data processing, computing and storage also requires a combination of technologies and interdisciplinary efforts from areas such as electronics, communication, information technology and computer.
Peer Review Status:Awaiting Review
Subjects: Astronomy >> Astrophysical processes submitted time 2022-06-28
Abstract：
The Square Kilometer Array (SKA) is the largest radio telescope, and the data generated by its observations will be transmitted from Australia and South Africa to the scientific data processing center about one hundred kilometers away at first, and then distributed to various SKA Regional Centres(SRC) with a distance of tens of thousands of kilometers through high-speed network.In the SKA Phase One (SKA1) stage with a scale of 10\% of SKA, it is estimated that about 750PB of data needs to be distributed to each SRC through a network of at least 100Gbps each year. Such high network bandwidth and data scale bring great challenges to data transmission and distribution. This paper analyzes different network protocols such as TCP/UDP/HTTP and uses different software in the field of radio astronomy for testing and research, and then the optimal transmission scheme parameters under the current infrastructure of 10Gbps network are obtained. In this paper, the factors affecting high-speed transmission are discussed, and the corresponding performance optimization strategies are given.Before the real observation data of SKA1 is generated, it will provide the technical foundation for the network construction and layout of China's SKA regional center. The technical details and methods described are available for reference and use in relevant scientific applications. Finally, the challenges of future SKA network requirements are discussed and prospected.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Geochemistry submitted time 2019-04-10
Abstract： " In the past two decades, Global Navigation Satellite System-Reflectometry (GNSS-R) has emerged as a new remote sensing technique for soil moisture monitoring. Some experiments showed that the antenna of V polarization is more favorable to receive the reflected signals, and the interference pattern technique (IPT) was used for soil moisture and other geophysical parameters retrieval. Meanwhile, the lower satellite elevation angles are most impacted by the multipath. However, electromagnetic theoretical properties are not clear for GNSS-R soil moisture retrieval. In this paper, the Advanced Integral Equation Model (AIEM) is employed using the wave synthesis technique to simulate different polarimetric scattering at the specular directions. Results show when the incidence angles are larger than 70º, scattering at RR polarization (The transmitted signal is Right Hand Circular Polarization (RHCP), while the received one is also RHCP) is larger than that one at LR polarization (The transmitted signal is RHCP, while the received one is Left Hand Circular Polarization (LHCP)), while scattering at LR polarization is larger than that at RR polarization for the other incident angles（1º~70º）. There is an apparent dip for VV and VR scattering due to the Brewster angle, which will result in the notch in the final receiving power and this phenomenon can be used for soil moisture retrieval or vegetation corrections. The volumetric soil moisture (vms) effects on their scattering are also presented. The larger soil moisture will result in lower scattering at RR polarization, and this is very different from the scattering of the other polarizations. It is interesting to note that the surface correlation function only affects the amplitudes of the scattering coefficients at much less level, but it has no effects on the angular trends of RR and LR polarizations.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Geodestics submitted time 2019-04-10
Abstract： " GNSS-R is a new promising remote sensing technique, which utilizes the reflected signals of GNSS constellation to remotely sense the ocean or land surface. At present, most of the existing research are based on the experimental observations, few theoretical studies have been carried out. This paper has developed a fully polarization GNSS-R delay Doppler map for land geophysical parameters study. This theoretical model was based on the ocean surface GPS scattering model, after the modifications, it has been used for the land surface. As for the calculations of land geophysical parameters (bare soil and vegetation), random surface scattering model and the first order radiation transfer equation model were used. Effects of bare soil and vegetation parameters on the delay Doppler maps were simulated. In order to use the polarization information for backward inversion, our developed theoretical model has the ability of fully polarizations calculations, i.e. RR, LR, HR and VR pol. This theoretical model is a mechanism tool for the data explanation of space borne mission, experimental campaign design, data simulations and the backward inversion algorithm development. "
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Geodestics submitted time 2019-04-10
Abstract： " GNSS-R has been emerged as a new and promising remote sensing technique in recent years. Due the strong penitration properties of L band microwave length, it is suitable to monitor soil moisture using this technique. According to different remote sening platforms, progresses of soil moisture monitoring using GNSS-R technique with ground-based, tower-based, airborne and space borne platforms are presented in this paper, while a detail review of GNSS-R joint with microwave radiometer is also given in this paper. "
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Geodestics submitted time 2019-04-04
Abstract： " In order to extend the applications GNSS-R/IR（GNSS-Reflectometry /Interferometric Reflectometry ) remote sensing technique to soil freeze/thaw process detection, soil(frozen/thawn) mixing permittivity models are employed to calculate the soil permittivity. Bistatic full-polarizationcoherentscattering model and random roughness surface scattering model are used to calculate the coherent and non-coherent scattering, which result in the variations of GPS multipath observables and DDM（Delay Doppler Map） waveforms, respectively. When the soil freeze/thaw process occurs, theoretical simulations indicate that soil freeze/thaw process induce the abrupt permittivity changes and affect the obvious variations of GNSS-R/IR signals.In this way, theoreticalfundamentals for soil freeze/thaw process detections are presented.
Peer Review Status:Awaiting Review
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