Hipparcos data repatriated to ESA

By Elena Puga, Daniel Michalik, Jos de Bruijne and the ESASky team

What were you doing in 1997? That year, ESA published the first Hipparcos Catalogue (118,218 stars with 1-milliarcsec-level astrometry) and the Tycho Catalogue (more than one million stars with 20-30 milliarcsec astrometry and two-colour photometry). Further improved catalogues were made available to the science community ten years later, like the Tycho-2 Catalogue with positions, motions, brightness and colours for 2,539,913 stars, more than doubling the number of stars in the original Tycho Catalogue.
The science value of these data is endorsed by the 2,576 refereed publications since its launch in 1989 (10 of them in the course of 2020). Yet, these data do not get out of style, as they complement the currently operating astrometric mission Gaia.

As of 21 December 2020, 37 of the planned 42 Hipparcos data products are available via the ESASky legacy TAP query. You can access them using the Topcat tool, selecting the option "Table Access Protocol (TAP) Query" in the VO menu, and introducing the TAP url in the "Select Service" pane.
While part of these catalogues are served to the community by CDS/VizieR, some data products can be queried from the Hipparcos homepage, and a few selected products are being served as public tables from within the Gaia Archive and ESASky.
This trailblazing Galaxy charter mission has produced four major catalogues referred to as the Hipparcos-1 Catalogue, the Tycho-1 Catalogue, the Hipparcos-2 Catalogue, and the Tycho-2 Catalogue. For most -but certainly not all- scientific applications, the Hipparcos-2 and Tycho-2 catalogues supersede the official, original ESA versions. However, the ESA 1997 publication –i.e. the version-1 catalogues– do contain unique information (e.g. astrometry of component binaries or photometric variability data) that is still relevant and not part of the version-2 catalogues.

ESA's goal is to serve the community a complete, self-standing catalogue collection of the ESA mission Hipparcos, providing a single unified method of accessing all Hipparcos/Tycho data products and their successors. Revisiting Hipparcos data will now be possible either together with Gaia science products or separately.
This first release comprises 37 data products (catalogues and annexes). For 23 out of 43 tables, we have redefined the table data models, and for 13 tables the curation work entailed going back to the original documentation. Hipparcos-1 data products are complete except for identification charts and light-curve figures. Finally, Tycho-1 will be completed with the Epoch Photometry Annex B, and Hipparcos-2 and Tycho-2 with Intermediate Astrometry data products. These data products are yet to come in a future release. Stay tuned!
Images: ESA/ESDC