text: Known sources of gamma ray emission can be mon- 
  itored with non-imaging detectors using the Earth oc- 
  cultation technique, as was successfully demonstrated 
  with BATSE [3, 4]. When a source of gamma rays 
  is occulted by the Earth, the count rate measured by 
  the detector will drop, producing a step-like feature. 
  When the source reappears from behind the Earths 
  limb, the count rate will increase, producing another 
  step. The diameter of the Earth seen from Fermi is 
  ∼ 140◦, so roughly 30% of the sky is occulted by the 
  Earth at any one time. Coupled with the ±35◦ slew- 
  ing of the pointing direction every orbit, this means 
  that the entire sky is occulted every two orbits. With 
  an altitude of 565 km, a period of 96 minutes, and 
  an orbital inclination of 26.5◦, individual occultation 
  steps last for ∼10 seconds (Fig. 1). 
  
  II. GBM AND THE EARTH OCCULTATION 
  OBSERVATIONAL TECHNIQUE 
  
  The Gamma ray Burst Monitor is the secondary 
  instrument onboard the Fermi satellite [1, 2]. It con- 