EG4 - Astrometric Tests |
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Speaker |
Abbas, Ummi |
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Co-autors |
Alberto Vecchiato, Beatrice Bucciarelli, Mario Lattanzi, Roberto Morbidelli |
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Talk Title |
Global Astrometric Sphere Reconstruction in Gaia. Challenges and First Results of the Verification Unit |
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Abstract |
Gaia will estimate the astrometric and physical data of approximately one billion objects, lying mostly within our galaxy. The global sphere reconstruction, represented by the reduction of a subset of the objects, constitutes the core of this process. These will then constitute the largest and most precise catalog of absolute astrometry in the history of Astronomy, thereby testing General Relativity through the estimation of the PPN parameter $\gamma$ to unprecedented accuracy. As the Hipparcos mission has shown, and as is quite natural to all kinds of absolute measurements, possible errors in the data reduction can hardly be identified at the end of the processing. This can then lead to systematic errors in all subsequent investigations dependent on the results. In order to avoid such kinds of problems, a Verification Unit was established by the Gaia Data Processing and Analysis Consortium (DPAC). One of its jobs is to implement and perform an independent global sphere reconstruction, parallel to the baseline one, compare the two results, and to report any significant differences. We will present here how we dealt with the challenges of such a task, and the first results obtained so far. |
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