scholarly journals Corrected μβ for stars of Hipparcos catalogue from independent latitude observations over many decades

2011 ◽  
pp. 35-41 ◽  
Author(s):  
G. Damljanovic ◽  
I.S. Milic
Keyword(s):  
International Organizations ◽  
Sufficient Accuracy ◽  
Proper Motions ◽  
Earth Orientation Parameters ◽  
Method Of Calculation ◽  
The Earth ◽  
Hipparcos Catalogue ◽  
International Polar ◽  
The Common ◽  
Orientation Parameters

During the last century, there were many so-called independent latitude (IL) stations with the observations which were included into data of a few international organizations (like Bureau International de l'Heure - BIH, International Polar Motion Service - IPMS) and the Earth rotation programmes for determining the Earth Orientation Parameters - EOP. Because of this, nowadays, there are numerous astrometric ground-based observations (made over many decades) of some stars included in the Hipparcos Catalogue (ESA 1997). We used these latitude data for the inverse investigations - to improve the proper motions in declination ?? of the mentioned Hipparcos stars. We determined the corrections ??? and investigated agreement of our ?? and those from the catalogues Hipparcos and new Hipparcos (van Leeuwen 2007). To do this we used the latitude variations of 7 stations (Belgrade, Blagoveschtschensk, Irkutsk, Poltava, Pulkovo, Warsaw and Mizusawa), covering different intervals in the period 1904.7 - 1992.0, obtained with 6 visual and 1 floating zenith telescopes (Mizusawa). On the other hand, with regard that about two decades have elapsed since the Hipparcos ESA mission observations (the epoch of Hipparcos catalogue is 1991.25), the error of apparent places of Hipparcos stars has increased by nearly 20 mas because of proper motion errors. Also, the mission lasted less than four years which was not enough for a sufficient accuracy of proper motions of some stars (such as double or multiple ones). Our method of calculation, and the calculated ?? for the common IL/Hipparcos stars are presented here. We constructed an IL catalogue of 1200 stars: there are 707 stars in the first part (with at least 20 years of IL observations) and 493 stars in the second one (less than 20 years). In the case of ?? of IL stars observed at some stations (Blagoveschtschensk, Irkutsk, Mizusawa, Poltava and Pulkovo) we find the formal errors less than the corresponding Hipparcos ones and for some of them (stations Blagoveschtschensk and Irkutsk) even less than the new Hipparcos ones.

scholarly journals Earth Orientation Parameters 1899.7-1992.0 In The Hipparcos Reference Frame

1998 ◽  
Vol 11 (1) ◽  
pp. 553-553
Author(s):  
J. Vondrák ◽  
C. Ron ◽  
I. Pešek ◽  
A. Čepek
Keyword(s):  
Polar Motion ◽  
Universal Time ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
The Earth ◽  
Hipparcos Catalogue ◽  
Time Variations ◽  
Celestial Reference System ◽  
Orientation Parameters ◽  
Made In

The optical astrometry observations of latitude/universal time variations made with 48 instruments at 31 observatories are used to determine the Earth orientation parameters (EOP) since the beginning of the century. The Hipparcos Catalogue is used to bring more than four million individual observations, made in the interval 1899.7-1992.0, into the International Celestial Reference System. The Earth orientation parameters (polar motion, celestial pole offsets and, since 1956.0, also universal time UT1) are determined at 5-day intervals, with average uncertainties ranging from 8 mas (in the eighties) to about 40 mas (in the forties). Making use of very long series of ground-based observations, the solution also leads to the improvement of proper motions of about ten per cent of the observed Hipparcos stars, with precision of ±0.2 — 0.5 mas/yr. In addition, 474 auxiliary parameters, describing the rheological properties of the Earth and seasonal deviations of the observations at contributing observatories, are found. The new solution provides the EOP series suitable for further analyses, e.g., for studying long-periodic polar motion, length-of-day changes or precession/nutation.

