GRID: a Student Project to Monitor the Transient Gamma-Ray Sky in the Multi-Messenger Astronomy Era

The Gamma-RayIntegrated Detectors (GRID) is a space mission concept dedicated to monitoring the transient gamma-raysky in the energy range from 10 keV to 2 MeV using scintillation detectors onboard CubeSatsin low Earth orbits. The primary targets of GRID are the gamma-raybursts (GRBs) in the local universe. The scientific goal of GRID is, in synergy with ground-based gravitational wave (GW) detectors such as LIGOand VIRGO, to accumulate a sample of GRBs associated with the merger of two compact starsand study jets and related physics of those objects. It also involves observing and studying other gamma-raytransients such as long GRBs, soft gamma-rayrepeaters, terrestrial gamma-ray flashes, and solar flares. With multiple CubeSatsin various orbits, GRID is unaffected by the Earth occultation and serves as a full-time and all-sky monitor. Assuming a horizon of 200 Mpc for ground-based GW detectors, we expect to see a few associated GW-GRB events per year. With about 10 CubeSatsin operation, GRID is capable of localizing a faint GRB like 170817A with a 90% error radius of about 10 degrees, through triangulation and flux modulation. GRID is proposed and developed by students, with considerable contribution from undergraduate students, and will remain operated as a student project in the future. The current GRID collaboration involves more than 20 institutes and keeps growing. On August 29th, the first GRID detector onboarda CubeSatwas launched into a Sun-synchronous orbitand is currently under test.