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A step to the decentralized real-time timekeeping network

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Chinese Physics B 2024年第1期33卷 183-191页

作者：王芳敏陈雨锋周建华蔺玉亭杨军王波王力军 State Key laboratory of Precision Space-time Information Sensing Technology Department of Precision InstrumentTsinghua UniversityBeijing 100084China Key laboratory of Photonic Control Technology Tsinghua UniversityBeijing 100084China Beijing satellite Navigation Center Beijing 100094China Beijing Institute of Radio Metrology and Measurement Beijing 100854China

The composite time scale(CTS) provides an accurate and stable time-frequency reference for modern science and technology. Conventional CTS always features a centralized network topology, which means that the CTS is accompanied by a local master clock. This largely restricts the stability and reliability of the CTS. We simulate the restriction and analyze the influence of the master clock on the CTS. It proves that the CTS's long-term stability is also positively related to that of the master clock, until the region dominated by the frequency drift of the H-maser(averaging time longer than ~10~5s).Aiming at this restriction, a real-time clock network is utilized. Based on the network, a real-time CTS referenced by a stable remote master clock is achieved. The experiment comparing two real-time CTSs referenced by a local and a remote master clock respectively reveals that under open-loop steering, the stability of the CTS is improved by referencing to a remote and more stable master clock instead of a local and less stable master clock. In this way, with the help of the proposed scheme, the CTS can be referenced to the most stable master clock within the network in real time, no matter whether it is local or remote, making democratic polycentric timekeeping possible.

关键词： frequency synchronization network composite time scale frequency stability democratic timekeeping

Unveiling three-dimensional sea surface signatures caused by internal solitary waves:insights from the surface water ocean topography mission

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Journal of Oceanology and Limnology 2024年第3期42卷 709-714页

作者： Xudong ZHANG Xiaofeng LI Key laboratory of Ocean Observation and Forecasting Key Laboratory of Ocean Circulation and WavesInstitute of OceanologyChinese Academy of SciencesQingdao 266071China

Internal solitary waves(ISW),characterized by large amplitude and long propagation distance,are widespread in global *** remote sensing images have played an essential role in studying ISWs,they mainly exploit two-dimensional image ***,with the launch of the surface water ocean topography(SWOT)satellite on December 16,2022,a unique opportunity has emerged to capture wide-swath three-dimensional ISW-induced sea surface *** this study,we examine ISWs in the Andaman Sea using data from the Ka-band Radar Interferometer(KaRIN),a crucial sensor onboard *** not only provides backscattering satellite images but also employs synthetic aperture interferometry techniques to retrieve wide-swath two-dimensional sea surface height *** observations in the Andaman Sea revealed the presence of ISWs characterized by dark-bright strips and surface elevation *** surface soliton has an amplitude of 0.32 m,resulting in an estimation of ISW amplitude of approximately 60 *** contrast to traditional two-dimensional satellite images or nadir-looking altimetry data,the SWOT mission’s capability to capture threedimensional sea surface information represents a significant *** breakthrough holds substantial promise for ISW studies,particularly in the context of ISW amplitude inversion.

关键词： internal solitary wave(ISW) surface water ocean topography(SWOT) altimeter

A rapid assessment of MWRI-RM/FY3G brightness temperature

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Atmospheric and Oceanic Science Letters 2024年第3期17卷 42-46页

作者： Wenying He Xinran Xia Shengli Wu Peng Zhang Hongbin Chen Xiang'ao Xia Yuquan Zhou Miao Cai LAGEO Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina School of Hydrology and Water Resources Nanjing University of Information Science&TechnologyNanjingChina National satellite Meteorological Centure Chinese Meteorological AdministrationBeijingChina College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijingChina Key laboratory of Cloud-Precipitation Physics and Weather Modification CMABeijingChina

