2558 20160701171707.0 ASTROimport-715 Soubiran, C. 2008 Ground-Based Observations for Gaia (GBOG) This contribution gives an overview of the ground-based observing efforts organized to collect the auxiliary data mandatory for the calibrations and tests of the Gaia data processing. Allende Prieto, C. Altmann, M. Bragaglia, A. Clementini, G. Frémat, Y. Heiter, U. Joliet, E. Pancino, E. Sartoretti, P. Smart, R. Thuillot, W. SF2A-2008 2008 35 http://esoads.eso.org/abs/2008sf2a.conf...35S published in NONREF