text: sists of 12 NaI detectors 5(cid:48)(cid:48) in diameter by 0.5(cid:48)(cid:48) thick 
  mounted on the corners of the spacecraft and oriented 
  such that they view the entire sky not occulted by the 
  Earth. GBM also contains 2 BGO detectors 5(cid:48)(cid:48) in di- 
  ameter by 5(cid:48)(cid:48) thick located on opposite sides of the 
  spacecraft. None of the GBM detectors have direct 
  imaging capability. 
  
  I.  INTRODUCTION 
  
  The Gamma ray Burst Monitor (GBM) on Fermi is 
  currently the only instrument in orbit providing nearly 
  continuous full sky coverage in the hard X-ray/low 
  energy gamma ray energy range. The Earth occul- 
  tation technique, used very successfully on BATSE, 
  has been adapted to GBM. An initial catalog of 64 
  sources is currently being monitored and continuously 
  augmented. At energies above 100 keV, six steady 
  sources (the Crab, Cyg X-1, Swift J1753.5-0127, 1E 
  1740-29, Cen A, GRS 1915+105) and one transient 
  source (XTE J1752-223) have been detected in the 
  ﬁrst year of observation. We describe the instrument, 
  outline the technique, and present light curves for the 
  seven sources. 