2023年4月发射的FY-3G上搭载17个频率的测雨微波成像仪(MWRI-RM),其业务定标的微波亮温(Tb)数据于2023年10月23日公开发布.本文比对了发布10天的MWRI-RM与全球降水测量(GPM)卫星上的微波成像仪(GMI)相匹配的Tb数据,并借助辐射传输模式... 详细信息

2023年4月发射的FY-3G上搭载17个频率的测雨微波成像仪(MWRI-RM),其业务定标的微波亮温(Tb)数据于2023年10月23日公开发布.本文比对了发布10天的MWRI-RM与全球降水测量(GPM)卫星上的微波成像仪(GMI)相匹配的Tb数据,并借助辐射传输模式进行双差分(DD)交叉定标分析,旨在快速评估新一代MWRI-RM观测数据质量.观测比较表明,MWR1-RM与GMI测量的Tb一致性很好,大多通道的平均偏差(MBE)和均方根误差(RMSE)均小于1K.两种传感器由于观测角度略有不同在水面产生约0.5 K差异.DD分析也展示出MWRI-RM的大多数通道性能与GMI相当接近,尤其是首次启用的高频166 GHz和183 GHz.

关键词： FY3G MWRI-RM GMI 亮度温度双差分方法

An integrative mathematical model of microwave ion thruster for mHz-frequency thrust noise analysis

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Chinese Journal of Aeronautics 2024年第4期37卷 121-136页

作者： Xiang NIU Hui LIU Daren YU Plasma Propulsion laboratory Harbin Institute of TechnologyHarbin 150001China

Many high-precision space missions need thrusters to produce thrust with low noise to compensate for disturbances and ensure satellite platform stability. Microwave ion thruster is characterized with a wide thrust range and potential for these missions. A cost-effective and accurate mathematical model is crucial for mHz-frequency thrust noise analysis and feedback controller design. The Particle-In-Cell(PIC) and global models are two common simulation tools. The PIC model is characterized with high accuracy but huge computation cost, which is difficult to analyze long-time performance characteristics. Now, the global model is only used for the discharge chamber with low accuracy and cannot reflect ion extraction properties. In this paper, an integrative mathematical model is built for a 1-cm microwave ion thruster and can reflect ion beamlet divergence and impingement on the Accelerator Grid(AG). Simulation results show good agreement with experiments at 0.06 sccm. However, the model demonstrates worse consistency with experiments when the flux increases to 0.1 sccm, which may be because the influence of neutral gas on the Electron Cyclotron Resonance(ECR) is not considered in the model. A long-time(1000 s) simulation is conducted with this model under 35 μN. It takes 3 hrs, and the thrust noise reaches 1 μN/Hz^(0.5) at 1 mHz.

关键词： Electric propulsion Microwave ion thruster Integrative model Sheath property Ion beamlet divergence Thrust noise Plasma

Atmospheric transmission algorithm for pulsed X-rays from high-altitude nuclear detonations based on scattering correction

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Nuclear Science and Techniques 2024年第3期35卷 40-52页

作者： Ding-Han Zhu Xiong Zhang Xiao-Qiang Li Peng Li Yan-Bin Wang Shuang Zhang State Key laboratory of NBC Protection for Civilian Beijing 102205China

In high-altitude nuclear detonations,the proportion of pulsed X-ray energy can exceed 70%,making it a specific monitoring signal for such *** pulsed X-rays can be captured using a satellite-borne X-ray detector following atmospheric *** quantitatively analyze the effects of different satellite detection altitudes,burst heights,and transmission angles on the physical processes of X-ray transport and energy fluence,we developed an atmospheric transmission algorithm for pulsed X-rays from high-altitude nuclear detonations based on scattering *** proposed method is an improvement over the traditional analytical method that only computes direct-transmission *** traditional analytical method exhibits a maximum relative error of 67.79% compared with the Monte Carlo *** improved method reduces this error to within 10% under the same conditions,even reaching 1% in certain ***,its computation time is 48,000 times faster than that of the Monte Carlo *** results have important theoretical significance and engineering application value for designing satellite-borne nuclear detonation pulsed X-ray detectors,inverting nuclear detonation source terms,and assessing ionospheric effects.

