  Gamma-Ray Integrated Detectors (GRID) mission is a student project designed
to use multiple gamma-ray detectors carried by nanosatellites (CubeSats),
forming a full-time all-sky gamma-ray detection network that monitors the
transient gamma-ray sky in the multi-messenger astronomy era. A compact CubeSat
gamma-ray detector, including its hardware and firmware, was designed and
implemented for the mission. The detector employs four Gd2Al2Ga3O12 : Ce
(GAGG:Ce) scintillators coupled with four silicon photomultiplier (SiPM) arrays
to achieve a high gamma-ray detection efficiency between 10 keV and 2 MeV with
low power and small dimensions. The first detector designed by the
undergraduate student team onboard a commercial CubeSat was launched into a
Sun-synchronous orbit on October 29, 2018. The detector was in a normal
observation state and accumulated data for approximately one month after
on-orbit functional and performance tests, which were conducted in 2019.
