scholarly journals Improvement and Maintenance of the Extragalactic Reference Frame

1995 ◽  
Vol 166 ◽  
pp. 284-284
Author(s):  
E.F. Arias ◽  
A.M. Gontier
Keyword(s):  
Reference Frame ◽  
Polar Axis ◽  
Terrestrial Reference Frame ◽  
Lunar Laser Ranging ◽  
The Best Approximation ◽  
Long Baseline ◽  
Lunar Laser ◽  
Celestial Reference Frame ◽  
Better Than

Very Long Baseline Interferometry (VLBI) is at present the most powerful technique to construct the best approximation to an inertial reference frame. After more than a decade of VLBI observations several hundreds of extragalactic objects have positions known within ±0.0003″. Since 1988 the International Earth Rotation Service (IERS) elaborates a global extragalactic celestial reference frame (IERS Celestial Reference Frame, ICRF) that is tied to the international terrestrial reference frame through the high precision monitoring of the Earth's rotation. The direction of the ICRF axes relative to the IAU definitions are known within better than ±0.001″ for the polar axis and ±0.003″ for the origin of right ascensions. The FK5 axes are consistent with the ICRF ones within their uncertainties (0.050″-0.100″). The maintenance of this high accuracy extragalactic frame will be necessary for the long term programs, such as the future monitoring of the tie of the Hipparcos galactic frame as well as of the dynamical planetary frame (millisecond pulsars, lunar laser ranging).

scholarly journals Geocentric Terrestrial Reference Frame Accuracy: DSN Spacecraft Tracking and VLBI/Lunar Laser Ranging

1988 ◽  
Vol 128 ◽  
pp. 115-120 ◽  
Author(s):  
A. E. Niell
Keyword(s):  
Reference Frame ◽  
Terrestrial Reference Frame ◽  
Spin Axis ◽  
Laser Ranging ◽  
Lunar Laser Ranging ◽  
Deep Space Network ◽  
Long Baseline ◽  
Lunar Laser ◽  
Spacecraft Tracking ◽  
Geocentric Coordinates

From a combination of 1) the location of McDonald Observatory from Lunar Laser Ranging, 2) relative station locations obtained from Very Long Baseline Interferometry (VLBI) measurements, and 3) a short tie by traditional geodesy, the geocentric coordinates of the 64 m antennas of the NASA/JPL Deep Space Network are obtained with an orientation which is related to the planetary ephemerides and to the celestial radio reference frame. Comparison with the geocentric positions of the same antennas obtained from tracking of interplanetary spacecraft shows that the two methods agree to 20 cm in distance off the spin axis and in relative longitude. The orientation difference of a 1 meter rotation about the spin axis is consistent with the error introduced into the tracking station locations due to an error in the ephemeris of Jupiter.

scholarly journals The Long Term Stability of VLBI Earth Orientation Measurements

1988 ◽  
Vol 129 ◽  
pp. 369-370
Author(s):  
T. M. Eubanks ◽  
J. A. Steppe
Keyword(s):  
Laser Ranging ◽  
Lunar Laser Ranging ◽  
Earth Orientation ◽  
Long Term Stability ◽  
Long Baseline ◽  
Lunar Laser ◽  
Tectonic Motion ◽  
Vlbi Data ◽  
Different Sources

Tectonic motions will, in general, change the orientation as well as the length of baselines used in Very Long Baseline Interferometry (VLBI), and will thus cause slow divergences between Earth orientation results obtained with different VLBI networks, as well as between VLBI results and those obtained by Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR). Such drifts (on the order of a milliarcsecond /year) are inherently interesting as well as being significant in combinations of orientation results from different sources. The geodetic study of tectonic motions is also closely connected to research into the nature and causes of systematic errors in data from the modern techniques of space geodesy. We describe both a special coordinate system found to be of use in the analysis of VLBI data and tectonic motion estimates for a VLBI baseline stretching from California to Australia.

scholarly journals Introduction of JD 19: Nutation

1995 ◽  
Vol 10 ◽  
pp. 209-213
Author(s):  
V. Dehant
Keyword(s):  
Global Positioning System ◽  
Laser Ranging ◽  
Lunar Laser Ranging ◽  
Long Baseline ◽  
Lunar Laser ◽  
Global Positioning ◽  
Nutation Series ◽  
Precise Time ◽  
Better Than ◽  
Precession Constant

