Jizhang Sang
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View article: Refinement methods to improve integrated precise orbit determination of GNSS/LEO satellites based on regional ground stations
Refinement methods to improve integrated precise orbit determination of GNSS/LEO satellites based on regional ground stations Open
Precise orbit determination (POD) of Global Navigation Satellite System (GNSS) satellites is not always reliable due to factors such as limited ground tracking stations (GTS), which result in weak observation geometry and inaccurate estima…
View article: Charity and Compassion: A Comparative Study of Philosophy of Friendship Between Thomistic Christianity and Mahayana Buddhism
Charity and Compassion: A Comparative Study of Philosophy of Friendship Between Thomistic Christianity and Mahayana Buddhism Open
In the current era, when civilizations are in constant conflict and humankind is facing a series of serious existential crises, there is an urgent need for universal love to unite humankind. As models of world religions, Christianity and B…
View article: Improving Orbit Prediction of the Two-Line Element with Orbit Determination Using a Hybrid Algorithm of the Simplex Method and Genetic Algorithm
Improving Orbit Prediction of the Two-Line Element with Orbit Determination Using a Hybrid Algorithm of the Simplex Method and Genetic Algorithm Open
With the rapidly increasing number of satellites and orbital debris, collision avoidance and reentry prediction are very important for space situational awareness. A precise orbital prediction through orbit determination is crucial to enha…
View article: Macrophage membrane functionalized composite microspheres promote bone regeneration in periodontitis via manipulating inflammation reversing-osteogenesis coupling
Macrophage membrane functionalized composite microspheres promote bone regeneration in periodontitis via manipulating inflammation reversing-osteogenesis coupling Open
Periodontitis is characterized by inflammation and alveolar bone loss, primarily caused by immune cells activated by oral bacteria, leading to an imbalance between osteogenesis and bone resorption. Traditional treatments have limited effic…
View article: High-precision Earth Rotation Parameters Prediction with Physical Excitation Factors and Deep Learning Methods
High-precision Earth Rotation Parameters Prediction with Physical Excitation Factors and Deep Learning Methods Open
The Earth is subject to complex internal and external forces in space. External forces include the gravitational attraction from the sun, moon, and other planets, and the internal forces include mass loads and frictional forces from the at…
View article: Evaluating the accuracy of earth rotation parameters based on the BDS observations
Evaluating the accuracy of earth rotation parameters based on the BDS observations Open
The BeiDou satellite system (BDS) has progressed with the full operationalization of the second-generation regional system (BDS-2) and the third-generation global system (BDS-3). This technology plays a crucial role in determining Earth Ro…
View article: Estimation of Earth Rotation Parameters Based on BDS-3 and Discontinuous VLBI Observations
Estimation of Earth Rotation Parameters Based on BDS-3 and Discontinuous VLBI Observations Open
Earth rotation parameters (ERPs) are fundamental to geodetic and astronomical studies. With its high measurement accuracy and stability, the Very Long Baseline Interferometry (VLBI) plays an irreplaceable role in estimating the ERPs and ma…
View article: Initial Orbit Determination Solution Distribution with Gooding Algorithm and Performance Enhancement
Initial Orbit Determination Solution Distribution with Gooding Algorithm and Performance Enhancement Open
An initial orbit determination (IOD) solution from angles-only observations of a single short orbit arc is often required for applications such as tracklet association and fast reacquisition of a newly detected space object. Modern optical…
View article: An Improved Range-Searching Initial Orbit-Determination Method and Correlation of Optical Observations for Space Debris
An Improved Range-Searching Initial Orbit-Determination Method and Correlation of Optical Observations for Space Debris Open
The Changchun Observatory of the National Astronomical Observatories, Chinese Academy of Sciences, and the Shanghai Astronomical Observatory are used to generate very short arc (VSA) angle observations of objects in low Earth orbit (LEO) a…
