Synergies
The TDT is the spectroscopic counterpart to the imaging surveys, space missions and multi-messenger observatories of the coming decades, and complements ESO’s own facilities.
Imaging surveys
Wide-field surveys from the ground, such as the Vera C. Rubin Observatory, ZTF, ATLAS, GOTO and BlackGEM/MeerLICHT, and from space, such as Gaia, Euclid and Roman, chart the variable sky in ever more depth and detail, together producing hundreds of alerts every night. Today fewer than 10% of transients are identified spectroscopically, and fewer than 1% are followed in detail. Reaching g ≈ 25, the TDT matches the imaging depth of Rubin, Euclid and Roman with spectroscopy.
Time-domain space missions
Missions such as TESS, Einstein Probe, SVOM and, soon, PLATO, ULTRASAT and UVEX find transiting exoplanets, stellar variability and high-energy transients that need spectroscopy, often at specific times. At R = 105 the full TDT array matches the photometric depth of TESS and PLATO (see exoplanets and the Galaxy).
Multi-messenger astronomy
Gravitational-wave detectors (LIGO, Virgo and KAGRA today; the Einstein Telescope, Cosmic Explorer and the LISA space mission next), neutrino observatories such as IceCube and KM3NeT, and the gamma-ray observatory CTAO will localise events whose electromagnetic counterparts are faint and fade fast. Binary neutron-star mergers found by next-generation detectors will peak at g ≈ 24, beyond the reach of any spectrograph except the TDT (see stellar deaths and cosmic elements).
ESO facilities
The TDT complements the current and near-future facilities available to the ESO community: the Very Large Telescope and its Interferometer, ALMA, the La Silla facilities and the Extremely Large Telescope. Its first step, proto-TDT/FAROS, would itself use the four Auxiliary Telescopes of the VLT Interferometer (see development path).
See the sign-up form if you are interested in joining the TDT effort.