scholarly journals The VLBI celestial reference frame of the NASA Crustal Dynamics Project

1988 ◽  
Vol 128 ◽  
pp. 73-81 ◽  
Author(s):  
C. Ma
Keyword(s):  
Reference Frame ◽  
Weighted Average ◽  
Radio Sources ◽  
Extragalactic Radio Sources ◽  
Statistical Errors ◽  
Crustal Dynamics ◽  
Vlbi Data ◽  
Celestial Reference Frame ◽  
Right Ascension ◽  
Average Position

A celestial reference frame can be defined by precise positions of extragalactic radio sources using Mark III VLBI data available to the NASA Crustal Dynamics Project for geodynamic research. Seven years of such data have been analyzed to generate a catalogue of 101 sources with formal statistical errors between 0.01 and 0.77 ms in right ascension and between 0.2 and 9.3 mas in declination. In order to achieve such precision it is necessary to adjust the standard IAU nutation model. The rotations and scatter of the positions from year to year are generally less than 1 mas. A comparison of this catalogue with a completely independent catalogue derived from Mark II data shows a weighted average position difference, after a rotation, of 1.9 mas.

scholarly journals The Celestial Reference Frame Defined by VLBI

1988 ◽  
Vol 129 ◽  
pp. 325-326
Author(s):  
C. Ma ◽  
D. B. Shaffer
Keyword(s):  
Reference Frame ◽  
Radio Sources ◽  
Arc Length ◽  
Dual Frequency ◽  
Extragalactic Radio Sources ◽  
Statistical Errors ◽  
Fundamental Quantity ◽  
Crustal Dynamics ◽  
Celestial Reference Frame ◽  
Right Ascension

VLBI currently produces the most accurate positions of celestial objects. From 1979 to 1987, 114 extragalactic radio sources have been observed with dual-frequency Mark III VLBI as part of the NASA Crustal Dynamics Project and the NGS POLARIS/IRIS program. The formal statistical errors of conventional celestial coordinates are as small as 0.3 milliarcseconds. The fundamental quantity measured by VLBI is the arc length between radio sources. Thus, we suggest that VLBI be used to establish a coordinate reference frame based solely on radio positions, and that this system not necessarily be coupled to right ascension and declination.

scholarly journals Stability of the Extragalactic Reference Frame Realized by VLBI

1991 ◽  
Vol 127 ◽  
pp. 135-144 ◽  
Author(s):  
C. Ma ◽  
D.B. Shaffer
Keyword(s):  
Reference Frame ◽  
Radio Sources ◽  
Dual Frequency ◽  
Real Motion ◽  
Rates Of Change ◽  
Upper Limits ◽  
Crustal Dynamics ◽  
Vlbi Data ◽  
Celestial Reference Frame ◽  
Right Ascension

AbstractThe 318 compact extragalactic radio sources with positions derived from dual frequency Mark III VLBI data acquired by the geodetic and astrometric programs of NASA, NOAA, NRL and USNO form a celestial reference frame with stability in orientation and relative position at the 1 mas level. This paper examines the reference frame realized using 461,000 observations from 1021 observing sessions between 1979 August and 1990 August in the NASA Crustal Dynamics Project VLBI data base. Catalogs of positions estimated from subsets of data (annual, seasonal, network) show differences in orientation typically less than 1 mas provided precession and nutation are adjusted using a reference day. For 17 sources with >5 year time span and >200 one-day position estimates, the rates of change of right ascension and declination are generally less than 5 mas/century, giving upper limits on real motion.

scholarly journals Secular Motions of Extragalactic Radio-Sources and the Stability of the Radio Reference Frame

1995 ◽  
Vol 166 ◽  
pp. 283-283 ◽  
Author(s):  
T.M. Eubanks ◽  
D.N. Matsakis ◽  
F.J. Josties ◽  
B.A. Archinal ◽  
K.A. Kingham ◽  
...  
Keyword(s):  
Reference Frame ◽  
Proper Motion ◽  
Current Source ◽  
Radio Sources ◽  
Data Set ◽  
Extragalactic Radio Sources ◽  
Secular Changes ◽  
Vlbi Data ◽  
The Stability ◽  
Mass Concentrations

The best current approximation to an inertial reference frame is provided by Very Long Baseline Interferometry (VLBI) observations of extragalactic radio sources with red shifts (z) up to 3.8. The stability of the resulting reference frame directly depends on the amount of any secular changes in the observed source positions.Two types of potentially observable secular motions should be present in extragalactic source positions. Gravitational accelerations of the solar system will cause secular motions through aberration, amounting to, e.g., about 4 microarcsec (μas) year–1 due to the mass of the galaxy. Extragalactic mass concentrations will cause gravitational deflections in the apparent positions of more distant radio sources, and these will change with time as the mass concentrations evolve. This effect could easily cause secular motions of order 1 μas year–1 in some, or even most, radio sources with z ≥ 1.The present astrometric VLBI data set contains about one million observations over a 15 year period, with current source proper motion formal errors being as small as 2.5 μas year–1. Proper motion estimates from these data reveal many sources with statistically significant proper motion estimates of order 30 μas year–1, about an order of magnitude larger than expected. Work continues to determine if the observed motions are due to systematic errors or reflect true secular changes in source positions. The results from a continued proper motion analysis of the complete astrometric VLBI data set will be presented.

scholarly journals Astrometry and Geodesy from VLBI

1993 ◽  
Vol 156 ◽  
pp. 159-171
Author(s):  
C. Ma ◽  
J. L. Russell
Keyword(s):  
Reference Frame ◽  
Reference Frames ◽  
Radio Sources ◽  
Dual Frequency ◽  
Terrestrial Reference Frames ◽  
Vlbi Observations ◽  
Using Data ◽  
Celestial Reference Frame ◽  
Right Ascension ◽  
Better Than

