Celestial fundamental catalogues are a prerequisite for the determination of absolute positions and motions in space. Presently, positional astrometry is at the watershed between classical fundamental catalogues, based on moving reference stars, and modern catalogues, based on extragalactic reference objects with non-measurable motion. This book addresses the concepts and methods of the respective construction techniques leading to the stellar frame of the FK5 (fifth fundamental catalogue) and to the newly adopted extragalactic radio reference frame, ICRF (international celestial reference frame), with its extension to optical wavelengths by the Hipparcos Catalogue. While principal outlines of meridian circle observations are given, emphasis is put in some detail on the VLBI technique as applied to astrometry, and to the observational techniques used in the Hipparcos mission, including the tie of the originally non-anchored rigid Hipparcos sphere into the ICRF.

Due to powerful computers and the internet there is a change of paradigm taking place in astrometry The authors, collaborators in the Hipparcos mission, present a final and definitive description of the concept of fundamental catalogues which will serve as a basis for future constructs

Inhalt

1. Fundamental Catalogues.- 1.1 Introductory Remarks.- 1.2 Objectives of Fundamental Catalogues.- 1.3 Background of Conventional Fundamental Catalogues.- 1.4 Inertial Reference Systems and Frames.- 1.5 Precession and Nutation.- 1.6 Determination of the Luni-solar Precession.- 1.7 Conventional Stellar Celestial Reference Systems.- 1.8 Conventional Extragalactic Celestial Reference Systems.- 2. The Conventional Fundamental Catalogue FK5.- 2.1 Historical Review.- 2.2 The FK5 Celestial Reference System.- 2.3 First Principles of Compiling the FK5.- 2.4 Scope of the FK5 Work.- 2.5 Transition to the Standard Epoch J2000.0.- 2.6 Organization of the FK5.- 3. Contributions of Space Astrometry to Fundamental Catalogues.- 3.1 Astrometric Space Missions.- 3.2 The Astrometry Satellite Hipparcos.- 3.3 Observing Principle.- 3.4 Organization of the Data Reduction.- 3.5 From Photons to Grid Coordinates.- 3.6 Reduction to Reference Great Circles.- 3.7 Sphere Solution.- 3.8 Construction of the Hipparcos Catalogue.- 4. Astrometry with Radio Interferometers.- 4.1 Radio Astronomy.- 4.2 Techniques of Radio Interferometry.- 4.3 The Observables.- 4.4 Requirements for Astrometry.- 5. Fundamental Catalogues of Extragalactic Radio Sources.- 5.1 System Definition.- 5.2 Some Specific Features of the ICRS Definition.- 5.3 The Extragalactic System Versus the FK5 System.- 5.4 Building Blocks for Catalogue Establishment.- 5.5 Methods of Fundamental Catalogue Construction.- 6. The International Celestial Reference Frame: ICRF.- 6.1 The Principles of ICRF Construction.- 6.2 Appraisal of the Origins, Context, and Role of the ICRF.- 6.3 Accuracy Assessment of the ICRF.- 6.4 Future Maintenance of the ICRF.- 7. Hipparcos Catalogue Tie with Conventional Celestial Reference Frames.- 7.1 Link with the Extragalactic Reference Frame.- 7.2 Link with the FK5 Reference Frame.- 7.3 Testing the Rigidity of the FK5 Frame.- 7.4 Refinement of the Hipparcos Link with the Extragalactic Reference Frame.- 8. Future Prospects.- 8.1 Interdependence of Astrometry and Fundamental Catalogues.- 8.2 Prospective Observational Techniques.- 8.3 Prospects for the Celestial Reference Frame.- Epilogue.- References.