View article: ScalableMap: Scalable Map Learning for Online Long-Range Vectorized HD Map Construction
ScalableMap: Scalable Map Learning for Online Long-Range Vectorized HD Map Construction Open
We propose a novel end-to-end pipeline for online long-range vectorized high-definition (HD) map construction using on-board camera sensors. The vectorized representation of HD maps, employing polylines and polygons to represent map elemen…
View article: New Space Object Cataloguing through Very-Short-Arc Data Mining
New Space Object Cataloguing through Very-Short-Arc Data Mining Open
The space surveillance network collects significant quantities of space object monitoring data on a daily basis, which varies in duration and contain observation errors. Cataloguing space objects based on these data may result in a large n…
View article: A Case Study on the Effect of Atmospheric Density Calibration on Orbit Predictions with Sparse Angular Data
A Case Study on the Effect of Atmospheric Density Calibration on Orbit Predictions with Sparse Angular Data Open
Accurately modeling the density of atmospheric mass is critical for orbit determination and prediction of space objects. Existing atmospheric mass density models (ADMs) have an accuracy of about 15%. Developing high-precision ADMs is a lon…
View article: TLE orbit determination using simplex method
TLE orbit determination using simplex method Open
Two-Line Element (TLE) datasets are the only orbital data source of Earth-orbiting space objects for many civil users for their research and applications. The datasets have uneven qualities that may affect the reliability of the propagated…
View article: A Data-driven Method for Realistic Covariance Prediction of Space Object with Sparse Tracking Data
A Data-driven Method for Realistic Covariance Prediction of Space Object with Sparse Tracking Data Open
Covariance of the orbital state of a resident space object (RSO) is a necessary requirement for various space situational awareness tasks, like the space collision warning. It describes an accuracy envelope of the RSO's location. However, …
View article: Precise real-time navigation of the small TJU-1 satellite using GPS, GLONASS and BDS
Precise real-time navigation of the small TJU-1 satellite using GPS, GLONASS and BDS Open
Precise real-time navigation of the small Tianjin University-1 (TJU-1) satellite based on GPS, GLONASS, BDS-2 and BDS-3 is studied in this contribution for the first time. Experimental results showed that (1) the real-time position accurac…
View article: An orbit determination approach to associating optical tracklets of space objects
An orbit determination approach to associating optical tracklets of space objects Open
The advances in the optical space surveillance technology and the possibly more deployments of space-based optical sensors enable more and more space objects detectable and make the catalog expansion more realistic. The cataloging of an op…
View article: Towards Fast and Reliable Evaluation of Detection Performance of Space Surveillance Sensors
Towards Fast and Reliable Evaluation of Detection Performance of Space Surveillance Sensors Open
Wide-area space surveillance sensors are the backbone to cataloging of Earth orbiting objects. Their core capability should be to efficiently detect as many space objects as possible over a large space domain. As such, the question of how …
View article: An analysis of close approaches and probability of collisions between LEO resident space objects and mega constellations
An analysis of close approaches and probability of collisions between LEO resident space objects and mega constellations Open
With the undergoing and planned implementations of mega constellations of thousands of Low Earth Orbiting (LEO) satellites, space will become even more congested for satellite operations. The enduring effects on the long-term space environ…
View article: Short-Arc Association and Orbit Determination for New GEO Objects with Space-Based Optical Surveillance
Short-Arc Association and Orbit Determination for New GEO Objects with Space-Based Optical Surveillance Open
For Geosynchronous Earth Orbit (GEO) objects, space-based optical surveillance has advantages over regional ground surveillance in terms of both the timeliness and space coverage. However, space-based optical surveillance may only collect …