关键词： High-altitude nuclear detonation Atmospheric transmission Pulsed X-rays Scattering correction Analytical method Monte Carlo method

Semantic-aware coordinated transmission in cohesive clustered satellites: utility of information perspective

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Science China(Information Sciences) 2024年第09期67卷 338-339页

作者： Liang XU Jian JIAO Shiyao JIANG Ye WANG Qinyu ZHANG Guangdong Provincial Key laboratory of Aerospace Communication and Networking Technology Harbin Institute of Technology (Shenzhen) Pengcheng laboratory

The cohesive clustered satellite(CCS) concept integrates diverse satellite payloads from different orbits, such as communication, remote sensing, and navigation satellites, into mobile, geometrically stable clusters for efficient collaborative networking [1]. By aggregating, reconstructing, and orchestrating heterogeneous satellite resources, such as computation, communication, and storage [2], the CCS enables resource ultra-sharing and provides information-centric and goal-oriented intelligent on-demand services [3] for a range of emerging Earth observation and deep space exploration missions [4].

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Long-lived lunar volcanism sustained by precession-driven core-mantle friction

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National Science Review 2024年第2期11卷 114-123页

作者： Shuoran Yu Xiao Xiao Shengxia Gong Nicola Tosi Jun Huang Doris Breuer Long Xiao Dongdong Ni State Key laboratory of Lunar and Planetary Sciences Macau University of Science and Technology Planetary Science Institute State Key Laboratory of Geological Processes and Mineral Resources School of Earth Sciences China University of Geosciences CAS Key laboratory of Planetary Sciences Shanghai Astronomical Observatory Institute of Planetary Research German Aerospace Centre(DLR)

Core-mantle friction induced by the precession of the Moon's spin axis is a strong heat source in the deep lunar mantle during the early phase of a satellite's evolution, but its influence on the long-term thermal evolution still remains poorly explored. Using a one-dimensional thermal evolution model, we show that core-mantle friction can sustain global-scale partial melting in the upper lunar mantle until ～3.1 Ga, thus accounting for the intense volcanic activity on the Moon before ～3.0 Ga. Besides, core-mantle friction tends to suppress the secular cooling of the lunar core and is unlikely to be an energy source for the long-lived lunar core dynamo. Our model also favours the transition of the Cassini state before the end of the lunar magma ocean phase(～4.2 Ga), which implies a decreasing lunar obliquity over time after the solidification of the lunar magma ocean. Such a trend of lunar obliquity evolution may allow volcanically released water to be buried in the lunar regolith of the polar regions. As a consequence, local water ice could be more abundant than previously thought when considering only its accumulation caused by solar wind and comet spreading.

关键词： Moon precession orbit volcanism

An assessment of the CMIP6 performance in simulating Arctic sea ice volume flux via Fram Strait

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Advances in Climate Change Research 2024年第4期15卷 584-595页

作者： Hui-Yan KUANG Shao-Zhe SUN Yu-Fang YE Shao-Yin WANG Hai-Bo BI Zhuo-Qi CHEN Xiao CHENG School of Geospatial Engineering and Science Sun Yat-sen UniversitySouthern Marine Science and Engineering Guangdong Laboratory(Zhuhai)Zhuhai 519082China Key laboratory of Comprehensive Observation of Polar Environment(Sun Yat-sen University) Ministry of EducationZhuhai 519082China CAS Key laboratory of Marine Geology and Environment Institute of OceanologyChinese Academy of Sciences(CAS)Qingdao 266071China laboratory for Marine Geology Qingdao National Laboratory for Marine Science and Technology Qingdao 266237China

