The payloads of each satellite include 25 gamma-ray detectors (GRDs), 8 charged particle detectors (CPDs), and Electronics module (EBOX) (see Dome module below, where the round one represents GRD and the square one represents CPD). The 25 GRD modules are all installed in the dome of the satellite, pointing to different directions. Such a design provides GRD with wide monitoring field of view. Among the eight CPDs, six CPDs are installed in the dome of the satellite and two remained CPDs are installed on the side of payload Electronics module. CPD is used to measure the flux changes of charged particles in the space environment, and can also be used to identify gamma-ray burst and charged particles event in the space in combination with GRD. Positioned in payload Electronics module, EBOX is used for acquiring and processing GRD and CPD data, realizing on-orbit triggering and positioning of gamma-ray burst, completing data storage, packaging, transmission and the interaction with satellite platform, and providing power supply for the entire payload.

Figure: Structure of payloads of GECAM

Time accuracy:

With the on-ground and in-flight calibrations, the relative time accuracy among all GRD and CPD detectors of GECAM-B is about 0.12 μs (1σ) and the absolute time difference between GECAM-B and Fermi/GBM is about 3± 6 μs (1σ).

Figure: The distribution of the maximum time difference for 20 000 shower events recorded by different detectors on board GECAM-B. The width of bin is 0.03 μs. (Xiao, 2022)

Figure: The Crab pulse profiles in the 20–500-keV energy band obtained with GECAM-B and GBM from UTC 2021-05-01T00:00:00 to UTC 2021-05-31T23:59:59. The phase resolution is 0.0001. (Xiao, 2022)