A proposed network of gamma-ray burst detectors on the global navigation satellite system Galileo G2

The accurate localization of gamma-ray bursts (GRBs) remains a crucial task. Historically, improved localizations have led to the discovery of afterglow emission and the realization of their cosmological distribution via redshift measurements; however, a more recent requirement comes with the potential of studying the kilonovae of neutron star mergers. Gravitational wave detectors are expected to provide locations to not better than 10 square degrees over the next decade. With their increasing horizon for merger detections the intensity of the gamma-ray and kilonova emission also drops, making their identification in large error boxes a challenge. Thus, a localization via the gamma-ray emission seems to be the best chance to mitigate this problem. Here we propose to equip some of the second-generation Galileo satellites with dedicated GRB detectors. This saves costs for launches and satellites for a dedicated GRB network, the large orbital radius is beneficial for triangulation, and perfect positional and timing accuracy come for free. We present simulations of the triangulation accuracy, demonstrating that short GRBs as faint as GRB 170817A can be localized to 1 degree radius (1 sigma).