Faint objects in motion: the new frontier of high precision astrometry
Authors: Malbet Fabien , Boehm Céline , Krone-Martins Alberto , Amorim Antonio , Anglada-Escudé Guillem , Brandeker Alexis , Courbin Frédéric , Enßlin Torsten , Falcão Antonio , Freese Katherine , Holl Berry , Labadie Lucas , Léger Alain , Mamon Gary A. , McArthur Barbara , Mora Alcione , Shao Mike , Sozzetti Alessandro , Spolyar Douglas , Villaver Eva , Abbas Ummi , Albertus Conrado , Alves João , Barnes Rory , Bonomo Aldo Stefano , Bouy Hervé , Brown Warren R. , Cardoso Vitor , Castellani Marco , Chemin Laurent , Clark Hamish , Correia Alexandre C. M. , Crosta Mariateresa , Crouzier Antoine , Damasso Mario , Darling Jeremy , Davies Melvyn B. , Diaferio Antonaldo , Fortin Morgane , Fridlund Malcolm , Gai Mario , Garcia Paulo , Gnedin Oleg , Goobar Ariel , Gordo Paulo , Goullioud Renaud , Hall David , Hambly Nigel , Harrison Diana , Hobbs David , Holland Andrew , Høg Erik , Jordi Carme , Klioner Sergei , Lançon Ariane , Laskar Jacques , Lattanzi Mario , Le Poncin-Lafitte Christophe , Luri Xavier , Michalik Daniel , de Almeida André Moitinho , Mourão Ana , Moustakas Leonidas , Murray Neil J. , Muterspaugh Matthew , Oertel Micaela , Ostorero Luisa , Portell Jordi , Prost Jean-Pierre , Quirrenbach Andreas , Schneider Jean , Scott Pat , Siebert Arnaud , Silva Antonio da , Silva Manuel , Thébault Philippe , Tomsick John , Traub Wesley , de Val-Borro Miguel , Valluri Monica , Walton Nicholas A. , Watkins Laura L. , White Glenn , Wyrzykowski Lukasz , Wyse Rosemary , Yamada Yoshiyuki 
Published: September 2021

Sky survey telescopes and powerful targeted telescopes play complementary roles in astronomy. In order to investigate the nature and characteristics of the motions of very faint objects, a flexibly-pointed instrument capable of high astrometric accuracy is an ideal complement to current astrometric surveys and a unique tool for precision astrophysics. Such a space-based mission will push the frontier of precision astrometry from evidence of Earth-mass habitable worlds around the nearest stars, to distant Milky Way objects, and out to the Local Group of galaxies. As we enter the era of the James Webb Space Telescope and the new ground-based, adaptive-optics-enabled giant telescopes, by obtaining these high precision measurements on key objects that Gaia could not reach, a mission that focuses on high precision astrometry science can consolidate our theoretical understanding of the local Universe, enable extrapolation of physical processes to remote redshifts, and derive a much more consistent picture of cosmological evolution and the likely fate of our cosmos. Already several missions have been proposed to address the science case of faint objects in motion using high precision astrometry missions: NEAT proposed for the ESA M3 opportunity, micro-NEAT for the S1 opportunity, and Theia for the M4 and M5 opportunities. Additional new mission configurations adapted with technological innovations could be envisioned to pursue accurate measurements of these extremely small motions. The goal of this White Paper is to address the fundamental science questions that are at stake when we focus on the motions of faint sky objects and to briefly review instrumentation and mission profiles.