NASA GSFC global geodetic VLBI solution gsf_2024d

NASA Goddard Space Flight Center global VLBI quarterly solution gsf_2024d provides estimates of stations positions, station velocities, harmonic variations in site positions, parameters of non-linear station motions, positinos of extragalactic radio sources, and the estimates of an expansion of the Earth orientation parameters into harmonic and B-spline bases from processing all publicly accessible Very Long Baseline Interferometry (VLBI) group delays derived from processing all available geodetic VLBI observations since 1980.04.11 through 2024.12.03 , in total, 19,535,536 group delays from 19,963 experiments.

Methods of data analysis are described in full detail in Petrov & Kovalev, "The Radio Fundamental Catalog", 2025, The Astrophysical Journal Supplement Series, 276:38 (51pp), doi: 10.3847/1538-4365/ad8c36.

Geophysics Results

  Station positions and velocities

Positions of 190 stations, their velocities, and parameters of non-liner motion were estimated as global parameters. The dependence of station position on time is expressed as

X(t) = X₀   +   X'(t - t₀)   +   ∑ j ( h^cj cos ω_j t + h^sj sin ω_j t )   +   ∑ n-1 k b_k B^mk (t _k),

 
where X₀ is the station positions at the reference epoch 2000.01.01, X' is its linear velocity, h^sj and h^cj are sine and cosine components of harmonic variations with frequency ω_j, and b_k are the coefficients of expansion of station position over the B-spline basis of the m-th degree at sequence of knots [1-m, 1-m+1, 1-m+2 ...]. The knots of the B-spline can me multiple. Non-linear motion is estimated only for some stations.

Boundary conditions were selected in such a way that source positions, station positions and velocities are compatible with IERS C04 series of the Earth orientation parameters IERS C04 time series, i.e. have no bias and not trend over a specified period of time.

Station positions catalogue — parameters X0		Format description
Station velocity catalogue — parameters X'		Format description
Empirical model of harmonic site motion — parameters hsj and hcj		Format description
Empirical model of aharmonic non-linear site motion — parameters bk		Format description

  Antenna axis offsets

Antenna axis offsets from LSQ estimation     gsf_2024d.axof

  Earth orientation parameters

Pole coordinates X, Y, UT1 angle, and their rate, daily correction to the nutation in longitude and nutation in obliquity were estimated for each session separately.

EOP time series in ERM format		Format description
EOP time series in EOB format		Format description
EOP harmonic constituents in HEO format		Format description

  Adjustments to path delays in the neutral atmosphere

• Adjustments to path delays in the neutral atmosphere     gsf_2024d.trp     Format description
• Statistics of the atmospheric parameters     gsf_2024d.trs

Statistics

Wrms for each session		Format description
List of detected sources
Summary of detected sources in each observing session

  Statistics of observing campaigns

• List of experiment names and experiment codes of 24-hr geodetic experiments.
• List of experiment names and experiment codes of 1-hr geodetic experiments.

Miscellaneous

Raw listing of the global geodetic solution.
Control file for batch Solve solution.		Description of Solve batch control language
Control file for VLBI Time Delay computation.		Description of VTD control language

  Acknowledgments

We acknowledge staff at VLBI observing stations, VLBI correlators, and VLBI data centers listed here for their support of VLBI operations.

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Web page was prepared by Leonid Petrov ()
Last update: 2025.02.19_13:58:56