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High Precision Astrometry over Large Angular Scales with Closure Constraints: the Triplet 1803+784/1928+738/2007+777

Published online by Cambridge University Press:  25 May 2016

E. Ros ,
J.M. Marcaide ,
J.C. Guirado ,
T.P. Krichbaum ,
R.A. Preston ,
M.I. Ratner ,
I.I. Shapiro  and
A. Witzel
E. Ros
Affiliation:
1 Departamento de Astronomía, Universitat de Valencia, Dr. Moliner 50, E-46100 Burjassot (València), Spain
J.M. Marcaide
Affiliation:
1 Departamento de Astronomía, Universitat de Valencia, Dr. Moliner 50, E-46100 Burjassot (València), Spain
J.C. Guirado
Affiliation:
2 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109
T.P. Krichbaum
Affiliation:
3 Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
R.A. Preston
Affiliation:
2 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109
M.I. Ratner
Affiliation:
4 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, Massachusetts 02138
I.I. Shapiro
Affiliation:
4 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, Massachusetts 02138
A. Witzel
Affiliation:
3 Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany

Extract

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The technique of differential astrometry using the phase-delay VLBI observable promises fractional precisions of ≃2 × 10–9 in the determination of the separation of sources 5° or 6° apart on the sky (Guirado et al. 1995a; Lara et al. 1996). In our present research we seek further improvement in this technique through using triplets of radio sources, which provide a closure constraint in the determination of relative angular positions. This constraint not only eases the resolution of the phase-cycle ambiguities (a major problem in the least-squares approach to astrometry with phase delays), but it also strongly constrains the space of allowable parameter values.

Type
Properties of Radio Sources
Information
Symposium - International Astronomical Union , Volume 175: Extragalactic Radio Sources , 1996 , pp. 120 - 121
Copyright
Copyright © Kluwer 1996 

References

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