E. Fraile

TL;DR: Gaia as discussed by the authors is a cornerstone mission in the science programme of the European Space Agency (ESA). The spacecraft construction was approved in 2006, following a study in which the original interferometric concept was changed to a direct-imaging approach.

TL;DR: The first Gaia data release, Gaia DR1 as discussed by the authors, consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the Hipparcos and Tycho-2 catalogues.

TL;DR: In this article, the authors describe the input data, models, and processing used for the astrometric content of Gaia DR2, and the validation of these results performed within the ASTR task.

TL;DR: In this article, the power of the Gaia DR2 in studying many fine structures of the Hertzsprung-Russell diagram (HRD) was highlighted, depending in particular on stellar population selections.

TL;DR: Gaia Data Release 1 (Gaia DR1) as discussed by the authors contains a large amount of data collected by the Gaia satellite during the first 14 months of its operational phase, including positions, parallaxes, and proper motions to Hipparcos-type precision or better.