A description of the DSN VLBI data set and of last year's analysis can be found in last year's report. Other than including another year's data, the main changes in this year's analysis from last year's are in the use of meteorological data for determining tropospheric parameters and in the weighting of the data to account for the uncertainty in the observables caused by tropospheric effects and source structure. A priori dry zenith tropospheric delays were determined from barometric pressure measurements at the DSN sites, corrected for height differences between the pressure sensor and the antennas. A priori wet zenith tropospheric delays were derived from tables of monthly average wet zenith delays for each station, which are based on historical radiosonde data. The Lanyi function was used for mapping zenith tropospheric delays to observed elevations. the temperature at the top of the boundary layer, a parameter in the Lanyi function, was taken to be the 24-hour average of the surface temperature at the station. Adjustments to the wet troposphere zenith delays were estimated every two to three hours.

Earth rotation, DSN, VLBI↗

NASA NTRS1994

Systematic Errors in Current Extragalactic Radio Source Catalogs

Explore the source record for details and available documents.

radio interferometric data VLBI↗

NASA NTRS1994

Preliminary Link of the Hipparcos and VLBI Reference Frames

We present a comparison of VLBI and Hipparcos astrometric parameters of several optically bright radio-emitting stars.

VLBI Hipparcos astrometry reference systems↗

NASA NTRS1994

Precession and Nutation from Joint Analysis of Radio Interferometric and Lunar Laser Ranging Observations

24 years of Lunar Laser Ranging (LLR) observations and 15 years of Very Long Baseline Interferometry (VLBI) observations are combined in a global analysis to yield improved estimates of the Earth precession and nutation.

earth↗

NASA NTRS1993

Earth Rotation Parameters from DSN VLBI: 1993

This year we have introduced several modeling improvements, including estimating a parametric model for the mearly-diurnal and nearly-semidiurnal tidal frequency variations of UTI and polar motion, and estimating site velocities.

earth rotation DSN VLBI IERS TEMPO↗

NASA NTRS1993

Vertical Ocean Loading Amplitudes From VLBI Measurements

Vertical ocean loading amplitudes are determined by analysis of IRIS geodetic VLBI data. Vertical ocean loading amplitudes can thus be inferred from VLBI data at a level which improves the overall model, but detailed assessment of individual tidal components is presently obscured by inadequacies in modeling other tidal effects.

ocean↗