How Consistent are The Current Conventional Celestial and Terrestrial Reference Frames and The Conventional Earth Orientation Parameters?

This study compares the earth orientation results obtained by the NASA CDP and the NGS IRIS experiments. The results agree at about one combined formal error (two milliarcseconds) after small biases (one to three milliarcseconds) have been removed from each component. Furthermore the biases are found to correspond to small rotations between the reference frames, principally the terrestrial frame, for the two sets of experiments. In the past the CDP data has not been used in combined solutions of earth orientation parameters prepared by the data centers at the U.S.N.O. and the B.I.H. The authors propose that these data should be included because they are distinct from the IRIS data and represent an important supplement to those data. We also point out that the total number of observations is about equal in the CDP and IRIS experiment sets.

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Indirect linking of the Hipparcos catalog to extragalactic reference frame via Earth orientation parameters

Symposium - International Astronomical Union ◽

10.1017/s0074180900127962 ◽

1996 ◽

Vol 172 ◽

pp. 491-496

Author(s):

J. Vondrák

Keyword(s):

Time Series ◽

Reference Frame ◽

Indirect Method ◽

Reference Frames ◽

Slow Rotation ◽

Earth Orientation Parameters ◽

Earth Orientation ◽

Vlbi Observations ◽

Orientation Parameters

The indirect method of linking the Hipparcos reference frame to the frame defined by extragalactic sources is described. To this end, two independent time series of Earth orientation parameters observed by two different techniques with respect to the two reference frames are used: a) Optical astrometry observations (referred to Hipparcos stars), b) VLBI observations (referred to extragalactic objects). The parallel use of both techniques during the last decade enables to determine the orientation of the two reference frames at a fixed epoch and their mutual slow rotation with precision of at least 1mas and 1mas/year, respectively. In order not to raise confusion, the potentiality of the method is demonstrated on the example based on the star catalogues originally used at the participating observatories, not on any of the existing preliminary versions of the Hipparcos catalog.

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Baseline-dependent clock offsets in VLBI data analysis

Journal of Geodesy ◽

10.1007/s00190-021-01579-5 ◽

2021 ◽

Vol 95 (12) ◽

Author(s):

Hana Krásná ◽

Frédéric Jaron ◽

Jakob Gruber ◽

Johannes Böhm ◽

Axel Nothnagel

Keyword(s):

Data Analysis ◽

Reference Frames ◽

Earth Orientation Parameters ◽

Earth Orientation ◽

Long Baseline ◽

Station Coordinates ◽

Vlbi Data ◽

Group Delays ◽

The Impact ◽

Orientation Parameters

AbstractThe primary goal of the geodetic Very Long Baseline Interferometry (VLBI) technique is to provide highly accurate terrestrial and celestial reference frames as well as Earth orientation parameters. In compliance with the concept of VLBI, additional parameters reflecting relative offsets and variations of the atomic clocks of the radio telescopes have to be estimated. In addition, reality shows that in many cases significant offsets appear in the observed group delays for individual baselines which have to be compensated for by estimating so-called baseline-dependent clock offsets (BCOs). For the first time, we systematically investigate the impact of BCOs to stress their importance for all kinds of VLBI data analyses. For our investigations, we concentrate on analyzing data from both legacy networks of the CONT17 campaign. Various aspects of BCOs including their impact on the estimates of geodetically important parameters, such as station coordinates and Earth orientation parameters, are investigated. In addition, some of the theory behind the BCO determination, e.g., the impact of changing the reference clock in the observing network on the BCO estimate is introduced together with the relationship between BCOs and triangle delay closures. In conclusion, missing channels, and here in particular at S band, affecting the ionospheric delay calibration, are identified to be the dominant cause for the occurrence of significant BCOs in VLBI data analysis.

