GECO: the galactic and extragalactic compact-object observatory

GECO is a mission concept recently proposed in response to a Small National Mission call jointly issued by INAF and ASI for a fast-track space mission, including a scientific payload not in excess of 100 kg and technologies with TRL ≥5. Launch of the selected mission is anticipated around 2033. GECO proposes an unprecedented combination of field of view (half-sky), point source location accuracy (1 arcmin), broad spectral response (2 keV – 2 MeV) and energy resolution (350 eV FWHM at 6 keV). The scientific payload is composed of 2 instruments. The coded-mask All Sky Monitor (ASM, 2– 50 keV) will detect, localize and study steady, variable and transient sources simultaneously appearing anywhere in the accessible 50% of the sky, downlinking real-time arcmin-accurate localizations and photon-by-photon data for deeper spectral and timing studies. The ASM design is based on the LEM-X instrument and it is inherited from the LOFT and eXTP designs. The Broadband Universal Radiation Spectrometer for Transients (BURST) instrument will extend the energy band of GECO up to 2 MeV, enabling the full spectral characterization of the hardest transients, from gamma ray bursts to magnetar flares and bright black hole transients. The BURST design is inherited from the HERMES scientific payload.