text: The shape of the individual occultation steps de- 
  pends on energy and occultation angle. Transmis- 
  sion as a function of time is modeled as T (t) = 
  exp[−µ(E)A(h)], where µ(E) is the mass attenuation 
  coeﬃcient of gamma rays at energy E in air and A(h) 
  is the air mass along the line of sight at a given alti- 
  tude h(t). Account is taken of the detector response 
  as it changes as a function of angle across the ﬁt win- 
  dow. For each source, occultation times are predicted. 
  Each step is ﬁt over a 4-minute window along with a 
  quadratic background and using an assumed spectrum 
  to determine the detector count rate due to the source. 
  The instrument response is used to convert the count 
  rate to a ﬂux. Up to 31 steps are possible for a given 
  source in a day, and these steps are summed to get a 
  single daily average ﬂux. The GBM occultation sensi- 
  tivity exceeds that of BATSE at energies below ∼ 25 
  keV and above ∼ 1.5 MeV [5]. 