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BKG’s new series of 24-hour and 1-hour VLBI experiments

10.5194/egusphere-egu21-8950 ◽

2021 ◽

Author(s):

Anastasiia Girdiuk ◽

Gerald Engelhardt ◽

Dieter Ullrich ◽

Daniela Thaller ◽

Hendrik Hellmers

Keyword(s):

Reference Frames ◽

Global Network ◽

Time Intervals ◽

Earth Orientation Parameters ◽

Terrestrial Reference Frames ◽

The Earth ◽

Station Coordinates ◽

Orientation Parameters

With the VLBI technique radio sources are observed in dedicated time intervals. The most usual length of these observing sessions are 24 and 1-hour long. 24-hour long experiments usually incorporate a global network of stations, and, thus, are the prominent source of a consistent determination of all Earth Orientation Parameters (EOPs), celestial and terrestrial reference frames. The shorter experiments are designed to determine dUT1 parameter only. The number of short or intensive sessions is growing every year. Also some of them involve 3-4 stations in observation programs instead of standard 2-station mode. This leads to a larger number of observations per session, a better coverage of the Earth, and, consequently more accurate dUT1 estimates.All 24-hour and 1-hour sessions since 1984 up to now were re-processed by BKG using the most up-to-date modelling within the parameter estimation. This results in new series of consistently estimated EOPs, station coordinates and troposphere parameters.In this contribution we present our new series and investigate the quality of the obtained geodetic products, especially the EOPs. The work is focused on the consistency between dUT1 parameters derived from 24-hour and 1-hour sessions, respectively. In this study we pinpoint challenges and prospects of the inclusion of 1-hour experiments into the standard analysis of the 24-hour experiments.

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The Earth Orientation Parameters Inaccuracy and Spacecraft Motion Prediction Errors. 1. LAGEOS-1

Russian Engineering Research ◽

10.3103/s1068798x20120369 ◽

2020 ◽

Vol 40 (12) ◽

pp. 1128-1131

Author(s):

D. A. Kozorez ◽

M. N. Krasil’shchikov ◽

D. M. Kruzhkov

Keyword(s):

Motion Prediction ◽

Prediction Errors ◽

Spacecraft Motion ◽

Earth Orientation Parameters ◽

Earth Orientation ◽

The Earth ◽

Orientation Parameters

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Effect of non-tidal station loading on Lunar Laser Ranging observatories and on the estimation of Earth orientation parameters

10.5194/egusphere-egu21-7827 ◽

2021 ◽

Author(s):

Vishwa Vijay Singh ◽

Liliane Biskupek ◽

Jürgen Müller ◽

Mingyue Zhang

Keyword(s):

Research Centre ◽

Laser Ranging ◽

The Moon ◽

Lunar Laser Ranging ◽

Earth Orientation Parameters ◽

Tidal Station ◽

Earth Orientation ◽

The Earth ◽

Lunar Laser ◽

Orientation Parameters

The distance between the observatories on Earth and the retro-reflectors on the Moon has been regularly observed by the Lunar Laser Ranging (LLR) experiment since 1970. In the recent years, observations with bigger telescopes (APOLLO) and at infra-red wavelength (OCA) are carried out, resulting in a better distribution of precise LLR data over the lunar orbit and the observed retro-reflectors on the Moon, and a higher number of LLR observations in total. Providing the longest time series of any space geodetic technique for studying the Earth-Moon dynamics, LLR can also support the estimation of Earth orientation parameters (EOP), like UT1. The increased number of highly accurate LLR observations enables a more accurate estimation of the EOP. In this study, we add the effect of non-tidal station loading (NTSL) in the analysis of the LLR data, and determine post-fit residuals and EOP. The non-tidal loading datasets provided by the German Research Centre for Geosciences (GFZ), the International Mass Loading Service (IMLS), and the EOST loading service of University of Strasbourg in France are included as corrections to the coordinates of the LLR observatories, in addition to the standard corrections suggested by the International Earth Rotation and Reference Systems Service (IERS) 2010 conventions. The Earth surface deforms up to the centimetre level due to the effect of NTSL. By considering this effect in the Institute of Geodesy (IfE) LLR model (called &#8216;LUNAR&#8217;), we obtain a change in the uncertainties of the estimated station coordinates resulting in an up to 1% improvement, an improvement in the post-fit LLR residuals of up to 9%, and a decrease in the power of the annual signal in the LLR post-fit residuals of up to 57%. In a second part of the study, we investigate whether the modelling of NTSL leads to an improvement in the determination of EOP from LLR data. Recent results will be presented.

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