scholarly journals Survey of Observational Techniques and Hipparcos Reanalysis

2000 ◽  
Vol 178 ◽  
pp. 237-250 ◽  
Author(s):  
Jan Vondrák ◽  
Cyril Ron ◽  
Ivan Pešek
Keyword(s):  
Polar Motion ◽  
Universal Time ◽  
Earth Orientation Parameters ◽  
The Past ◽  
The Earth ◽  
Celestial Pole ◽  
Hipparcos Catalogue ◽  
Individual Star ◽  
Observational Techniques ◽  
Orientation Parameters

AbstractPolar motion and Universal Time have been regularly determined since 1899 and 1956, respectively, at a number of observatories all over the world. Before the International Earth Rotation Service (IERS) was established in 1988, the classical astrometry instruments such as visual zenith-telescopes, PZTs, transit instruments, astrolabes etc. were used. The survey of all these instruments and the methods of observation used is described. The values of instantaneous latitude and UT0-UTC made at a set of selected observatories and based on individual star observations have been collected at the Astronomical Institute in Prague during the past years. They were recalculated using the most recent astronomical standards and the Hipparcos Catalogue, and used to determine the Earth orientation parameters (polar motion, celestial pole offsets and Universal Time). The most recent solution, based on about 4.5 million observations with 47 different instruments at 33 observatories, is described and the results of polar motion presented.

scholarly journals The Observations of the Earth Rotation and the Stellar System

1986 ◽  
Vol 109 ◽  
pp. 133-141
Author(s):  
Koichi Sato ◽  
Koichi Yokoyama ◽  
Kiyotaka Tanikawa ◽  
Yukio Goto
Keyword(s):  
Coordinate System ◽  
Earth Rotation ◽  
Stellar System ◽  
Proper Motions ◽  
Earth Orientation Parameters ◽  
Reference Coordinate System ◽  
Earth Orientation ◽  
The Earth ◽  
Orientation Parameters ◽  
Fundamental Reference

The fundamental reference of the Earth rotation observation by the method of optical astrometry, such as VZT, PZT, astrolabe, transit instrument and so on, relies upon the stellar system. Hence the stellar positions and proper motions, and the celestial reference coordinate system are essential to preserve the system of the Earth orientation parameters determined by the optical astrometry.

scholarly journals Corrections of proper motions in declination by using ILS data

2006 ◽  
pp. 95-99 ◽  
Author(s):  
G. Damljanovic ◽  
N. Pejovic
Keyword(s):  
Earth Rotation ◽  
Sufficient Accuracy ◽  
Proper Motions ◽  
Satellite Mission ◽  
Earth Orientation ◽  
The Earth ◽  
Hipparcos Catalogue ◽  
Order Of Magnitude ◽  
Astronomical Satellite ◽  
Good Agreement

There are nowadays numerous astrometric ground{based observations of some stars referred to Hipparcos Catalogue, made at many observatories during the last century. We used the data on latitude variations, covering the period 1899.7 - 1979.0, of visual Zenith Telescopes (ZT) of International Latitude Service (ILS), to improve the Hipparcos proper motions in declination for stars observed at seven ILS stations: Carloforte, Cincinnati, Gaithersburg Kitab, Mizusawa, Tschardjui and Ukiah. About 15 years elapsed since the HIPPARCOS ESA mission (ESA 1997) observations (1991.25 is the epoch of this catalogue), and with the errors of the Hipparcos proper motions close to 1 mas/yr, the error of apparent places of stars is now more than 15 mas; so that it exceeds the error of the Hipparcos positions by one order of magnitude (which is about 1 mas). Also, for some Hipparcos stars, the errors of proper motions are much larger than the averaged value itself, even not realistic at all (Vondr?k et al. 1998); the Hipparcos astronomical satellite mission lasted less than four years, not enough to get a sufficient accuracy of the proper motions. To improve the accuracy of the proper motions for some Hipparcos stars, the ground-based data were used and some new catalogues were published (such as ARIHIP, EOC-2, etc) during the last decade. Our investigations are in accordance with the Earth Orientation Catalogue - EOC (Vondr?k and Ron 2003) one, based on the Earth rotation programmes ground{based data, but we used different method here. Our results yield better proper motions in declination for stars common to ILS and HIPPARCOS and a good agreement with those from EOC-2.

