The Fermi Gamma Ray Burst Monitor (GBM) enhances the science return from the Fermi mission by providing observations of GRBs in the energy range 8 keV to 40 MeV, thereby extending GRB spectra three decades below the Large Area Telescope (LAT) threshold of ~20 MeV. GBM employs twelve sodium iodide scintillation detectors and two bismuth germinate scintillation detectors to observe the full unocculted sky. The flight software localizes GRBs and can generate a request to autonomously repoint the spacecraft to place a burst within the LAT field of view. GBM has a trigger threshold of 0.74 photons-cm-2-s-1 and triggers on ~260 bursts per year, as well as a variety of other gamma-ray transients.
