The formal uncertainties of the simulated TGAS solution, shown in this figure, depend strongly on the sky coverage. However, in many well-observed areas the accuracy of the resulting five astrometric parameters is potentially in the sub-milliarcsecond range. This assumes that several very preliminary calibrations can actually be achieved with the necessary precision on just half a year of data.

Attempting TGAS within DPAC thus provides the opportunity of identifying issues in Gaia's processing chain early on, and an interesting challenge to test our readiness on real data.

credits: Daniel Michalik, Lennart Lindegren, David Hobbs (Lund University)