Due to both precise time measurements and precise geodetic positioning methods (like Very Long Baseline Interferometry (VLBI), Lunar Laser Ranging (LLR), Satellite Laser Ranging (SLR) and Global Positioning System (GPS)), the position of the instantaneous axis of the Earth’s rotation in space is measured with a precision better than a tenth of milliarcsecond. Simultaneously the amplitudes of the nutations of the Celestial Ephemeris Pole (CEP) deduced from the observations, i.e. the periodic motions in space of the CEP due to the luni-solar attraction or to other planetary attractions, have also been improved. However, these observed nutation amplitudes differ with respect to the computated ones based on an elliptical, uniformly rotating and deformable Earth responding to the lunar and solar attractions, as adopted by the IAU in 1980. The first session on “Observations and data reduction” dealt with Earth’s orientation observations and data analysis for deriving precession and nutations, as well as the associated residuals with respect to the adopted precession constant and nutation series. Comparisons between the different results have been presented including in-phase and out-of-phase components of the prograde and retrograde nutations or of nutations in longitude and in obliquity (see Session 1 of our JD: Newhall et al., McCarthy and Luzum, Herring, and Session 2: Gross). These differences “observed - adopted” nutations achieve several milliarcseconds and exhibit periodic as well as secular characteristics.

scholarly journals The Progress of The Reference Frame

1998 ◽  
Vol 11 (1) ◽  
pp. 280-280
Author(s):  
L.V. Morrison
Keyword(s):  
International Cooperation ◽  
Reference Frame ◽  
Radio Astronomy ◽  
International Collaboration ◽  
Very Long Baseline Interferometry ◽  
Long Baseline ◽  
Celestial Reference Frame ◽  
Northern And Southern Hemispheres ◽  
Global Reference Frame ◽  
Better Than

F.W. Argelander proposed to a meeting of the Astronomischen Gessellschaft in 1867 that an accurate catalogue of all stars down to 9th magnitude should be compiled. The sky was divided into zones of declination and observations were undertaken with transit circles at a number of observatories in an international collaboration. The importance of fitting these zonal observations to one global reference frame was realized, and for this purpose A. Auwers produced a Fundamental Catalog (FC) for the Northern and Southern hemispheres in 1879 and 1883, respectively. The accuracy of the positions was about half of an arcsecond. This was the first international celestial reference frame. This reference frame was improved over the next hundred years by continued international cooperation which was later coordinated through the IAU. These efforts culminated in the FK5 which was issued in 1988. The progress in accuracy from the FC to the FK5 is shown in Figure 1. Meanwhile, radio astronomy through the technique of Very Long Baseline Interferometry (VLBI) began to produce positions of extragalactic sources with an accuracy of a milliarcsecond (mas), which is almost two orders of magnitude better than that of the optical positions of the stars in the FK5.

scholarly journals The Contribution of the IERS to Astrophysics and Geodynamics

1993 ◽  
Vol 156 ◽  
pp. 406-406
Author(s):  
M. Feissel ◽  
Yaroslav Yatskiv
Keyword(s):  
Reference Frame ◽  
Global Positioning System ◽  
Terrestrial Reference Frame ◽  
International Earth Rotation Service ◽  
Earth Orientation Parameters ◽  
Long Baseline ◽  
The Earth ◽  
Global Positioning ◽  
Orientation Parameters ◽  
Celestial Reference Frame

The International Earth Rotation Service (IERS) maintains a celestial reference frame and a terrestrial reference frame based on observations in Very Long Baseline radio Interferometry, Lunar and Satellite Laser Ranging, and Global Positioning System, as well as a time series of the Earth Orientation Parameters in a system that is consistent at the level of 0.001″.

scholarly journals Commision 19: Earth Rotation (Rotation de la Terre)

1991 ◽  
Vol 21 (1) ◽  
pp. 169-186
Keyword(s):  
Reference Frame ◽  
Earth Rotation ◽  
Very Long Baseline Interferometry ◽  
International Association ◽  
High Accuracy ◽  
Terrestrial Reference Frame ◽  
International Earth Rotation Service ◽  
Long Baseline ◽  
Compact Sources ◽  
Celestial Reference Frame

The period has been marked by the start of the new International Earth Rotation Service (IERS), which benefits from a tight cooperation between astronomers, geodesists, and specialists in satellite geodesy, as well as meteorologists. The scope of the IERS covers not only the Earth’s rotation per se, but also the conventional terrestrial reference frame, of direct interest to the International Association of Geodesy, and a high accuracy (0.001”) celestial reference frame based on extragalactic compact sources observed in Very Long Baseline Interferometry. The IERS conventional celestial reference frame is consistent with the FK5 within the uncertainties of the latter (0.04”). The IERS Standards (1989) which contain the current best estimates of astronomical models and constants are used in many fields of astronomy and geodesy.

