Gaia Space Observatory (2013–present)

Gaia Space Observatory has cataloged the positions and motions of nearly two billion stars with micro-arcsecond precision, creating the most detailed 3D map of the Milky Way ever assembled. Since its launch in 2013, ESA's astrometric mission has revealed our galaxy's complex merger history, including tidal streams from dwarf galaxy collisions. Its Data Release 3 in 2022 provided 1.8 billion-star positions with ±0.2 milliarcsecond accuracy, enabling studies of stellar dynamics and dark matter distribution. Gaia's star-count resolution outperforms #8 Hubble's field-by-field surveys by offering a comprehensive census across the entire sky, and its 1.5 million quasar catalog enhances the celestial reference frame better than the typical astrometric mission. The observatory carries a 1-meter telescope and two photometric instruments, generating 40 terabytes of data annually. Gaia's ongoing measurements will refine distance scales for 10,000 Cepheid variables, anchoring cosmic yardsticks used by its peers.