Summary: In order to build the Gaia celestial map with an accuracy of micro-arcseconds it has been demonstrated that we have to recover the attitude of the spacecraft and calibrate the instruments with the same accuracy. Gaia will be calibrated by adjusting all the parameters to fit all the measurements as good as possible. From a mathematical point of view, this problem has been formulated as a least-square system. In this note we investigate its sparseness structure.

Bibtex entry for this abstract:

@UNPUBLISHED{LL:APB-001,
author = {A.~Bombrun},
title={{S}parseness structure of the {G}aia least-square problem and the (non-)feasibility of a direct method},
institution={Astronomisches Rechen-Institut, Heidelberg (part of ZAH, Zentrum fuer Astronomie, Heidelberg)},
year={2008},
month={April},
url={http://www.rssd.esa.int/doc_fetch.php?id=2812482},
note={GAIA-C3-TN-ARI-APB-001},
type={Tecnical note}
}