Volume 620, December 2018
|Number of page(s)||19|
|Section||Celestial mechanics and astrometry|
|Published online||27 November 2018|
The global sphere reconstruction (GSR)
Demonstrating an independent implementation of the astrometric core solution for Gaia
1 INAF – Astrophysical Observatory of Torino, Pino Torinese, Italy
2 INAF – Astrophysical Observatory of Catania, Italy
3 EURIX, Torino, Italy
4 ALTEC, Torino, Italy
Accepted: 4 September 2018
Context. The Gaia ESA mission will estimate the astrometric and physical data of more than one billion objects, providing the largest and most precise catalog of absolute astrometry in the history of astronomy. The core of this process, the so-called global sphere reconstruction, is represented by the reduction of a subset of these objects which will be used to define the celestial reference frame. As the HIPPARCOS mission showed, and as is inherent to all kinds of absolute measurements, possible errors in the data reduction can hardly be identified from the catalog, thus potentially introducing systematic errors in all derived work.
Aims. Following up on the lessons learned from HIPPARCOS, our aim is thus to develop an independent sphere reconstruction method that contributes to guarantee the quality of the astrometric results without fully reproducing the main processing chain.
Methods. Indeed, given the unfeasibility of a complete replica of the data reduction pipeline, an astrometric verification unit (AVU) was instituted by the Gaia Data Processing and Analysis Consortium (DPAC). One of its jobs is to implement and operate an independent global sphere reconstruction (GSR), parallel to the baseline one (AGIS, namely Astrometric Global Iterative Solution) but limited to the primary stars and for validation purposes, to compare the two results, and to report on any significant differences.
Results. Tests performed on simulated data show that GSR is able to reproduce at the sub-μas level the results of the AGIS demonstration run.
Conclusions. Further development is ongoing to improve on the treatment of real data and on the software modules that compare the AGIS and GSR solutions to identify possible discrepancies above the tolerance level set by the accuracy of the Gaia catalog.
Key words: astrometry / reference systems / catalogs / methods: numerical / space vehicles
© ESO 2018
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.