Dual frequency Mark III VLBI observations acquired since 1979 by several geodetic and astrometric observing programs have been used to establish precise celestial and terrestrial reference frames. The program to establish a uniformly distributed celestial reference frame of ∼400 compact radio sources with optical counterparts was begun in 1987. Some 700 sources have been considered as part of this effort and a preliminary list of ∼400 has been observed. At present, 308 sources have formal 1σ errors less than 1 mas in right ascension and 308 have similar precision in declination. The astrometric results include some data acquired for geodetic purposes. The geodetic results using data to September, 1992 include the positions of 105 sites with formal 1σ horizontal errors generally less than 1 cm at 1992.6 and the velocities of 64 sites with formal 1σ horizontal errors generally better than 2 mm/yr.

scholarly journals Radio Reference Frame Stability from VLBI Data

1988 ◽  
Vol 129 ◽  
pp. 331-332
Author(s):  
O. J. Sovers ◽  
R. N. Treuhaft
Keyword(s):  
Reference Frame ◽  
Independent Sets ◽  
Radio Sources ◽  
Deep Space ◽  
Deep Space Network ◽  
Space Network ◽  
Rates Of Change ◽  
Upper Limits ◽  
Vlbi Data ◽  
Almost All

Intercontinental radio interferometric measurements between NASA's Deep Space Network stations yield a catalog of positions of 106 extragalactic radio sources, uniformly distributed between −45° and +85° declination. Almost all of the source positions have formal uncertainties between 0.5 and 3 milliarcseconds. Estimates of three independent sets of 32 source coordinates at average epochs 1980.0, 1983.2, and 1984.5 assess the level of stability of the reference frame over a five-year period. Comparisons of the three sets of source coordinates show a number of cases of > 2σ differences, particularly betwen the 1984–85 and 1981–83 periods. No sources, however, show 2σ shifts among both pairs of epochs. Upper limits of the order of 1 mas/yr can be placed on the time rates of change of the 32 source coordinates.

scholarly journals Structure Effects for 3417 Celestial Reference Frame Radio Sources

2019 ◽  
Vol 242 (1) ◽  
pp. 5 ◽  
Author(s):  
M. H. Xu ◽  
J. M. Anderson ◽  
R. Heinkelmann ◽  
S. Lunz ◽  
H. Schuh ◽  
...  
Keyword(s):  
Reference Frame ◽  
Radio Sources ◽  
Celestial Reference Frame

scholarly journals The Possibility to Link Radio and Optical Reference Frames With Artificial Satellites

1990 ◽  
Vol 141 ◽  
pp. 194-194
Author(s):  
Tong Fu
Keyword(s):  
Reference Frame ◽  
Reference Frames ◽  
Artificial Satellites ◽  
Radio Sources ◽  
Bl Lac Objects ◽  
Extragalactic Radio Sources ◽  
Bl Lac ◽  
Optical Reference ◽  
Radio Stars ◽  
Fundamental Reference

Based on extragalactic radio sources, a new high precision extragalactic radio reference frame can be established from radio interferometric measurements. To link the optical fundamental reference frame presently represented by the FK4/5 to the extragalactic radio frame, the optical counterparts of extragalactic radio sources (quasars, BL Lac objects etc.) and radio stars are the most important classes of objects. Besides these two classes of objects, are there any other objects which can be used to link the optical and radio frames? A posible answer is that artificial satellites could be a candidate class of objects contributing to this subject.

scholarly journals OPTICAL SPECTRA OF CANDIDATE SOUTHERN HEMISPHERE INTERNATIONAL CELESTIAL REFERENCE FRAME (ICRF) RADIO SOURCES

2011 ◽  
Vol 142 (5) ◽  
pp. 165 ◽  
Author(s):  
O. Titov ◽  
D. L. Jauncey ◽  
H. M. Johnston ◽  
R. W. Hunstead ◽  
L. Christensen
Keyword(s):  
Reference Frame ◽  
Southern Hemisphere ◽  
Optical Spectra ◽  
Radio Sources ◽  
Celestial Reference Frame

scholarly journals Instability of the celestial reference frame and effect on UT1

2009 ◽  
Vol 5 (H15) ◽  
pp. 209-209
Author(s):  
Vladimir E. Zharov
Keyword(s):  
Reference Frame ◽  
Apparent Motion ◽  
Radio Sources ◽  
Secular Variations ◽  
Celestial Reference Frame

AbstractIt was shown that the ICRF radio sources including the defining sources have significant apparent motion that leads to rotation of the ICRF. This rotation is transformed to secular variations of EOP that is decreased or removed if motion of sources is took into account.

scholarly journals AGN Variability from the USNO Radio Reference Frame Image Database

2002 ◽  
Vol 19 (1) ◽  
pp. 19-21
Author(s):  
Alan L. Fey
Keyword(s):  
Reference Frame ◽  
Preliminary Analysis ◽  
Image Database ◽  
Radio Sources ◽  
Valuable Insight ◽  
Extragalactic Radio Sources ◽  
Structural Variability ◽  
Naval Observatory ◽  
The Us ◽  
Insight Into

AbstractWe present results from preliminary analysis of radio interferometric data taken from the US Naval Observatory Radio Reference Frame Image Database. The results presented here reveal valuable insight into the structural variability of the two extragalactic radio sources 0552+398 and 1308+326. We are actively pursuing analysis of additional objects.

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