The GECAM and its payload

The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) monitors gamma-ray bursts (GRBs) coincident with gravitational wave events over the whole sky. It also monitors other burst events, such as the high-energy radiation of fast radio bursts, various GRBs, and magnetar bursts. GECAM can measure the energy spectra, light curves, and location of all kinds of bursts. GECAM consists of two small satellites which operate in the same low earth orbit but in opposite geocentric directions. To obtain an all-sky field of view, the two satellites operate in opposite orbital phases. The GECAM payload includes two kinds of detectors: charged particle detector (CPD) and gamma-ray detector (GRD). Each GRD module consists of a LaBr3:Ce scintillator and a SiPM array, and its gamma-ray detection range is 5 keV–5 MeV. GECAM retrieves the locations of events such as GRBs through analyzing the data of the multiple GRDs on both satellites. Meanwhile, the CPD consists of a plastic scintillator and a SiPM array that detects charged particles of energies from 300 keV to 5 MeV. The GECAM distinguishes the charged particle burst events in space by jointly analyzing the GRD and CPD data. The payload electronic box (EBOX) provides in-flight trigger and burst localization. The trigger and burst location data are transmitted by a BeiDou Short Message system, which allows GECAM to guide other telescopes to do follow-up observations.