Hipparcos, the New Reduction of the Raw Data

The new reduction of the Hipparcos data presents a very significant improvement in the overall reliability of the astrometric catalogue derived from this mission. Improvements by up to a factor 4 in the accuracies for in particular brighter stars have been obtained. This has been achieved mainly through careful study of the satellite dynamics, and incorporating results from these studies in the attitude modelling. Data correlations, caused by attitude-modelling errors in the original catalogue, have all but disappeared. This book provides overviews of the new reduction as well as on the use of the Hipparcos data in a variety of astrophysical implementations. A range of new results, like cluster distances and luminosity calibrations, is presented. The Hipparcos data provide a unique opportunity for the study of satellite dynamics. The orbit covered a wide range of altitudes, showing in detail the different torques acting on the satellite. One part of the book details these studies and their impact on the new reduction. It furthermore presents an extensive summary on a wide range of spacecraft and payload calibrations, which provide a detailed record of the conditions under which these unique Hipparcos data have been obtained.

Zusammenfassung
Thepublication oftheHipparcos andTycho Catalogues in 1997 transformed astrometry, and as a consequence astronomers' perception of astrometry. What had before often been regarded as a somewhat quaint specialty of limited re- vance to modern astrophysics, was suddenly seen to produce a wealth of data of immediate practical use. The ready availability of many thousand precise trigonometric stellar distances and the access to an accurate and dense - tical reference frame have changed the way astronomers think about certain problems and plan their experiments. Inevitably, the exploitation of so much new data not only solved some old problems, tidied up several confused areas and sharpened many observational constraints, but it also generated new qu- tions about established theory and about the data themselves. The author of this book has taken a radical approach to answer some of these questions: a complete re-examination of the satellite data and the models used to represent them, in particular the attitude modelling. Eventually this resulted in the new and very signi?cantly improved Hipparcos reduction described in this book. This remarkable achievement was made possible by a combination of many factors, including time and the exponential growth of computing power, but mainly an incredible amount of detailed, tedious and ingenious work by the author and the resulting insight into what really went on with the satellite in its unhappy orbit. Dr.

Inhalt

to the Hipparcos Mission.- The Hipparcos Mission.- Hipparcos Astrometry.- Exploring the Hipparcos Astrometric Data.- Individual, Single Stars.- The Astrometric Data for Composite Images and Orbital Binaries.- Groups of Single Stars.- Kinematics of the Solar Neighbourhood.- A Description of the Contents and Peculiarities of the Hipparcos Photometric Data.- The Photometric Data.- Hipparcos Attitude Modelling.- A Free-Floating Rigid Body in Space.- The Torques on Hipparcos As Observed Over the Mission.- Fully-Dynamic Attitude Fitting.- Summary of Selected Spacecraft and Payload Calibration Results.- The Mission Timeline.- Payload Calibrations.- Spacecraft-Parameter Calibrations.- The Next Generation.- Gaia.