Numerical models serve as an essential tool to investigate the causes and effects of Arctic sea ice *** the simulation capabilities of the most recent CMIP6 models in sea ice volume flux provides references for model applications and ***,reliable long-term simulation results of the ice volume fux contribute to a deeper understanding of the sea ice response to global climate *** this study,the sea ice volume flux through six Arctic gateways over the past four decades(1979-2014)were estimated in combination of satellite observations of sea ice concentration(SIC)and sea ice motion(SIM)as well as the Pan-Arctic Ice-Ocean Modeling and Assimilation System(PIOMAS)reanalysis sea ice thickness(SIT)*** simulation capability of 17 CMIP6 historical models for the volume flux through Fram Strait were quantitatively *** ice volume flux simulated from the ensemble mean of 17 CMIP6 models demonstrates better performance than that from the individual model,yet IPSL-CM6A-LR and EC-Earth3-Veg-LR outperform the ensemble mean in the annual volume flux,with Taylor scores of 0.86 and 0.50,***6 models display relatively robust capability in simulating the seasonal variations of volume *** them,CESM2-WACCM performs the best,with a correlation coefficient of 0.96 and a Taylor score of ***,NESM3 demonstrates the largest devi-ation from the observation/reanalysis data,with the lowest Taylor score of *** variability of sea ice volume flux is primarily influenced by SIM and SIT,followed by *** extreme large sea ice export through Fram Strait is linked to the occurrence of anomalously low air temperatures,which in turn promote increased SIC and SIT in the corresponding ***,the intensified activity of Arctic cyclones and Arctic dipole anomaly could boost the southward sea ice velocity through Fram Strait,which further enhance the sea ice outflow.

关键词： Sea ice volume flux CMIP6 models Fram Strait Attribution analysis

Inter-annual variations of dissolved oxygen and hypoxia off the northern Changjiang River(Yangtze River) Estuary in summer from 1997 to 2014

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Acta Oceanologica Sinica 2024年第6期43卷 119-130页

作者： Anqi Liu Feng Zhou Xiao Ma Qiang Zhao Guanghong Liao Yuntao Zhou Di Tian Xiaobo Ni Ruibin Ding College of Oceanography Hohai UniversityNanjing 210098China State Key laboratory of satellite Ocean Environment Dynamics Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China Observation and Research Station of Changjiang River Delta Marine Ecosystems Ministry of Natural ResourcesZhoushan 316022China Ningbo Marine Center Ministry of Natural ResourcesNingbo 315000China School of Oceanography Shanghai Jiao Tong UniversityShanghai 200240China Institute of Polar and Ocean Technology Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China

Hypoxia off the Changjiang River Estuary has been the subject of much attention,yet systematic observations have been lacking,resulting in a lack of knowledge regarding its long-term change and *** revisiting the repeated surveys of dissolved oxygen(DO) and other relevant hydrographic parameters along the section from the Changjiang River Estuary to the Jeju-do in the summer from 1997 to 2014,rather different trends were revealed for the dual low-DO *** nearshore low-DO core,located close to the river mouth and relatively stable,shows that hypoxia has become more severe with the lowest DO descen ding at a rate of -0.07 mg/(L·a) and the thickness of low-DO zone rising at a rate of 0.43 m/*** offshore core,centered around 40-m isobath but moving back and forth between 123.5°-125°E,shows large fluctuations in the minimum DO concentration,with the thickness of low-DO zone falling at a rate of -1.55 m/*** probable factors affecting the minimum DO concentration in the two regions also *** the nearshore region,the decreasing minimum DO is driven by the increase in both stratification and primary productivity,with the enhanced extension of the Changjiang River Diluted Water(CDW) strengthening *** the offshore region,the fluctuating trend of the minimum DO concentration indicates that both DO loss and DO supplement are *** DO loss is primarily attributed to bottom apparent oxygen utilization caused by the organic matter decay and is also relevant to the advection of low-DO water from the nearshore *** DO supplement is primarily due to weakened *** analysis also shows that the minimum DO concentration in the nearshore region was extremely low in 1998,2003,2007 and 2010,related to El Ni?o signal in these summers.

关键词： dissolved oxygen low-DO Changjiang River Estuary interannual variations dual-core