Results 81 to 90 of about 166,231 (222)

Representations of Time Coordinates in FITS

, 2014
In a series of three previous papers, formulation and specifics of the representation of World Coordinate Transformations in FITS data have been presented. This fourth paper deals with encoding time.
Allen, Steven L., Bunclark, Peter S., Calabretta, Mark R., Manchester, Richard N., Rots, Arnold H., Thompson, William T.   +5 more
core   +1 more source

A Satellite Drift Scan Approach for Establishing the Pointing Model of Radio Telescopes

Advances in Astronomy, Volume 2025, Issue 1, 2025.
In the era of large satellite constellations, there are more than 1000 satellites in orbit. While the signals from these satellites may pose a risk of radio frequency interference (RFI) to radio telescopes, they also present a potential advantage by serving as high‐spatial‐density pointing references for radio telescopes.
Ye Yuan, Zhi-Yong Liu, Na Wang, Hao Yan, Arpan Hazra   +4 more
wiley   +1 more source

Investigation on the Impact of Tropospheric Delay on GPS Height Variation near the Equator

, 2009
One of the major problems currently facing satellite-based positioning is the atmospheric refraction of the GPS signal caused by the troposphere. The tropospheric effect is much more pronounced at the equatorial region due to its hot and wet conditions ...
Dodo, Joseph D, Kamarudin, Nor bin, Yahya, Mohd Hafiz   +2 more
core   +1 more source

Robust factor graph optimisation method for shipborne GNSS/INS integrated navigation system

IET Radar, Sonar &Navigation, Volume 18, Issue 5, Page 782-798, May 2024.
An adaptive factor based on pseudorange residual judgement is proposed to improve the accuracy of ship‐borne robust factor graph optimisation integrated navigation method. Using the historical information in the sliding window to estimate the occluded satellite signal.
Yuan Hu, Haozheng Li, Wei Liu
wiley   +1 more source

Method and Validation of Real‐Time Global Ionosphere Modeling Constraint by Multi‐Source GNSS/LEO Data

Space Weather, Volume 22, Issue 4, April 2024.
Abstract This study applies the zero‐differenced integer ambiguity method, named PPP‐Fixed, to extract real‐time ionospheric data and eliminate the latencies of rapid/final Global Ionosphere Maps (GIMs). The PPP‐Fixed method is also used to derive ionospheric data for post‐processed GIM generation, named SGG Post‐GIM, combined with low earth orbit ...
Jun Chen, Xiaodong Ren, Guozhen Xu, Pengxin Yang, Hang Liu, Xiaohong Zhang   +5 more
wiley   +1 more source

Recognition of objects in orbit and their intentions with space‐borne sub‐THz Inverse Synthetic Aperture Radar

IET Radar, Sonar &Navigation, Volume 18, Issue 4, Page 564-576, April 2024.
The paper describes a processing scheme to extract discriminating features from Inverse Synthetic Aperture Radar images of objects in space and how these discriminators can be used to recognise or to estimate the intention of these objects. It describes how electromagnetic simulation can be used to create images to train the object recognition ...
Mikhail Cherniakov, Edward G. Hoare, Marina Gashinova, Emidio Marchetti, Andrew G. Stove   +4 more
wiley   +1 more source

The Influence of Application a Simplified Transformation Model Between Reference Frames ECEF and ECI onto Prediction Accuracy of Position and Velocity of GLONASS Satellites

Reports on Geodesy and Geoinformatics, 2015
In computational tasks of satellite geodesy there is a need for transformation of coordinates between reference frames ECEF – Earth Centered, Earth Fixed and ECI – Earth Centered, Inertial.
Krzyżek Robert, Skorupa Bogdan
doaj   +1 more source

Orbit Determination of China’s Space Station Using Real ISL Measurements of the Tianzhou‐6 Spacecraft

International Journal of Aerospace Engineering, Volume 2024, Issue 1, 2024.
Under most circumstances, the current studies related to precision orbit determination (POD) using intersatellite link (ISL) measurements are limited to ISL ranging components. In this article, we would like to discuss the idea of jointly using the GNSS observations and ISL ranging and orientation measurements of the Tianzhou‐6 (TZ‐6) spacecraft to ...
Haijian Fang, Fan Wang, Xueming Yu, Baohua Wang, Jiasong Wang, Yufan He, Minzhang Han, Dan Wang, Jingqi Huang, Zhiguang Song   +9 more
wiley   +1 more source

BeiDou Satellite Unhealthy States and the Impact on System Performance

Sensors, 2018
The BeiDou system satellites may be unhealthy due to many reasons, affecting system performance in different ways. Therefore, it is important to analyze the causes and characteristics of the satellites’ unhealthy states. In this study, these states
Caibo Hu, Chuang Shi, Jinping Chen, Yidong Lou, Fei Wang   +4 more
doaj   +1 more source

Analysis and Assessment of BDS‐3 Five Single‐Frequency Civilian Signals Single Point Positioning Considering Time Group Delay and Intersignal Correction

International Journal of Aerospace Engineering, Volume 2024, Issue 1, 2024.
The BeiDou Global Navigation Satellite System (BDS‐3) has been providing global positioning, navigation, and timing (PNT) services for over 3 years. Single‐frequency single point positioning (SPP) receivers have significant advantages such as low hardware cost and easy implementation, making them widely used in engineering practice.
Xingli Sun, Dakun Sun
wiley   +1 more source