Building on SVOM : the CATCH satellite constellation for transient astronomy

Abstract: Building on the success of the French-Chinese SVOM mission, our consortium proposes CATCH (Chasing All Transients Constellation of Hunters), targeting Gamma-Ray Bursts and X-ray transients. Its first step, CATCH-PM (Precursor Mission), consists of three satellites: (i) the Trigger Scout Satellite (TSS), providing real-time detection and localization of transients from soft X-rays to gamma-rays; (ii) the X-ray Hunter Satellite (XHS), performing rapid X-ray afterglow follow-up and refined localization with Wolter-I optics; and (iii) the Infrared Hunter Satellite (IHS), enabling precise localization and follow-up in the visible and near-infrared, including obscured and high-redshift transients. CATCH-PM is both a technological demonstrator and a standalone time-domain astrophysics mission. In addition to Scout triggers, it will accept numerous external Targets of Opportunity and conduct a broad observing program. By reusing available spare hardware, a launch within five years is feasible. Operating alongside SVOM and EinsteinProbe, it would significantly enhance the overall scientific return.