The Contribution of LARES to Global Climate Change Studies With Geodetic Satellites

2015 ◽  
Author(s):  
Giampiero Sindoni ◽  
Claudio Paris ◽  
Cristian Vendittozzi ◽  
Erricos C. Pavlis ◽  
Ignazio Ciufolini ◽  
...  
Keyword(s):  
Reference Frame ◽  
Earth Science ◽  
Global Climate ◽  
Temporal Variations ◽  
Terrestrial Reference Frame ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Long Baseline ◽  
Geophysical Processes ◽  
Global Navigation Satellite

Satellite Laser Ranging (SLR) makes an important contribution to Earth science providing the most accurate measurement of the long-wavelength components of Earth’s gravity field, including their temporal variations. Furthermore, SLR data along with those from the other three geometric space techniques, Very Long Baseline Interferometry (VLBI), Global Navigation Satellite Systems (GNSS) and DORIS, generate and maintain the International Terrestrial Reference Frame (ITRF) that is used as a reference by all Earth Observing systems and beyond. As a result we obtain accurate station positions and linear velocities, a manifestation of tectonic plate movements important in earthquake studies and in geophysics in general. The “geodetic” satellites used in SLR are passive spheres characterized by very high density, with little else than gravity perturbing their orbits. As a result they define a very stable reference frame, defining primarily and uniquely the origin of the ITRF, and in equal shares, its scale. The ITRF is indeed used as “the” standard to which we can compare regional, GNSS-derived and alternate frames. The melting of global icecaps, ocean and atmospheric circulation, sea-level change, hydrological and internal Earth-mass redistribution are nowadays monitored using satellites. The observations and products of these missions are geolocated and referenced using the ITRF. This allows scientists to splice together records from various missions sometimes several years apart, to generate useful records for monitoring geophysical processes over several decades. The exchange of angular momentum between the atmosphere and solid Earth for example is measured and can be exploited for monitoring global change. LARES, an Italian Space Agency (ASI) satellite, is the latest geodetic satellite placed in orbit. Its main contribution is in the area of geodesy and the definition of the ITRF in particular and this presentation will discuss the improvements it will make in the aforementioned areas.

scholarly journals The Celestial Frame and the Weighting of the Celestial Pole Offsets in the Computation of VLBI-Based Corrections for the Main Lunisolar Nutation Terms

Sensors ◽  
2021 ◽  
Vol 21 (24) ◽  
pp. 8276
Author(s):  
Víctor Puente ◽  
Marta Folgueira
Keyword(s):  
Stochastic Model ◽  
Least Squares ◽  
Reference Frame ◽  
Very Long Baseline Interferometry ◽  
Long Baseline ◽  
Celestial Pole ◽  
Two Factors ◽  
Least Squares Adjustment ◽  
Empirical Corrections ◽  
Celestial Reference Frame

Very long baseline interferometry (VLBI) is the only technique in space geodesy that can determine directly the celestial pole offsets (CPO). In this paper, we make use of the CPO derived from global VLBI solutions to estimate empirical corrections to the main lunisolar nutation terms included in the IAU 2006/2000A precession–nutation model. In particular, we pay attention to two factors that affect the estimation of such corrections: the celestial reference frame used in the production of the global VLBI solutions and the stochastic model employed in the least-squares adjustment of the corrections. In both cases, we have found that the choice of these aspects has an effect of a few μas in the estimated corrections.

scholarly journals Erratum to: Determination of a terrestrial reference frame via Kalman filtering of very long baseline interferometry data

2016 ◽  
Vol 90 (12) ◽  
pp. 1329-1329 ◽  
Author(s):  
Benedikt Soja ◽  
Tobias Nilsson ◽  
Kyriakos Balidakis ◽  
Susanne Glaser ◽  
Robert Heinkelmann ◽  
...  
Keyword(s):  
Reference Frame ◽  
Kalman Filtering ◽  
Very Long Baseline Interferometry ◽  
Terrestrial Reference Frame ◽  
Long Baseline

Results from lunar laser ranging (summary only)

1977 ◽  
Vol 284 (1326) ◽  
pp. 587-587
Keyword(s):  
Three Dimensional ◽  
Lunar Laser Ranging ◽  
Lunar Laser Range ◽  
Lunar Laser ◽  
Inertia Parameters ◽  
Null Value ◽  
Rotation Of The Earth ◽  
The Moment ◽  
Geocentric Coordinates ◽  
Better Than

Over 1500 lunar laser range measurements have been made during the past six years at McDonald Observatory. These data have been fitted with a 41 cm r. m. s. residual. The geocentric coordinates of McDonald Observatory are now known to better than 1 m, the three-dimensional coordinates of the Moon and the selenocentric coordinates of the retroreflectors are accurate to about 25 m, and the mass ratio Sun/(Earth + Moon) is determined to 2 parts in 107. A search for the Nordtvedt term in the Moon’s orbit, a term predicted by some relativity theories, gives a null value, a result consistent with general relativity. The measurement of the physical librations determines very accurately the moment of inertia parameters β = (C - A)/B and γ = (B - A)/C, and significantly determines the third degree gravitational harmonics C 30 , C 32 , S 32 and S 33 The postfit residuals are not random but yield corrections to the rotation of the Earth, values of U. T. 0 for individual days having typical accuracies of 0.5 ms (20cm). The anticipated regular operation of two or more stations will allow the separation of U. T. 1 and polar motion.

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