scholarly journals Link of the Hipparcos Catalogue to the ICRS

1998 ◽  
Vol 11 (1) ◽  
pp. 307-309
Author(s):  
J. Kovalevsky
Keyword(s):  
Reference Frames ◽  
Optical Observations ◽  
Proper Motions ◽  
Earth Orientation Parameters ◽  
Hipparcos Catalogue ◽  
Optical Wavelengths ◽  
The Individual ◽  
Celestial Reference System ◽  
Orientation Parameters ◽  
Radio Stars

Abstract In compliance with the 1991 IAU resolutions on reference frames, the merged Hipparcos Catalogue had to be aligned in such a way that it represents at optical wavelengths the International Celestial Reference System (ICRS). This was realized as a combination of particular solutions obtained from observations of radio stars by radio interferometry, observation of quasars relative to Hipparcos stars, photographic plates including galaxies and Hipparcos stars, star catalogues referred to extragalactic objects, HST observations, and comparison of Earth orientation parameters obtained by VLBI and ground-based optical observations reduced with Hipparcos positions and proper motions. The individual results generally agree within 10 mas in orientation at epoch and 1 mas/yr in spin of the system. Two methods were used to combine the results and yielded uncertainties of 0.6 mas in orientation and 0.25 mas/yr in spin.

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

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

<p>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 ‘LUNAR’), 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.</p>

Overview and Proposition for a Modern Definition of the CEP

2000 ◽  
Vol 178 ◽  
pp. 571-584
Author(s):  
Nicole Capitaine
Keyword(s):  
Working Group ◽  
Polar Motion ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
The Earth ◽  
Conventional Models ◽  
Definition Of ◽  
Orientation Parameters ◽  
Observational Procedure

AbstractThe current IAU conventional models for precession and nutation are referred to the Celestial Ephemeris Pole (CEP). However, the concept corresponding to the CEP is not clear and cannot easily be extended to the most recent models and observations. Its realization is actually dependent both on the model used for precession, nutation and polar motion and on the observational procedure for estimating the Earth orientation parameters. A new definition of the CEP should therefore be given in order to be in agreement with modern models and observations at a microarsecond level. This paper reviews the various realizations of the pole according to the models and observations and discusses the proposals for a modern definition of the CEP that are under consideration within the work of the subgroup T5 entitled “Computational Consequences” of the “ICRS” IAU Working Group.

scholarly journals Perturbing Effects in Past Optical Astrometric Data. Statistical Modelisation and Separation

1993 ◽  
Vol 156 ◽  
pp. 101-106
Author(s):  
M. L. Bougeard
Keyword(s):  
Sidereal Time ◽  
Multivariate Statistical ◽  
Earth Orientation Parameters ◽  
Time Effects ◽  
Preliminary Step ◽  
The Earth ◽  
Observer Effects ◽  
Astrometric Data ◽  
Orientation Parameters ◽  
Detection And Separation

Past optical astrometric observations are to be re-reduced in order to get a new evaluation of the Earth Orientation Parameters in the more accurate Hipparcos reference frame. Among the selected instruments is the Paris astrolabe, considered here. In this Paper, through multivariate statistical procedures, we deal with the preliminary step of the new evaluation which consists in detection and separation of sources of significant inconsistency and outstanding errors in the Paris reductions so far performed. The analysis is performed over two test periods — one per instrumental setting-that are compared in particular in terms of observer effects, magnitude, colour and sidereal time effects. The Paper also gives a synthetic overview on the statistical methods we used to obtain the main results so that they can be applied to other astrometric data.

scholarly journals Consistency of CDP and IRIS VLBI Earth orientation results

1988 ◽  
Vol 128 ◽  
pp. 187-192 ◽  
Author(s):  
A. Mallama ◽  
T. A. Clark ◽  
J. W. Ryan
Keyword(s):  
Data Centers ◽  
Reference Frames ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
The Past ◽  
The Earth ◽  
Formal Error ◽  
Orientation Parameters ◽  
Iris Data

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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