View article: TLE outlier detection based on expectation maximization algorithm
TLE outlier detection based on expectation maximization algorithm Open
The most widely-used data for civilian Space Situational Awareness are the Two-Line Element sets (TLEs) provided by the USSTRATCOM. TLEs play critical roles in space monitoring and analysis activities, and are also used in many application…
View article: An Empirical Atmospheric Density Calibration Model Based on Long Short-Term Memory Neural Network
An Empirical Atmospheric Density Calibration Model Based on Long Short-Term Memory Neural Network Open
The accuracy of the atmospheric mass density is one of the most important factors affecting the orbital precision of spacecraft at low Earth orbits (LEO). Although there are a number of empirical density models available to use in the orbi…
View article: Modify the Accuracy of MODIS PWV in China: A Performance Comparison Using Random Forest, Generalized Regression Neural Network and Back-Propagation Neural Network
Modify the Accuracy of MODIS PWV in China: A Performance Comparison Using Random Forest, Generalized Regression Neural Network and Back-Propagation Neural Network Open
Water vapor plays an important role in climate change and water cycling, but there are few water vapor products with both high spatial resolution and high accuracy that effectively monitor the change of water vapor. The high precision Glob…
View article: Fusing Precipitable Water Vapor Data in CHINA at Different Timescales Using an Artificial Neural Network
Fusing Precipitable Water Vapor Data in CHINA at Different Timescales Using an Artificial Neural Network Open
Global climate change has noticeable influences on the water vapor redistribution in China, which is embodied by the fact that both wetting and drying tendencies were observed across China. This poses the necessity to monitor and understan…
View article: A More Reliable Orbit Initialization Method for LEO Precise Orbit Determination Using GNSS
A More Reliable Orbit Initialization Method for LEO Precise Orbit Determination Using GNSS Open
Precise orbit determination (POD) using GNSS has been rapidly developed and is the mainstream technology for the navigation of low Earth orbit (LEO) satellites. The initialization of orbit parameters is a key prerequisite for LEO POD proce…
View article: LEO Onboard Real-Time Orbit Determination Using GPS/BDS Data with an Optimal Stochastic Model
LEO Onboard Real-Time Orbit Determination Using GPS/BDS Data with an Optimal Stochastic Model Open
The advancements of Earth observations, remote sensing, communications and navigation augmentation based on low Earth orbit (LEO) platforms present strong requirements for accurate, real-time and autonomous navigation of LEO satellites. Pr…
View article: Comparisons of Performance Using Data Assimilation and Data Fusion Approaches in Acquiring Precipitable Water Vapor: A Case Study of a Western United States of America Area
Comparisons of Performance Using Data Assimilation and Data Fusion Approaches in Acquiring Precipitable Water Vapor: A Case Study of a Western United States of America Area Open
There are two main types of methods available to obtain precipitable water vapor (PWV) with high accuracy. One is to assimilate observations into a numerical weather prediction (NWP) model, for example, the Weather Research and Forecasting…
View article: Characteristics Analysis of Raw Multi-GNSS Measurement from Xiaomi Mi 8 and Positioning Performance Improvement with L5/E5 Frequency in an Urban Environment
Characteristics Analysis of Raw Multi-GNSS Measurement from Xiaomi Mi 8 and Positioning Performance Improvement with L5/E5 Frequency in an Urban Environment Open
Achieving continuous and high-precision positioning services via smartphone under a Global Navigation Satellite System (GNSS)-degraded environment is urgently demanded by the mass market. In 2018, Xiaomi launched the world’s first dual-fre…
View article: Research on Image Simulation for Space-based Space Debris Surveillance
Research on Image Simulation for Space-based Space Debris Surveillance Open
空间碎片天基光学监测可以有效弥补地基监测的时空覆盖缺陷.目前天基观测数据不足甚至没有数据，这给监测系统研制、数据处理算法研究及软件系统研发和验证造成了一定困难.因此，研发能够为相关研究提供空间监测图像的空间碎片天基监测图像仿真软件系统具有重要意义.本文根据天基监测图像的特点，研究基本算法，设计仿真流程，给出仿真图像并对结果进行分析.为得到符合实际观测场景的高精度仿真图像，软件系统采用瞬时惯性坐标系；基于Tycho2星表提出了采用基于索引文件的快速星表查询方法来生成背景星图；…