Results 31 to 40 of about 9,456 (175)

Calibrating VLBI Polarization Data Using GPCAL. II. Time-dependent Calibration

The Astrophysical Journal, 2023
We present a new method of time-dependent instrumental polarization calibration for very long baseline interferometry (VLBI). This method has been implemented in the recently developed polarization calibration pipeline GPCAL.
Jongho Park, Keiichi Asada, Do-Young Byun   +2 more
doaj   +1 more source

Quantum-enabled optical large-baseline interferometry: applications, protocols and feasibility

Advances in Physics: X
Optical Very Long Baseline Interferometry (VLBI) offers the potential for unprecedented angular resolution in both astronomical imaging and geodesy measurements.
Zixin Huang, Oleg Titov, Mikołaj K. Schmidt, Benjamin Pope, Gavin K. Brennen, Daniel K. L. Oi, Pieter Kok   +6 more
doaj   +1 more source

Precessing Jet in the High-Redshift Blazar J0017+8135

Galaxies, 2016
The prominent flat-spectrum radio quasar J0017+8135 (S5 0014+81) at z = 3.366 is one of the most luminous active galactic nuclei (AGN) known. Its milliarcsecond-scale radio jet structure has been studied with very long baseline interferometry (VLBI ...
Kristóf Rozgonyi, Sándor Frey
doaj   +1 more source

Toward an Optimal Selection of Constraints for Terrestrial Reference Frame (TRF)

Remote Sensing, 2022
Given that the observations from current space geodetic techniques do not carry all the necessary datum information to realize a Terrestrial Reference System (TRS), and each of the four space geodetic techniques has limits, for instance: Very Long ...
Shize Song, Zhongkai Zhang, Guangli Wang
doaj   +1 more source

The Short-Arc Precise Orbit Determination of GEO Satellites Using VLBI and Transfer Ranging

Remote Sensing, 2022
It is important for a geostationary Earth orbit (GEO) satellite to rapidly recover its orbit after a maneuver with short-arc precise orbit determination (POD).
Kai Nan, Fen Cao, Jianjun Gong, Hui Lei, Zhigang Li, Xuhai Yang   +5 more
doaj   +1 more source

Integration of Statistical Models and Deep Learning: A CEEMDAN‐Based Hybrid Framework for Frequency‐Domain Prediction of Polar Motion

Earth and Space Science, Volume 12, Issue 10, October 2025.
Abstract High‐precision Earth Rotation Parameter (ERP) products often experience delays that range from several days to weeks. The use of precise forecasting models can effectively compensate for the impact of such delays. Based on a systematic analysis of the forecasting capabilities of the traditional harmonic least squares fitting and autoregressive
Chen Ren, Chen Wang, Zhenhong Li, Haoran Gong, Jialiang Liu   +4 more
wiley   +1 more source

Comparison of VLBI and GNSS common view for time transfer

International Journal of Metrology and Quality Engineering, 2019
With the rapid development of optical clock, the stability and system uncertainty of optical clocks has reached a 1.0e–18 level. Optical clocks will likely constitute the next generation of time-frequency standards for redefining the SI second.
Wang Pingli, Wang Guangli, Gao Yuping, Cai Hongbing, Liu Na   +4 more
doaj   +1 more source

Estimation and Attribution of Horizontal Land Motion Measured by the Greenland GNSS Network

Journal of Geophysical Research: Solid Earth, Volume 130, Issue 9, September 2025.
Abstract Horizontal land motion, as observed by geodetic techniques such as Global Navigation Satellite Systems (GNSS), is generally dominated by tectonic plate movement. However, in regions that are currently or formerly glaciated, such as Greenland, the deformation of the solid Earth due to surface loading complicates the separation of tectonic and ...
D. Longfors Berg, S. Adhikari, J. Hassan, R. Steffen, H. Steffen, M. Willis, S. A. Khan   +6 more
wiley   +1 more source

Radiometric Interferometry for Deep Space Navigation Using Geostationary Satellites

Aerospace
Deep space navigation, defined as spacecraft position tracking beyond the lunar orbit, presents significant challenges due to the extremely weak Global Navigation Satellite System (GNSS) signals and severe signal attenuation over interplanetary distances.
Moshe Golani, Yoram Rozen, Hector Rotstein   +2 more
doaj   +1 more source

A Review of Machine Learning‐Based Ionospheric Spatial and Temporal Modeling

Journal of Geophysical Research: Machine Learning and Computation, Volume 2, Issue 3, September 2025.
Abstract The ionosphere introduces disturbances and errors in radio signals for satellite communication and navigation, requiring precise modeling to mitigate these effects. However, accurate ionospheric modeling faces challenges due to the complex spatio‐temporal variations caused by intricate coupling with the lower atmosphere and Earth's magnetic ...
Shuyin Mao, Manuel Hernández‐Pajares, Benedikt Soja   +2 more
wiley   +1 more source