Acknowledgements. The acknowledgements are available in Appendix A. Marie Curie Research Training Network ( MRTN-CT-2006-033481 ), through  Marie Curie  project  PIOF-GA-2009-255267  ( Space AsteroSeismology & RR Lyrae  stars, SAS-RRL), and through a  Marie Curie Transfer -of-Knowledge (ToK) fellowship  ( MTKD- CT-2004-014188 ); the  European Commission 's  Seventh Framework Programme  through grant  FP7-606740  ( FP7-SPACE-2013-1 ) for the  Gaia European Network for Improved data User Services (GENIUS ) and through grant  264895  for the  Gaia Research for European Astronomy Training  ( GREAT-ITN ) network; the  European Cooperation in Science and Technology (COST)  through  COST Action   CA18104  ' Revealing the Milky Way with Gaia (MW-Gaia )'; the  European Research Council (ERC)  through grants  320360 ,  647208 , and  834148  and through the  European Union 's  Horizon 2020 research and innovation and excellent science programmes  through  Marie Skłodowska-Curie  grant  745617  (Our Galaxy at full  HD -Gal-HD ) and  895174  (The build-up and fate of self- gravitating systems in the Universe)  as well as grants  687378  ( Small Bodies: Near and Far ),  682115  (Using the  Magellanic Clouds to Understand the Interaction of Galaxies) ,  695099  (A sub-percent distance scale from binaries and  Cepheids -CepBin ),  716155  (Structured  ACCREtion Disks -SACCRED ),  951549  (Sub-percent calibration of the extragalactic  distance scale in the era of big surveys -UniverScale) , and  101004214  ( Innovative Scientific Data Exploration and Exploitation Applications for Space Sciences -EXPLORE ); the  European Science Foundation (ESF) , in the framework of the  Gaia Research for European Astronomy Training Research Network Programme (GREAT-ESF ); the  European Space Agency (ESA)  in the framework of the  Gaia project , through the  Plan for European Cooperating States   (PECS) programme  through contracts  C98090  and  4000106398/12/NL/KML  for Hungary, through contract  4000115263/15/NL/IB for   Germany , and through  PROgramme de Développement d'Expériences scientifiques (PRODEX)  grant  4000127986  for Slovenia; the  Academy of Finland  through grants  299543 ,  307157 ,  325805 ,  328654 ,  336546 , and  345115  and the  Magnus Ehrnrooth Foundation ; the  French Centre National d'Études Spatiales (CNES) , the  Agence Nationale de la Recherche (ANR)  through grant  ANR-10-IDEX-0001-02  for the ' Investissements d'avenir' programme , through grant  ANR-15-CE31-0007  for project ' Modelling the Milky Way in the Gaia era' (MOD4Gaia) , through grant  ANR-14-CE33-0014-01  for project 'The  Milky Way disc formation in the Gaia era' (ARCHEOGAL) , through grant  ANR-15-CE31-0012-01  for project ' Unlocking the potential of Cepheids as primary distance calibrators' (UnlockCepheids) , through grant  ANR-19-CE31-0017  for project ' Secular evolution of galxies' (SEGAL ), and through grant  ANR-18-CE31-0006  for project ' Galactic Dark Matter' (GaDaMa ), the  Centre National de la Recherche Scientifique (CNRS)  and its  SNO Gaia of the Institut des Sciences de l'Univers (INSU) , its  Programmes Nationaux: Cosmologie et Galaxies (PNCG) ,  Gravitation Références Astronomie Métrologie (PNGRAM) ,  Planétologie (PNP) ,  Physique et Chimie du Milieu Interstellaire (PCMI) , and  Physique Stellaire (PNPS) , the ' Action Fédératrice Gaia' of the Observatoire de Paris , the  Région de Franche-Comté , the  Institut National Polytechnique (INP)  and the  Institut National de Physique nucléaire et de Physique des Particules (IN2P3)  co-funded by  CNES ; the  German Aerospace Agency  ( Deutsches Zentrum für Luft-und Raumfahrt e.